indexer: support data exporting/forwarding (#103)

To support more effective and flexible blockchain info exploring, we add
`indexer` package, defines the flow of indexer dameon, and integrate
into dex.Dexon fullnode.

For more export options, we use Golang built-in `plugin` package to
support mulitple implementations.

3 files changed, 32 insertions, 0 deletions

diff --git a/cmd/gdex/main.go b/cmd/gdex/main.go
index 9a1ef7bc9..c054e3ad5 100644
--- a/cmd/gdex/main.go
+++ b/cmd/gdex/main.go
@@ -137,6 +137,8 @@ var (
 		utils.GpoPercentileFlag,
 		utils.EWASMInterpreterFlag,
 		utils.EVMInterpreterFlag,
+		utils.IndexerEnableFlag,
+		utils.IndexerPluginFlag,
 		configFileFlag,
 	}
 
diff --git a/cmd/gdex/usage.go b/cmd/gdex/usage.go
index d67817096..880e447f3 100644
--- a/cmd/gdex/usage.go
+++ b/cmd/gdex/usage.go
@@ -240,6 +240,13 @@ var AppHelpFlagGroups = []flagGroup{
 		},
 	},
 	{
+		Name: "INDEXER",
+		Flags: []cli.Flag{
+			utils.IndexerEnableFlag,
+			utils.IndexerPluginFlag,
+		},
+	},
+	{
 		Name:  "WHISPER (EXPERIMENTAL)",
 		Flags: whisperFlags,
 	},
diff --git a/cmd/utils/flags.go b/cmd/utils/flags.go
index 971ccd349..96a642850 100644
--- a/cmd/utils/flags.go
+++ b/cmd/utils/flags.go
@@ -648,6 +648,17 @@ var (
 		Usage: "External EVM configuration (default = built-in interpreter)",
 		Value: "",
 	}
+
+	// Data sources options.
+	IndexerEnableFlag = cli.BoolFlag{
+		Name:  "indexer",
+		Usage: "Enable indexer",
+	}
+	IndexerPluginFlag = cli.StringFlag{
+		Name:  "indexer.plugin",
+		Usage: "External indexer plugin shared object path",
+		Value: "",
+	}
 )
 
 // MakeDataDir retrieves the currently requested data directory, terminating
@@ -1282,6 +1293,18 @@ func SetDexConfig(ctx *cli.Context, stack *node.Node, cfg *dex.Config) {
 			now.Hour(), now.Minute(), (now.Second()/5+1)*5,
 			0, now.Location()).Unix()
 	}
+
+	// Set indexer config.
+	setIndexerConfig(ctx, cfg)
+}
+
+func setIndexerConfig(ctx *cli.Context, cfg *dex.Config) {
+	cfg.Indexer.Enable = ctx.GlobalBool(IndexerEnableFlag.Name)
+	if !cfg.Indexer.Enable {
+		return
+	}
+
+	cfg.Indexer.Plugin = ctx.GlobalString(IndexerPluginFlag.Name)
 }
 
 // SetDashboardConfig applies dashboard related command line flags to the config.