Profiling native extension does not detect libdatadog upgrades/downgrades

This is a bit of a corner case that occurred to me the other day, and I want to track it so that we don't forget about it.

TL;DR: The workaround for this is to reinstall `ddtrace` after changing `libdatadog` versions.

**Current behaviour**:

Because `ddtrace` compiles and links against `libdatadog` at installation time, it becomes "bound" to the `libdatadog` that was available at that time, and does not respect any changes that are made after that.

Consider this `gems.rb` file:

```ruby
source 'https://rubygems.org'

gem 'google-protobuf'
gem 'ddtrace'
gem 'libdatadog', '= 0.7.0.1.0'
```

and a Ruby installation that has no `libdatadog` or `ddtrace` version installed:

```
root@c7311b47f69d:/app/libdatadog-detect-missing# gem uninstall libdatadog ddtrace
Gem 'libdatadog' is not installed
Gem 'ddtrace' is not installed
```

Now let's run `bundle install`:

```
root@c7311b47f69d:/app/libdatadog-detect-missing# bundle install
Fetching gem metadata from https://rubygems.org/...
Resolving dependencies...
Using bundler 2.3.6
Using debase-ruby_core_source 0.10.16
Using ffi 1.15.5
Using msgpack 1.5.6
Using google-protobuf 3.21.5 (x86_64-linux)
Using libddwaf 1.3.0.2.0 (x86_64-linux)
Fetching libdatadog 0.7.0.1.0 (x86_64-linux)
Installing libdatadog 0.7.0.1.0 (x86_64-linux)
Fetching ddtrace 1.3.0
Installing ddtrace 1.3.0 with native extensions
Bundle complete! 3 Gemfile dependencies, 8 gems now installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.
```

At this point, `ddtrace` gets installed and links to `libdatadog` 0.7.0.1.0.

```
root@c7311b47f69d:/app/libdatadog-detect-missing# ldd /usr/local/bundle/gems/ddtrace-1.3.0/ext/ddtrace_profiling_native_extension/ddtrace_profiling_native_extension.2.7.3_x86_64-linux.so
	linux-vdso.so.1 (0x00007fff51b8e000)
	libruby.so.2.7 => /usr/local/lib/libruby.so.2.7 (0x00007f1942476000)
	libddprof_ffi.so => /usr/local/bundle/gems/libdatadog-0.7.0.1.0-x86_64-linux/vendor/libdatadog-0.7.0/x86_64-linux/libdatadog-x86_64-unknown-linux-gnu/lib/pkgconfig/../../lib/libddprof_ffi.so (0x00007f19421c5000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f1942038000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f1941e77000)
	libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f1941c59000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f1941c36000)
	librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f1941c2c000)
	libgmp.so.10 => /usr/lib/x86_64-linux-gnu/libgmp.so.10 (0x00007f1941ba9000)
	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f1941ba4000)
	libcrypt.so.1 => /lib/x86_64-linux-gnu/libcrypt.so.1 (0x00007f1941b6a000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f1942833000)
	libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f1941b50000)
```

But, let's say as a regular Ruby user, you pick a different version of libdatadog and run `bundle install`:

```ruby
source 'https://rubygems.org'

gem 'google-protobuf'
gem 'ddtrace'
gem 'libdatadog', '= 0.7.0.1.1' # this was changed from 0.7.0.1.0 to 0.7.0.1.1
```

```
root@c7311b47f69d:/app/libdatadog-detect-missing# bundle install
Fetching gem metadata from https://rubygems.org/..
Resolving dependencies...
Using bundler 2.3.6
Using msgpack 1.5.6
Using ffi 1.15.5
Using google-protobuf 3.21.5 (x86_64-linux)
Using debase-ruby_core_source 0.10.16
Using libddwaf 1.3.0.2.0 (x86_64-linux)
Fetching libdatadog 0.7.0.1.1 (x86_64-linux) (was 0.7.0.1.0)
Installing libdatadog 0.7.0.1.1 (x86_64-linux) (was 0.7.0.1.0)
Using ddtrace 1.3.0
Bundle complete! 3 Gemfile dependencies, 8 gems now installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.
```

