Nikita Amelchev created IGNITE-29082:
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Summary: Fix repeated iterations over local partitions in cache
metrics
Key: IGNITE-29082
URL: https://issues.apache.org/jira/browse/IGNITE-29082
Project: Ignite
Issue Type: Improvement
Reporter: Nikita Amelchev
Assignee: Nikita Amelchev
{{CacheMetricsMessage(CacheMetrics)}} reads the 10 entries and partitions
counters of {{CacheMetricsImpl}} through separate getters, and each getter
calls {{getEntriesStat()}}, which iterates over all local partitions 4 times
({{offHeapEntriesCount()}}, {{localSize(null)}}, {{localSizeLong(null)}} and
its own loop): 40 passes per snapshot instead of one. The snapshots are taken
on each metrics update for every cache with statistics enabled, in the
{{tcp-disco-msg-worker}} thread. The {{CacheSize}}, {{HeapEntriesCount}} and
{{OffHeap*EntriesCount}} gauges also make 4 passes each on every read by metric
exporters.
JMH, 50 caches with 1024 partitions: snapshots of all caches 39.8 ms -> 2.45
ms, reading of the cache metric registries 22.4 ms -> 3.9 ms.
Also fix the {{CacheMetrics}} javadoc: {{getSize()}} and {{getKeySize()}} don't
always return 0, {{getCacheSize()}} counts only primary copies.
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