Trigger refresh when shard becomes search active #96321
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martijnvg
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(accidentally pushed 'ready for review' on this PR... too many open browser tabs) |
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…ot register refresh listener.
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Did a quick benchmark run to see what the impact this change has using the k8s query benchmark (it tests performance of queries on search idle shards). Depending on the query a 15% to a 75% reduction in query time has been observed: |
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of adding a new method to IndexShard
martijnvg
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May 31, 2023
server/src/main/java/org/elasticsearch/index/shard/IndexShard.java
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updated the testScheduledRefresh(...) test.
martijnvg
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Jun 1, 2023
| assertFalse(primary.scheduledRefresh()); | ||
| assertEquals(lastSearchAccess, primary.getLastSearcherAccess()); | ||
| // wait until the thread-pool has moved the timestamp otherwise we can't assert on this below | ||
| assertBusy(() -> assertThat(primary.getThreadPool().relativeTimeInMillis(), greaterThan(lastSearchAccess))); | ||
| CountDownLatch latch = new CountDownLatch(10); | ||
| for (int i = 0; i < 10; i++) { |
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Because makeShardSearchActive(...) now triggers a refresh, we can no longer invoke this method many times without a refresh to happen. Before this was possible in this test and then just invoke scheduleRefresh(...) and all the listeners were invoked.
| @@ -3831,14 +3831,17 @@ public void afterRefresh(boolean didRefresh) { | |||
| * @param listener the listener to invoke once the pending refresh location is visible. The listener will be called with | |||
| * <code>true</code> if the listener was registered to wait for a refresh. | |||
| */ | |||
| public final void awaitShardSearchActive(Consumer<Boolean> listener) { | |||
| public final void makeShardSearchActive(Consumer<Boolean> listener) { | |||
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I'd probably call this ensureShardSearchActive, though not too important.
| markSearcherAccessed(); // move the shard into non-search idle | ||
| final Translog.Location location = pendingRefreshLocation.get(); | ||
| if (location != null) { | ||
| addRefreshListener(location, (result) -> { | ||
| pendingRefreshLocation.compareAndSet(location, null); | ||
| listener.accept(true); | ||
| }); | ||
| // TODO: maybe just invoke getEngine().maybeRefresh(...) here? | ||
| // (schedule refresh does a few more things that I don't is necessary here?) | ||
| scheduledRefresh(); |
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I think it will work fine, but one problem with maybeRefresh is that it will not provoke a refresh if there is an ongoing one. But there is no certainty that another ongoing refresh will contain the location. However, such a refresh would have to be an explicit one. I find the risk small and regardless an improvement over current state.
I think we can switch to maybeRefresh instead, though I'd like to check that pendingRefreshLocation is still location then, i.e.:
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| scheduledRefresh(); | |
| if (pendingRefreshLocation.get() == location) { | |
| getEngine().maybeRefresh(); | |
| } |
both to handle racy cases and the case where there are no more refresh listener slots.
elasticsearchmachine
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Hi @martijnvg, I've created a changelog YAML for you. |
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Pinging @elastic/es-analytics-geo (Team:Analytics) |
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Pinging @elastic/es-distributed (Team:Distributed) |
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henningandersen
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Jun 9, 2023
| markSearcherAccessed(); // move the shard into non-search idle | ||
| final Translog.Location location = pendingRefreshLocation.get(); | ||
| if (location != null) { | ||
| addRefreshListener(location, (result) -> { | ||
| pendingRefreshLocation.compareAndSet(location, null); | ||
| listener.accept(true); | ||
| }); | ||
| // trigger a refresh to avoid waiting for scheduledRefresh(...) to be invoked from index level refresh scheduler. | ||
| // (The if statement should avoid doing an additional refresh if scheduled refresh was invoked between getting | ||
| // the current refresh location and adding a refresh listener.) |
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In particular, addRefreshListener might have performed the refresh already in edge cases.
server/src/test/java/org/elasticsearch/index/shard/IndexShardTests.java
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Co-authored-by: Henning Andersen <[email protected]>
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@elasticmachine update branch |
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This change invokes
Engine#maybeRefresh()when a shard is search-idle and becomes search-active inIndexShard#ensureShardSearchActive(...)(used to be namedwaitShardSearchActive(...)).Prior to this change shard level search execution is idle until the schedule refresh has been execute. This includes the time it takes for the refresh to be scheduled (which is a full second). This unnecessarily increases the query time of a search request.
Closes #95544