Log only the bookie settings that differ from the built-in defaults

[merlimat]

Descriptions of the changes in this PR:

Follow-up to #4768.

Motivation

The Starting Bookie server log line introduced in #4768 was meant to print only the settings overridden from the defaults, but in practice it printed every key ever set on the configuration. It compared each key against an empty ServerConfiguration, and the defaults are not stored in the configuration object: they are hard-coded inside the getters (e.g. getInt(BOOKIE_PORT, 3181)). The lookup therefore returned null for every key, and all of them were reported as overrides.

This is especially noisy when the configuration is shared with other components. Pulsar standalone loads the broker settings into the same properties object, so the bookie printed hundreds of unrelated broker entries at startup.

Changes

• BookieServer.overriddenConfig() now invokes every public get*/is* getter of ServerConfiguration on both the actual configuration and an empty one, through a small subclass that records which property keys each getter reads. When the two results differ, the recorded keys that are explicitly set in the configuration are reported with their raw values.
• Keys that no ServerConfiguration getter reads are not reported. This drops the unrelated entries (e.g. Pulsar broker settings), but also component-owned keys such as dbStorage_*. DbLedgerStorage already logs its cache sizes at startup.
• A getter that throws on the configured value (e.g. an unknown class name) counts as differing, so the offending setting is still shown.
• CompositeConfiguration implements getList/getStringArray by reading its child configurations directly, bypassing getPropertyInternal, so the recording subclass overrides getList as well. Without it, list-valued settings such as ledgerDirectories were missed.
• Added BookieServerOverriddenConfigTest covering values equal to the defaults, changed values, fallback keys, unknown keys and values rejected by a getter.

Example output for a bookie started by BookieClientTest; only the settings the test configuration explicitly changes are listed:

Starting Bookie server {overrides={allocatorPoolingPolicy=UnpooledHeap, allowLoopback=true, bookiePort=13645, diskUsageThreshold=0.999, diskUsageWarnThreshold=0.99, gcWaitTime=100000, journalDirectories=/tmp/.../bookieClient...test, journalFlushWhenQueueEmpty=true, journalFormatVersionToWrite=5, ledgerDirectories=/tmp/.../bookieClient...test, listeningInterface=lo0, tlsEnabledProtocols=[TLSv1.2, TLSv1.1], zkRetryBackoffMaxRetries=0}}

[Copilot]

🟢 Approval recommended

Changes are fully reviewed, tested, and introduce no unresolved blocking issues.

Pull request overview

Updates bookie startup logging to report only explicitly configured settings that differ from built-in defaults.

Changes:

• Compares configuration getters against an empty configuration while recording accessed keys.
• Excludes unrelated and unknown properties.
• Adds tests covering defaults, overrides, fallback keys, unknown keys, and invalid values.

File summaries

File	Description
bookkeeper-server/src/test/java/org/apache/bookkeeper/proto/BookieServerOverriddenConfigTest.java	Tests override detection behavior and edge cases.
bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/BookieServer.java	Implements getter-based override detection and key recording.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Lite

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