fix: use least loaded broker to refresh metadata #2645
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HaoSunUber
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functional_test.go
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| @@ -228,7 +228,7 @@ mainLoop: | |||
| } | |||
| for _, broker := range brokers { | |||
| err := broker.Open(client.Config()) | |||
| if err != nil { | |||
| if err != nil && err != ErrAlreadyConnected { | |||
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Updated the functional tests to skip the ErrAlreadyConnected error because this change will use one broker from the broker list to refresh metadata, which is already connected when reaching the following validation.
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@dnwe Could you please review my change? Thanks |
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Seed brokers never change after client initialization. If the first seed broker became stale (still online, but moved to other Kafka cluster), Sarama client may use this stale broker to get the wrong metadata. To avoid using the stale broker to do metadata refresh, we will choose the least loaded broker in the cached broker list which is the similar to how the Java client implementation works: https://github.com/apache/kafka/blob/7483991a/clients/src/main/java/org/apache/kafka/clients/NetworkClient.java#L671-L736 Contributes-to: IBM#2637 Signed-off-by: Hao Sun <[email protected]>
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| // deregisterBroker removes a broker from the broker list, and if it's | ||
| // not in the broker list, removes it from seedBrokers. | ||
| func (client *client) deregisterBroker(broker *Broker) { | ||
| client.lock.Lock() | ||
| defer client.lock.Unlock() | ||
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| _, ok := client.brokers[broker.ID()] | ||
| if ok { | ||
| Logger.Printf("client/brokers deregistered broker #%d at %s", broker.ID(), broker.Addr()) | ||
| delete(client.brokers, broker.ID()) | ||
| return | ||
| } | ||
| if len(client.seedBrokers) > 0 && broker == client.seedBrokers[0] { | ||
| client.deadSeeds = append(client.deadSeeds, broker) | ||
| client.seedBrokers = client.seedBrokers[1:] |
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Currently we only seem to deregister the broker from the seedBrokers list if it's the first element in the list (after the most recent shuffle) — is that still the desired behaviour?
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Yes, I think it is expected. seed brokers only shuffle during client initialization or hard RefreshBrokers. After that, the cached broker list is empty, and the client will use the first seed broker to fetch metadata. deregisterBroker method deregisters the first seed broker will apply that moment when this first seed broker is unavailable.
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Do you know when we have a new release including this change so that our side can use it? @dnwe
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Seed brokers never change after client initialization. If the first seed
broker became stale (still online, but moved to other Kafka cluster),
Sarama client may use this stale broker to get the wrong metadata. To
avoid using the stale broker to do metadata refresh, we will choose the
least loaded broker in the cached broker list which is the similar to
how the Java client implementation works:
https://github.com/apache/kafka/blob/7483991a/clients/src/main/java/org/apache/kafka/clients/NetworkClient.java#L671-L736
Contributes-to: #2637