nsq源码阅读 nsqd源码一 apps/nsqd/nsqd.go

之前已经将NSQ的nsqlookupd模块源码大致的看了一遍了，现在开始阅读nsqd模块的源码。作为NSQ的核心模块，代码量也相对多点。废话不多说，开始读代码。

首先从mai()方法开始：

func main() {
	prg := &program{}
	if err := svc.Run(prg, syscall.SIGINT, syscall.SIGTERM); err != nil {
		log.Fatal(err)
	}
}

main()方法很简单，就几行代码，但理解起来却不简单。大量的操作都封装在了svc.Run()里了，其主要作用是运行程序并阻塞，直到接受到SIGINT或SIGTERM信号，关闭程序。

关于系统调用和信号处理，可以看自己看看相关的介绍，就不再赘述了。

文采不行，写不出什么长篇大论的，还是老样子，直接贴代码吧：

package main

import (
	"crypto/tls"
	"flag"
	"fmt"
	"log"
	"math/rand"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"syscall"
	"time"

	"github.com/BurntSushi/toml"
	"github.com/judwhite/go-svc/svc"
	"github.com/mreiferson/options"
	"github.com/nsqio/nsq/internal/app"
	"github.com/nsqio/nsq/internal/version"
	"github.com/nsqio/nsq/nsqd"
)

type tlsRequiredOption int

func (t *tlsRequiredOption) Set(s string) error {
	s = strings.ToLower(s)
	if s == "tcp-https" {
		*t = nsqd.TLSRequiredExceptHTTP
		return nil
	}
	required, err := strconv.ParseBool(s)
	if required {
		*t = nsqd.TLSRequired
	} else {
		*t = nsqd.TLSNotRequired
	}
	return err
}

func (t *tlsRequiredOption) Get() interface{} { return int(*t) }

func (t *tlsRequiredOption) String() string {
	return strconv.FormatInt(int64(*t), 10)
}

func (t *tlsRequiredOption) IsBoolFlag() bool { return true }

type tlsMinVersionOption uint16

func (t *tlsMinVersionOption) Set(s string) error {
	s = strings.ToLower(s)
	switch s {
	case "":
		return nil
	case "ssl3.0":
		*t = tls.VersionSSL30
	case "tls1.0":
		*t = tls.VersionTLS10
	case "tls1.1":
		*t = tls.VersionTLS11
	case "tls1.2":
		*t = tls.VersionTLS12
	default:
		return fmt.Errorf("unknown tlsVersionOption %q", s)
	}
	return nil
}

func (t *tlsMinVersionOption) Get() interface{} { return uint16(*t) }

func (t *tlsMinVersionOption) String() string {
	return strconv.FormatInt(int64(*t), 10)
}

//通过命令行参数，修改默认配置
func nsqdFlagSet(opts *nsqd.Options) *flag.FlagSet {
	flagSet := flag.NewFlagSet("nsqd", flag.ExitOnError)

	// basic options
	flagSet.Bool("version", false, "print version string")
	flagSet.Bool("verbose", false, "enable verbose logging")
	flagSet.String("config", "", "path to config file")
	flagSet.String("log-prefix", "[nsqd] ", "log message prefix")
	flagSet.Int64("node-id", opts.ID, "unique part for message IDs, (int) in range [0,1024) (default is hash of hostname)")
	flagSet.Bool("worker-id", false, "do NOT use this, use --node-id")

	flagSet.String("https-address", opts.HTTPSAddress, "<addr>:<port> to listen on for HTTPS clients")
	flagSet.String("http-address", opts.HTTPAddress, "<addr>:<port> to listen on for HTTP clients")
	flagSet.String("tcp-address", opts.TCPAddress, "<addr>:<port> to listen on for TCP clients")
	authHTTPAddresses := app.StringArray{}
	flagSet.Var(&authHTTPAddresses, "auth-http-address", "<addr>:<port> to query auth server (may be given multiple times)")
	flagSet.String("broadcast-address", opts.BroadcastAddress, "address that will be registered with lookupd (defaults to the OS hostname)")
	lookupdTCPAddrs := app.StringArray{}
	flagSet.Var(&lookupdTCPAddrs, "lookupd-tcp-address", "lookupd TCP address (may be given multiple times)")
	flagSet.Duration("http-client-connect-timeout", opts.HTTPClientConnectTimeout, "timeout for HTTP connect")
	flagSet.Duration("http-client-request-timeout", opts.HTTPClientRequestTimeout, "timeout for HTTP request")

