Re: New producer: metadata update problem on 2 Node cluster.
Creating a new consumer instance *does not* solve this problem. Attaching the producer/consumer code that I used for testing. On Wed, May 6, 2015 at 6:31 AM, Ewen Cheslack-Postava e...@confluent.io wrote: I'm not sure about the old producer behavior in this same failure scenario, but creating a new producer instance would resolve the issue since it would start with the list of bootstrap nodes and, assuming at least one of them was up, it would be able to fetch up to date metadata. On Tue, May 5, 2015 at 5:32 PM, Jason Rosenberg j...@squareup.com wrote: Can you clarify, is this issue here specific to the new producer? With the old producer, we routinely construct a new producer which makes a fresh metadata request (via a VIP connected to all nodes in the cluster). Would this approach work with the new producer? Jason On Tue, May 5, 2015 at 1:12 PM, Rahul Jain rahul...@gmail.com wrote: Mayuresh, I was testing this in a development environment and manually brought down a node to simulate this. So the dead node never came back up. My colleague and I were able to consistently see this behaviour several times during the testing. On 5 May 2015 20:32, Mayuresh Gharat gharatmayures...@gmail.com wrote: I agree that to find the least Loaded node the producer should fall back to the bootstrap nodes if its not able to connect to any nodes in the current metadata. That should resolve this. Rahul, I suppose the problem went off because the dead node in your case might have came back up and allowed for a metadata update. Can you confirm this? Thanks, Mayuresh On Tue, May 5, 2015 at 5:10 AM, Rahul Jain rahul...@gmail.com wrote: We observed the exact same error. Not very clear about the root cause although it appears to be related to leastLoadedNode implementation. Interestingly, the problem went away by increasing the value of reconnect.backoff.ms to 1000ms. On 29 Apr 2015 00:32, Ewen Cheslack-Postava e...@confluent.io wrote: Ok, all of that makes sense. The only way to possibly recover from that state is either for K2 to come back up allowing the metadata refresh to eventually succeed or to eventually try some other node in the cluster. Reusing the bootstrap nodes is one possibility. Another would be for the client to get more metadata than is required for the topics it needs in order to ensure it has more nodes to use as options when looking for a node to fetch metadata from. I added your description to KAFKA-1843, although it might also make sense as a separate bug since fixing it could be considered incremental progress towards resolving 1843. On Tue, Apr 28, 2015 at 9:18 AM, Manikumar Reddy ku...@nmsworks.co.in wrote: Hi Ewen, Thanks for the response. I agree with you, In some case we should use bootstrap servers. If you have logs at debug level, are you seeing this message in between the connection attempts: Give up sending metadata request since no node is available Yes, this log came for couple of times. Also, if you let it continue running, does it recover after the metadata.max.age.ms timeout? It does not reconnect. It is continuously trying to connect with dead node. -Manikumar -- Thanks, Ewen -- -Regards, Mayuresh R. Gharat (862) 250-7125 -- Thanks, Ewen
Re: New producer: metadata update problem on 2 Node cluster.
Sorry, I meant creating a new producer, not consumer. Here's the code. Producer - http://pastebin.com/Kqq1ymCX Consumer - http://pastebin.com/i2Z8PTYB Callback - http://pastebin.com/x253z7bG As you'll notice, I am creating a new producer for each message. So the bootstrap nodes should be refreshed. I have a single topic (receive.queue) replicated across 3 nodes. I add all 3 nodes to the bootstrap list. On bringing one of the nodes down, some messages start failing (metadata update timeout error). As I mentioned earlier, the problem goes away simply by setting the reconnect.backoff.ms property to 1000ms. On 7 May 2015 23:18, Ewen Cheslack-Postava e...@confluent.io wrote: Rahul, the mailing list filters attachments, you'd have to post the code somewhere else for people to be able to see it. But I don't think anyone suggested that creating a new consumer would fix anything. Creating a new producer *and discarding the old one* basically just makes it start from scratch using the bootstrap nodes, which is why that would allow recovery from that condition. But that's just a workaround. The real issue is that the producer only maintains metadata for the nodes that are replicas for the partitions of the topics the producer sends data to. In some cases, this is a small set of servers and can get the producer stuck if a node goes offline and it doesn't have any other nodes that it can try to communicate with to get updated metadata (since the topic partitions should have a new leader). Falling back on the original bootstrap servers is one solution to this problem. Another would be to maintain metadata for additional servers so you always have extra bootstrap nodes in your current metadata set, even if they aren't replicas for any of the topics you're working with. -Ewen On Thu, May 7, 2015 at 12:06 AM, Rahul Jain rahul...@gmail.com wrote: Creating a new consumer instance *does not* solve this problem. Attaching the producer/consumer code that I used for testing. On Wed, May 6, 2015 at 6:31 AM, Ewen Cheslack-Postava e...@confluent.io wrote: I'm not sure about the old producer behavior in this same failure scenario, but creating a new producer instance would resolve the issue since it would start with the list of bootstrap nodes and, assuming at least one of them was up, it would be able to fetch up to date metadata. On Tue, May 5, 2015 at 5:32 PM, Jason Rosenberg j...@squareup.com wrote: Can you clarify, is this issue here specific to the new producer? With the old producer, we routinely construct a new producer which makes a fresh metadata request (via a VIP connected to all nodes in the cluster). Would this approach work with the new producer? Jason On Tue, May 5, 2015 at 1:12 PM, Rahul Jain rahul...