log, vendor: vendor in log15 inline into our codebase

26 files changed, 2006 insertions, 0 deletions

diff --git a/log/CONTRIBUTORS b/log/CONTRIBUTORS
new file mode 100644
index 000000000..a0866713b
--- /dev/null
+++ b/log/CONTRIBUTORS
@@ -0,0 +1,11 @@
+Contributors to log15:
+
+- Aaron L 
+- Alan Shreve 
+- Chris Hines 
+- Ciaran Downey 
+- Dmitry Chestnykh 
+- Evan Shaw 
+- Péter Szilágyi 
+- Trevor Gattis 
+- Vincent Vanackere 
diff --git a/log/LICENSE b/log/LICENSE
new file mode 100644
index 000000000..5f0d1fb6a
--- /dev/null
+++ b/log/LICENSE
@@ -0,0 +1,13 @@
+Copyright 2014 Alan Shreve
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
diff --git a/log/README.md b/log/README.md
new file mode 100644
index 000000000..0951b21cb
--- /dev/null
+++ b/log/README.md
@@ -0,0 +1,77 @@
+![obligatory xkcd](http://imgs.xkcd.com/comics/standards.png)
+
+# log15 [![godoc reference](https://godoc.org/github.com/inconshreveable/log15?status.png)](https://godoc.org/github.com/inconshreveable/log15) [![Build Status](https://travis-ci.org/inconshreveable/log15.svg?branch=master)](https://travis-ci.org/inconshreveable/log15)
+
+Package log15 provides an opinionated, simple toolkit for best-practice logging in Go (golang) that is both human and machine readable. It is modeled after the Go standard library's [`io`](http://golang.org/pkg/io/) and [`net/http`](http://golang.org/pkg/net/http/) packages and is an alternative to the standard library's [`log`](http://golang.org/pkg/log/) package.
+
+## Features
+- A simple, easy-to-understand API
+- Promotes structured logging by encouraging use of key/value pairs
+- Child loggers which inherit and add their own private context
+- Lazy evaluation of expensive operations
+- Simple Handler interface allowing for construction of flexible, custom logging configurations with a tiny API.
+- Color terminal support
+- Built-in support for logging to files, streams, syslog, and the network
+- Support for forking records to multiple handlers, buffering records for output, failing over from failed handler writes, + more
+
+## Versioning
+The API of the master branch of log15 should always be considered unstable. If you want to rely on a stable API,
+you must vendor the library.
+
+## Importing
+
+```go
+import log "github.com/inconshreveable/log15"
+```
+
+## Examples
+
+```go
+// all loggers can have key/value context
+srvlog := log.New("module", "app/server")
+
+// all log messages can have key/value context
+srvlog.Warn("abnormal conn rate", "rate", curRate, "low", lowRate, "high", highRate)
+
+// child loggers with inherited context
+connlog := srvlog.New("raddr", c.RemoteAddr())
+connlog.Info("connection open")
+
+// lazy evaluation
+connlog.Debug("ping remote", "latency", log.Lazy{pingRemote})
+
+// flexible configuration
+srvlog.SetHandler(log.MultiHandler(
+    log.StreamHandler(os.Stderr, log.LogfmtFormat()),
+    log.LvlFilterHandler(
+        log.LvlError,
+        log.Must.FileHandler("errors.json", log.JsonFormat()))))
+```
+
+Will result in output that looks like this:
+
+```
+WARN[06-17|21:58:10] abnormal conn rate                       module=app/server rate=0.500 low=0.100 high=0.800
+INFO[06-17|21:58:10] connection open                          module=app/server raddr=10.0.0.1
+```
+
+## Breaking API Changes
+The following commits broke API stability. This reference is intended to help you understand the consequences of updating to a newer version
+of log15.
+
+- 57a084d014d4150152b19e4e531399a7145d1540 - Added a `Get()` method to the `Logger` interface to retrieve the current handler
+- 93404652ee366648fa622b64d1e2b67d75a3094a - `Record` field `Call` changed to `stack.Call` with switch to `github.com/go-stack/stack`
+- a5e7613673c73281f58e15a87d2cf0cf111e8152 - Restored `syslog.Priority` argument to the `SyslogXxx` handler constructors
+
+## FAQ
+
+### The varargs style is brittle and error prone! Can I have type safety please?
+Yes. Use `log.Ctx`:
+
+```go
+srvlog := log.New(log.Ctx{"module": "app/server"})
+srvlog.Warn("abnormal conn rate", log.Ctx{"rate": curRate, "low": lowRate, "high": highRate})
+```
+
+## License
+Apache
diff --git a/log/README_ETHEREUM.md b/log/README_ETHEREUM.md
new file mode 100644
index 000000000..6a0b0141b
--- /dev/null
+++ b/log/README_ETHEREUM.md
@@ -0,0 +1,4 @@
+This package is a fork of https://github.com/inconshreveable/log15, with some
+minor modifications required by the go-ethereum codebase:
+
+ * Support for log level `trace`
diff --git a/log/doc.go b/log/doc.go
new file mode 100644
index 000000000..83ad8c54f
--- /dev/null
+++ b/log/doc.go
@@ -0,0 +1,333 @@
+/*
+Package log15 provides an opinionated, simple toolkit for best-practice logging that is
+both human and machine readable. It is modeled after the standard library's io and net/http
+packages.
+
+This package enforces you to only log key/value pairs. Keys must be strings. Values may be
+any type that you like. The default output format is logfmt, but you may also choose to use
+JSON instead if that suits you. Here's how you log:
+
+    log.Info("page accessed", "path", r.URL.Path, "user_id", user.id)
+
+This will output a line that looks like:
+
+     lvl=info t=2014-05-02T16:07:23-0700 msg="page accessed" path=/org/71/profile user_id=9
+
+Getting Started
+
+To get started, you'll want to import the library:
+
+    import log "github.com/inconshreveable/log15"
+
+
+Now you're ready to start logging:
+
+    func main() {
+        log.Info("Program starting", "args", os.Args())
+    }
+
+
+Convention
+
+Because recording a human-meaningful message is common and good practice, the first argument to every
+logging method is the value to the *implicit* key 'msg'.
+
+Additionally, the level you choose for a message will be automatically added with the key 'lvl', and so
+will the current timestamp with key 't'.
+
+You may supply any additional context as a set of key/value pairs to the logging function. log15 allows
+you to favor terseness, ordering, and speed over safety. This is a reasonable tradeoff for
+logging functions. You don't need to explicitly state keys/values, log15 understands that they alternate
+in the variadic argument list:
+
+    log.Warn("size out of bounds", "low", lowBound, "high", highBound, "val", val)
+
+If you really do favor your type-safety, you may choose to pass a log.Ctx instead:
+
+    log.Warn("size out of bounds", log.Ctx{"low": lowBound, "high": highBound, "val": val})
+
+
+Context loggers
+
+Frequently, you want to add context to a logger so that you can track actions associated with it. An http
+request is a good example. You can easily create new loggers that have context that is automatically included
+with each log line:
+
+    requestlogger := log.New("path", r.URL.Path)
+
+    // later
+    requestlogger.Debug("db txn commit", "duration", txnTimer.Finish())
+
+This will output a log line that includes the path context that is attached to the logger:
+
+    lvl=dbug t=2014-05-02T16:07:23-0700 path=/repo/12/add_hook msg="db txn commit" duration=0.12
+
+
+Handlers
+
+The Handler interface defines where log lines are printed to and how they are formated. Handler is a
+single interface that is inspired by net/http's handler interface:
+
+    type Handler interface {
+        Log(r *Record) error
+    }
+
+
+Handlers can filter records, format them, or dispatch to multiple other Handlers.
+This package implements a number of Handlers for common logging patterns that are
+easily composed to create flexible, custom logging structures.
+
+Here's an example handler that prints logfmt output to Stdout:
+
+    handler := log.StreamHandler(os.Stdout, log.LogfmtFormat())
+
+Here's an example handler that defers to two other handlers. One handler only prints records
+from the rpc package in logfmt to standard out. The other prints records at Error level
+or above in JSON formatted output to the file /var/log/service.json
+
+    handler := log.MultiHandler(
+        log.LvlFilterHandler(log.LvlError, log.Must.FileHandler("/var/log/service.json", log.JsonFormat())),
+        log.MatchFilterHandler("pkg", "app/rpc" log.StdoutHandler())
+    )
+
+Logging File Names and Line Numbers
+
+This package implements three Handlers that add debugging information to the
+context, CallerFileHandler, CallerFuncHandler and CallerStackHandler. Here's
+an example that adds the source file and line number of each logging call to
+the context.
