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Profiler incompatible with Ruby 3.3-head #3053

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ivoanjo opened this issue Aug 17, 2023 · 0 comments · Fixed by #3167
Closed

Profiler incompatible with Ruby 3.3-head #3053

ivoanjo opened this issue Aug 17, 2023 · 0 comments · Fixed by #3167
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bug Involves a bug profiling Involves Datadog profiling

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ivoanjo commented Aug 17, 2023

Current behaviour

Profiler is incompatible with Ruby 3.3-head. It's not possible to build or run the profiler on the latest development Ruby versions.

Expected behaviour

Profiler should work on Ruby 3.3-head.

I'm opening this issue for wider community visibility that we're aware of this issue.

I spotted two problems:

  1. Current ruby-head is incompatible with the 3.3.0-preview1 headers in the debase-ruby_core_source gem. This is an easy fix, once preview2/rc1 gets released, the updated headers can be added to the gem.

  2. Even with the correct headers, the profiler is failing to load with

RuntimeError Failure to load ddtrace_profiling_native_extension.3.3.0_x86_64-linux due to ddtrace_profiling_native_extension.3.3.0_x86_64-linux.so: undefined symbol: ruby_current_ec' at 'lib/datadog/profiling/load_native_extension.rb:26

... this one seems a bit more harder to fix.

I plan to open a PR so the profiler is disabled on Ruby 3.3 until we can address these issues.
@ivoanjo ivoanjo added bug Involves a bug community Was opened by a community member labels Aug 17, 2023
ivoanjo added a commit that referenced this issue Aug 17, 2023
@ivoanjo
Disable profiler on Ruby 3.3 due to incompatibility
9e812f0 
**What does this PR do?**:

In #3053 I reported the discovery that the profiler is currently not
working on Ruby 3.3-head (reported by a customer that tests with
head in CI).

A full fix for #3053 seems like it may take a while, so until it's
available, let's gracefully disable the profiler in Ruby 3.3, so that
instead of a compilation failure, customers just get a nice message
saying we don't support 3.3 right now.

**Motivation**:

Improve experience for current customers testing with 3.3-head and
future customers trying to profile 3.3.

**Additional Notes**:

Customers will be shown the following message when trying to profile
on Ruby 3.3:

```
WARN -- ddtrace: [ddtrace] Profiling was requested but is not supported,
profiling disabled: Your ddtrace installation is missing support for the
Continuous Profiler because the profiler in the current version of
ddtrace does not yet support Ruby version 3.3. (See
#3053 for details). Try
upgrading to the latest ddtrace, as this issue may have been fixed by
now. For help solving this issue, please contact Datadog support at
<https://docs.datadoghq.com/help/>. You can also check out the
Continuous Profiler troubleshooting page at
<https://dtdg.co/ruby-profiler-troubleshooting>.
```

**How to test the change?**:

Try to profile ruby-3.3 (any version) and confirm the profiler
disables itself gracefully.
@ivoanjo ivoanjo mentioned this issue Aug 17, 2023
Merged
@ivoanjo ivoanjo self-assigned this Aug 18, 2023
@ivoanjo ivoanjo added profiling Involves Datadog profiling and removed community Was opened by a community member labels Aug 18, 2023
ivoanjo added a commit that referenced this issue Sep 27, 2023
@ivoanjo
Bump debase-ruby_core_source dependency to 3.2.2
650e21d 
**What does this PR do?**:

This PR bumps our dependency on `debase-ruby_core_source` to version
3.2.2. This version is needed to support profiling Ruby 3.3.0-preview2.

**Motivation**:

Support profiling on Ruby 3.3.0-preview2.

**Additional Notes**:

I've updated the appraisal gemfiles as well.

The profiler is currently disabled on Ruby 3.3 (see #3053 for
details). This PR is the first step towards re-enabling it again.

**How to test the change?**:

Validate that CI is green.
@ivoanjo ivoanjo mentioned this issue Sep 27, 2023
Merged
2 tasks
ivoanjo added a commit that referenced this issue Sep 28, 2023
@ivoanjo
[PROF-8074] Restore support for Ruby 3.3
f052704 
**What does this PR do?**

Back in #3053, a customer reported that profiling was not working
on ruby-head (for Ruby 3.3).

At the time, I tracked it down to two issues:
1. A bunch of headers had changed, and thus we needed a new
   release of `debase-ruby_core_source` to include them
2. We were getting errors when loading the profiler due to the
   `ruby_current_ec` VM symbol no longer being available.

At the time, I chose to disable profiling on Ruby 3.3 (#3054) until
we could tackle these two items.

Item 1. was fixed in #3163, that pulls in a new release of
`debase-ruby_core_source` that includes the 3.3-preview2 headers.

This PR fixes item 2. and re-enables profiling on Ruby 3.3
(and thus reverts #3054).

**Motivation:**

Make sure we're in good shape for the Ruby 3.3 final release in
December.

**Additional Notes:**

We didn't use the magic `ruby_current_ec` VM symbol directly.
Instead, we were using `GET_RACTOR()` and `GET_EC()` which call
a few methods that are defined as `inline` in `vm_core.h`.

Those methods all relied on `ruby_current_ec`, and thus hiding
that symbol made them break.

As an alternative, we can get to the same objects by starting
with the current thread, and navigating the object graph a bit.

The `rb_thread_current()` also relies on `ruby_current_ec` but
crucially **is not inline** and is actually a public API of the VM,
so that one kept working.

I hesitated on if we should use `rb_thread_current()` on all
Rubies with Ractors, or if we should keep the fast path for
3.0 to 3.2. I ended up deciding to keep the fast path since
it was quite easy to do, but in the future we could instead
choose to simplify this whole thing.

P.s.: This is one of those PRs where a lot of work went into
a handful of unimpressive lines of code 😅 .

**How to test the change?**

Validate that CI is passing on Ruby 3.3!

Fixes #3053
@ivoanjo ivoanjo mentioned this issue Sep 28, 2023
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[PROF-8074] Restore support for Ruby 3.3 DataDog/dd-trace-rb
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