tracing: observe modes and other tracing improvements. #5611
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It is not safe to access a global hashtable from multiple threads, even if the operations are read-only (it may be concurrently changed by another thread, which then may result in errors in the racing thread). This means we must always take the mutex, and because OCaml doesn't have a reader-writer mutex, we need to take the exclusive mutex. Eventually we should use a better datastructure here (immutable maps, or lock-free datastructures), but for now fix the datastructure that we currently use to be thread-safe. Signed-off-by: Edwin Török <edwin.torok@cloud.com>
In preparation for OCaml 5, on OCaml 4 they'd be equivalent. Note that adding Atomic doesn't make operations on these values always atomic: that is the responsibility of surrounding code. E.g. Atomic.get + Atomic.set is not atomic, because another domain might've raced and changed the value inbetween (so in that case Atomic.compare_and_set should be used). However for global flags that are read multiple times, but set from a central place this isn't a problem. Signed-off-by: Edwin Török <edwin.torok@cloud.com>
Sets `observe` to `false` until at least one tracer provider is enbaled. If all tracer proveder are become disabled we set it back to `false`. Prior to this `observe` seemed to be always `true` (apart from unit tests). This would cause `with_tracing` to spam the logs with warnings `No provider found...` until at least one tracer provider is enabled. By setting `observe` to `false` as default and updating it depending on the state of the trecing providers, `with_tracing` should now execute no extra operations. Therefore, we avoid spamming the logs unnecesarrly. Signed-off-by: Gabriel Buica <danutgabriel.buica@cloud.com>
Create a new unit test file `test_tracing.ml` for the `tracing` library. Add tests for `create`/`set`/`destroy` tracer providers. Now that we change the library to have `observe` modes based on weather or not we have `tracer providers` enabled, we want to make sure that functions on applied on tracer providers set the correct mode for the library. Signed-off-by: Gabriel Buica <danutgabriel.buica@cloud.com>
Removes code duplication in `storage_mux.ml` by using already the already existing `with_dbg` implementation from `debuginfo` module. This should lower the chances of unintetionally introducing bugs by having to maintain two version of the same functions. e.g. Not using the no op when tracing is disabled and generating unwanted warning messages. Signed-off-by: Gabriel Buica <danutgabriel.buica@cloud.com>
Moves the following: - `create` under `TracerProvider`; - `set` under `TracerProvider`; - `destroy` under `TracerProvider; - `get_tracer_providers` unde `TracerProvider`; - `get_tracer` under `Tracer`. Adds documentation for `TracerProvider` module. It kept being confusing of what `Tracing.set` does unless I was going through the implementation again and again. Therefore, I moved some of the functions so that their functionality becomes (hopefully) more intuitive. Signed-off-by: Gabriel Buica <danutgabriel.buica@cloud.com>
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As a follow-up to commenting out the warning when no tracer providers were enabled here #5583. This is meant to solve the issue of spamming the logs by properly setting the
observemode inside the library.This is based on top of #5601 that addresses missing lock in the library.
Some other improvements:
TracerProvidermodule.