SOLR-17419: Introduce ParallelHttpShardHandler #2681
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The default ShardHandler implementation, HttpShardHandler, sends all shard-requests serially, only parallelizing the waiting and parsing of responses. This works great for collections with few shards, but as the number of shards increases the serialized sending of shard-requests adds a larger and larger overhead to the overall request (especially when auth and PKI are done at request-sending time). This commit fixes this by introducing an alternate ShardHandler implementation, geared towards collections with many shards. This ShardHandler uses an executor to parallelize both request sending and response waiting/parsing. This consumes more CPU, but reduces greatly reduces the latency/QTime observed by users querying many-shard collections. Remaining TODOs: - tests for ParallelHttpShardHandler - precommit/check - Javadocs - ref-guide docs for shard handler abstraction - test randomization for http vs parallel SH
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The default ShardHandler implementation, HttpShardHandler, sends all shard-requests serially, only parallelizing the waiting and parsing of responses. This works great for collections with few shards, but as the number of shards increases the serialized sending of shard-requests adds a larger and larger overhead to the overall request (especially when auth and PKI are done at request-sending time). This commit fixes this by introducing an alternate ShardHandler implementation, geared towards collections with many shards. This ShardHandler uses an executor to parallelize both request sending and response waiting/parsing. This consumes more CPU, but reduces greatly reduces the latency/QTime observed by users querying many-shard collections.
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@gerlowskija I think the Jira item is wrong (SOLR-17419 vs SOLR-17149). [EDIT] Oh actually the CHANGE file is correct. I was confused because this PR got linked to another Jira. Sorry for the noise. |
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https://issues.apache.org/jira/browse/SOLR-17419
Description
The default ShardHandler implementation, HttpShardHandler, sends all shard-requests serially, only parallelizing the waiting and parsing of responses. This works great for collections with few shards, but as the number of shards increases the serialized sending of shard-requests adds a larger and larger overhead. This is especially stark when auth is enabled, and PKI header-generation happens at request-sending time.
Solution
This commit fixes this by introducing an alternate ShardHandler implementation, geared towards collections with many shards. This ShardHandler uses an executor to parallelize both request sending and response waiting/parsing. This consumes more CPU, but reduces greatly reduces the latency/QTime observed by users querying many-shard collections.
See the perf-test results shared on SOLR-17149 for more details!
Tests
Consolidates two related test files into the single
TestShardHandlerFactory, and adds randomization to cover the new ParallelSHF implementation.Checklist
Please review the following and check all that apply:
mainbranch../gradlew check.