+
+    h := log.CallerFileHandler(log.StdoutHandler)
+    log.Root().SetHandler(h)
+    ...
+    log.Error("open file", "err", err)
+
+This will output a line that looks like:
+
+    lvl=eror t=2014-05-02T16:07:23-0700 msg="open file" err="file not found" caller=data.go:42
+
+Here's an example that logs the call stack rather than just the call site.
+
+    h := log.CallerStackHandler("%+v", log.StdoutHandler)
+    log.Root().SetHandler(h)
+    ...
+    log.Error("open file", "err", err)
+
+This will output a line that looks like:
+
+    lvl=eror t=2014-05-02T16:07:23-0700 msg="open file" err="file not found" stack="[pkg/data.go:42 pkg/cmd/main.go]"
+
+The "%+v" format instructs the handler to include the path of the source file
+relative to the compile time GOPATH. The github.com/go-stack/stack package
+documents the full list of formatting verbs and modifiers available.
+
+Custom Handlers
+
+The Handler interface is so simple that it's also trivial to write your own. Let's create an
+example handler which tries to write to one handler, but if that fails it falls back to
+writing to another handler and includes the error that it encountered when trying to write
+to the primary. This might be useful when trying to log over a network socket, but if that
+fails you want to log those records to a file on disk.
+
+    type BackupHandler struct {
+        Primary Handler
+        Secondary Handler
+    }
+
+    func (h *BackupHandler) Log (r *Record) error {
+        err := h.Primary.Log(r)
+        if err != nil {
+            r.Ctx = append(ctx, "primary_err", err)
+            return h.Secondary.Log(r)
+        }
+        return nil
+    }
+
+This pattern is so useful that a generic version that handles an arbitrary number of Handlers
+is included as part of this library called FailoverHandler.
+
+Logging Expensive Operations
+
+Sometimes, you want to log values that are extremely expensive to compute, but you don't want to pay
+the price of computing them if you haven't turned up your logging level to a high level of detail.
+
+This package provides a simple type to annotate a logging operation that you want to be evaluated
+lazily, just when it is about to be logged, so that it would not be evaluated if an upstream Handler
+filters it out. Just wrap any function which takes no arguments with the log.Lazy type. For example:
+
+    func factorRSAKey() (factors []int) {
+        // return the factors of a very large number
+    }
+
+    log.Debug("factors", log.Lazy{factorRSAKey})
+
+If this message is not logged for any reason (like logging at the Error level), then
+factorRSAKey is never evaluated.
+
+Dynamic context values
+
+The same log.Lazy mechanism can be used to attach context to a logger which you want to be
+evaluated when the message is logged, but not when the logger is created. For example, let's imagine
+a game where you have Player objects:
+
+    type Player struct {
+        name string
+        alive bool
+        log.Logger
+    }
+
+You always want to log a player's name and whether they're alive or dead, so when you create the player
+object, you might do:
+
+    p := &Player{name: name, alive: true}
+    p.Logger = log.New("name", p.name, "alive", p.alive)
+
+Only now, even after a player has died, the logger will still report they are alive because the logging
+context is evaluated when the logger was created. By using the Lazy wrapper, we can defer the evaluation
+of whether the player is alive or not to each log message, so that the log records will reflect the player's
+current state no matter when the log message is written:
+
+    p := &Player{name: name, alive: true}
+    isAlive := func() bool { return p.alive }
+    player.Logger = log.New("name", p.name, "alive", log.Lazy{isAlive})
+
+Terminal Format
+
+If log15 detects that stdout is a terminal, it will configure the default
+handler for it (which is log.StdoutHandler) to use TerminalFormat. This format
+logs records nicely for your terminal, including color-coded output based
+on log level.
+
+Error Handling
+
+Becasuse log15 allows you to step around the type system, there are a few ways you can specify
+invalid arguments to the logging functions. You could, for example, wrap something that is not
+a zero-argument function with log.Lazy or pass a context key that is not a string. Since logging libraries
+are typically the mechanism by which errors are reported, it would be onerous for the logging functions
+to return errors. Instead, log15 handles errors by making these guarantees to you:
+
+- Any log record containing an error will still be printed with the error explained to you as part of the log record.
+
+- Any log record containing an error will include the context key LOG15_ERROR, enabling you to easily
+(and if you like, automatically) detect if any of your logging calls are passing bad values.
+
+Understanding this, you might wonder why the Handler interface can return an error value in its Log method. Handlers
+are encouraged to return errors only if they fail to write their log records out to an external source like if the
+syslog daemon is not responding. This allows the construction of useful handlers which cope with those failures
+like the FailoverHandler.
+
+Library Use
+
+log15 is intended to be useful for library authors as a way to provide configurable logging to
+users of their library. Best practice for use in a library is to always disable all output for your logger
+by default and to provide a public Logger instance that consumers of your library can configure. Like so:
+
+    package yourlib
+
+    import "github.com/inconshreveable/log15"
+
+    var Log = log.New()
+
+    func init() {
+        Log.SetHandler(log.DiscardHandler())
+    }
+
+Users of your library may then enable it if they like:
+
+    import "github.com/inconshreveable/log15"
+    import "example.com/yourlib"
+
+    func main() {
+        handler := // custom handler setup
+        yourlib.Log.SetHandler(handler)
+    }
+
+Best practices attaching logger context
+
+The ability to attach context to a logger is a powerful one. Where should you do it and why?
+I favor embedding a Logger directly into any persistent object in my application and adding
+unique, tracing context keys to it. For instance, imagine I am writing a web browser:
+
+    type Tab struct {
+        url string
+        render *RenderingContext
+        // ...
+
+        Logger
+    }
+
+    func NewTab(url string) *Tab {
+        return &Tab {
+            // ...
+            url: url,
+
+            Logger: log.New("url", url),
+        }
+    }
+
+When a new tab is created, I assign a logger to it with the url of
+the tab as context so it can easily be traced through the logs.
+Now, whenever we perform any operation with the tab, we'll log with its
+embedded logger and it will include the tab title automatically:
+
+    tab.Debug("moved position", "idx", tab.idx)
+
+There's only one problem. What if the tab url changes? We could
+use log.Lazy to make sure the current url is always written, but that
+would mean that we couldn't trace a tab's full lifetime through our
+logs after the user navigate to a new URL.
+
+Instead, think about what values to attach to your loggers the
+same way you think about what to use as a key in a SQL database schema.
+If it's possible to use a natural key that is unique for the lifetime of the
+object, do so. But otherwise, log15's ext package has a handy RandId
+function to let you generate what you might call "surrogate keys"
+They're just random hex identifiers to use for tracing. Back to our
+Tab example, we would prefer to set up our Logger like so:
+
+        import logext "github.com/inconshreveable/log15/ext"
+
+        t := &Tab {
+            // ...
+            url: url,
+        }
+
+        t.Logger = log.New("id", logext.RandId(8), "url", log.Lazy{t.getUrl})
+        return t
+
+Now we'll have a unique traceable identifier even across loading new urls, but
+we'll still be able to see the tab's current url in the log messages.
+
+Must
+
+For all Handler functions which can return an error, there is a version of that
+function which will return no error but panics on failure. They are all available
+on the Must object. For example:
+
+    log.Must.FileHandler("/path", log.JsonFormat)
+    log.Must.NetHandler("tcp", ":1234", log.JsonFormat)
+
+Inspiration and Credit
+
+All of the following excellent projects inspired the design of this library:
+
+code.google.com/p/log4go
+
+github.com/op/go-logging
+
+github.com/technoweenie/grohl
+
+github.com/Sirupsen/logrus
+
+github.com/kr/logfmt
+
+github.com/spacemonkeygo/spacelog
+
+golang's stdlib, notably io and net/http
+
+The Name
+
+https://xkcd.com/927/
+
+*/
+package log
diff --git a/log/format.go b/log/format.go
new file mode 100644
index 000000000..376376183
--- /dev/null
+++ b/log/format.go
@@ -0,0 +1,279 @@
+package log
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+)
+
+const (
+	timeFormat     = "2006-01-02T15:04:05-0700"
+	termTimeFormat = "01-02|15:04:05"
+	floatFormat    = 'f'
+	termMsgJust    = 40
+)
+
+type Format interface {
+	Format(r *Record) []byte
+}
+
+// FormatFunc returns a new Format object which uses
+// the given function to perform record formatting.
