Shulou(Shulou.com)05/31 Report--

In this issue, Xiaobian will bring you about how to realize nsqlookupd entry file analysis. The article is rich in content and analyzes and narrates from a professional perspective. After reading this article, I hope you can gain something.

The nsqlookupd role in nsq is relatively simple and suitable as an entry point for analyzing nsq

apps/nsqlookupd/nsqlookupd.go

nsqlookupd is a stand-alone program, so put it in the apps directory, relying on the internal package nsqlookupd, util, and the external package:

github.com/BurntSushi/toml # TOML is a profile specification, this package is a parse package for golang

github.com/mreiferson/go-options #Toolkit for injecting command line and profile parameters into struct, only one file

Key Code Parsing

1. Definition of global variables

The command line parameter in go becomes flag, and the flag collection becomes FlagSet. Before parsing the command line parameter, you need to create FlagSet first, define each flag, as shown in the global variable below, and provide important default values.

var (

flagSet = flag.NewFlagSet("nsqlookupd", flag.ExitOnError)

config = flagSet.String("config", "", "path to config file")

///////////////

)

2. Command line parameter analysis

flagSet.Parse(os.Args[1:])

os.Args is all command-line arguments;os.Args[0] is the full pathname of the executable program;

flagSet.Parse parses command-line parameters, overriding flag default definition in flagSet

3. How to exit the nsqlookupd process

Two chan are defined, signalChan receives the exit signal sent by OS, anonymous coroutine receives data, sends a 1 to exitChan, and waits for the main coroutine on exitChan to call nsqlookupd Exit method.

signalChan := make(chan os.Signal, 1)

exitChan := make(chan int)

go func() {

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