@gmail.com wrote: Mayuresh, I was testing this in a development environment and manually brought down a node to simulate this. So the dead node never came back up. My colleague and I were able to consistently see this behaviour several times during the testing. On 5 May 2015 20:32, Mayuresh Gharat gharatmayures...@gmail.com wrote: I agree that to find the least Loaded node the producer should fall back to the bootstrap nodes if its not able to connect to any nodes in the current metadata. That should resolve this. Rahul, I suppose the problem went off because the dead node in your case might have came back up and allowed for a metadata update. Can you confirm this? Thanks, Mayuresh On Tue, May 5, 2015 at 5:10 AM, Rahul Jain rahul...@gmail.com wrote: We observed the exact same error. Not very clear about the root cause although it appears to be related to leastLoadedNode implementation. Interestingly, the problem went away by increasing the value of reconnect.backoff.ms to 1000ms. On 29 Apr 2015 00:32, Ewen Cheslack-Postava e...@confluent.io wrote: Ok, all of that makes sense. The only way to possibly recover from that state is either for K2 to come back up allowing the metadata refresh to eventually succeed or to eventually try some other node in the cluster. Reusing the bootstrap nodes is one possibility. Another would be for the client to get more metadata than is required for the topics it needs in order to ensure it has more nodes to use as options when looking for a node to fetch metadata from. I added your description to KAFKA-1843, although it might also make sense as a separate bug since fixing it could be considered incremental progress towards resolving 1843. On Tue, Apr 28, 2015 at 9:18 AM, Manikumar Reddy ku...@nmsworks.co.in wrote: Hi Ewen,
Re: New producer: metadata update problem on 2 Node cluster.
Rahul, the mailing list filters attachments, you'd have to post the code somewhere else for people to be able to see it. But I don't think anyone suggested that creating a new consumer would fix anything. Creating a new producer *and discarding the old one* basically just makes it start from scratch using the bootstrap nodes, which is why that would allow recovery from that condition. But that's just a workaround. The real issue is that the producer only maintains metadata for the nodes that are replicas for the partitions of the topics the producer sends data to. In some cases, this is a small set of servers and can get the producer stuck if a node goes offline and it doesn't have any other nodes that it can try to communicate with to get updated metadata (since the topic partitions should have a new leader). Falling back on the original bootstrap servers is one solution to this problem. Another would be to maintain metadata for additional servers so you always have extra bootstrap nodes in your current metadata set, even if they aren't replicas for any of the topics you're working with. -Ewen On Thu, May 7, 2015 at 12:06 AM, Rahul Jain rahul...@gmail.com wrote: Creating a new consumer instance *does not* solve this problem. Attaching the producer/consumer code that I used for testing. On Wed, May 6, 2015 at 6:31 AM, Ewen Cheslack-Postava e...@confluent.io wrote: I'm not sure about the old producer behavior in this same failure scenario, but creating a new producer instance would resolve the issue since it would start with the list of bootstrap nodes and, assuming at least one of them was up, it would be able to fetch up to date metadata. On Tue, May 5, 2015 at 5:32 PM, Jason Rosenberg j...@squareup.com wrote: Can you clarify, is this issue here specific to the new producer? With the old producer, we routinely construct a new producer which makes a fresh metadata request (via a VIP connected to all nodes in the cluster). Would this approach work with the new producer? Jason On Tue, May 5, 2015 at 1:12 PM, Rahul Jain rahul...@gmail.com wrote: Mayuresh, I was testing this in a development environment and manually brought down a node to simulate this. So the dead node never came back up. My colleague and I were able to consistently see this behaviour several times during the testing. On 5 May 2015 20:32, Mayuresh Gharat gharatmayures...@gmail.com wrote: I agree that to find the least Loaded node the producer should fall back to the bootstrap nodes if its not able to connect to any nodes in the current metadata. That should resolve this. Rahul, I suppose the problem went off because the dead node in your case might have came back up and allowed for a metadata update. Can you confirm this? Thanks, Mayuresh On Tue, May 5, 2015 at 5:10 AM, Rahul Jain rahul...@gmail.com wrote: We observed the exact same error. Not very clear about the root cause although it appears to be related to leastLoadedNode implementation. Interestingly, the problem went away by increasing the value of reconnect.backoff.ms to 1000ms. On 29 Apr 2015 00:32, Ewen Cheslack-Postava e...@confluent.io wrote: Ok, all of that makes sense. The only way to possibly recover from that state is either for K2 to come back up allowing the metadata refresh to eventually succeed or to eventually try some other node in the cluster. Reusing the bootstrap nodes is one possibility. Another would be for the client to get more metadata than is required for the topics it needs in order to ensure it has more nodes to use as options when looking for a node to fetch metadata from. I added your description to KAFKA-1843, although it might also make sense as a separate bug since fixing it could be considered incremental progress towards resolving 1843. On Tue, Apr 28, 2015 at 9:18 AM, Manikumar Reddy ku...@nmsworks.co.in wrote: Hi Ewen, Thanks for the response. I agree with you, In some case we should use bootstrap servers. If you have logs at debug level, are you seeing this message in between the connection attempts: Give up sending metadata request since no node is available Yes, this log came for couple of times. Also, if you let it continue running, does it recover after the metadata.max.age.ms timeout? It does not reconnect. It is continuously trying to connect with dead node. -Manikumar -- Thanks, Ewen -- -Regards, Mayuresh R. Gharat (862) 250-7125
Re: New producer: metadata update problem on 2 Node cluster.
