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32 lines
1.1 KiB
ReStructuredText
32 lines
1.1 KiB
ReStructuredText
====
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PG
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====
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Concepts
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--------
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*Peering Interval*
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See PG::start_peering_interval.
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See PG::up_acting_affected.
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See PG::RecoveryState::Reset
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A peering interval is a maximal set of contiguous map epochs in which the
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up and acting sets did not change. PG::RecoveryMachine represents a
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transition from one interval to another as passing through
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RecoveryState::Reset. On PG;:RecoveryState::AdvMap PG::up_acting_affected can
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cause the pg to transition to Reset.
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Peering Details and Gotchas
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---------------------------
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For an overview of peering, see Peering.
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* PG::flushed defaults to false and is set to false in
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PG::start_peering_interval. Upon transitioning to PG::RecoveryState::Started
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we send a transaction through the pg op sequencer which, upon complete,
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sends a FlushedEvt which sets flushed to true. The primary cannot go
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active until this happens (See PG::RecoveryState::WaitFlushedPeering).
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Replicas can go active but cannot serve ops (writes or reads).
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This is necessary because we cannot read our ondisk state until unstable
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transactions from the previous interval have cleared.
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