Change plugin config to be specified as a list

This makes plugin configuration more similar to output configuration,
where we can specify multiple plugins as a list. The idea behind this is
that the Telegraf agent can handle the multi-processing and error
handling better than each plugin handling that internally. This will
also allow for having different plugin configurations for different
instances of the same type of plugin.

agent.go

@@ -24,9 +24,10 @@ type runningOutput struct {
 }
 
 type runningPlugin struct {
-	name   string
-	plugin plugins.Plugin
-	config *ConfiguredPlugin
+	name       string
+	filtername string
+	plugin     plugins.Plugin
+	config     *ConfiguredPlugin
 }
 
 // Agent runs telegraf and collects data based on the given config
@@ -176,9 +177,11 @@ func (a *Agent) LoadPlugins(filters []string, config *Config) ([]string, error)
 	var names []string
 
 	for name, plugin := range config.PluginsDeclared() {
-		if sliceContains(name, filters) || len(filters) == 0 {
+		// Trim the ID off the output name for filtering
+		filtername := strings.TrimRight(name, "-0123456789")
+		if sliceContains(filtername, filters) || len(filters) == 0 {
 			config := config.GetPluginConfig(name)
-			a.plugins = append(a.plugins, &runningPlugin{name, plugin, config})
+			a.plugins = append(a.plugins, &runningPlugin{name, filtername, plugin, config})
 			names = append(names, name)
 		}
 	}
@@ -207,7 +210,7 @@ func (a *Agent) gatherParallel(pointChan chan *client.Point) error {
 
 			acc := NewAccumulator(plugin.config, pointChan)
 			acc.SetDebug(a.Debug)
-			acc.SetPrefix(plugin.name + "_")
+			acc.SetPrefix(plugin.filtername + "_")
 			acc.SetDefaultTags(a.Tags)
 
 			if err := plugin.plugin.Gather(acc); err != nil {
@@ -240,7 +243,7 @@ func (a *Agent) gatherSeparate(
 
 		acc := NewAccumulator(plugin.config, pointChan)
 		acc.SetDebug(a.Debug)
-		acc.SetPrefix(plugin.name + "_")
+		acc.SetPrefix(plugin.filtername + "_")
 		acc.SetDefaultTags(a.Tags)
 
 		if err := plugin.plugin.Gather(acc); err != nil {
@@ -286,7 +289,7 @@ func (a *Agent) Test() error {
 	for _, plugin := range a.plugins {
 		acc := NewAccumulator(plugin.config, pointChan)
 		acc.SetDebug(true)
-		acc.SetPrefix(plugin.name + "_")
+		acc.SetPrefix(plugin.filtername + "_")
 
 		fmt.Printf("* Plugin: %s, Collection 1\n", plugin.name)
 		if plugin.config.Interval != 0 {
@@ -299,7 +302,7 @@ func (a *Agent) Test() error {
 
 		// Special instructions for some plugins. cpu, for example, needs to be
 		// run twice in order to return cpu usage percentages.
-		switch plugin.name {
+		switch plugin.filtername {
 		case "cpu", "mongodb":
 			time.Sleep(500 * time.Millisecond)
 			fmt.Printf("* Plugin: %s, Collection 2\n", plugin.name)

config.go

@@ -236,6 +236,8 @@ var pluginHeader = `
 ###############################################################################
 #                                  PLUGINS                                    #
 ###############################################################################
+
+[plugins]
 `
 
 var servicePluginHeader = `
@@ -311,7 +313,7 @@ type printer interface {
 }
 
 func printConfig(name string, p printer) {
-	fmt.Printf("\n# %s\n[%s]", p.Description(), name)
+	fmt.Printf("\n# %s\n[[plugins.%s]]", p.Description(), name)
 	config := p.SampleConfig()
 	if config == "" {
 		fmt.Printf("\n  # no configuration\n")
@@ -540,8 +542,34 @@ func LoadConfig(path string) (*Config, error) {
 						outputName)
 				}
 			}
+		case "plugins":
+			for pluginName, pluginVal := range subTable.Fields {
+				switch pluginSubTable := pluginVal.(type) {
+				case *ast.Table:
+					err = c.parsePlugin(pluginName, pluginSubTable, 0)
+					if err != nil {
+						log.Printf("Could not parse config for plugin: %s\n",
+							pluginName)
+						return nil, err
+					}
+				case []*ast.Table:
+					for id, t := range pluginSubTable {
+						err = c.parsePlugin(pluginName, t, id)
+						if err != nil {
+							log.Printf("Could not parse config for plugin: %s\n",
+								pluginName)
+							return nil, err
+						}
+					}
+				default:
+					return nil, fmt.Errorf("Unsupported config format: %s",
+						pluginName)
+				}
+			}
+		// Assume it's a plugin for legacy config file support if no other
+		// identifiers are present
 		default:
-			err = c.parsePlugin(name, subTable)
+			err = c.parsePlugin(name, subTable, 0)
 			if err != nil {
 				return nil, err
 			}
@@ -590,7 +618,7 @@ func (c *Config) parseOutput(name string, outputAst *ast.Table, id int) error {
 }
 
 // Parse a plugin config, plus plugin meta-config, out of the given *ast.Table.
-func (c *Config) parsePlugin(name string, pluginAst *ast.Table) error {
+func (c *Config) parsePlugin(name string, pluginAst *ast.Table, id int) error {
 	creator, ok := plugins.Plugins[name]
 	if !ok {
 		return fmt.Errorf("Undefined but requested plugin: %s", name)
@@ -682,13 +710,14 @@ func (c *Config) parsePlugin(name string, pluginAst *ast.Table) error {
 	delete(pluginAst.Fields, "interval")
 	delete(pluginAst.Fields, "tagdrop")
 	delete(pluginAst.Fields, "tagpass")
-	c.pluginFieldsSet[name] = extractFieldNames(pluginAst)
-	c.pluginConfigurationFieldsSet[name] = cpFields
+	nameID := fmt.Sprintf("%s-%d", name, id)
+	c.pluginFieldsSet[nameID] = extractFieldNames(pluginAst)
+	c.pluginConfigurationFieldsSet[nameID] = cpFields
 	err := toml.UnmarshalTable(pluginAst, plugin)
 	if err != nil {
 		return err
 	}
-	c.plugins[name] = plugin
-	c.pluginConfigurations[name] = cp
+	c.plugins[nameID] = plugin
+	c.pluginConfigurations[nameID] = cp
 	return nil
 }