Clean up code and update docs

README.md

@@ -92,5 +92,6 @@ Improvement:
   - [] Implement leveled logging (maybe glog or logrus)
   - [] Consider switching from YAML to TOML
   - [] Consider value of templating vs injecting values into Env variables
+  - [] Consider dropping `alert_up` and `alert_down` in favor of using Go templates that offer more control of messaging
   - [] Async checking
   - [] Use durations rather than seconds checked in event loop

alert.go

@@ -8,6 +8,7 @@ import (
 	"time"
 )
 
+// Alert is a config driven mechanism for sending a notice
 type Alert struct {
 	Name                 string
 	Command              []string
@@ -16,12 +17,25 @@ type Alert struct {
 	commandShellTemplate *template.Template
 }
 
+// AlertNotice captures the context for an alert to be sent
+type AlertNotice struct {
+	MonitorName     string
+	AlertCount      int16
+	FailureCount    int16
+	LastCheckOutput string
+	LastSuccess     time.Time
+	IsUp            bool
+}
+
+// IsValid returns a boolean indicating if the Alert has been correctly
+// configured
 func (alert Alert) IsValid() bool {
 	atLeastOneCommand := (alert.CommandShell != "" || alert.Command != nil)
 	atMostOneCommand := (alert.CommandShell == "" || alert.Command == nil)
 	return atLeastOneCommand && atMostOneCommand
 }
 
+// BuildTemplates compiles command templates for the Alert
 func (alert *Alert) BuildTemplates() {
 	if alert.commandTemplate == nil && alert.Command != nil {
 		// build template
@@ -40,17 +54,12 @@ func (alert *Alert) BuildTemplates() {
 		)
 		log.Printf("Template built: %v", alert.commandShellTemplate)
 	} else {
-		panic("No template provided?")
+		panic("No template provided for alert %s", alert.Name)
 	}
 }
 
-func (alert *Alert) Send(notice AlertNotice) {
+// Send will send an alert notice by executing the command template
-	// TODO: Validate and build templates in a better place and make this immutable
+func (alert Alert) Send(notice AlertNotice) {
-	if !alert.IsValid() {
-		log.Fatalf("Alert is invalid: %v", alert)
-	}
-	alert.BuildTemplates()
-
 	var cmd *exec.Cmd
 
 	if alert.commandTemplate != nil {
@@ -86,12 +95,3 @@ func (alert *Alert) Send(notice AlertNotice) {
 		panic(err)
 	}
 }
-
-type AlertNotice struct {
-	MonitorName     string
-	AlertCount      int16
-	FailureCount    int16
-	LastCheckOutput string
-	LastSuccess     time.Time
-	IsUp            bool
-}

config.go

@@ -7,12 +7,42 @@ import (
 	"os"
 )
 
+// Config type is contains all provided user configuration
 type Config struct {
 	CheckInterval int64 `yaml:"check_interval"`
 	Monitors      []*Monitor
 	Alerts        map[string]*Alert
 }
 
+// IsValid checks config validity and returns true if valid
+func (config Config) IsValid() (isValid bool) {
+	isValid = true
+	for _, monitor := range config.Monitors {
+		if !monitor.IsValid() {
+			log.Printf("ERROR: Invalid monitor configuration: %s", monitor.Name)
+			isValid = false
+		}
+	}
+
+	for _, alert := range config.Alerts {
+		if !alert.IsValid() {
+			log.Printf("ERROR: Invalid alert configuration: %s", alert.Name)
+			isValid = false
+		}
+	}
+
+	return
+}
+
+// Init performs extra initialization on top of loading the config from file
+func (config *Config) Init() {
+	for name, alert := range config.Alerts {
+		alert.Name = name
+		alert.BuildTemplates()
+	}
+}
+
+// LoadConfig will read config from the given path and parse it
 func LoadConfig(filePath string) (config Config) {
 	data, err := ioutil.ReadFile(filePath)
 	if err != nil {
@@ -20,9 +50,8 @@ func LoadConfig(filePath string) (config Config) {
 	}
 
 	// TODO: Decide if this is better expanded here, or only when executing
-	env_expanded := os.ExpandEnv(string(data))
+	envExpanded := os.ExpandEnv(string(data))
-
+	err = yaml.Unmarshal([]byte(envExpanded), &config)
-	err = yaml.Unmarshal([]byte(env_expanded), &config)
 	if err != nil {
 		log.Fatalf("ERROR: %v", err)
 		panic(err)
@@ -30,5 +59,12 @@ func LoadConfig(filePath string) (config Config) {
 
 	log.Printf("config:\n%v\n", config)
 
+	if !config.IsValid() {
+		panic("Cannot continue with invalid configuration")
+	}
+
+	// Finish initializing configuration
+	config.Init()
+
 	return config
 }

main.go

@@ -12,6 +12,8 @@ func main() {
 		for _, monitor := range config.Monitors {
 			if monitor.ShouldCheck() {
 				_, alertNotice := monitor.Check()
+
+				// Should probably consider refactoring everything below here
 				if alertNotice != nil {
 					//log.Printf("Recieved an alert notice: %v", alertNotice)
 					var alerts []string

util.go

@@ -5,7 +5,7 @@ import (
 	"strings"
 )
 
-/// escapeCommandShell accepts a command to be executed by a shell and escapes it
+// escapeCommandShell accepts a command to be executed by a shell and escapes it
 func escapeCommandShell(command string) string {
 	// Remove extra spaces and newlines from ends
 	command = strings.TrimSpace(command)
@@ -15,7 +15,7 @@ func escapeCommandShell(command string) string {
 	return command
 }
 
-/// ShellCommand takes a string and executes it as a command using `sh`
+// ShellCommand takes a string and executes it as a command using `sh`
 func ShellCommand(command string) *exec.Cmd {
 	shellCommand := []string{"sh", "-c", escapeCommandShell(command)}
 	//log.Printf("Shell command: %v", shellCommand)