path: root/vendor/github.com/rcrowley/go-metrics/registry.go

package metrics

import (
    "fmt"
    "reflect"
    "strings"
    "sync"
)

// DuplicateMetric is the error returned by Registry.Register when a metric
// already exists.  If you mean to Register that metric you must first
// Unregister the existing metric.
type DuplicateMetric string

func (err DuplicateMetric) Error() string {
    return fmt.Sprintf("duplicate metric: %s", string(err))
}

// A Registry holds references to a set of metrics by name and can iterate
// over them, calling callback functions provided by the user.
//
// This is an interface so as to encourage other structs to implement
// the Registry API as appropriate.
type Registry interface {

    // Call the given function for each registered metric.
    Each(func(string, interface{}))

    // Get the metric by the given name or nil if none is registered.
    Get(string) interface{}

    // Gets an existing metric or registers the given one.
    // The interface can be the metric to register if not found in registry,
    // or a function returning the metric for lazy instantiation.
    GetOrRegister(string, interface{}) interface{}

    // Register the given metric under the given name.
    Register(string, interface{}) error

    // Run all registered healthchecks.
    RunHealthchecks()

    // Unregister the metric with the given name.
    Unregister(string)

    // Unregister all metrics.  (Mostly for testing.)
    UnregisterAll()
}

// The standard implementation of a Registry is a mutex-protected map
// of names to metrics.
type StandardRegistry struct {
    metrics map[string]interface{}
    mutex   sync.Mutex
}

// Create a new registry.
func NewRegistry() Registry {
    return &StandardRegistry{metrics: make(map[string]interface{})}
}

// Call the given function for each registered metric.
func (r *StandardRegistry) Each(f func(string, interface{})) {
    for name, i := range r.registered() {
        f(name, i)
    }
}

// Get the metric by the given name or nil if none is registered.
func (r *StandardRegistry) Get(name string) interface{} {
    r.mutex.Lock()
    defer r.mutex.Unlock()
    return r.metrics[name]
}

// Gets an existing metric or creates and registers a new one. Threadsafe
// alternative to calling Get and Register on failure.
// The interface can be the metric to register if not found in registry,
// or a function returning the metric for lazy instantiation.
func (r *StandardRegistry) GetOrRegister(name string, i interface{}) interface{} {
    r.mutex.Lock()
    defer r.mutex.Unlock()
    if metric, ok := r.metrics[name]; ok {
        return metric
    }
    if v := reflect.ValueOf(i); v.Kind() == reflect.Func {
        i = v.Call(nil)[0].Interface()
    }
    r.register(name, i)
    return i
}

// Register the given metric under the given name.  Returns a DuplicateMetric
// if a metric by the given name is already registered.
func (r *StandardRegistry) Register(name string, i interface{}) error {
    r.mutex.Lock()
    defer r.mutex.Unlock()
    return r.register(name, i)
}

// Run all registered healthchecks.
func (r *StandardRegistry) RunHealthchecks() {
    r.mutex.Lock()
    defer r.mutex.Unlock()
    for _, i := range r.metrics {
        if h, ok := i.(Healthcheck); ok {
            h.Check()
        }
    }
}

// Unregister the metric with the given name.
func (r *StandardRegistry) Unregister(name string) {
    r.mutex.Lock()
    defer r.mutex.Unlock()
    delete(r.metrics, name)
}

