Fix discovery flow for PartitionedHttpClient
#3001
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Motivation: Our load balancers have an ability to cancel and re-subscribe to the `ServiceDiscovery` publisher as an attempt to trigger re-discovery when LB turns into unhealthy state for all addresses. However, for `PartitionedHttpClient` it will result in `DuplicateSubscribeException` because `groupToMany` operator does not support re-subscribes. Modifications: - Apply `multicast` operator with `cancelUpstream=false` flag to allow LB of a single-address client to re-subscribe to the same group publisher; - Disable a retry strategy for `ServiceDiscovery` at single-address client level for partitioned client; - Implement `NoRetriesStrategy.toString()` for better logging; - Reproduce described scenario in `PublisherGroupToManyTest`; Result: Single-address clients under partitioned client won't fail with `DuplicateSubscribeException` if LB decides to re-subscribe to the group's stream.
idelpivnitskiy
commented
Jul 10, 2024
| subscription1New.request(1); | ||
| assertThat(group1SubNew.takeOnNext(), is(3)); | ||
| } else { | ||
| assertThat(group1SubNew.awaitOnError(), is(instanceOf(DuplicateSubscribeException.class))); |
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It was hard to implement a full reproducer for the partitioned client, so I decided to show the problem in PublisherGroupToManyTest
bryce-anderson
approved these changes
Jul 10, 2024
...-http-netty/src/main/java/io/servicetalk/http/netty/DefaultPartitionedHttpClientBuilder.java
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Discussed with Scott offline, we agreed on the approach |
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Motivation:
Our load balancers have an ability to cancel and re-subscribe to the
ServiceDiscoverypublisher as an attempt to trigger re-discovery when LB turns into unhealthy state for all addresses. However, forPartitionedHttpClientit will result inDuplicateSubscribeExceptionbecausegroupToManyoperator does not support re-subscribes.Modifications:
multicastoperator withcancelUpstream=falseflag to allow LB of a single-address client to re-subscribe to the same group publisher;ServiceDiscoveryat single-address client level for partitioned client;NoRetriesStrategy.toString()for better logging;PublisherGroupToManyTest;Result:
Single-address clients under partitioned client won't fail with
DuplicateSubscribeExceptionif LB decides to re-subscribe to the group's stream.