rac2: introduce cluster setting to reset token counters #133202
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kvoli
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Oct 23, 2024
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Reviewed 3 of 3 files at r1, all commit messages.
Reviewable status:complete! 1 of 0 LGTMs obtained (waiting on @pav-kv and @sumeerbhola)
pkg/kv/kvserver/kvflowcontrol/kvflowcontrol.go line 129 at r1 (raw file):
// such work from unblocking, this setting may be useful. var TokenCounterResetEpoch = settings.RegisterIntSetting( settings.SystemOnly, "kvadmission.flow_controller.token_reset_epoch",
nit: haven't seen more than one arg on a line for a setting declaration before, consider moving the name to a new line.
kvadmission.flow_controller.token_reset_epoch is an escape hatch for cluster operators to reset RACv2 token counters to the full state. The operator should increment this epoch (or change it to a value different than before). This can be used to counteract a token leakage bug, but note that if there is indeed a bug, the leakage may resume, and tokens may again be exhausted. So it is expected that this will be used together with disabling replication admission control by setting kvadmission.flow_control.enabled=false. Note that disabling replication admission control should be sufficient, since it should unblock work that is waiting-for-eval. But in case there is another bug that is preventing such work from unblocking, this setting may be useful. Epic: CRDB-37515 Release note (ops change): The cluster setting kvadmission.flow_controller.token_reset_epoch is an advanced setting that can be used to refill replication admission control v2 tokens. It should only be used after consultation with an expert.
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sumeerbhola
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Oct 23, 2024
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TFTR!
Reviewable status:
pkg/kv/kvserver/kvflowcontrol/kvflowcontrol.go line 129 at r1 (raw file):
Previously, kvoli (Austen) wrote…
nit: haven't seen more than one arg on a line for a setting declaration before, consider moving the name to a new line.
Done
sumeerbhola
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kvadmission.flow_controller.token_reset_epoch is an escape hatch for cluster operators to reset RACv2 token counters to the full state.
The operator should increment this epoch (or change it to a value different than before). This can be used to counteract a token leakage bug, but note that if there is indeed a bug, the leakage may resume, and tokens may again be exhausted. So it is expected that this will be used together with disabling replication admission control by setting kvadmission.flow_control.enabled=false. Note that disabling replication admission control should be sufficient, since it should unblock work that is waiting-for-eval. But in case there is another bug that is preventing such work from unblocking, this setting may be useful.
Epic: CRDB-37515
Release note (ops change): The cluster setting
kvadmission.flow_controller.token_reset_epoch is an advanced setting that can be used to refill replication admission control v2 tokens. It should only be used after consultation with an expert.