Moving away from passing around *ast.Tables.

Config in the config directory will need to be merged into the main
config, which is difficult to do using the *ast.Tables. Get the config
into structs as soon as possible and then merge the structs.

agent.go

@@ -52,7 +52,7 @@ type Agent struct {
 	Debug    bool
 	Hostname string
 
-	Config *Config
+	Tags map[string]string
 
 	outputs []*runningOutput
 	plugins []*runningPlugin
@@ -61,7 +61,7 @@ type Agent struct {
 // NewAgent returns an Agent struct based off the given Config
 func NewAgent(config *Config) (*Agent, error) {
 	agent := &Agent{
-		Config:        config,
+		Tags:          make(map[string]string),
 		Interval:      Duration{10 * time.Second},
 		FlushInterval: Duration{10 * time.Second},
 		FlushRetries:  2,
@@ -84,11 +84,7 @@ func NewAgent(config *Config) (*Agent, error) {
 		agent.Hostname = hostname
 	}
 
-	if config.Tags == nil {
-		config.Tags = map[string]string{}
-	}
-
-	config.Tags["host"] = agent.Hostname
+	agent.Tags["host"] = agent.Hostname
 
 	return agent, nil
 }
@@ -125,10 +121,10 @@ func (a *Agent) Close() error {
 }
 
 // LoadOutputs loads the agent's outputs
-func (a *Agent) LoadOutputs(filters []string) ([]string, error) {
+func (a *Agent) LoadOutputs(filters []string, config *Config) ([]string, error) {
 	var names []string
 
-	for _, name := range a.Config.OutputsDeclared() {
+	for _, name := range config.OutputsDeclared() {
 		creator, ok := outputs.Outputs[name]
 		if !ok {
 			return nil, fmt.Errorf("Undefined but requested output: %s", name)
@@ -140,7 +136,7 @@ func (a *Agent) LoadOutputs(filters []string) ([]string, error) {
 			}
 			output := creator()
 
-			err := a.Config.ApplyOutput(name, output)
+			err := config.ApplyOutput(name, output)
 			if err != nil {
 				return nil, err
 			}
@@ -156,10 +152,10 @@ func (a *Agent) LoadOutputs(filters []string) ([]string, error) {
 }
 
 // LoadPlugins loads the agent's plugins
-func (a *Agent) LoadPlugins(filters []string) ([]string, error) {
+func (a *Agent) LoadPlugins(filters []string, config *Config) ([]string, error) {
 	var names []string
 
-	for _, name := range a.Config.PluginsDeclared() {
+	for _, name := range config.PluginsDeclared() {
 		creator, ok := plugins.Plugins[name]
 		if !ok {
 			return nil, fmt.Errorf("Undefined but requested plugin: %s", name)
@@ -168,7 +164,7 @@ func (a *Agent) LoadPlugins(filters []string) ([]string, error) {
 		if sliceContains(name, filters) || len(filters) == 0 {
 			plugin := creator()
 
-			config, err := a.Config.ApplyPlugin(name, plugin)
+			config, err := config.ApplyPlugin(name, plugin)
 			if err != nil {
 				return nil, err
 			}
@@ -203,7 +199,7 @@ func (a *Agent) gatherParallel(pointChan chan *client.Point) error {
 			acc := NewAccumulator(plugin.config, pointChan)
 			acc.SetDebug(a.Debug)
 			acc.SetPrefix(plugin.name + "_")
-			acc.SetDefaultTags(a.Config.Tags)
+			acc.SetDefaultTags(a.Tags)
 
 			if err := plugin.plugin.Gather(acc); err != nil {
 				log.Printf("Error in plugin [%s]: %s", plugin.name, err)
@@ -236,7 +232,7 @@ func (a *Agent) gatherSeparate(
 		acc := NewAccumulator(plugin.config, pointChan)
 		acc.SetDebug(a.Debug)
 		acc.SetPrefix(plugin.name + "_")
-		acc.SetDefaultTags(a.Config.Tags)
+		acc.SetDefaultTags(a.Tags)
 
 		if err := plugin.plugin.Gather(acc); err != nil {
 			log.Printf("Error in plugin [%s]: %s", plugin.name, err)

cmd/telegraf/telegraf.go

@@ -90,7 +90,7 @@ func main() {
 		ag.Debug = true
 	}
 
-	outputs, err := ag.LoadOutputs(outputFilters)
+	outputs, err := ag.LoadOutputs(outputFilters, config)
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -99,7 +99,7 @@ func main() {
 		os.Exit(1)
 	}
 