	// diskqueue options
	flagSet.String("data-path", opts.DataPath, "path to store disk-backed messages")
	flagSet.Int64("mem-queue-size", opts.MemQueueSize, "number of messages to keep in memory (per topic/channel)")
	flagSet.Int64("max-bytes-per-file", opts.MaxBytesPerFile, "number of bytes per diskqueue file before rolling")
	flagSet.Int64("sync-every", opts.SyncEvery, "number of messages per diskqueue fsync")
	flagSet.Duration("sync-timeout", opts.SyncTimeout, "duration of time per diskqueue fsync")

	// msg and command options
	flagSet.String("msg-timeout", opts.MsgTimeout.String(), "duration to wait before auto-requeing a message")
	flagSet.Duration("max-msg-timeout", opts.MaxMsgTimeout, "maximum duration before a message will timeout")
	flagSet.Int64("max-msg-size", opts.MaxMsgSize, "maximum size of a single message in bytes")
	flagSet.Duration("max-req-timeout", opts.MaxReqTimeout, "maximum requeuing timeout for a message")
	flagSet.Int64("max-body-size", opts.MaxBodySize, "maximum size of a single command body")

	// client overridable configuration options
	flagSet.Duration("max-heartbeat-interval", opts.MaxHeartbeatInterval, "maximum client configurable duration of time between client heartbeats")
	flagSet.Int64("max-rdy-count", opts.MaxRdyCount, "maximum RDY count for a client")
	flagSet.Int64("max-output-buffer-size", opts.MaxOutputBufferSize, "maximum client configurable size (in bytes) for a client output buffer")
	flagSet.Duration("max-output-buffer-timeout", opts.MaxOutputBufferTimeout, "maximum client configurable duration of time between flushing to a client")

	// statsd integration options
	flagSet.String("statsd-address", opts.StatsdAddress, "UDP <addr>:<port> of a statsd daemon for pushing stats")
	flagSet.String("statsd-interval", opts.StatsdInterval.String(), "duration between pushing to statsd")
	flagSet.Bool("statsd-mem-stats", opts.StatsdMemStats, "toggle sending memory and GC stats to statsd")
	flagSet.String("statsd-prefix", opts.StatsdPrefix, "prefix used for keys sent to statsd (%s for host replacement)")

	// End to end percentile flags
	e2eProcessingLatencyPercentiles := app.FloatArray{}
	flagSet.Var(&e2eProcessingLatencyPercentiles, "e2e-processing-latency-percentile", "message processing time percentiles (as float (0, 1.0]) to track (can be specified multiple times or comma separated '1.0,0.99,0.95', default none)")
	flagSet.Duration("e2e-processing-latency-window-time", opts.E2EProcessingLatencyWindowTime, "calculate end to end latency quantiles for this duration of time (ie: 60s would only show quantile calculations from the past 60 seconds)")

	// TLS config
	flagSet.String("tls-cert", opts.TLSCert, "path to certificate file")
	flagSet.String("tls-key", opts.TLSKey, "path to key file")
	flagSet.String("tls-client-auth-policy", opts.TLSClientAuthPolicy, "client certificate auth policy ('require' or 'require-verify')")
	flagSet.String("tls-root-ca-file", opts.TLSRootCAFile, "path to certificate authority file")
	tlsRequired := tlsRequiredOption(opts.TLSRequired)
	tlsMinVersion := tlsMinVersionOption(opts.TLSMinVersion)
	flagSet.Var(&tlsRequired, "tls-required", "require TLS for client connections (true, false, tcp-https)")
	flagSet.Var(&tlsMinVersion, "tls-min-version", "minimum SSL/TLS version acceptable ('ssl3.0', 'tls1.0', 'tls1.1', or 'tls1.2')")