+func FormatFunc(f func(*Record) []byte) Format {
+	return formatFunc(f)
+}
+
+type formatFunc func(*Record) []byte
+
+func (f formatFunc) Format(r *Record) []byte {
+	return f(r)
+}
+
+// TerminalFormat formats log records optimized for human readability on
+// a terminal with color-coded level output and terser human friendly timestamp.
+// This format should only be used for interactive programs or while developing.
+//
+//     [TIME] [LEVEL] MESAGE key=value key=value ...
+//
+// Example:
+//
+//     [May 16 20:58:45] [DBUG] remove route ns=haproxy addr=127.0.0.1:50002
+//
+func TerminalFormat() Format {
+	return FormatFunc(func(r *Record) []byte {
+		var color = 0
+		switch r.Lvl {
+		case LvlCrit:
+			color = 35
+		case LvlError:
+			color = 31
+		case LvlWarn:
+			color = 33
+		case LvlInfo:
+			color = 32
+		case LvlDebug:
+			color = 36
+		}
+
+		b := &bytes.Buffer{}
+		lvl := strings.ToUpper(r.Lvl.String())
+		if color > 0 {
+			fmt.Fprintf(b, "\x1b[%dm%s\x1b[0m[%s] %s ", color, lvl, r.Time.Format(termTimeFormat), r.Msg)
+		} else {
+			fmt.Fprintf(b, "[%s] [%s] %s ", lvl, r.Time.Format(termTimeFormat), r.Msg)
+		}
+
+		// try to justify the log output for short messages
+		if len(r.Ctx) > 0 && len(r.Msg) < termMsgJust {
+			b.Write(bytes.Repeat([]byte{' '}, termMsgJust-len(r.Msg)))
+		}
+
+		// print the keys logfmt style
+		logfmt(b, r.Ctx, color)
+		return b.Bytes()
+	})
+}
+
+// LogfmtFormat prints records in logfmt format, an easy machine-parseable but human-readable
+// format for key/value pairs.
+//
+// For more details see: http://godoc.org/github.com/kr/logfmt
+//
+func LogfmtFormat() Format {
+	return FormatFunc(func(r *Record) []byte {
+		common := []interface{}{r.KeyNames.Time, r.Time, r.KeyNames.Lvl, r.Lvl, r.KeyNames.Msg, r.Msg}
+		buf := &bytes.Buffer{}
+		logfmt(buf, append(common, r.Ctx...), 0)
+		return buf.Bytes()
+	})
+}
+
+func logfmt(buf *bytes.Buffer, ctx []interface{}, color int) {
+	for i := 0; i < len(ctx); i += 2 {
+		if i != 0 {
+			buf.WriteByte(' ')
+		}
+
+		k, ok := ctx[i].(string)
+		v := formatLogfmtValue(ctx[i+1])
+		if !ok {
+			k, v = errorKey, formatLogfmtValue(k)
+		}
+
+		// XXX: we should probably check that all of your key bytes aren't invalid
+		if color > 0 {
+			fmt.Fprintf(buf, "\x1b[%dm%s\x1b[0m=%s", color, k, v)
+		} else {
+			buf.WriteString(k)
+			buf.WriteByte('=')
+			buf.WriteString(v)
+		}
+	}
+
+	buf.WriteByte('\n')
+}
+
+// JsonFormat formats log records as JSON objects separated by newlines.
+// It is the equivalent of JsonFormatEx(false, true).
+func JsonFormat() Format {
+	return JsonFormatEx(false, true)
+}
+
+// JsonFormatEx formats log records as JSON objects. If pretty is true,
+// records will be pretty-printed. If lineSeparated is true, records
+// will be logged with a new line between each record.
+func JsonFormatEx(pretty, lineSeparated bool) Format {
+	jsonMarshal := json.Marshal
+	if pretty {
+		jsonMarshal = func(v interface{}) ([]byte, error) {
+			return json.MarshalIndent(v, "", "    ")
+		}
+	}
+
+	return FormatFunc(func(r *Record) []byte {
+		props := make(map[string]interface{})
+
+		props[r.KeyNames.Time] = r.Time
+		props[r.KeyNames.Lvl] = r.Lvl.String()
+		props[r.KeyNames.Msg] = r.Msg
+
+		for i := 0; i < len(r.Ctx); i += 2 {
+			k, ok := r.Ctx[i].(string)
+			if !ok {
+				props[errorKey] = fmt.Sprintf("%+v is not a string key", r.Ctx[i])
+			}
+			props[k] = formatJsonValue(r.Ctx[i+1])
+		}
+
+		b, err := jsonMarshal(props)
+		if err != nil {
+			b, _ = jsonMarshal(map[string]string{
+				errorKey: err.Error(),
+			})
+			return b
+		}
+
+		if lineSeparated {
+			b = append(b, '\n')
+		}
+
+		return b
+	})
+}
+
+func formatShared(value interface{}) (result interface{}) {
+	defer func() {
+		if err := recover(); err != nil {
+			if v := reflect.ValueOf(value); v.Kind() == reflect.Ptr && v.IsNil() {
+				result = "nil"
+			} else {
+				panic(err)
+			}
+		}
+	}()
+
+	switch v := value.(type) {
+	case time.Time:
+		return v.Format(timeFormat)
+
+	case error:
+		return v.Error()
+
+	case fmt.Stringer:
+		return v.String()
+
+	default:
+		return v
+	}
+}
+
+func formatJsonValue(value interface{}) interface{} {
+	value = formatShared(value)
+	switch value.(type) {
+	case int, int8, int16, int32, int64, float32, float64, uint, uint8, uint16, uint32, uint64, string:
+		return value
+	default:
+		return fmt.Sprintf("%+v", value)
+	}
+}
+
+// formatValue formats a value for serialization
+func formatLogfmtValue(value interface{}) string {
+	if value == nil {
+		return "nil"
+	}
+
+	if t, ok := value.(time.Time); ok {
+		// Performance optimization: No need for escaping since the provided
+		// timeFormat doesn't have any escape characters, and escaping is
+		// expensive.
+		return t.Format(timeFormat)
+	}
+	value = formatShared(value)
+	switch v := value.(type) {
+	case bool:
+		return strconv.FormatBool(v)
+	case float32:
+		return strconv.FormatFloat(float64(v), floatFormat, 3, 64)
+	case float64:
+		return strconv.FormatFloat(v, floatFormat, 3, 64)
+	case int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64:
+		return fmt.Sprintf("%d", value)
+	case string:
+		return escapeString(v)
+	default:
+		return escapeString(fmt.Sprintf("%+v", value))
+	}
+}
+
+var stringBufPool = sync.Pool{
+	New: func() interface{} { return new(bytes.Buffer) },
+}
+
+func escapeString(s string) string {
+	needsQuotes := false
+	needsEscape := false
+	for _, r := range s {
+		if r <= ' ' || r == '=' || r == '"' {
+			needsQuotes = true
+		}
+		if r == '\\' || r == '"' || r == '\n' || r == '\r' || r == '\t' {
+			needsEscape = true
+		}
+	}
+	if needsEscape == false && needsQuotes == false {
+		return s
+	}
+	e := stringBufPool.Get().(*bytes.Buffer)
+	e.WriteByte('"')
+	for _, r := range s {
+		switch r {
+		case '\\', '"':
+			e.WriteByte('\\')
+			e.WriteByte(byte(r))
+		case '\n':
+			e.WriteString("\\n")
+		case '\r':
+			e.WriteString("\\r")
+		case '\t':
+			e.WriteString("\\t")
+		default:
+			e.WriteRune(r)
+		}
+	}
+	e.WriteByte('"')
+	var ret string
+	if needsQuotes {
+		ret = e.String()
+	} else {
+		ret = string(e.Bytes()[1 : e.Len()-1])
+	}
+	e.Reset()
+	stringBufPool.Put(e)
+	return ret
+}
diff --git a/log/handler.go b/log/handler.go
new file mode 100644
index 000000000..abb17b4c4
--- /dev/null
+++ b/log/handler.go
@@ -0,0 +1,356 @@
+package log
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"os"
+	"reflect"
+	"sync"
+
+	"github.com/go-stack/stack"
+)
+
+// A Logger prints its log records by writing to a Handler.
+// The Handler interface defines where and how log records are written.
+// Handlers are composable, providing you great flexibility in combining
+// them to achieve the logging structure that suits your applications.
+type Handler interface {
+	Log(r *Record) error
+}
+
+// FuncHandler returns a Handler that logs records with the given
+// function.