-	plugins, err := ag.LoadPlugins(pluginFilters)
+	plugins, err := ag.LoadPlugins(pluginFilters, config)
 	if err != nil {
 		log.Fatal(err)
 	}

config.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"io/ioutil"
+	"reflect"
 	"sort"
 	"strings"
 	"time"
@@ -35,20 +36,28 @@ func (d *Duration) UnmarshalTOML(b []byte) error {
 // will be logging to, as well as all the plugins that the user has
 // specified
 type Config struct {
+	// This lives outside the agent because mergeStruct doesn't need to handle maps normally.
+	// We just copy the elements manually in applyAgent.
 	Tags map[string]string
 
-	agent   *ast.Table
-	plugins map[string]*ast.Table
-	outputs map[string]*ast.Table
+	agent                *Agent
+	plugins              map[string]plugins.Plugin
+	pluginConfigurations map[string]*ConfiguredPlugin
+	outputs              map[string]outputs.Output
+
+	agentFieldsSet               []string
+	pluginFieldsSet              map[string][]string
+	pluginConfigurationFieldsSet map[string][]string
+	outputFieldsSet              map[string][]string
 }
 
-// Plugins returns the configured plugins as a map of name -> plugin toml
-func (c *Config) Plugins() map[string]*ast.Table {
+// Plugins returns the configured plugins as a map of name -> plugins.Plugin
+func (c *Config) Plugins() map[string]plugins.Plugin {
 	return c.plugins
 }
 
-// Outputs returns the configured outputs as a map of name -> output toml
-func (c *Config) Outputs() map[string]*ast.Table {
+// Outputs returns the configured outputs as a map of name -> outputs.Output
+func (c *Config) Outputs() map[string]outputs.Output {
 	return c.outputs
 }
 
@@ -123,187 +132,65 @@ func (cp *ConfiguredPlugin) ShouldPass(measurement string, tags map[string]strin
 	return true
 }
 
-// ApplyOutput loads the toml config into the given interface
+// ApplyOutput loads the Output struct built from the config into the given Output struct.
+// Overrides only values in the given struct that were set in the config.
 func (c *Config) ApplyOutput(name string, v interface{}) error {
 	if c.outputs[name] != nil {
-		return toml.UnmarshalTable(c.outputs[name], v)
+		return mergeStruct(v, c.outputs[name], c.outputFieldsSet[name])
 	}
 	return nil
 }
 
-// ApplyAgent loads the toml config into the given Agent object, overriding
-// defaults (such as collection duration) with the values from the toml config.
+// ApplyAgent loads the Agent struct built from the config into the given Agent struct.
+// Overrides only values in the given struct that were set in the config.
 func (c *Config) ApplyAgent(a *Agent) error {
 	if c.agent != nil {
-		return toml.UnmarshalTable(c.agent, a)
+		return mergeStruct(a, c.agent, c.agentFieldsSet)
+	}
+	for key, value := range c.Tags {
+		a.Tags[key] = value
 	}
 
 	return nil
 }
 
-// ApplyPlugin takes defined plugin names and applies them to the given
-// interface, returning a ConfiguredPlugin object in the end that can
-// be inserted into a runningPlugin by the agent.
+// ApplyPlugin loads the Plugin struct built from the config into the given Plugin struct.
+// Overrides only values in the given struct that were set in the config.
+// Additionally return a ConfiguredPlugin, which is always generated from the config.
 func (c *Config) ApplyPlugin(name string, v interface{}) (*ConfiguredPlugin, error) {
-	cp := &ConfiguredPlugin{Name: name}
-
-	if tbl, ok := c.plugins[name]; ok {
-
-		if node, ok := tbl.Fields["pass"]; ok {
-			if kv, ok := node.(*ast.KeyValue); ok {
-				if ary, ok := kv.Value.(*ast.Array); ok {
-					for _, elem := range ary.Value {
-						if str, ok := elem.(*ast.String); ok {
-							cp.Pass = append(cp.Pass, str.Value)
-						}
-					}
-				}
-			}
-		}
-
-		if node, ok := tbl.Fields["drop"]; ok {
-			if kv, ok := node.(*ast.KeyValue); ok {
-				if ary, ok := kv.Value.(*ast.Array); ok {
-					for _, elem := range ary.Value {
-						if str, ok := elem.(*ast.String); ok {
-							cp.Drop = append(cp.Drop, str.Value)
-						}
-					}
-				}
-			}
-		}
-
-		if node, ok := tbl.Fields["interval"]; ok {
-			if kv, ok := node.(*ast.KeyValue); ok {
-				if str, ok := kv.Value.(*ast.String); ok {
-					dur, err := time.ParseDuration(str.Value)
+	if c.plugins[name] != nil {
+		err := mergeStruct(v, c.plugins[name], c.pluginFieldsSet[name])
 		if err != nil {
 			return nil, err
 		}
-
-					cp.Interval = dur
-				}
-			}
+		return c.pluginConfigurations[name], nil
 	}
 
