RFC: Add helper to easily enable core dumps #2010
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Enabling core dumps on an application can get confusing/fiddly
when the application may be running in a container and thus adding the
needed `ulimit -c ...` configuration may be non-trivial.
Last year while debugging what turned out to be a Ruby VM bug, I
created a helper that allows a Ruby app to turn core dumps on for
itself.
Is this something we're interested in shipping? The advantage here
is that to get a core dump, you'd only need to add
`require 'datadog/enable_core_dumps'` to an application.
Here's a simple example using the Ruby VM crash I referenced
above.
Without helper (no core dump):
```
$ docker-compose run --rm tracer-2.6 /bin/bash --init-file .config
Creating dd-trace-rb_tracer-2.6_run ... done
root# bundle exec ruby -e "Process.detach(fork { sleep }).instance_variable_get(:@hello)"
-e:1: [BUG] Segmentation fault at 0x0000000000000008
ruby 2.6.7p197 (2021-04-05 revision 67941) [x86_64-linux]
...
Aborted
```
With helper:
```
root# bundle exec ruby -e "require 'datadog/enable_core_dumps'; Process.detach(fork { sleep }).instance_variable_get(:@hello)"
[DDTRACE] Enabled core dumps. Maximum size: 18446744073709551615 Output pattern: 'core'
-e:1: [BUG] Segmentation fault at 0x0000000000000008
ruby 2.6.7p197 (2021-04-05 revision 67941) [x86_64-linux]
...
Aborted (core dumped)
```
lloeki
requested changes
May 10, 2022
lib/datadog/enable_core_dumps.rb
Outdated
| @@ -0,0 +1,40 @@ | |||
| # This helper is used to enable core dumps for the current Ruby app. This is useful when debugging native-level | |||
There was a problem hiding this comment.
This has a significant side effect, so it needs # typed: ignore otherwise Sorbet will evaluate the file!
marcotc
approved these changes
May 10, 2022
|
I've also added specs for it; yesterday I was a bit hesitant because this may be thrown away, but if we're keeping it, specs it gets! |
lloeki
approved these changes
May 13, 2022
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Enabling core dumps on an application can get confusing/fiddly when the application may be running in a container and thus adding the needed
ulimit -c ...configuration may be non-trivial.Last year while debugging what turned out to be a Ruby VM bug, I created a helper that allows a Ruby app to turn core dumps on for itself.
Is this something we're interested in shipping? The advantage here is that to get a core dump, you'd only need to add
require 'datadog/kit/enable_core_dumps'to an application.Here's a simple example using the Ruby VM crash I referenced above.
Without helper (no core dump):
With helper: