erlang记录何时进程开始？ [英] Does erlang record when a process started?

问题描述

我正在监控Erlang应用程序，目前正在尝试确定特定PID运行多长时间。绝对时间戳或持续时间对我来说是有效的，但是我没有看到process_info或sys模块中的任何一个数据。有没有办法从Erlang VM中获取这些信息？

I'm working with monitoring an Erlang application and I'm currently trying to determine how long a specific PID has been running. Absolute timestamp or duration would work for me, but I do not see either of those bits of data in process_info or via the sys module. Is there a way to get this information from within the Erlang VM?

我可以从ps命令获取整个VM的开始时间，但是没有任何可见性的单个Erlang进程。

I can get the start time of the overall VM from the ps command, but that doesn't have any visibility of individual Erlang processes.

编辑：

我注意到，当VM崩溃时，erl_crash.dump包含一个开始的时间戳对于每个过程，所以我知道它在那里！

I've noticed that when the VM crashes, the erl_crash.dump contains a started timestamp for each process, so I know it's in there!

推荐答案

tl; dr：是的，但你不能

如果您在 https://github.com/erlang/otp ，您会发现（通过搜索erl_crash），负责编写崩溃转储的文件称为 erts / emulator / beam / break.c 。

If you dig into the OTP source code at https://github.com/erlang/otp, you'll find (by searching for "erl_crash") that the file responsible for writing the crash dump is called erts/emulator/beam/break.c.

搜索该文件为开始（这是一个很好的猜测，这是出现的在崩溃转储）将会让你到第248-249行（基于OTP-18.3.1标签的所有行号），如下所示：

Searching that file for "started" (it's both a good guess, and it's what appears in the crash dump) will get you to lines 248-249 (all line numbers based on the OTP-18.3.1 tag), which look like this:

approx_started = (time_t) p->approx_started;
erts_print(to, to_arg, "Started: %s", ctime(&approx_started));

搜索其余的源代码约_started 显示它在 erts / emulator / beam / erl_process.h 中声明为 struct process 的成员。在 erts / emulator / beam / erl_process.c 中写入。 只有的位置是 在 break.c 中写入崩溃转储。

Searching the rest of the source code for approx_started shows it being declared in erts/emulator/beam/erl_process.h as a member of struct process. It is written in erts/emulator/beam/erl_process.c. The only place it is read is in break.c, when writing the crash dump.

所以，是的，Erlang 记录一个进程开始的（大概）时间。但是，不，你不能得到它。

So, yes, Erlang does record the (approximate) time that a process was started. But, no, you can't get to it.

我不知道为什么是近似。

I have no idea why it's "approximate".

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