-		if node, ok := tbl.Fields["tagpass"]; ok {
-			if subtbl, ok := node.(*ast.Table); ok {
-				for name, val := range subtbl.Fields {
-					if kv, ok := val.(*ast.KeyValue); ok {
-						tagfilter := &TagFilter{Name: name}
-						if ary, ok := kv.Value.(*ast.Array); ok {
-							for _, elem := range ary.Value {
-								if str, ok := elem.(*ast.String); ok {
-									tagfilter.Filter = append(tagfilter.Filter, str.Value)
-								}
-							}
-						}
-						cp.TagPass = append(cp.TagPass, *tagfilter)
-					}
-				}
-			}
-		}
-
-		if node, ok := tbl.Fields["tagdrop"]; ok {
-			if subtbl, ok := node.(*ast.Table); ok {
-				for name, val := range subtbl.Fields {
-					if kv, ok := val.(*ast.KeyValue); ok {
-						tagfilter := &TagFilter{Name: name}
-						if ary, ok := kv.Value.(*ast.Array); ok {
-							for _, elem := range ary.Value {
-								if str, ok := elem.(*ast.String); ok {
-									tagfilter.Filter = append(tagfilter.Filter, str.Value)
-								}
-							}
-						}
-						cp.TagDrop = append(cp.TagDrop, *tagfilter)
-					}
-				}
-			}
-		}
-
-		delete(tbl.Fields, "drop")
-		delete(tbl.Fields, "pass")
-		delete(tbl.Fields, "interval")
-		delete(tbl.Fields, "tagdrop")
-		delete(tbl.Fields, "tagpass")
-		return cp, toml.UnmarshalTable(tbl, v)
-	}
-
-	return cp, nil
+	return nil, nil
 }
 
+// Couldn't figure out how to get this to work with the declared function.
+
 // PluginsDeclared returns the name of all plugins declared in the config.
 func (c *Config) PluginsDeclared() []string {
-	return declared(c.plugins)
+	var names []string
+	for name := range c.plugins {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+	return names
 }
 
 // OutputsDeclared returns the name of all outputs declared in the config.
 func (c *Config) OutputsDeclared() []string {
-	return declared(c.outputs)
-}
-
-func declared(endpoints map[string]*ast.Table) []string {
 	var names []string
-
-	for name := range endpoints {
+	for name := range c.outputs {
 		names = append(names, name)
 	}
-
 	sort.Strings(names)
-
 	return names
 }
 
