一款好用的 Go 调用链可视化工具

在接手他人代码或调研一些开源项目时，如果能够理清其中的代码调用链路，这将加速我们对实现的理解。

本文介绍一款工具 go-callvis，它能够将 Go 代码的调用关系可视化出来，并提供了可交互式的 web 服务。

go-callvis 使用

依赖

• Go 1.17+
• Graphviz (可选，当工具指定了 -graphviz 时需要)

工具安装

go get -u github.com/ofabry/go-callvis
# or
git clone https://github.com/ofabry/go-callvis.git
cd go-callvis && make install

示例

package main

import (

func main() {
 // Part 1: create a listener
 l, err := net.Listen("tcp", ":8000")
 if err != nil {
  log.Fatalf("Error listener returned: %s", err)
 }
 defer l.Close()

 for {
  // Part 2: accept new connection
  c, err := l.Accept()
  if err != nil {
   log.Fatalf("Error to accept new connection: %s", err)
  }

  // Part 3: create a goroutine that reads and write back data
  go func() {
   log.Printf("TCP session open")
   defer c.Close()

   for {
    d := make([]byte, 1024)

    // Read from TCP buffer
    _, err := c.Read(d)
    if err != nil {
     log.Printf("Error reading TCP session: %s", err)
     break
    }
    log.Printf("reading data from client: %s\n", string(d))

    // write back data to TCP client
    _, err = c.Write(d)
    if err != nil {
     log.Printf("Error writing TCP session: %s", err)
     break
    }
   }
  }()
 }
}

以上是一个简单的TCP服务端代码，通过 go-callvis 工具，可将其代码调用关系梳理出来。

$ go-callvis main.go
2022/08/14 21:23:03 http serving at http://localhost:7878
2022/08/14 21:23:03 converting dot to svg..
2022/08/14 21:23:03 serving file: /var/folders/xk/gn46n46d503dsztbc6_9qb2h0000gn/T/go-callvis_export.svg

go-callvis 默认将代码调用关系存储成 svg 格式的图形，并会在 http://localhost:7878 服务上进行展示。

在浏览器界面上，如果点击 log 单元，将会进入 log 模块的代码调用交互图中。

使用参数

go-callvis 默认以 main 作为链路起点进行分析，因此 package 需要为 main 包。

go-callvis [flags] package

如果不想从 main 方法开始，那么需要使用 -tests 参数，并且在 yourpackage 下创建单元测试，在测试中调用你想要的起始点方法。

go-callvis -tests yourpackage

详细使用说明可通过执行 go-callvis 命令查看

$ go-callvis
go-callvis: visualize call graph of a Go program.

Usage:

  go-callvis [flags] package

  Package should be main package, otherwise -tests flag must be used.

Flags:

  -algo string
     The algorithm used to construct the call graph. Possible values inlcude: "static", "cha", "rta", "pointer" (default "pointer")
  -cacheDir string
     Enable caching to avoid unnecessary re-rendering, you can force rendering by adding 'refresh=true' to the URL query or emptying the cache directory
  -debug
     Enable verbose log.
  -file string
     output filename - omit to use server mode
  -focus string
     Focus specific package using name or import path. (default "main")
  -format string
     output file format [svg | png | jpg | ...] (default "svg")
  -graphviz
     Use Graphviz's dot program to render images.
  -group string
     Grouping functions by packages and/or types [pkg, type] (separated by comma) (default "pkg")
  -http string
     HTTP service address. (default ":7878")
  -ignore string
     Ignore package paths containing given prefixes (separated by comma)
  -include string
     Include package paths with given prefixes (separated by comma)
  -limit string
     Limit package paths to given prefixes (separated by comma)
  -minlen uint
     Minimum edge length (for wider output). (default 2)
  -nodesep float
     Minimum space between two adjacent nodes in the same rank (for taller output). (default 0.35)
  -nodeshape string
     graph node shape (see graphvis manpage for valid values) (default "box")
  -nodestyle string
     graph node style (see graphvis manpage for valid values) (default "filled,rounded")
  -nointer
     Omit calls to unexported functions.
  -nostd
     Omit calls to/from packages in standard library.
  -rankdir string
     Direction of graph layout [LR | RL | TB | BT] (default "LR")
  -skipbrowser
     Skip opening browser.
  -tags build tags
     a list of build tags to consider satisfied during the build. For more information about build tags, see the description of build constraints in the documentation for the go/build package
  -tests
     Include test code.
  -version
     Show version and exit.
[slp@slpdeMacBook-Pro:] ~/repo/MongoShake/cmd/collector $ go-callvis --help
Usage of go-callvis:
  -algo string
     The algorithm used to construct the call graph. Possible values inlcude: "static", "cha", "rta", "pointer" (default "pointer")
  -cacheDir string
     Enable caching to avoid unnecessary re-rendering, you can force rendering by adding 'refresh=true' to the URL query or emptying the cache directory
  -debug
     Enable verbose log.
  -file string
     output filename - omit to use server mode
  -focus string
     Focus specific package using name or import path. (default "main")
  -format string
     output file format [svg | png | jpg | ...] (default "svg")
  -graphviz
     Use Graphviz's dot program to render images.
  -group string
     Grouping functions by packages and/or types [pkg, type] (separated by comma) (default "pkg")
  -http string
     HTTP service address. (default ":7878")
  -ignore string
     Ignore package paths containing given prefixes (separated by comma)
  -include string
     Include package paths with given prefixes (separated by comma)
  -limit string
     Limit package paths to given prefixes (separated by comma)
  -minlen uint
     Minimum edge length (for wider output). (default 2)
  -nodesep float
     Minimum space between two adjacent nodes in the same rank (for taller output). (default 0.35)
  -nodeshape string
     graph node shape (see graphvis manpage for valid values) (default "box")
  -nodestyle string
     graph node style (see graphvis manpage for valid values) (default "filled,rounded")
  -nointer
     Omit calls to unexported functions.
  -nostd
     Omit calls to/from packages in standard library.
  -rankdir string
     Direction of graph layout [LR | RL | TB | BT] (default "LR")
  -skipbrowser
     Skip opening browser.
  -tags build tags
     a list of build tags to consider satisfied during the build. For more information about build tags, see the description of build constraints in the documentation for the go/build package
  -tests
     Include test code.
  -version
     Show version and exit.

每个参数都有对应的说明，无需详细介绍。

有几个比较有用的参数可以注意：nostd用以忽略标准库的调用；style="font-size: 15px;">limit、ignore参数则用以控制过滤或保留调用关系。

总结

go-callvis 工具将 Go 程序函数调用关系通过图形可视化出来，它能帮助开发人员更好地梳理程序脉络。且 go-callvis 的使用非常简单，可以开箱即用。

之后同学们在接触复杂项目时，不妨用 go-callvis 试试看。