ecs-init.go

// Copyright 2015-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License"). You may
// not use this file except in compliance with the License. A copy of the
// License is located at
//
//     http://aws.amazon.com/apache2.0/
//
// or in the "license" file accompanying this file. This file is distributed
// on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
// express or implied. See the License for the specific language governing
// permissions and limitations under the License.

package main

import (
	"flag"
	"fmt"
	"os"

	"github.com/aws/amazon-ecs-agent/ecs-init/config"
	"github.com/aws/amazon-ecs-agent/ecs-init/engine"
	"github.com/aws/amazon-ecs-agent/ecs-init/version"

	log "github.com/cihub/seelog"
)

// all supported commands
const (
	VERSION  = "version"
	PRESTART = "pre-start"
	START    = "start"
	PRESTOP  = "pre-stop"
	STOP     = "stop"
	POSTSTOP = "post-stop"
	RECACHE  = "reload-cache"
)

func main() {
	defer log.Flush()
	flag.Parse()
	args := flag.Args()

	if len(args) == 0 {
		usage(actions(nil))
		os.Exit(1)
	}

	logger, err := log.LoggerFromConfigAsString(config.Logger())
	if err != nil {
		die(err, engine.DefaultInitErrorExitCode)
	}
	log.ReplaceLogger(logger)

	if args[0] == VERSION {
		err := version.PrintVersion()
		if err != nil {
			log.Errorf("failed print version info, err: %v", err)
		}
		return
	}

	init, err := engine.New()
	if err != nil {
		die(err, engine.DefaultInitErrorExitCode)
	}
	log.Info(args[0])
	actions := actions(init)
	action, ok := actions[args[0]]
	if !ok {
		usage(actions)
		os.Exit(1)
	}
	err = action.function()

	if err != nil {
		if err, ok := err.(*engine.TerminalError); ok {
			die(err, engine.TerminalFailureAgentExitCode)
		}
		die(err, engine.DefaultInitErrorExitCode)
	}
}

type action struct {
	function    func() error
	description string
}

func actions(engine *engine.Engine) map[string]action {
	return map[string]action{
		PRESTART: action{
			function:    engine.PreStart,
			description: "Prepare the ECS Agent for starting",
		},
		START: action{
			function:    engine.StartSupervised,
			description: "Start the ECS Agent and wait for it to stop",
		},
		// This is a deprecated command for stopping the agent
		// when using upstart jobs
		PRESTOP: action{
			function:    engine.PreStop,
			description: "Stop the ECS Agent",
		},
		STOP: action{
			function:    engine.PreStop,
			description: "Stop the ECS Agent",
		},
		RECACHE: action{
			function:    engine.ReloadCache,
			description: "Reload the cached image of the ECS Agent into Docker",
		},
		POSTSTOP: action{
			function:    engine.PostStop,
			description: "Cleanup procedure for the ECS Agent",
		},
	}
}

func usage(actions map[string]action) {
	fmt.Printf("Usage: %s ACTION\n", os.Args[0])
	fmt.Println("")
	fmt.Println(" Available actions:")
	for command, action := range actions {
		fmt.Printf("  %-15s  %s\n", command, action.description)
	}
	fmt.Println("")
}

func die(err error, exitCode int) {
	log.Error(err.Error())
	log.Flush()
	os.Exit(exitCode)
}