[ https://issues.apache.org/jira/browse/IGNITE-18209 ]
Ilya Shishkov deleted comment on IGNITE-18209:
----------------------------------------
was (Author: shishkovilja):
Tests of [PR #196|https://github.com/apache/ignite-extensions/pull/196] passed
without timeout:
#
[TC1|https://ci.ignite.apache.org/buildConfiguration/IgniteExtensions_Tests_Cdc/6944155?hideProblemsFromDependencies=false&hideTestsFromDependencies=false&expandBuildChangesSection=true]
#
[TC2|https://ci2.ignite.apache.org/buildConfiguration/IgniteExtensions_Tests_Cdc/6947355?hideProblemsFromDependencies=false&hideTestsFromDependencies=false&expandBuildChangesSection=true&expandBuildTestsSection=true]
> Reduce binary metadata synchronization time for CDC through Kafka
> -----------------------------------------------------------------
>
> Key: IGNITE-18209
> URL: https://issues.apache.org/jira/browse/IGNITE-18209
> Project: Ignite
> Issue Type: Improvement
> Components: extensions
> Reporter: Ilya Shishkov
> Assignee: Ilya Shishkov
> Priority: Minor
> Labels: IEP-59, ise
>
> Currently, there is a possible bottleneck in synchronized method
> {{KafkaToIgniteMetadataUpdater#updateMetadata}} for cases, when all
> {{KafkaToIgniteCdcStreamerApplier}} instances will try to update metadata at
> the same moment.
> Scenario:
> # {{KafkaToIgniteCdcStreamer}} contains multiple
> {{KafkaToIgniteCdcStreamerApplier}} which shares _single_
> {{KafkaToIgniteMetadataUpdater}}.
> # All appliers handle corrsponding partitions consequently.
> # Insertion of unknown type is performed and leads to type and mapping
> registrations on all nodes.
> # {{META_UPDATE_MARKER}} is sent twice to each Kafka partition of event topic
> _from every node_: firstly, in case of type mappings updates, secondly, in
> case of binary types update.
> # When first {{KafkaToIgniteCdcStreamerApplier}} meets {{META_UPDATE_MARKER}}
> it calls {{KafkaToIgniteMetadataUpdater#updateMetadata}} which in turn calls
> {{KafkaConsumer#poll}}, which returns immediately [1] when data is present in
> metadata topic. If there are few binary types and mappings to update, some
> {{KafkaToIgniteCdcStreamerApplier}} thread will consume all entries from
> metadata topic.
> # All other threads of all {{KafkaToIgniteCdcStreamerApplier}} will call
> {{KafkaConsumer#poll}} from empty metadata topic, which will remain blocked
> until new data becomes available or request timeout occurs [1].
> # Because of {{synchronized}} access to
> {{KafkaToIgniteMetadataUpdater#updateMetadata}} all threads of all
> {{KafkaToIgniteCdcStreamerApplier}} will form a sequence of calls. Each call
> will block remaining appliers threads for {{kafkaReqTimeout}} period (if
> metadata topic remains empty).
> # The last call, i.e. last Kafka partition polling in this chain will happen
> at least after {{clusterSize x (topicPartitions x 2 - 1) x kafkaReqTimeout}}
> period. For example for default timeout and 16 Kafka partitions _last
> partition will be consumed after 1.5 minutes_ in case of 1 node cluser.
> # Amount of threads in {{KafkaToIgniteCdcStreamer}} does not make sence.
> # Data updates are blocked for Kafka partitions with unhandled update markers.
> As I understand possible solutions are:
> # Eleminate blocking in {{KafkaToIgniteMetadataUpdater#updateMetadata}}
> caused by calling {{KafkaConsumer#poll}} over empty metadata topic. We can
> try to calculate a lag for topic and poll data only when the lag is present.
> [PR#199|https://github.com/apache/ignite-extensions/pull/199]
> # Hold information about replicated types or get it from {{BinaryContext}}.
> Information about type can be sent with {{META_UPDATE_MARKER}}: see PoC
> [PR#187|https://github.com/apache/ignite-extensions/pull/187].
> # Completely remove metadata topic, and send metadata merged with marker
> directly into event topic: see PoC
> [PR#196|https://github.com/apache/ignite-extensions/pull/196]
> # Any other ways to sync appliers?
> Links:
> #
> https://kafka.apache.org/27/javadoc/org/apache/kafka/clients/consumer/KafkaConsumer.html#poll-java.time.Duration-
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