Instruments

• db.client.operation.duration (Histogram, s) — semconv Stable

Attributes: db.system.name, db.namespace, server.address, server.port,
db.operation.name (leading SQL keyword), db.collection.name (primary table when
unambiguous), error.type on failure.

Config

open_telemetry:
    metrics:
        enabled: true
        doctrine:
            enabled: true

Behaviour

• Stacks as a regular DBAL middleware. MeteredDriver resolves the per-connection context
  (db.system.name from the driver string, db.namespace from dbname, server address/port from
  connection params) once at connect time and binds it to a single DbMetricRecorder shared by
  the connection wrapper and its prepared statements.
• Records duration for Connection::query(), Connection::exec(), prepared
  Statement::execute(), and the transaction control methods
  (beginTransaction/commit/rollBack).
• SQL text is never recorded. Only the leading keyword and the table name when extractable,
  both reused from the existing SqlOperationExtractor to keep cardinality bounded.

Notes

• Review patterns from Feat/metrics foundation #27 applied up-front: error.type uses FQCN with parent-class
  fallback, histogram declares second-based buckets, every recording path is wrapped in a
  swallowing try/catch so a broken meter provider cannot mask the original DBAL exception.
• DBAL 3 statement signature differs (execute($params = null) returning bool); the
  MeteredConnectionDbal3/MeteredStatementDbal3 pair mirrors the existing
  TraceableConnectionDbal3/TraceableStatementDbal3 split and is excluded from PHPStan analysis
  the same way (validated via the DBAL 3 CI matrix instead).
• Same Util\ErrorTypeResolver as the parallel http-client and http-server PRs; whichever
  merges first lands it on master, the others rebase clean.
• 22 new tests covering recorder, connection, statement, driver, attributes, transaction
  aggregation, anonymous-class fallback, bucket boundaries, broken-recorder swallow.