Slow document GC starves moving buckets to ideal nodes #4165
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vekterli
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Nov 16, 2017
Having GC be higher priority than move-only merges meant that slow GC could effectively inhibit node retirement. Furthermore, move-only merges are finite while GC happens indefinitely, so it makes sense to give merging higher priority overall. This fixes #4165
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Maintenance operations are generated with a fixed internal priority depending on their assumed importance. An operation's priority affects how many of its type may be pending at any given point in time. Higher priority operations, if present, effectively pre-empt lower priority operations.
Currently, bucket GC has priority
LOW, while a move-only merge has priorityVERY_LOW. This means that if a cluster is falling behind on its GC duties (usually due to a too short configured GC period or an expensive GC expression), move-only merges will end up being entirely preempted. This can cause stalls in moving documents away from retired nodes and/or onto a newly introduced node.I'm tempted to either flip the two priorities, or bring GC down to
VERY_LOW.The text was updated successfully, but these errors were encountered: