系统技术非业余研究

erlang虚拟机挂掉的时候会产生个crashdump, 尽可能多的保存当时的现场，相关的使用和配置之前我写了不少的 博文 来介绍。
但是实际使用中的时候，每次crash的时候这个现场文件都叫erl_crash.dump，会把前一次的覆盖掉，不利于生产环境定位问题。

当然我们可以透过环境变量来配置：

ERL_CRASH_DUMP
If the emulator needs to write a crash dump, the value of this variable will be the file name of the crash dump file. If the variable is not set, the name of the crash dump file will be erl_crash.dump in the current directory

或者我们还有heroku_crashdumps项目可以帮我们更省力，项目参见这里，核心代码就这几行:

  case dumpdir() of
        undefined -> ok;
        Dir ->
            File = string:join([os:getenv("INSTANCE_NAME"),
                                "boot",
                                datetime(now)], "_"),
            DumpFile = filename:join(Dir, File),
            error_logger:info_msg("at=setup_crashdumps dumpfile=~p", [DumpFile]),
            os:putenv("ERL_CRASH_DUMP", DumpFile)
    end.

它的价值在于以application方式来进行的，有二个好处：
1. 容易打包。因为包括rebar在内的打包工具都是以app为单位的。
2. 使用起来更简单。 crashdump自动会把日期时间加上去。

具体使用够简单，参见项目说明，我就不罗嗦了，我来演示下效果：

$ git clone https://github.com/heroku/heroku_crashdumps.git
Initialized empty Git repository in /home/chuba/heroku_crashdumps/heroku_crashdumps/.git/
remote: Counting objects: 11, done.
remote: Compressing objects: 100% (8/8), done.
cremote: Total 11 (delta 2), reused 11 (delta 2)
Unpacking objects: 100% (11/11), done.
$ cd heroku_crashdumps/
$ ./rebar compile
==> heroku_crashdumps (compile)
Compiled src/heroku_crashdumps_app.erl

$ ERL_CRASH_DUMP="." INSTANCE_NAME="erl_crash.dump"  erl -pa ebin
Erlang R16B02 (erts-5.10.3) [source] [64-bit] [smp:16:16] [async-threads:10] [hipe] [kernel-poll:false]

Eshell V5.10.3  (abort with ^G)
1> heroku_crashdumps_app:start().

=INFO REPORT==== 22-Dec-2013::16:12:41 ===
at=setup_crashdumps dumpfile="./erl_crash.dump_boot_2013-12-22T08:12:41+00:00"true
2> 
BREAK: (a)bort (c)ontinue (p)roc info (i)nfo (l)oaded
       (v)ersion (k)ill (D)b-tables (d)istribution
A

Crash dump was written to: ./erl_crash.dump_boot_2013-12-22T08:12:41+00:00
Crash dump requested by userAborted
$ ls ./erl_crash.dump_boot_2013-12-22T08:12:41+00:00
./erl_crash.dump_boot_2013-12-22T08:12:41+00:00

小结：偷懒是美德！

祝玩得开心！