// Unregister all metrics.  (Mostly for testing.)
func (r *StandardRegistry) UnregisterAll() {
    r.mutex.Lock()
    defer r.mutex.Unlock()
    for name, _ := range r.metrics {
        delete(r.metrics, name)
    }
}

func (r *StandardRegistry) register(name string, i interface{}) error {
    if _, ok := r.metrics[name]; ok {
        return DuplicateMetric(name)
    }
    switch i.(type) {
    case Counter, Gauge, GaugeFloat64, Healthcheck, Histogram, Meter, Timer:
        r.metrics[name] = i
    }
    return nil
}

func (r *StandardRegistry) registered() map[string]interface{} {
    r.mutex.Lock()
    defer r.mutex.Unlock()
    metrics := make(map[string]interface{}, len(r.metrics))
    for name, i := range r.metrics {
        metrics[name] = i
    }
    return metrics
}

type PrefixedRegistry struct {
    underlying Registry
    prefix     string
}

func NewPrefixedRegistry(prefix string) Registry {
    return &PrefixedRegistry{
        underlying: NewRegistry(),
        prefix:     prefix,
    }
}

func NewPrefixedChildRegistry(parent Registry, prefix string) Registry {
    return &PrefixedRegistry{
        underlying: parent,
        prefix:     prefix,
    }
}

// Call the given function for each registered metric.
func (r *PrefixedRegistry) Each(fn func(string, interface{})) {
    wrappedFn := func(prefix string) func(string, interface{}) {
        return func(name string, iface interface{}) {
            if strings.HasPrefix(name, prefix) {
                fn(name, iface)
            } else {
                return
            }
        }
    }

    baseRegistry, prefix := findPrefix(r, "")
    baseRegistry.Each(wrappedFn(prefix))
}

func findPrefix(registry Registry, prefix string) (Registry, string) {
    switch r := registry.(type) {
    case *PrefixedRegistry:
        return findPrefix(r.underlying, r.prefix+prefix)
    case *StandardRegistry:
        return r, prefix
    }
    return nil, ""
}

// Get the metric by the given name or nil if none is registered.
func (r *PrefixedRegistry) Get(name string) interface{} {
    realName := r.prefix + name
    return r.underlying.Get(realName)
}

// Gets an existing metric or registers the given one.
// The interface can be the metric to register if not found in registry,
// or a function returning the metric for lazy instantiation.
func (r *PrefixedRegistry) GetOrRegister(name string, metric interface{}) interface{} {
    realName := r.prefix + name
    return r.underlying.GetOrRegister(realName, metric)
}

// Register the given metric under the given name. The name will be prefixed.
func (r *PrefixedRegistry) Register(name string, metric interface{}) error {
    realName := r.prefix + name
    return r.underlying.Register(realName, metric)
}

// Run all registered healthchecks.
func (r *PrefixedRegistry) RunHealthchecks() {
    r.underlying.RunHealthchecks()
}

// Unregister the metric with the given name. The name will be prefixed.
func (r *PrefixedRegistry) Unregister(name string) {
    realName := r.prefix + name
    r.underlying.Unregister(realName)
}

// Unregister all metrics.  (Mostly for testing.)
func (r *PrefixedRegistry) UnregisterAll() {
    r.underlying.UnregisterAll()
}

var DefaultRegistry Registry = NewRegistry()

// Call the given function for each registered metric.
func Each(f func(string, interface{})) {
    DefaultRegistry.Each(f)
}

// Get the metric by the given name or nil if none is registered.
func Get(name string) interface{} {
    return DefaultRegistry.Get(name)
}

// Gets an existing metric or creates and registers a new one. Threadsafe
// alternative to calling Get and Register on failure.
func GetOrRegister(name string, i interface{}) interface{} {
    return DefaultRegistry.GetOrRegister(name, i)
}

// Register the given metric under the given name.  Returns a DuplicateMetric
// if a metric by the given name is already registered.
func Register(name string, i interface{}) error {
    return DefaultRegistry.Register(name, i)
}

// Register the given metric under the given name.  Panics if a metric by the
// given name is already registered.
func MustRegister(name string, i interface{}) {
    if err := Register(name, i); err != nil {
        panic(err)
    }
}

// Run all registered healthchecks.
func RunHealthchecks() {
    DefaultRegistry.RunHealthchecks()
}

// Unregister the metric with the given name.
func Unregister(name string) {
    DefaultRegistry.Unregister(name)
}