+func FuncHandler(fn func(r *Record) error) Handler {
+	return funcHandler(fn)
+}
+
+type funcHandler func(r *Record) error
+
+func (h funcHandler) Log(r *Record) error {
+	return h(r)
+}
+
+// StreamHandler writes log records to an io.Writer
+// with the given format. StreamHandler can be used
+// to easily begin writing log records to other
+// outputs.
+//
+// StreamHandler wraps itself with LazyHandler and SyncHandler
+// to evaluate Lazy objects and perform safe concurrent writes.
+func StreamHandler(wr io.Writer, fmtr Format) Handler {
+	h := FuncHandler(func(r *Record) error {
+		_, err := wr.Write(fmtr.Format(r))
+		return err
+	})
+	return LazyHandler(SyncHandler(h))
+}
+
+// SyncHandler can be wrapped around a handler to guarantee that
+// only a single Log operation can proceed at a time. It's necessary
+// for thread-safe concurrent writes.
+func SyncHandler(h Handler) Handler {
+	var mu sync.Mutex
+	return FuncHandler(func(r *Record) error {
+		defer mu.Unlock()
+		mu.Lock()
+		return h.Log(r)
+	})
+}
+
+// FileHandler returns a handler which writes log records to the give file
+// using the given format. If the path
+// already exists, FileHandler will append to the given file. If it does not,
+// FileHandler will create the file with mode 0644.
+func FileHandler(path string, fmtr Format) (Handler, error) {
+	f, err := os.OpenFile(path, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644)
+	if err != nil {
+		return nil, err
+	}
+	return closingHandler{f, StreamHandler(f, fmtr)}, nil
+}
+
+// NetHandler opens a socket to the given address and writes records
+// over the connection.
+func NetHandler(network, addr string, fmtr Format) (Handler, error) {
+	conn, err := net.Dial(network, addr)
+	if err != nil {
+		return nil, err
+	}
+
+	return closingHandler{conn, StreamHandler(conn, fmtr)}, nil
+}
+
+// XXX: closingHandler is essentially unused at the moment
+// it's meant for a future time when the Handler interface supports
+// a possible Close() operation
+type closingHandler struct {
+	io.WriteCloser
+	Handler
+}
+
+func (h *closingHandler) Close() error {
+	return h.WriteCloser.Close()
+}
+
+// CallerFileHandler returns a Handler that adds the line number and file of
+// the calling function to the context with key "caller".
+func CallerFileHandler(h Handler) Handler {
+	return FuncHandler(func(r *Record) error {
+		r.Ctx = append(r.Ctx, "caller", fmt.Sprint(r.Call))
+		return h.Log(r)
+	})
+}
+
+// CallerFuncHandler returns a Handler that adds the calling function name to
+// the context with key "fn".
+func CallerFuncHandler(h Handler) Handler {
+	return FuncHandler(func(r *Record) error {
+		r.Ctx = append(r.Ctx, "fn", fmt.Sprintf("%+n", r.Call))
+		return h.Log(r)
+	})
+}
+
+// CallerStackHandler returns a Handler that adds a stack trace to the context
+// with key "stack". The stack trace is formated as a space separated list of
+// call sites inside matching []'s. The most recent call site is listed first.
+// Each call site is formatted according to format. See the documentation of
+// package github.com/go-stack/stack for the list of supported formats.
+func CallerStackHandler(format string, h Handler) Handler {
+	return FuncHandler(func(r *Record) error {
+		s := stack.Trace().TrimBelow(r.Call).TrimRuntime()
+		if len(s) > 0 {
+			r.Ctx = append(r.Ctx, "stack", fmt.Sprintf(format, s))
+		}
+		return h.Log(r)
+	})
+}
+
+// FilterHandler returns a Handler that only writes records to the
+// wrapped Handler if the given function evaluates true. For example,
+// to only log records where the 'err' key is not nil:
+//
+//    logger.SetHandler(FilterHandler(func(r *Record) bool {
+//        for i := 0; i < len(r.Ctx); i += 2 {
+//            if r.Ctx[i] == "err" {
+//                return r.Ctx[i+1] != nil
+//            }
+//        }
+//        return false
+//    }, h))
+//
+func FilterHandler(fn func(r *Record) bool, h Handler) Handler {
+	return FuncHandler(func(r *Record) error {
+		if fn(r) {
+			return h.Log(r)
+		}
+		return nil
+	})
+}
+
+// MatchFilterHandler returns a Handler that only writes records
+// to the wrapped Handler if the given key in the logged
+// context matches the value. For example, to only log records
+// from your ui package:
+//
+//    log.MatchFilterHandler("pkg", "app/ui", log.StdoutHandler)
+//
+func MatchFilterHandler(key string, value interface{}, h Handler) Handler {
+	return FilterHandler(func(r *Record) (pass bool) {
+		switch key {
+		case r.KeyNames.Lvl:
+			return r.Lvl == value
+		case r.KeyNames.Time:
+			return r.Time == value
+		case r.KeyNames.Msg:
+			return r.Msg == value
+		}
+
+		for i := 0; i < len(r.Ctx); i += 2 {
+			if r.Ctx[i] == key {
+				return r.Ctx[i+1] == value
+			}
+		}
+		return false
+	}, h)
+}
+
+// LvlFilterHandler returns a Handler that only writes
+// records which are less than the given verbosity
+// level to the wrapped Handler. For example, to only
+// log Error/Crit records:
+//
+//     log.LvlFilterHandler(log.LvlError, log.StdoutHandler)
+//
+func LvlFilterHandler(maxLvl Lvl, h Handler) Handler {
+	return FilterHandler(func(r *Record) (pass bool) {
+		return r.Lvl <= maxLvl
+	}, h)
+}
+
+// A MultiHandler dispatches any write to each of its handlers.
+// This is useful for writing different types of log information
+// to different locations. For example, to log to a file and
+// standard error:
+//
+//     log.MultiHandler(
+//         log.Must.FileHandler("/var/log/app.log", log.LogfmtFormat()),
+//         log.StderrHandler)
+//
+func MultiHandler(hs ...Handler) Handler {
+	return FuncHandler(func(r *Record) error {
+		for _, h := range hs {
+			// what to do about failures?
+			h.Log(r)
+		}
+		return nil
+	})
+}
+
+// A FailoverHandler writes all log records to the first handler
+// specified, but will failover and write to the second handler if
+// the first handler has failed, and so on for all handlers specified.
+// For example you might want to log to a network socket, but failover
+// to writing to a file if the network fails, and then to
+// standard out if the file write fails:
+//
+//     log.FailoverHandler(
+//         log.Must.NetHandler("tcp", ":9090", log.JsonFormat()),
+//         log.Must.FileHandler("/var/log/app.log", log.LogfmtFormat()),
+//         log.StdoutHandler)
+//
+// All writes that do not go to the first handler will add context with keys of
+// the form "failover_err_{idx}" which explain the error encountered while
+// trying to write to the handlers before them in the list.
+func FailoverHandler(hs ...Handler) Handler {
+	return FuncHandler(func(r *Record) error {
+		var err error
+		for i, h := range hs {
+			err = h.Log(r)
+			if err == nil {
+				return nil
+			} else {
+				r.Ctx = append(r.Ctx, fmt.Sprintf("failover_err_%d", i), err)
+			}
+		}
+
+		return err
+	})
+}
+
+// ChannelHandler writes all records to the given channel.
+// It blocks if the channel is full. Useful for async processing
+// of log messages, it's used by BufferedHandler.
+func ChannelHandler(recs chan<- *Record) Handler {
+	return FuncHandler(func(r *Record) error {
+		recs <- r
+		return nil
+	})
+}
+
+// BufferedHandler writes all records to a buffered
+// channel of the given size which flushes into the wrapped
+// handler whenever it is available for writing. Since these
+// writes happen asynchronously, all writes to a BufferedHandler
+// never return an error and any errors from the wrapped handler are ignored.
+func BufferedHandler(bufSize int, h Handler) Handler {
+	recs := make(chan *Record, bufSize)
+	go func() {
+		for m := range recs {
+			_ = h.Log(m)
+		}
+	}()
+	return ChannelHandler(recs)
+}
+
+// LazyHandler writes all values to the wrapped handler after evaluating
+// any lazy functions in the record's context. It is already wrapped
+// around StreamHandler and SyslogHandler in this library, you'll only need
+// it if you write your own Handler.
