[I] [Bug][client] V5 ConnectionPolicy.connectionBackoff is ignored [pulsar]

["lhotari (via GitHub)" <gi...@apache.org>]

lhotari opened a new issue, #26788:
URL: https://github.com/apache/pulsar/issues/26788

   ### Search before reporting
   
   - [x] I searched in the [issues](https://github.com/apache/pulsar/issues) and found nothing similar.
   
   ### Read release policy
   
   - [x] I understand that [unsupported versions](https://pulsar.apache.org/contribute/release-policy/#supported-versions) don't get bug fixes. I will attempt to reproduce the issue on a supported version of Pulsar client and Pulsar broker.
   
   ### User environment
   
   - Pulsar `master` (5.0.0 development), Java V5 client (`pulsar-client-v5`)
   
   ### Issue Description
   
   `ConnectionPolicy.Builder.connectionBackoff(BackoffPolicy)` in the V5 client API is documented as the "Backoff strategy for broker reconnection attempts", but the value is silently ignored. `PulsarClientBuilderV5.connectionPolicy(...)` copies every other `ConnectionPolicy` field into the underlying v4 `ClientConfigurationData` but skips the backoff:
   
   ```java
   // PulsarClientBuilderV5.connectionPolicy(...)
           // BackoffPolicy adaptation will be implemented when the v4 client exposes
           // a public way to override the reconnection backoff.
           return this;
   ```
   
   As a result, producers, consumers and the other connection handlers always reconnect with the v4 defaults (initial 100 ms, max 60 s), whatever the application configures.
   
   The reason given in the comment no longer holds. The V5 builder writes directly to `ClientConfigurationData`, which already has `initialBackoffIntervalNanos` and `maxBackoffIntervalNanos`, and the v4 `ClientBuilder` exposes them publicly as `startingBackoffInterval(...)` and `maxBackoffInterval(...)`. `ProducerImpl`, `ConsumerImpl` (via `PulsarClientImpl`) and `TransactionMetaStoreHandler` build their `Backoff` from those two fields.
   
   Expected: `BackoffPolicy.initialInterval()` and `maxInterval()` are applied to the reconnection backoff.
   
   `BackoffPolicy` also has `multiplier()` and `jitterPercent()`, which have no counterpart in `ClientConfigurationData` (the v4 `Backoff` doubles on each attempt and takes its jitter from the `Backoff` builder). Either those need to be carried through to where the `Backoff` instances are built, or it should be documented or validated that only the defaults are supported for now, rather than being silently dropped.
   
   ### Error messages
   
   ```text
   None; the setting is silently ignored.
   ```
   
   ### Reproducing the issue
   
   1. Build a V5 client with a non-default reconnection backoff:
      ```java
      PulsarClient client = PulsarClient.builder()
              .serviceUrl(serviceUrl)
              .connectionPolicy(ConnectionPolicy.builder()
                      .connectionBackoff(BackoffPolicy.exponential(Duration.ofSeconds(5), Duration.ofSeconds(30)))
                      .build())
              .build();
      ```
   2. Create a consumer and have the broker disconnect it (for example by unloading the topic).
   3. `ConnectionHandler.connectionClosed` schedules the reconnect from `backoff.next()`, and that `Backoff` was built from the unchanged `ClientConfigurationData` defaults. So the client logs `Closed connection - Will try again` with a `delaySec` of about 0.1 (the 100 ms default), not 5.
   
   ### Additional information
   
   Found while fixing a flaky test, `V5CumulativeAckTest.testRetryingAnAckThatFailedWhileDisconnectedAdvancesTheCursor`. A longer reconnection backoff on a dedicated client would have been the simplest way to keep the consumer off the broker for the duration of an ack, but it had no effect because of this issue.
   
   ### Are you willing to submit a PR?
   
   - [ ] I'm willing to submit a PR!
   


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Re: [I] [Bug][client] V5 ConnectionPolicy.connectionBackoff is ignored [pulsar]

["lhotari (via GitHub)" <gi...@apache.org>]

lhotari closed issue #26788: [Bug][client] V5 ConnectionPolicy.connectionBackoff is ignored
URL: https://github.com/apache/pulsar/issues/26788


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