Hi all, I'd like to open discussion on BP-69: Adopt slog for structured logging.
* Proposal (PR): https://github.com/apache/bookkeeper/pull/4751 * Tracking issue: https://github.com/apache/bookkeeper/issues/4750 BookKeeper currently uses SLF4J with unstructured {} format strings. Every log site restates identity context inline (ledgerId, bookieId, entryId, ...), there's no consistent attribute naming, and hot paths are sprinkled with isDebugEnabled() guards to avoid String.format/toString cost. This is painful to query in modern log backends (Loki, Elastic, Splunk, CloudWatch, etc.) and makes cross-project correlation with Pulsar essentially impossible. The proposal is to adopt the slog library (https://github.com/merlimat/slog) for structured logging across the codebase, mirroring the decision Apache Pulsar made in PIP-467 (https://github.com/apache/pulsar/blob/master/pip/pip-467.md), whose migration is complete. SLF4J stays on the classpath as the rendering backend; no log-config change is required to upgrade. Migration is phased one module per commit, each independently mergeable. Two additional items in scope: 1. Cross-boundary logger context through the client API. Adds withLoggerContext(Map<String, Object>) to CreateBuilder / OpenBuilder / DeleteBuilder. When set, the caller's attributes (e.g. Pulsar's managedLedger=<topic>) are bound to the resulting WriteHandle/ReadHandle's logger, so every BookKeeper client log line on behalf of that handle automatically carries them — without BookKeeper knowing about Pulsar concepts. The parameter is a plain Map, so clients are not forced to take a slog dependency. 2. Retire bookkeeper-slogger. The existing module is @Unstable, used by only 5 files in bookkeeper-server, and missing features (no debug/trace levels, no zero-overhead disabled levels, no composable context). Nothing else inside or outside the project depends on it. Not in scope: wire protocol, binary formats, metadata formats, metrics, and CLI are untouched. SLF4J is not being deprecated. Looking forward to feedback — particularly on the client API shape (withLoggerContext on the three builders) and on retiring bookkeeper-slogger. Thanks, Matteo -- Matteo Merli <[email protected]>