-var errInvalidConfig = errors.New("invalid configuration")
-
-// LoadConfig loads the given config file and returns a *Config pointer
-func LoadConfig(path string) (*Config, error) {
-	data, err := ioutil.ReadFile(path)
-	if err != nil {
-		return nil, err
-	}
-
-	tbl, err := toml.Parse(data)
-	if err != nil {
-		return nil, err
-	}
-
-	c := &Config{
-		Tags:    make(map[string]string),
-		plugins: make(map[string]*ast.Table),
-		outputs: make(map[string]*ast.Table),
-	}
-
-	for name, val := range tbl.Fields {
-		subtbl, ok := val.(*ast.Table)
-		if !ok {
-			return nil, errInvalidConfig
-		}
-
-		switch name {
-		case "agent":
-			c.agent = subtbl
-		case "tags":
-			if err := toml.UnmarshalTable(subtbl, c.Tags); err != nil {
-				return nil, errInvalidConfig
-			}
-		case "outputs":
-			for outputName, outputVal := range subtbl.Fields {
-				outputSubtbl, ok := outputVal.(*ast.Table)
-				if !ok {
-					return nil, errInvalidConfig
-				}
-				c.outputs[outputName] = outputSubtbl
-			}
-		default:
-			c.plugins[name] = subtbl
-		}
-	}
-
-	return c, nil
-}
-
 // ListTags returns a string of tags specified in the config,
 // line-protocol style
 func (c *Config) ListTags() string {
@@ -474,3 +361,240 @@ func PrintPluginConfig(name string) error {
 	}
 	return nil
 }
+
+// Used for fuzzy matching struct field names in FieldByNameFunc calls below
+func fieldMatch(field string) func(string) bool {
+	return func(name string) bool {
+		r := strings.NewReplacer("_", "")
+		return strings.ToLower(name) == strings.ToLower(r.Replace(field))
+	}
+}
+
+// A very limited merge. Merges the fields named in the fields parameter, replacing most values, but appending to arrays.
+func mergeStruct(base, overlay interface{}, fields []string) error {
+	baseValue := reflect.ValueOf(base).Elem()
+	overlayValue := reflect.ValueOf(overlay).Elem()
+	if baseValue.Kind() != reflect.Struct {
+		return fmt.Errorf("Tried to merge something that wasn't a struct: type %v was %v", baseValue.Type(), baseValue.Kind())
+	}
+	if baseValue.Type() != overlayValue.Type() {
+		return fmt.Errorf("Tried to merge two different types: %v and %v", baseValue.Type(), overlayValue.Type())
+	}
+	for _, field := range fields {
+		overlayFieldValue := overlayValue.FieldByNameFunc(fieldMatch(field))
+		if !overlayFieldValue.IsValid() {
+			return fmt.Errorf("could not find field in %v matching %v", overlayValue.Type(), field)
+		}
+		if overlayFieldValue.Kind() == reflect.Slice {
+			baseFieldValue := baseValue.FieldByNameFunc(fieldMatch(field))
+			baseFieldValue.Set(reflect.AppendSlice(baseFieldValue, overlayFieldValue))
+		} else {
+			baseValue.FieldByNameFunc(fieldMatch(field)).Set(overlayFieldValue)
+		}
+	}
+	return nil
+}
+
+// hazmat area. Keeping the ast parsing here.
+
+// LoadConfig loads the given config file and returns a *Config pointer
+func LoadConfig(path string) (*Config, error) {
+	data, err := ioutil.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+
+	tbl, err := toml.Parse(data)
+	if err != nil {
+		return nil, err
+	}
+
+	c := &Config{
+		Tags:                         make(map[string]string),
+		plugins:                      make(map[string]plugins.Plugin),
+		pluginConfigurations:         make(map[string]*ConfiguredPlugin),
+		outputs:                      make(map[string]outputs.Output),
+		pluginFieldsSet:              make(map[string][]string),
+		pluginConfigurationFieldsSet: make(map[string][]string),
+		outputFieldsSet:              make(map[string][]string),
+	}
+
+	for name, val := range tbl.Fields {
+		subtbl, ok := val.(*ast.Table)
+		if !ok {
+			return nil, errors.New("invalid configuration")
+		}
+
+		switch name {
+		case "agent":
+			err := c.parseAgent(subtbl)
+			if err != nil {
+				return nil, err
+			}
+		case "tags":
+			if err = toml.UnmarshalTable(subtbl, c.Tags); err != nil {
+				return nil, err
+			}
+		case "outputs":
+			for outputName, outputVal := range subtbl.Fields {
+				outputSubtbl, ok := outputVal.(*ast.Table)
+				if !ok {
+					return nil, err
+				}
+				err = c.parseOutput(outputName, outputSubtbl)
+				if err != nil {
