PCBC-1039: Add LoggingMeter implementation

[DemetrisChr]

Motivation

When no external meter is configured, the SDK must default to the LoggingMeter. Now that metrics are created on the PHP-side, we need to implement the LoggingMeter PHP class.

Changes

• Implement the LoggingMeter. It acts as a wrapper over the C++ core's meter.
• Add coreMeterRecordOperationDuration in the C++ bindings.
• When recordValue is called in the LoggingValueRecorder the metric is recorded to the core's logging meter via the C++ core API.

[Copilot]

Pull request overview

Adds a PHP LoggingMeter implementation and wires it to the C++ core meter via new PHP/C++ bindings so the SDK can default to logging-based metrics when no external meter is configured.

Changes:

• Implement LoggingMeter / LoggingValueRecorder in PHP and default to it when no meter is provided.
• Add a new PHP extension binding coreMeterRecordOperationDuration and plumb it through connection_handle.
• Update the embedded C++ client submodule to include the underlying meter support.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/wrapper/core_span_resource.cxx	Minor cleanup of span resource implementation/includes.
src/wrapper/connection_handle.hxx	Exposes a new method to record operation duration into the core meter.
src/wrapper/connection_handle.cxx	Implements PHP-array-to-tag-map conversion and forwards duration to the core meter wrapper.
src/php_couchbase.cxx	Adds the new PHP function + arginfo and registers it.
src/deps/couchbase-cxx-client	Updates C++ core dependency to a revision that supports meter wrapper usage.
Couchbase/LoggingValueRecorder.php	Implements a PHP ValueRecorder that calls into the extension binding.
Couchbase/LoggingMeter.php	Implements the PHP Meter that returns either a logging recorder or a noop recorder.
Couchbase/ClusterOptions.php	Changes meter retrieval to return nullable to enable defaulting to LoggingMeter.
Couchbase/Cluster.php	Defaults to LoggingMeter when user didn’t configure a meter.

Comments suppressed due to low confidence (3)

src/wrapper/connection_handle.hxx:119

• tags is only read/converted and not mutated; consider taking const zval* tags here (and in the .cxx) to better document intent and prevent accidental modification.

  COUCHBASE_API
  void record_core_meter_operation_duration(std::int64_t duration_us, zval* tags);

Couchbase/LoggingMeter.php:45

• With strict_types=1, prefer !== for string comparisons to avoid unintended type coercion ($name !== ...). Also, explicitly declare method visibility (public function close(): void) for consistency and clarity.

        if ($name != ObservabilityConstants::METER_NAME_OPERATION_DURATION) {
            // The logging meter only uses the db.client.operation.duration metric
            return new NoopValueRecorder();
        }

Couchbase/LoggingMeter.php:51

• With strict_types=1, prefer !== for string comparisons to avoid unintended type coercion ($name !== ...). Also, explicitly declare method visibility (public function close(): void) for consistency and clarity.

    function close(): void
    {
    }

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[avsej]

nitpick, but I think second is_null is not necessary, the caller expects null and the signature is ?Meter.

We should either create new LoggingMeter here or just let it to return null.

Suggested change

	if (is_null($options) || is_null($options->meter)) {
	return null;
	if (is_null($options)) {
	return null;

[DemetrisChr]

Yes, that is_null is not necessary. I've updated this.

[avsej]

But maybe it will make sense to emit some warning or stringify them?

I am okay if we will just ignore them, but add API reference note about that to ‎Couchbase/LoggingMeter.php

    public function valueRecorder(string $name, array $tags): ValueRecorder

[DemetrisChr]

The LoggingMeter ignores all attributes except db.operation.name and couchbase.service, both of which are strings. So I think in a way this is an implementation detail. I don't think it would be necessary to mention this in the API docs. But I will add a comment in the bindings to point this out.