+func LazyHandler(h Handler) Handler {
+	return FuncHandler(func(r *Record) error {
+		// go through the values (odd indices) and reassign
+		// the values of any lazy fn to the result of its execution
+		hadErr := false
+		for i := 1; i < len(r.Ctx); i += 2 {
+			lz, ok := r.Ctx[i].(Lazy)
+			if ok {
+				v, err := evaluateLazy(lz)
+				if err != nil {
+					hadErr = true
+					r.Ctx[i] = err
+				} else {
+					if cs, ok := v.(stack.CallStack); ok {
+						v = cs.TrimBelow(r.Call).TrimRuntime()
+					}
+					r.Ctx[i] = v
+				}
+			}
+		}
+
+		if hadErr {
+			r.Ctx = append(r.Ctx, errorKey, "bad lazy")
+		}
+
+		return h.Log(r)
+	})
+}
+
+func evaluateLazy(lz Lazy) (interface{}, error) {
+	t := reflect.TypeOf(lz.Fn)
+
+	if t.Kind() != reflect.Func {
+		return nil, fmt.Errorf("INVALID_LAZY, not func: %+v", lz.Fn)
+	}
+
+	if t.NumIn() > 0 {
+		return nil, fmt.Errorf("INVALID_LAZY, func takes args: %+v", lz.Fn)
+	}
+
+	if t.NumOut() == 0 {
+		return nil, fmt.Errorf("INVALID_LAZY, no func return val: %+v", lz.Fn)
+	}
+
+	value := reflect.ValueOf(lz.Fn)
+	results := value.Call([]reflect.Value{})
+	if len(results) == 1 {
+		return results[0].Interface(), nil
+	} else {
+		values := make([]interface{}, len(results))
+		for i, v := range results {
+			values[i] = v.Interface()
+		}
+		return values, nil
+	}
+}
+
+// DiscardHandler reports success for all writes but does nothing.
+// It is useful for dynamically disabling logging at runtime via
+// a Logger's SetHandler method.
+func DiscardHandler() Handler {
+	return FuncHandler(func(r *Record) error {
+		return nil
+	})
+}
+
+// The Must object provides the following Handler creation functions
+// which instead of returning an error parameter only return a Handler
+// and panic on failure: FileHandler, NetHandler, SyslogHandler, SyslogNetHandler
+var Must muster
+
+func must(h Handler, err error) Handler {
+	if err != nil {
+		panic(err)
+	}
+	return h
+}
+
+type muster struct{}
+
+func (m muster) FileHandler(path string, fmtr Format) Handler {
+	return must(FileHandler(path, fmtr))
+}
+
+func (m muster) NetHandler(network, addr string, fmtr Format) Handler {
+	return must(NetHandler(network, addr, fmtr))
+}
diff --git a/log/handler_go13.go b/log/handler_go13.go
new file mode 100644
index 000000000..0843ed0e5
--- /dev/null
+++ b/log/handler_go13.go
@@ -0,0 +1,26 @@
+// +build !go1.4
+
+package log
+
+import (
+	"sync/atomic"
+	"unsafe"
+)
+
+// swapHandler wraps another handler that may be swapped out
+// dynamically at runtime in a thread-safe fashion.
+type swapHandler struct {
+	handler unsafe.Pointer
+}
+
+func (h *swapHandler) Log(r *Record) error {
+	return h.Get().Log(r)
+}
+
+func (h *swapHandler) Get() Handler {
+	return *(*Handler)(atomic.LoadPointer(&h.handler))
+}
+
+func (h *swapHandler) Swap(newHandler Handler) {
+	atomic.StorePointer(&h.handler, unsafe.Pointer(&newHandler))
+}
diff --git a/log/handler_go14.go b/log/handler_go14.go
new file mode 100644
index 000000000..05dedbf2a
--- /dev/null
+++ b/log/handler_go14.go
@@ -0,0 +1,23 @@
+// +build go1.4
+
+package log
+
+import "sync/atomic"
+
+// swapHandler wraps another handler that may be swapped out
+// dynamically at runtime in a thread-safe fashion.
+type swapHandler struct {
+	handler atomic.Value
+}
+
+func (h *swapHandler) Log(r *Record) error {
+	return (*h.handler.Load().(*Handler)).Log(r)
+}
+
+func (h *swapHandler) Swap(newHandler Handler) {
+	h.handler.Store(&newHandler)
+}
+
+func (h *swapHandler) Get() Handler {
+	return *h.handler.Load().(*Handler)
+}
diff --git a/log/logger.go b/log/logger.go
new file mode 100644
index 000000000..a9d42b8da
--- /dev/null
+++ b/log/logger.go
@@ -0,0 +1,208 @@
+package log
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/go-stack/stack"
+)
+
+const timeKey = "t"
+const lvlKey = "lvl"
+const msgKey = "msg"
+const errorKey = "LOG15_ERROR"
+
+type Lvl int
+
+const (
+	LvlCrit Lvl = iota
+	LvlError
+	LvlWarn
+	LvlInfo
+	LvlDebug
+)
+
+// Returns the name of a Lvl
+func (l Lvl) String() string {
+	switch l {
+	case LvlDebug:
+		return "dbug"
+	case LvlInfo:
+		return "info"
+	case LvlWarn:
+		return "warn"
+	case LvlError:
+		return "eror"
+	case LvlCrit:
+		return "crit"
+	default:
+		panic("bad level")
+	}
+}
+
+// Returns the appropriate Lvl from a string name.
+// Useful for parsing command line args and configuration files.
+func LvlFromString(lvlString string) (Lvl, error) {
+	switch lvlString {
+	case "debug", "dbug":
+		return LvlDebug, nil
+	case "info":
+		return LvlInfo, nil
+	case "warn":
+		return LvlWarn, nil
+	case "error", "eror":
+		return LvlError, nil
+	case "crit":
+		return LvlCrit, nil
+	default:
+		return LvlDebug, fmt.Errorf("Unknown level: %v", lvlString)
+	}
+}
+
+// A Record is what a Logger asks its handler to write
+type Record struct {
+	Time     time.Time
+	Lvl      Lvl
+	Msg      string
+	Ctx      []interface{}
+	Call     stack.Call
+	KeyNames RecordKeyNames
+}
+
+type RecordKeyNames struct {
+	Time string
+	Msg  string
+	Lvl  string
+}
+
+// A Logger writes key/value pairs to a Handler
+type Logger interface {
+	// New returns a new Logger that has this logger's context plus the given context
+	New(ctx ...interface{}) Logger
+
+	// GetHandler gets the handler associated with the logger.
+	GetHandler() Handler
+
+	// SetHandler updates the logger to write records to the specified handler.
+	SetHandler(h Handler)
+
+	// Log a message at the given level with context key/value pairs
+	Debug(msg string, ctx ...interface{})
+	Info(msg string, ctx ...interface{})
+	Warn(msg string, ctx ...interface{})
+	Error(msg string, ctx ...interface{})
+	Crit(msg string, ctx ...interface{})
+}
+
+type logger struct {
+	ctx []interface{}
+	h   *swapHandler
+}
+
+func (l *logger) write(msg string, lvl Lvl, ctx []interface{}) {
+	l.h.Log(&Record{
+		Time: time.Now(),
+		Lvl:  lvl,
+		Msg:  msg,
+		Ctx:  newContext(l.ctx, ctx),
+		Call: stack.Caller(2),
+		KeyNames: RecordKeyNames{
+			Time: timeKey,
+			Msg:  msgKey,
+			Lvl:  lvlKey,
+		},
+	})
+}
+
+func (l *logger) New(ctx ...interface{}) Logger {
+	child := &logger{newContext(l.ctx, ctx), new(swapHandler)}
+	child.SetHandler(l.h)
+	return child
+}
+
+func newContext(prefix []interface{}, suffix []interface{}) []interface{} {
+	normalizedSuffix := normalize(suffix)
+	newCtx := make([]interface{}, len(prefix)+len(normalizedSuffix))
+	n := copy(newCtx, prefix)
+	copy(newCtx[n:], normalizedSuffix)
+	return newCtx
+}
+
+func (l *logger) Debug(msg string, ctx ...interface{}) {
+	l.write(msg, LvlDebug, ctx)
+}
+
+func (l *logger) Info(msg string, ctx ...interface{}) {
+	l.write(msg, LvlInfo, ctx)
+}
+
+func (l *logger) Warn(msg string, ctx ...interface{}) {
+	l.write(msg, LvlWarn, ctx)
+}
+
+func (l *logger) Error(msg string, ctx ...interface{}) {
+	l.write(msg, LvlError, ctx)
+}
+
+func (l *logger) Crit(msg string, ctx ...interface{}) {
+	l.write(msg, LvlCrit, ctx)
+}
+
+func (l *logger) GetHandler() Handler {
+	return l.h.Get()
+}
+
+func (l *logger) SetHandler(h Handler) {
+	l.h.Swap(h)
+}
+
+func normalize(ctx []interface{}) []interface{} {
+	// if the caller passed a Ctx object, then expand it
+	if len(ctx) == 1 {
+		if ctxMap, ok := ctx[0].(Ctx); ok {
+			ctx = ctxMap.toArray()
+		}
+	}
+
+	// ctx needs to be even because it's a series of key/value pairs
+	// no one wants to check for errors on logging functions,
+	// so instead of erroring on bad input, we'll just make sure
+	// that things are the right length and users can fix bugs
+	// when they see the output looks wrong
+	if len(ctx)%2 != 0 {
+		ctx = append(ctx, nil, errorKey, "Normalized odd number of arguments by adding nil")
+	}
+
+	return ctx
+}
+
+// Lazy allows you to defer calculation of a logged value that is expensive
+// to compute until it is certain that it must be evaluated with the given filters.