+					return nil, err
+				}
+			}
+		default:
+			err = c.parsePlugin(name, subtbl)
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	return c, nil
+}
+
+// Needs to have the field names, for merging later.
+func extractFieldNames(ast *ast.Table) []string {
+	// A reasonable capacity?
+	var names []string
+	for name := range ast.Fields {
+		names = append(names, name)
+	}
+	return names
+}
+
+// Parse the agent config out of the given *ast.Table.
+func (c *Config) parseAgent(agentAst *ast.Table) error {
+	c.agentFieldsSet = extractFieldNames(agentAst)
+	agent := &Agent{}
+	err := toml.UnmarshalTable(agentAst, agent)
+	if err != nil {
+		return err
+	}
+	c.agent = agent
+	return nil
+}
+
+// Parse an output config out of the given *ast.Table.
+func (c *Config) parseOutput(name string, outputAst *ast.Table) error {
+	c.outputFieldsSet[name] = extractFieldNames(outputAst)
+	creator, ok := outputs.Outputs[name]
+	if !ok {
+		return fmt.Errorf("Undefined but requested output: %s", name)
+	}
+	output := creator()
+	err := toml.UnmarshalTable(outputAst, output)
+	if err != nil {
+		return err
+	}
+	c.outputs[name] = output
+	return nil
+}
+
+// Parse a plugin config, plus plugin meta-config, out of the given *ast.Table.
+func (c *Config) parsePlugin(name string, pluginAst *ast.Table) error {
+	creator, ok := plugins.Plugins[name]
+	if !ok {
+		return fmt.Errorf("Undefined but requested plugin: %s", name)
+	}
+	plugin := creator()
+	cp := &ConfiguredPlugin{Name: name}
+	cpFields := make([]string, 0, 5)
+
+	if node, ok := pluginAst.Fields["pass"]; ok {
+		if kv, ok := node.(*ast.KeyValue); ok {
+			if ary, ok := kv.Value.(*ast.Array); ok {
+				for _, elem := range ary.Value {
+					if str, ok := elem.(*ast.String); ok {
+						cp.Pass = append(cp.Pass, str.Value)
+					}
+				}
+				cpFields = append(cpFields, "pass")
+			}
+		}
+	}
+
+	if node, ok := pluginAst.Fields["drop"]; ok {
+		if kv, ok := node.(*ast.KeyValue); ok {
+			if ary, ok := kv.Value.(*ast.Array); ok {
+				for _, elem := range ary.Value {
+					if str, ok := elem.(*ast.String); ok {
+						cp.Drop = append(cp.Drop, str.Value)
+					}
+				}
+				cpFields = append(cpFields, "drop")
+			}
+		}
+	}
+
+	if node, ok := pluginAst.Fields["interval"]; ok {
+		if kv, ok := node.(*ast.KeyValue); ok {
+			if str, ok := kv.Value.(*ast.String); ok {
+				dur, err := time.ParseDuration(str.Value)
+				if err != nil {
+					return err
+				}
+
+				cp.Interval = dur
+				cpFields = append(cpFields, "interval")
+			}
+		}
+	}
+
+	if node, ok := pluginAst.Fields["tagpass"]; ok {
+		if subtbl, ok := node.(*ast.Table); ok {
+			for name, val := range subtbl.Fields {
+				if kv, ok := val.(*ast.KeyValue); ok {
+					tagfilter := &TagFilter{Name: name}
+					if ary, ok := kv.Value.(*ast.Array); ok {
+						for _, elem := range ary.Value {
+							if str, ok := elem.(*ast.String); ok {
+								tagfilter.Filter = append(tagfilter.Filter, str.Value)
+							}
+						}
+					}
+					cp.TagPass = append(cp.TagPass, *tagfilter)
+					cpFields = append(cpFields, "tagpass")
+				}
+			}
+		}
+	}
+
+	if node, ok := pluginAst.Fields["tagdrop"]; ok {
+		if subtbl, ok := node.(*ast.Table); ok {
+			for name, val := range subtbl.Fields {
+				if kv, ok := val.(*ast.KeyValue); ok {
+					tagfilter := &TagFilter{Name: name}
+					if ary, ok := kv.Value.(*ast.Array); ok {
+						for _, elem := range ary.Value {
+							if str, ok := elem.(*ast.String); ok {
+								tagfilter.Filter = append(tagfilter.Filter, str.Value)
+							}
+						}
+					}
+					cp.TagDrop = append(cp.TagDrop, *tagfilter)
+					cpFields = append(cpFields, "tagdrop")
+				}
+			}
+		}
+	}
+
+	delete(pluginAst.Fields, "drop")
+	delete(pluginAst.Fields, "pass")
+	delete(pluginAst.Fields, "interval")
+	delete(pluginAst.Fields, "tagdrop")
+	delete(pluginAst.Fields, "tagpass")
+	c.pluginFieldsSet[name] = extractFieldNames(pluginAst)
+	c.pluginConfigurationFieldsSet[name] = cpFields
+	err := toml.UnmarshalTable(pluginAst, plugin)
+	if err != nil {
+		return err
+	}
+	c.plugins[name] = plugin
+	c.pluginConfigurations[name] = cp
+	return nil
+}