refactor: meta-service: compact immutable levels periodically #18757
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Add a background task to compact immutable levels into bigger one. Thus the size of the top writable level won't grow too big before building a snapshot. with config `compact_immutables_ms = 2000`(default enabled: 1000ms), the `snapshot_logs_since_last` is allowed to set a larger value, in order to reduce the rate of building a snapshot. To reduce cache invalidation, a recommended config is: ``` compact_immutables_ms = 1000 snapshot_logs_since_last = 55000 ``` I.e., build a snapshot for each 55,000 applied raft-log entries. `compact_immutables_ms` is enabled by default with interval `1000 ms`, set to `0` to disable it for testing. #### Testing Add a learner node with `databend-meta --join ... --learner` to replciate the data with `compact_immutables_ms` enabeld, and with a larger `snapshot_logs_since_last` value, ensure the `last_seq` matches the leaders.
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Summary
refactor: meta-service: compact immutable levels periodically
Add a background task to compact immutable levels into bigger one.
Thus the size of the top writable level won't grow too big before
building a snapshot.
with config
compact_immutables_ms = 2000(default enabled: 1000ms), thesnapshot_logs_since_lastis allowed to set a larger value, in order toreduce the rate of building a snapshot.
To reduce cache invalidation, a recommended config is:
I.e., build a snapshot for each 55,000 applied raft-log entries.
compact_immutables_msis enabled by default with interval1000 ms,set to
0to disable it for testing.Testing
Add a learner node with
databend-meta --join ... --learnerto replciate the data with
compact_immutables_msenabeld, and with alarger
snapshot_logs_since_lastvalue, ensure thelast_seqmatchesthe leaders.
Tests
Type of change
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