+//
+// Lazy may also be used in conjunction with a Logger's New() function
+// to generate a child logger which always reports the current value of changing
+// state.
+//
+// You may wrap any function which takes no arguments to Lazy. It may return any
+// number of values of any type.
+type Lazy struct {
+	Fn interface{}
+}
+
+// Ctx is a map of key/value pairs to pass as context to a log function
+// Use this only if you really need greater safety around the arguments you pass
+// to the logging functions.
+type Ctx map[string]interface{}
+
+func (c Ctx) toArray() []interface{} {
+	arr := make([]interface{}, len(c)*2)
+
+	i := 0
+	for k, v := range c {
+		arr[i] = k
+		arr[i+1] = v
+		i += 2
+	}
+
+	return arr
+}
diff --git a/log/root.go b/log/root.go
new file mode 100644
index 000000000..39b4c9429
--- /dev/null
+++ b/log/root.go
@@ -0,0 +1,67 @@
+package log
+
+import (
+	"os"
+
+	"github.com/ethereum/go-ethereum/log/term"
+	"github.com/mattn/go-colorable"
+)
+
+var (
+	root          *logger
+	StdoutHandler = StreamHandler(os.Stdout, LogfmtFormat())
+	StderrHandler = StreamHandler(os.Stderr, LogfmtFormat())
+)
+
+func init() {
+	if term.IsTty(os.Stdout.Fd()) {
+		StdoutHandler = StreamHandler(colorable.NewColorableStdout(), TerminalFormat())
+	}
+
+	if term.IsTty(os.Stderr.Fd()) {
+		StderrHandler = StreamHandler(colorable.NewColorableStderr(), TerminalFormat())
+	}
+
+	root = &logger{[]interface{}{}, new(swapHandler)}
+	root.SetHandler(StdoutHandler)
+}
+
+// New returns a new logger with the given context.
+// New is a convenient alias for Root().New
+func New(ctx ...interface{}) Logger {
+	return root.New(ctx...)
+}
+
+// Root returns the root logger
+func Root() Logger {
+	return root
+}
+
+// The following functions bypass the exported logger methods (logger.Debug,
+// etc.) to keep the call depth the same for all paths to logger.write so
+// runtime.Caller(2) always refers to the call site in client code.
+
+// Debug is a convenient alias for Root().Debug
+func Debug(msg string, ctx ...interface{}) {
+	root.write(msg, LvlDebug, ctx)
+}
+
+// Info is a convenient alias for Root().Info
+func Info(msg string, ctx ...interface{}) {
+	root.write(msg, LvlInfo, ctx)
+}
+
+// Warn is a convenient alias for Root().Warn
+func Warn(msg string, ctx ...interface{}) {
+	root.write(msg, LvlWarn, ctx)
+}
+
+// Error is a convenient alias for Root().Error
+func Error(msg string, ctx ...interface{}) {
+	root.write(msg, LvlError, ctx)
+}
+
+// Crit is a convenient alias for Root().Crit
+func Crit(msg string, ctx ...interface{}) {
+	root.write(msg, LvlCrit, ctx)
+}
diff --git a/log/syslog.go b/log/syslog.go
new file mode 100644
index 000000000..4f1097ff9
--- /dev/null
+++ b/log/syslog.go
@@ -0,0 +1,55 @@
+// +build !windows,!plan9
+
+package log
+
+import (
+	"log/syslog"
+	"strings"
+)
+
+// SyslogHandler opens a connection to the system syslog daemon by calling
+// syslog.New and writes all records to it.
+func SyslogHandler(priority syslog.Priority, tag string, fmtr Format) (Handler, error) {
+	wr, err := syslog.New(priority, tag)
+	return sharedSyslog(fmtr, wr, err)
+}
+
+// SyslogNetHandler opens a connection to a log daemon over the network and writes
+// all log records to it.
+func SyslogNetHandler(net, addr string, priority syslog.Priority, tag string, fmtr Format) (Handler, error) {
+	wr, err := syslog.Dial(net, addr, priority, tag)
+	return sharedSyslog(fmtr, wr, err)
+}
+
+func sharedSyslog(fmtr Format, sysWr *syslog.Writer, err error) (Handler, error) {
+	if err != nil {
+		return nil, err
+	}
+	h := FuncHandler(func(r *Record) error {
+		var syslogFn = sysWr.Info
+		switch r.Lvl {
+		case LvlCrit:
+			syslogFn = sysWr.Crit
+		case LvlError:
+			syslogFn = sysWr.Err
+		case LvlWarn:
+			syslogFn = sysWr.Warning
+		case LvlInfo:
+			syslogFn = sysWr.Info
+		case LvlDebug:
+			syslogFn = sysWr.Debug
+		}
+
+		s := strings.TrimSpace(string(fmtr.Format(r)))
+		return syslogFn(s)
+	})
+	return LazyHandler(&closingHandler{sysWr, h}), nil
+}
+
+func (m muster) SyslogHandler(priority syslog.Priority, tag string, fmtr Format) Handler {
+	return must(SyslogHandler(priority, tag, fmtr))
+}
+
+func (m muster) SyslogNetHandler(net, addr string, priority syslog.Priority, tag string, fmtr Format) Handler {
+	return must(SyslogNetHandler(net, addr, priority, tag, fmtr))
+}
diff --git a/log/term/LICENSE b/log/term/LICENSE
new file mode 100644
index 000000000..f090cb42f
--- /dev/null
+++ b/log/term/LICENSE
@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2014 Simon Eskildsen
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
diff --git a/log/term/terminal_appengine.go b/log/term/terminal_appengine.go
new file mode 100644
index 000000000..c1b5d2a3b
--- /dev/null
+++ b/log/term/terminal_appengine.go
@@ -0,0 +1,13 @@
+// Based on ssh/terminal:
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build appengine
+
+package term
+
+// IsTty always returns false on AppEngine.
+func IsTty(fd uintptr) bool {
+	return false
+}
diff --git a/log/term/terminal_darwin.go b/log/term/terminal_darwin.go
new file mode 100644
index 000000000..d8f351b1b
--- /dev/null
+++ b/log/term/terminal_darwin.go
@@ -0,0 +1,13 @@
+// Based on ssh/terminal:
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+// +build !appengine
+
+package term
+
+import "syscall"
+
+const ioctlReadTermios = syscall.TIOCGETA
+
+type Termios syscall.Termios
diff --git a/log/term/terminal_freebsd.go b/log/term/terminal_freebsd.go
new file mode 100644
index 000000000..cfaceab33
--- /dev/null
+++ b/log/term/terminal_freebsd.go
@@ -0,0 +1,18 @@
+package term
+
+import (
+	"syscall"
+)
+
+const ioctlReadTermios = syscall.TIOCGETA
+
+// Go 1.2 doesn't include Termios for FreeBSD. This should be added in 1.3 and this could be merged with terminal_darwin.
