KafkaConsumer keeps getting InstanceAlreadyExistsException
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KafkaConsumer keeps getting InstanceAlreadyExistsException
 
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Hey,
I've been using Flink for a while now without any problems when running apps with a FlinkKafkaConsumer.
All my apps have the same overall logic (consume from kafka -> transform event -> write to file) and the only way they differ from each other is the topic they read (remaining kafka config remains identical) and the way they transform the event.
But suddenly, I've been starting to get the following error:
2020-03-15 12:13:56,911 WARN org.apache.kafka.common.utils.AppInfoParser - Error registering AppInfo mbean
javax.management.InstanceAlreadyExistsException: kafka.consumer:type=app-info,id=consumer-1 at com.sun.jmx.mbeanserver.Repository.addMBean(Repository.java:437) at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerWithRepository(DefaultMBeanServerInterceptor.java:1898) at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerDynamicMBean(DefaultMBeanServerInterceptor.java:966) at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerObject(DefaultMBeanServerInterceptor.java:900) at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerMBean(DefaultMBeanServerInterceptor.java:324) at com.sun.jmx.mbeanserver.JmxMBeanServer.registerMBean(JmxMBeanServer.java:522) at org.apache.kafka.common.utils.AppInfoParser.registerAppInfo(AppInfoParser.java:62) at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:805) at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:659) at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:639) at org.apache.flink.streaming.connectors.kafka.internal.KafkaPartitionDiscoverer.initializeConnections(KafkaPartitionDiscoverer.java:58) at org.apache.flink.streaming.connectors.kafka.internals.AbstractPartitionDiscoverer.open(AbstractPartitionDiscoverer.java:94) at org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumerBase.open(FlinkKafkaConsumerBase.java:505) at org.apache.flink.api.common.functions.util.FunctionUtils.openFunction(FunctionUtils.java:36) at org.apache.flink.streaming.api.operators.AbstractUdfStreamOperator.open(AbstractUdfStreamOperator.java:102) at org.apache.flink.streaming.runtime.tasks.StreamTask.openAllOperators(StreamTask.java:552) at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:416) at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:705) at org.apache.flink.runtime.taskmanager.Task.run(Task.java:530) at java.lang.Thread.run(Thread.java:748)
I've tried setting the "client.id" on my consumer to a random UUID, making sure I don't have any duplicates but that didn't help either.
Any idea what could be causing this?
Thanks 🙂
Sidney Feiner / Data
Platform Developer
M: +972.528197720 / Skype: sidney.feiner.startapp
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Re: KafkaConsumer keeps getting InstanceAlreadyExistsException
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We also had seen this issue before running Flink apps in a shared cluster environment. Basically, Kafka is trying to register a JMX MBean[1] for application monitoring. This is only a WARN suggesting that you are registering more than one MBean with the same client id "consumer-1", it should not affect your normal application behavior. This is most likely occurring if you have more than one Kafka consumer within the same JVM, are you using a session cluster[2]? can you share more on your application configuration including parallelism and slot configs? Also based on the log, you are not configuring the "client.id" correctly. which config key are you using? could you also share your fill Kafka properties map? -- Rong On Sun, Mar 15, 2020 at 8:28 AM Sidney Feiner <[hidden email]> wrote:
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Re: KafkaConsumer keeps getting InstanceAlreadyExistsException
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Hi Sidney, The WARN logging you saw was from the AbstractPartitionDiscoverer which is created by FlinkKafkaConsumer itself. It has an internal consumer which shares the client.id of the actual consumer fetching data. This is a bug that we should fix. As Rong said, this won't affect the normal operation of the consumer. It is just an AppInfo MBean for reporting some information. There might be some slight impact on the accuracy of the consumer metrics, but should be almost ignorable because the partition discoverer is quite inactive compared with the actual consumer. Thanks, Jiangjie (Becket) Qin On Mon, Mar 16, 2020 at 12:44 AM Rong Rong <[hidden email]> wrote:
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Re: KafkaConsumer keeps getting InstanceAlreadyExistsException
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@Becket do we already have a JIRA ticket to track this effort? Cheers, Till On Mon, Mar 16, 2020 at 4:07 AM Becket Qin <[hidden email]> wrote:
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Re: KafkaConsumer keeps getting InstanceAlreadyExistsException
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Hi Till, It looks FLINK-8093 reports the same issue, although the reported information is not exactly correct, as this should not cause the producer to fail. I'll take care of the ticket. Thanks, Jiangjie (Becket) Qin On Tue, Mar 17, 2020 at 6:00 PM Till Rohrmann <[hidden email]> wrote:
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Re: KafkaConsumer keeps getting InstanceAlreadyExistsException
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Actually it might be better to create another ticket, FLINK-8093 was mainly complaining about the JMX bean collision when there are multiple tasks running in the same TM. Jiangjie (Becket) Qin On Tue, Mar 17, 2020 at 6:33 PM Becket Qin <[hidden email]> wrote:
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Re: KafkaConsumer keeps getting InstanceAlreadyExistsException
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Hi Becket/Till, Thanks for the detail explanation. Just to confirm: the issue in FLINK-8093 refers to multiple Kafka consumer within the same TM - thus the fix should be to make consumer client.id unique for different tasks ? and the issue here is an issue internal to the Kafka consumer, where both the polling consumer thread and the MBean JMX reporter thread share the same client.id - thus we should fix this in the Kafka level? If this is the correct understanding, I think we should separate them since they are in fact 2 different issues. -- Rong On Tue, Mar 17, 2020 at 3:36 AM Becket Qin <[hidden email]> wrote:
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Re: KafkaConsumer keeps getting InstanceAlreadyExistsException
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Hi Rong, The issue here is that the PartitionDiscoverer has an internal KafkaConsumer which reuses the client.id set by the users for the actual fetching KafkaConsumer. Different KafkaConsumers distinguish their metrics by client.id, therefore if there are two KafkaConsumers in the same JVM with the same client.id, their metrics will collide with each other. This is why the exception was reported. Thanks, Jiangjie (Becket) Qin On Thu, Mar 19, 2020 at 12:04 AM Rong Rong <[hidden email]> wrote:
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