Now asking for the version of libdatadog on the system will state that you're supposedly using 0.7.0.1.1:

```
root@c7311b47f69d:/app/libdatadog-detect-missing# bundle exec ruby -e "require 'libdatadog'; puts Libdatadog::VERSION"
0.7.0.1.1
```

but actually `ddtrace` is not using that version:

```
root@c7311b47f69d:/app/libdatadog-detect-missing# ldd /usr/local/bundle/gems/ddtrace-1.3.0/ext/ddtrace_profiling_native_extension/ddtrace_profiling_native_extension.2.7.3_x86_64-linux.so
	linux-vdso.so.1 (0x00007ffc33deb000)
	libruby.so.2.7 => /usr/local/lib/libruby.so.2.7 (0x00007f034211c000)
	libddprof_ffi.so => /usr/local/bundle/gems/libdatadog-0.7.0.1.0-x86_64-linux/vendor/libdatadog-0.7.0/x86_64-linux/libdatadog-x86_64-unknown-linux-gnu/lib/pkgconfig/../../lib/libddprof_ffi.so (0x00007f0341e6b000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f0341cde000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f0341b1d000)
	libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f03418ff000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f03418dc000)
	librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f03418d2000)
	libgmp.so.10 => /usr/lib/x86_64-linux-gnu/libgmp.so.10 (0x00007f034184f000)
	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f034184a000)
	libcrypt.so.1 => /lib/x86_64-linux-gnu/libcrypt.so.1 (0x00007f0341810000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f03424d9000)
	libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f03417f6000)
```

So you think you've upgraded/downgraded where in fact you haven't.

Further proof happens if you actually remove the old version:

```
root@c7311b47f69d:/app/libdatadog-detect-missing# gem uninstall libdatadog

Select gem to uninstall:
 1. libdatadog-0.7.0.1.0-x86_64-linux
 2. libdatadog-0.7.0.1.1-x86_64-linux
 3. All versions
> 1
Successfully uninstalled libdatadog-0.7.0.1.0-x86_64-linux

root@c7311b47f69d:/app/libdatadog-detect-missing# DD_PROFILING_ENABLED=true bundle exec ddtracerb exec ruby -e "require 'libdatadog'; puts Libdatadog::VERSION"
W, [2022-08-25T09:27:43.103258 #337]  WARN -- ddtrace: [ddtrace] Profiling was requested but is not supported, profiling disabled: There was an error loading the profiling native extension due to 'RuntimeError Failure to load ddtrace_profiling_native_extension.2.7.3_x86_64-linux due to libddprof_ffi.so: cannot open shared object file: No such file or directory' at '/usr/local/bundle/gems/ddtrace-1.3.0/lib/datadog/profiling/load_native_extension.rb:22:in `<top (required)>''
0.7.0.1.1
```

Bundler is still able to resolve a valid version BUT the profiler is broken since it's not actually using that version.

Since this only happens with libdatadog point releases, and we don't do those often, I doubt anyone's been bitten by this, but it's definitely a sharp edge that we should address.

**Expected behaviour**:

Ideally, the profiling native extension should automatically pick up and work with updated versions of libdatadog.

**At minimum**, it should a) detect that there's a mismatched libdatadog version; and b) provide a good error message stating what happened and how to fix it.

**Steps to reproduce**

(See above)


Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Profiling native extension does not detect libdatadog upgrades/downgrades #2242

Metadata

Assignees

Labels

Type

Fields

Projects

Milestone

Relationships

Development

Uh oh!

Profiling native extension does not detect libdatadog upgrades/downgrades #2242

Description

Metadata

Metadata

Assignees

Labels

Type

Fields

Projects

Milestone

Relationships

Development

Issue actions