// Starts listening for commands through the given app's connection.
// Since this is a blocking function, it should likely be called in
// a goroutine.
// At the end of the function, closes the application's network resources.
func ListenForCommands(a *app.App) {
defer closeApp(a)
// loop forever consuming messages
for {
// get the next command
strategy, err := getCommand(a)
if err != nil {
id := "NO_ID_FOUND"
if a.Manifest != nil {
id = a.Manifest.InstanceId
}
logging.Error("Application %s encountered fatal error: %s",
id,
err.Error())
return
}
// do the command
if strategy.GetVerb() == "APP_MANIFEST" {
if !strategy.Execute() {
logging.Error("Application's manifest did not parse correctly")
return
}
} else {
// HACK to get around golang compiler error
// originally:
// go strategy.Execute()
// message:
// "go requires function call not conversion"
go performStrategy(strategy)
}
}
}
func (c *commandStrategy) Execute() bool {
var err error
ret := true
switch c.verb {
case "APP_MANIFEST":
ret = c.appManifest()
case "APP_UP", "APP_DOWN", "APP_IN_USE":
err = c.statusChange()
case "MSG_QUERY":
err = c.msgQuery()
case "MSG_BROADCAST":
err = c.msgBroadcast()
case "MSG_QUERY_SUCCESS":
err = c.msgQuerySuccess()
case "MSG_QUERY_FAIL":
err = c.msgQueryFail()
default:
err = fmt.Errorf("No matching verb found for %s", c.verb)
}
if err != nil {
id := "NO_ID_FOUND"
if c.app.Manifest != nil {
id = c.app.Manifest.InstanceId
}
logging.Error("Application %s had command error %s", id, err.Error())
b, _ := json.Marshal(c.body)
return newFailedCommandStrategy(c.app, string(b), err.Error()).Execute()
}
return ret
}
// Parses a command given the command's message string
// (verb and body, no message length)
func ParseCommand(a *app.App, message string) (CommandStrategy, bool) {
id := "NO_ID_FOUND"
if a.Manifest != nil {
id = a.Manifest.InstanceId
}
logging.Debug("Parsing from app %s: \n%s", id, message)
ret, err := internalParseCommand(a, message)
if err != nil {
logging.Error("Parse failed from app %s: %s", id, err.Error())
return newFailedCommandStrategy(a, message, err.Error()), false
}
return ret, true
}
// construct the app based on its manifest
func (c *commandStrategy) appManifest() bool {
c.app.RWMutex.Lock()
defer c.app.RWMutex.Unlock()
logging.Debug("Parsing application's manifest")
man, err := decodeManifest(c.body)
if err != nil {
logging.Error("App's manifest is invalid: %s", err)
sendManifestFail(c.app, err.Error())
return false
}
if _, exists := registry.GetInstance(man.InstanceId); exists {
logging.Error("App's instance id is already taken: %s", man.InstanceId)
sendManifestFail(c.app, fmt.Sprintf("instanceId %s is in use", man.InstanceId))
return false
}
c.app.Status = app.STATUS_DOWN
c.app.Manifest = man
registry.Register(c.app)
sendManifestOkAndDependencies(c.app)
logging.Info("App '%s' now connected with manifest parsed", c.app.Manifest.InstanceId)
return true
}