	// compression
	flagSet.Bool("deflate", opts.DeflateEnabled, "enable deflate feature negotiation (client compression)")
	flagSet.Int("max-deflate-level", opts.MaxDeflateLevel, "max deflate compression level a client can negotiate (> values == > nsqd CPU usage)")
	flagSet.Bool("snappy", opts.SnappyEnabled, "enable snappy feature negotiation (client compression)")

	return flagSet
}

type config map[string]interface{}

// Validate settings in the config file, and fatal on errors
func (cfg config) Validate() {
	// special validation/translation
	if v, exists := cfg["tls_required"]; exists {
		var t tlsRequiredOption
		err := t.Set(fmt.Sprintf("%v", v))
		if err == nil {
			cfg["tls_required"] = t.String()
		} else {
			log.Fatalf("ERROR: failed parsing tls required %v", v)
		}
	}
	if v, exists := cfg["tls_min_version"]; exists {
		var t tlsMinVersionOption
		err := t.Set(fmt.Sprintf("%v", v))
		if err == nil {
			newVal := fmt.Sprintf("%v", t.Get())
			if newVal != "0" {
				cfg["tls_min_version"] = newVal
			} else {
				delete(cfg, "tls_min_version")
			}
		} else {
			log.Fatalf("ERROR: failed parsing tls min version %v", v)
		}
	}
}

type program struct {
	nsqd *nsqd.NSQD
}

func main() {
	prg := &program{}
	//系统调用，向系统发送SIGINT、SIGTERM信号
	//SIGINT：用户发送INTR字符(Ctrl+C)触发
	//SIGTERM：结束程序(可以被捕获、阻塞或忽略)
	//程序将在这里阻塞，除非Ctrl+C或程序结束
	//查看svc.Run()方法源码，可知通过调用prg参数的Init()方法初始化，Start()方法开始程序，Stop()方法结束程序
	if err := svc.Run(prg, syscall.SIGINT, syscall.SIGTERM); err != nil {
		log.Fatal(err)
	}
}

func (p *program) Init(env svc.Environment) error {
	if env.IsWindowsService() {
		dir := filepath.Dir(os.Args[0])
		return os.Chdir(dir)
	}
	return nil
}

func (p *program) Start() error {
	//加载nsqd/options.go中的默认配置
	opts := nsqd.NewOptions()

	//修改默认配置
	flagSet := nsqdFlagSet(opts)
	flagSet.Parse(os.Args[1:])

	//TODO 随机数？？没明白这里，标记一下
	rand.Seed(time.Now().UTC().UnixNano())

	if flagSet.Lookup("version").Value.(flag.Getter).Get().(bool) {
		fmt.Println(version.String("nsqd"))
		os.Exit(0)
	}

	//解析配置文件
	var cfg config
	configFile := flagSet.Lookup("config").Value.String()
	if configFile != "" {
		_, err := toml.DecodeFile(configFile, &cfg)
		if err != nil {
			log.Fatalf("ERROR: failed to load config file %s - %s", configFile, err.Error())
		}
	}
	//验证配置是否合法，主要关于TLS的验证
	cfg.Validate()

	options.Resolve(opts, flagSet, cfg)
	//这里和上面导入的包命名一样，防止混淆，修改这里的变量名称
	//根据配置信息，新建nsqd实例
	nsqdInstance := nsqd.New(opts)

	//加载元数据
	err := nsqdInstance.LoadMetadata()
	if err != nil {
		log.Fatalf("ERROR: %s", err.Error())
	}
	//将元数据保存到本地
	err = nsqdInstance.PersistMetadata()
	if err != nil {
		log.Fatalf("ERROR: failed to persist metadata - %s", err.Error())
	}
	//nsqd的Main()方法
	nsqdInstance.Main()

	p.nsqd = nsqdInstance
	return nil
}

//终止程序
func (p *program) Stop() error {
	if p.nsqd != nil {
		p.nsqd.Exit()
	}
	return nil
}

关于TLS的一些验证，先忽略。这里有一篇 关于SSL/TLS的文章，大家可以去看看。