+type Termios struct {
+	Iflag  uint32
+	Oflag  uint32
+	Cflag  uint32
+	Lflag  uint32
+	Cc     [20]uint8
+	Ispeed uint32
+	Ospeed uint32
+}
diff --git a/log/term/terminal_linux.go b/log/term/terminal_linux.go
new file mode 100644
index 000000000..5290468d6
--- /dev/null
+++ b/log/term/terminal_linux.go
@@ -0,0 +1,14 @@
+// Based on ssh/terminal:
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !appengine
+
+package term
+
+import "syscall"
+
+const ioctlReadTermios = syscall.TCGETS
+
+type Termios syscall.Termios
diff --git a/log/term/terminal_netbsd.go b/log/term/terminal_netbsd.go
new file mode 100644
index 000000000..f9bb9e1c2
--- /dev/null
+++ b/log/term/terminal_netbsd.go
@@ -0,0 +1,7 @@
+package term
+
+import "syscall"
+
+const ioctlReadTermios = syscall.TIOCGETA
+
+type Termios syscall.Termios
diff --git a/log/term/terminal_notwindows.go b/log/term/terminal_notwindows.go
new file mode 100644
index 000000000..c9af534f6
--- /dev/null
+++ b/log/term/terminal_notwindows.go
@@ -0,0 +1,20 @@
+// Based on ssh/terminal:
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build linux,!appengine darwin freebsd openbsd netbsd
+
+package term
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+// IsTty returns true if the given file descriptor is a terminal.
+func IsTty(fd uintptr) bool {
+	var termios Termios
+	_, _, err := syscall.Syscall6(syscall.SYS_IOCTL, fd, ioctlReadTermios, uintptr(unsafe.Pointer(&termios)), 0, 0, 0)
+	return err == 0
+}
diff --git a/log/term/terminal_openbsd.go b/log/term/terminal_openbsd.go
new file mode 100644
index 000000000..f9bb9e1c2
--- /dev/null
+++ b/log/term/terminal_openbsd.go
@@ -0,0 +1,7 @@
+package term
+
+import "syscall"
+
+const ioctlReadTermios = syscall.TIOCGETA
+
+type Termios syscall.Termios
diff --git a/log/term/terminal_solaris.go b/log/term/terminal_solaris.go
new file mode 100644
index 000000000..033c16324
--- /dev/null
+++ b/log/term/terminal_solaris.go
@@ -0,0 +1,9 @@
+package term
+
+import "golang.org/x/sys/unix"
+
+// IsTty returns true if the given file descriptor is a terminal.
+func IsTty(fd uintptr) bool {
+	_, err := unix.IoctlGetTermios(int(fd), unix.TCGETA)
+	return err == nil
+}
diff --git a/log/term/terminal_windows.go b/log/term/terminal_windows.go
new file mode 100644
index 000000000..df3c30c15
--- /dev/null
+++ b/log/term/terminal_windows.go
@@ -0,0 +1,26 @@
+// Based on ssh/terminal:
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build windows
+
+package term
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+var kernel32 = syscall.NewLazyDLL("kernel32.dll")
+
+var (
+	procGetConsoleMode = kernel32.NewProc("GetConsoleMode")
+)
+
+// IsTty returns true if the given file descriptor is a terminal.
+func IsTty(fd uintptr) bool {
+	var st uint32
+	r, _, e := syscall.Syscall(procGetConsoleMode.Addr(), 2, fd, uintptr(unsafe.Pointer(&st)), 0)
+	return r != 0 && e == 0
+}
diff --git a/vendor/github.com/go-stack/stack/LICENSE.md b/vendor/github.com/go-stack/stack/LICENSE.md
new file mode 100644
index 000000000..c8ca66c5e
--- /dev/null
+++ b/vendor/github.com/go-stack/stack/LICENSE.md
@@ -0,0 +1,13 @@
+Copyright 2014 Chris Hines
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
diff --git a/vendor/github.com/go-stack/stack/README.md b/vendor/github.com/go-stack/stack/README.md
new file mode 100644
index 000000000..f11ccccaa
--- /dev/null
+++ b/vendor/github.com/go-stack/stack/README.md
@@ -0,0 +1,38 @@
+[![GoDoc](https://godoc.org/github.com/go-stack/stack?status.svg)](https://godoc.org/github.com/go-stack/stack)
+[![Go Report Card](https://goreportcard.com/badge/go-stack/stack)](https://goreportcard.com/report/go-stack/stack)
+[![TravisCI](https://travis-ci.org/go-stack/stack.svg?branch=master)](https://travis-ci.org/go-stack/stack)
+[![Coverage Status](https://coveralls.io/repos/github/go-stack/stack/badge.svg?branch=master)](https://coveralls.io/github/go-stack/stack?branch=master)
+
+# stack
+
+Package stack implements utilities to capture, manipulate, and format call
+stacks. It provides a simpler API than package runtime.
+
+The implementation takes care of the minutia and special cases of interpreting
+the program counter (pc) values returned by runtime.Callers.
+
+## Versioning
+
+Package stack publishes releases via [semver](http://semver.org/) compatible Git
+tags prefixed with a single 'v'. The master branch always contains the latest
+release. The develop branch contains unreleased commits.
+
+## Formatting
+
+Package stack's types implement fmt.Formatter, which provides a simple and
+flexible way to declaratively configure formatting when used with logging or
+error tracking packages.
+
+```go
+func DoTheThing() {
+    c := stack.Caller(0)
+    log.Print(c)          // "source.go:10"
+    log.Printf("%+v", c)  // "pkg/path/source.go:10"
+    log.Printf("%n", c)   // "DoTheThing"
+
+    s := stack.Trace().TrimRuntime()
+    log.Print(s)          // "[source.go:15 caller.go:42 main.go:14]"
+}
+```
+
+See the docs for all of the supported formatting options.
diff --git a/vendor/github.com/go-stack/stack/stack.go b/vendor/github.com/go-stack/stack/stack.go
new file mode 100644
index 000000000..a614eeebf
--- /dev/null
+++ b/vendor/github.com/go-stack/stack/stack.go
@@ -0,0 +1,349 @@
+// Package stack implements utilities to capture, manipulate, and format call
+// stacks. It provides a simpler API than package runtime.
+//
+// The implementation takes care of the minutia and special cases of
+// interpreting the program counter (pc) values returned by runtime.Callers.
+//
+// Package stack's types implement fmt.Formatter, which provides a simple and
+// flexible way to declaratively configure formatting when used with logging
+// or error tracking packages.
+package stack
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"runtime"
+	"strconv"
+	"strings"
+)
+
+// Call records a single function invocation from a goroutine stack.
+type Call struct {
+	fn *runtime.Func
+	pc uintptr
+}
+
+// Caller returns a Call from the stack of the current goroutine. The argument
+// skip is the number of stack frames to ascend, with 0 identifying the
+// calling function.
+func Caller(skip int) Call {
+	var pcs [2]uintptr
+	n := runtime.Callers(skip+1, pcs[:])
+
+	var c Call
+
+	if n < 2 {
+		return c
+	}
+
+	c.pc = pcs[1]
+	if runtime.FuncForPC(pcs[0]) != sigpanic {
+		c.pc--
+	}
+	c.fn = runtime.FuncForPC(c.pc)
+	return c
+}
+
+// String implements fmt.Stinger. It is equivalent to fmt.Sprintf("%v", c).
+func (c Call) String() string {
+	return fmt.Sprint(c)
+}
+
+// MarshalText implements encoding.TextMarshaler. It formats the Call the same
+// as fmt.Sprintf("%v", c).
+func (c Call) MarshalText() ([]byte, error) {
+	if c.fn == nil {
+		return nil, ErrNoFunc
+	}
+	buf := bytes.Buffer{}
+	fmt.Fprint(&buf, c)
+	return buf.Bytes(), nil
+}
+
+// ErrNoFunc means that the Call has a nil *runtime.Func. The most likely
+// cause is a Call with the zero value.
+var ErrNoFunc = errors.New("no call stack information")
+
+// Format implements fmt.Formatter with support for the following verbs.
+//
+//    %s    source file
+//    %d    line number
+//    %n    function name
+//    %v    equivalent to %s:%d
+//
+// It accepts the '+' and '#' flags for most of the verbs as follows.
+//
+//    %+s   path of source file relative to the compile time GOPATH
+//    %#s   full path of source file
+//    %+n   import path qualified function name
+//    %+v   equivalent to %+s:%d
+//    %#v   equivalent to %#s:%d
+func (c Call) Format(s fmt.State, verb rune) {
+	if c.fn == nil {
+		fmt.Fprintf(s, "%%!%c(NOFUNC)", verb)
+		return
+	}
+
+	switch verb {
+	case 's', 'v':
+		file, line := c.fn.FileLine(c.pc)
+		switch {
+		case s.Flag('#'):
+			// done
+		case s.Flag('+'):
+			file = file[pkgIndex(file, c.fn.Name()):]
+		default:
+			const sep = "/"
+			if i := strings.LastIndex(file, sep); i != -1 {
+				file = file[i+len(sep):]
+			}
+		}
+		io.WriteString(s, file)
+		if verb == 'v' {
+			buf := [7]byte{':'}
+			s.Write(strconv.AppendInt(buf[:1], int64(line), 10))
+		}
+
+	case 'd':
+		_, line := c.fn.FileLine(c.pc)
+		buf := [6]byte{}
+		s.Write(strconv.AppendInt(buf[:0], int64(line), 10))
+
+	case 'n':
+		name := c.fn.Name()
+		if !s.Flag('+') {
+			const pathSep = "/"
+			if i := strings.LastIndex(name, pathSep); i != -1 {
+				name = name[i+len(pathSep):]
+			}
+			const pkgSep = "."
