go-delve 实战

发表于

Delve 是go语言的一款调试器

调试方式

  • 命令行调试
  • 配合goland等ide进行remote debug

命令行调试

dlv exec

如果你已经有一个编译好的应用，可以直接通过dlv exec执行一个预编译好的二进制程序并开启debug会话

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//path/to/demo
$ go build .
$ dlv exec ./demo

dlv attach

如果程序已经运行，可以直接attach

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dlv attach pid

dlv attach 会导致程序阻塞，千万要注意

dlv core

如果程序出core，使用dlv core命令来检查core dump，帮助调查core发生时的进程运行状态

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dlv core 二进制文件 core文件

A core dump file is a file that contains the memory dump of a running process and its process status

dlv debug

在禁用编译优化条件下编译程序，开启并attach

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dlv debug .
等同于
go build -gcflags="-all=-N -l" .
go exec ./xxxx

输入 help 显示所有可以操作的命令

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Running the program:
    call ------------------------ Resumes process, injecting a function call (EXPERIMENTAL!!!)
    continue (alias: c) --------- Run until breakpoint or program termination.
    next (alias: n) ------------- Step over to next source line.
    restart (alias: r) ---------- Restart process.
    step (alias: s) ------------- Single step through program.
    step-instruction (alias: si)  Single step a single cpu instruction.
    stepout (alias: so) --------- Step out of the current function.
Manipulating breakpoints:
    break (alias: b) ------- Sets a breakpoint.
    breakpoints (alias: bp)  Print out info for active breakpoints.
    clear ------------------ Deletes breakpoint.
    clearall --------------- Deletes multiple breakpoints.
    condition (alias: cond)  Set breakpoint condition.
    on --------------------- Executes a command when a breakpoint is hit.
    trace (alias: t) ------- Set tracepoint. tracepoint是一个不会中断程序的点，在该点上可以执行自定义的命令
Viewing program variables and memory:
    args ----------------- Print function arguments.
    display -------------- Print value of an expression every time the program stops.
    examinemem (alias: x)  Examine memory:
    locals --------------- Print local variables.
    print (alias: p) ----- Evaluate an expression.
    regs ----------------- Print contents of CPU registers.
    set ------------------ Changes the value of a variable.
    vars ----------------- Print package variables.
    whatis --------------- Prints type of an expression.
Listing and switching between threads and goroutines:
    goroutine (alias: gr) -- Shows or changes current goroutine
    goroutines (alias: grs)  List program goroutines.
    thread (alias: tr) ----- Switch to the specified thread.
    threads ---------------- Print out info for every traced thread.
Viewing the call stack and selecting frames:
    deferred --------- Executes command in the context of a deferred call.
    down ------------- Move the current frame down.
    frame ------------ Set the current frame, or execute command on a different frame.
    stack (alias: bt)  Print stack trace.
    up --------------- Move the current frame up.
Other commands:
    config --------------------- Changes configuration parameters.
    disassemble (alias: disass)  Disassembler.
    edit (alias: ed) ----------- Open where you are in $DELVE_EDITOR or $EDITOR
    exit (alias: quit | q) ----- Exit the debugger.
    funcs ---------------------- Print list of functions. *
    help (alias: h) ------------ Prints the help message.
    libraries ------------------ List loaded dynamic libraries
    list (alias: ls | l) ------- Show source code.
    source --------------------- Executes a file containing a list of delve commands
    sources -------------------- Print list of source files.
    types ---------------------- Print list of types

按回车键可以重复上次的操作

远程debug(配合goland使用)

第一步: 在远端机器项目下开启dlv API服务端口

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dlv debug --headless --listen=:8333 --api-version=2 --accept-multiclient

第二步: 本机goland配置远端ip:端口,点击启动程序并开启debug会话

交互模式

delve提供两种交互模式 命令行交互模式 与 headless模式, 其中命令行交互模式是默认模式，这里重点说一下headless模式。

通过--headless开启模式。该模式下delve对外暴露API接口，通过这些接口，其他IDE或编辑器可以与delve进行交互。
举例: dlv debug —headless —log —listen=127.0.0.1:8181 —accept-multiclient

  • —headless表示以headless启动
  • —listen指明要监听的端口
  • —accept-multiclient表明开启多客户端访问支持

你可以通过connect命令直接连接这台headless调试服务器
dlv connect 127.0.0.1:8181

FAQ

线上环境使用须知

无论是debug还是attach都会导致程序的阻塞,对于线上服务谨慎使用(举个例子，在A方法中打断点，来请求暂停至A方法后，整个程序阻塞，对于不会调用A方法的请求同样也会阻塞)

…

删除断点时通常只需要删除某个方法内的断点，如何操作

clearall
例: clearall main.main

观测程序栈帧信息时如何同时显示源码

使用bt -full

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(dlv) bt
0  0x00000000014960ed in main.main
   at ./demo.go:7
1  0x000000000103dd28 in runtime.main
   at /usr/local/Cellar/go/1.14/libexec/src/runtime/proc.go:203
2  0x0000000001070b41 in runtime.goexit
   at /usr/local/Cellar/go/1.14/libexec/src/runtime/asm_amd64.s:1373
(dlv) bt -full
0  0x00000000014960ed in main.main
   at ./demo.go:7
1  0x000000000103dd28 in runtime.main
   at /usr/local/Cellar/go/1.14/libexec/src/runtime/proc.go:203
       g = (*runtime.g)(0xc000000180)
       needUnlock = false
       fn = (unreadable empty OP stack)
2  0x0000000001070b41 in runtime.goexit
   at /usr/local/Cellar/go/1.14/libexec/src/runtime/asm_amd64.s:1373

如何在delve中重新加载源文件

Delve目前不支持重新加载正在运行的编译代码并保存断点及跟踪等状态。
暂时可以用source命令来加速重新编译运行后设置断点、跟踪等的时间
例如debug.txt存在以下内容

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break foo.go:171
on 1 print myVar

回到dlv debug

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$ dlv debug
Type 'help' for list of commands.
(dlv) source debug.txt
Breakpoint 1 set at 0x1b0f5e5 for /path/to/foo.MyFunction() ./foo.go:171
(dlv)

相关资料

delve api
使用 Delve 调试 Go 服务的一次经历
Using the Go Delve Debugger from the command line

注释1. all=-N -l表示关闭编译优化及内联。go build 可以用-gcflags向go编译器传入参数，也就是传给go tool compile的参数，可以通过go tool compile —help查看所有可用参数。 ↩