+			if i := strings.Index(name, pkgSep); i != -1 {
+				name = name[i+len(pkgSep):]
+			}
+		}
+		io.WriteString(s, name)
+	}
+}
+
+// PC returns the program counter for this call frame; multiple frames may
+// have the same PC value.
+func (c Call) PC() uintptr {
+	return c.pc
+}
+
+// name returns the import path qualified name of the function containing the
+// call.
+func (c Call) name() string {
+	if c.fn == nil {
+		return "???"
+	}
+	return c.fn.Name()
+}
+
+func (c Call) file() string {
+	if c.fn == nil {
+		return "???"
+	}
+	file, _ := c.fn.FileLine(c.pc)
+	return file
+}
+
+func (c Call) line() int {
+	if c.fn == nil {
+		return 0
+	}
+	_, line := c.fn.FileLine(c.pc)
+	return line
+}
+
+// CallStack records a sequence of function invocations from a goroutine
+// stack.
+type CallStack []Call
+
+// String implements fmt.Stinger. It is equivalent to fmt.Sprintf("%v", cs).
+func (cs CallStack) String() string {
+	return fmt.Sprint(cs)
+}
+
+var (
+	openBracketBytes  = []byte("[")
+	closeBracketBytes = []byte("]")
+	spaceBytes        = []byte(" ")
+)
+
+// MarshalText implements encoding.TextMarshaler. It formats the CallStack the
+// same as fmt.Sprintf("%v", cs).
+func (cs CallStack) MarshalText() ([]byte, error) {
+	buf := bytes.Buffer{}
+	buf.Write(openBracketBytes)
+	for i, pc := range cs {
+		if pc.fn == nil {
+			return nil, ErrNoFunc
+		}
+		if i > 0 {
+			buf.Write(spaceBytes)
+		}
+		fmt.Fprint(&buf, pc)
+	}
+	buf.Write(closeBracketBytes)
+	return buf.Bytes(), nil
+}
+
+// Format implements fmt.Formatter by printing the CallStack as square brackets
+// ([, ]) surrounding a space separated list of Calls each formatted with the
+// supplied verb and options.
+func (cs CallStack) Format(s fmt.State, verb rune) {
+	s.Write(openBracketBytes)
+	for i, pc := range cs {
+		if i > 0 {
+			s.Write(spaceBytes)
+		}
+		pc.Format(s, verb)
+	}
+	s.Write(closeBracketBytes)
+}
+
+// findSigpanic intentionally executes faulting code to generate a stack trace
+// containing an entry for runtime.sigpanic.
+func findSigpanic() *runtime.Func {
+	var fn *runtime.Func
+	var p *int
+	func() int {
+		defer func() {
+			if p := recover(); p != nil {
+				var pcs [512]uintptr
+				n := runtime.Callers(2, pcs[:])
+				for _, pc := range pcs[:n] {
+					f := runtime.FuncForPC(pc)
+					if f.Name() == "runtime.sigpanic" {
+						fn = f
+						break
+					}
+				}
+			}
+		}()
+		// intentional nil pointer dereference to trigger sigpanic
+		return *p
+	}()
+	return fn
+}
+
+var sigpanic = findSigpanic()
+
+// Trace returns a CallStack for the current goroutine with element 0
+// identifying the calling function.
+func Trace() CallStack {
+	var pcs [512]uintptr
+	n := runtime.Callers(2, pcs[:])
+	cs := make([]Call, n)
+
+	for i, pc := range pcs[:n] {
+		pcFix := pc
+		if i > 0 && cs[i-1].fn != sigpanic {
+			pcFix--
+		}
+		cs[i] = Call{
+			fn: runtime.FuncForPC(pcFix),
+			pc: pcFix,
+		}
+	}
+
+	return cs
+}
+
+// TrimBelow returns a slice of the CallStack with all entries below c
+// removed.
+func (cs CallStack) TrimBelow(c Call) CallStack {
+	for len(cs) > 0 && cs[0].pc != c.pc {
+		cs = cs[1:]
+	}
+	return cs
+}
+
+// TrimAbove returns a slice of the CallStack with all entries above c
+// removed.
+func (cs CallStack) TrimAbove(c Call) CallStack {
+	for len(cs) > 0 && cs[len(cs)-1].pc != c.pc {
+		cs = cs[:len(cs)-1]
+	}
+	return cs
+}
+
+// pkgIndex returns the index that results in file[index:] being the path of
+// file relative to the compile time GOPATH, and file[:index] being the
+// $GOPATH/src/ portion of file. funcName must be the name of a function in
+// file as returned by runtime.Func.Name.
+func pkgIndex(file, funcName string) int {
+	// As of Go 1.6.2 there is no direct way to know the compile time GOPATH
+	// at runtime, but we can infer the number of path segments in the GOPATH.
+	// We note that runtime.Func.Name() returns the function name qualified by
+	// the import path, which does not include the GOPATH. Thus we can trim
+	// segments from the beginning of the file path until the number of path
+	// separators remaining is one more than the number of path separators in
+	// the function name. For example, given:
+	//
+	//    GOPATH     /home/user
+	//    file       /home/user/src/pkg/sub/file.go
+	//    fn.Name()  pkg/sub.Type.Method
+	//
+	// We want to produce:
+	//
+	//    file[:idx] == /home/user/src/
+	//    file[idx:] == pkg/sub/file.go
+	//
+	// From this we can easily see that fn.Name() has one less path separator
+	// than our desired result for file[idx:]. We count separators from the
+	// end of the file path until it finds two more than in the function name
+	// and then move one character forward to preserve the initial path
+	// segment without a leading separator.
+	const sep = "/"
+	i := len(file)
+	for n := strings.Count(funcName, sep) + 2; n > 0; n-- {
+		i = strings.LastIndex(file[:i], sep)
+		if i == -1 {
+			i = -len(sep)
+			break
+		}
+	}
+	// get back to 0 or trim the leading separator
+	return i + len(sep)
+}
+
+var runtimePath string
+
+func init() {
+	var pcs [1]uintptr
+	runtime.Callers(0, pcs[:])
+	fn := runtime.FuncForPC(pcs[0])
+	file, _ := fn.FileLine(pcs[0])
+
+	idx := pkgIndex(file, fn.Name())
+
+	runtimePath = file[:idx]
+	if runtime.GOOS == "windows" {
+		runtimePath = strings.ToLower(runtimePath)
+	}
+}
+
+func inGoroot(c Call) bool {
+	file := c.file()
+	if len(file) == 0 || file[0] == '?' {
+		return true
+	}
+	if runtime.GOOS == "windows" {
+		file = strings.ToLower(file)
+	}
+	return strings.HasPrefix(file, runtimePath) || strings.HasSuffix(file, "/_testmain.go")
+}
+
+// TrimRuntime returns a slice of the CallStack with the topmost entries from
+// the go runtime removed. It considers any calls originating from unknown
+// files, files under GOROOT, or _testmain.go as part of the runtime.
+func (cs CallStack) TrimRuntime() CallStack {
+	for len(cs) > 0 && inGoroot(cs[len(cs)-1]) {
+		cs = cs[:len(cs)-1]
+	}
+	return cs
+}
diff --git a/vendor/vendor.json b/vendor/vendor.json
index e19d011f1..eda007745 100644
--- a/vendor/vendor.json
+++ b/vendor/vendor.json
@@ -53,6 +53,12 @@
 			"revisionTime": "2017-01-17T22:23:42Z"
 		},
 		{
+			"checksumSHA1": "2sj/DbXoXdnPAfjAEyhS0Jj5QL0=",
+			"path": "github.com/go-stack/stack",
+			"revision": "100eb0c0a9c5b306ca2fb4f165df21d80ada4b82",
+			"revisionTime": "2016-05-14T03:44:11Z"
+		},
+		{
 			"checksumSHA1": "p/8vSviYF91gFflhrt5vkyksroo=",
 			"path": "github.com/golang/snappy",
 			"revision": "553a641470496b2327abcac10b36396bd98e45c9",