We observed the exact same error. Not very clear about the root cause although it appears to be related to leastLoadedNode implementation. Interestingly, the problem went away by increasing the value of reconnect.backoff.ms to 1000ms. On 29 Apr 2015 00:32, Ewen Cheslack-Postava e...@confluent.io wrote: Ok, all of that makes sense. The only way to possibly recover from that state is either for K2 to come back up allowing the metadata refresh to eventually succeed or to eventually try some other node in the cluster. Reusing the bootstrap nodes is one possibility. Another would be for the client to get more metadata than is required for the topics it needs in order to ensure it has more nodes to use as options when looking for a node to fetch metadata from. I added your description to KAFKA-1843, although it might also make sense as a separate bug since fixing it could be considered incremental progress towards resolving 1843. On Tue, Apr 28, 2015 at 9:18 AM, Manikumar Reddy ku...@nmsworks.co.in wrote: Hi Ewen, Thanks for the response. I agree with you, In some case we should use bootstrap servers. If you have logs at debug level, are you seeing this message in between the connection attempts: Give up sending metadata request since no node is available Yes, this log came for couple of times. Also, if you let it continue running, does it recover after the metadata.max.age.ms timeout? It does not reconnect. It is continuously trying to connect with dead node. -Manikumar -- Thanks, Ewen
Re: New producer: metadata update problem on 2 Node cluster.
I'm not sure about the old producer behavior in this same failure scenario, but creating a new producer instance would resolve the issue since it would start with the list of bootstrap nodes and, assuming at least one of them was up, it would be able to fetch up to date metadata. On Tue, May 5, 2015 at 5:32 PM, Jason Rosenberg j...@squareup.com wrote: Can you clarify, is this issue here specific to the new producer? With the old producer, we routinely construct a new producer which makes a fresh metadata request (via a VIP connected to all nodes in the cluster). Would this approach work with the new producer? Jason On Tue, May 5, 2015 at 1:12 PM, Rahul Jain rahul...@gmail.com wrote: Mayuresh, I was testing this in a development environment and manually brought down a node to simulate this. So the dead node never came back up. My colleague and I were able to consistently see this behaviour several times during the testing. On 5 May 2015 20:32, Mayuresh Gharat gharatmayures...@gmail.com wrote: I agree that to find the least Loaded node the producer should fall back to the bootstrap nodes if its not able to connect to any nodes in the current metadata. That should resolve this. Rahul, I suppose the problem went off because the dead node in your case might have came back up and allowed for a metadata update. Can you confirm this? Thanks, Mayuresh On Tue, May 5, 2015 at 5:10 AM, Rahul Jain rahul...@gmail.com wrote: We observed the exact same error. Not very clear about the root cause although it appears to be related to leastLoadedNode implementation. Interestingly, the problem went away by increasing the value of reconnect.backoff.ms to 1000ms. On 29 Apr 2015 00:32, Ewen Cheslack-Postava e...@confluent.io wrote: Ok, all of that makes sense. The only way to possibly recover from that state is either for K2 to come back up allowing the metadata refresh to eventually succeed or to eventually try some other node in the cluster. Reusing the bootstrap nodes is one possibility. Another would be for the client to get more metadata than is required for the topics it needs in order to ensure it has more nodes to use as options when looking for a node to fetch metadata from. I added your description to KAFKA-1843, although it might also make sense as a separate bug since fixing it could be considered incremental progress towards resolving 1843. On Tue, Apr 28, 2015 at 9:18 AM, Manikumar Reddy ku...@nmsworks.co.in wrote: Hi Ewen, Thanks for the response. I agree with you, In some case we should use bootstrap servers. If you have logs at debug level, are you seeing this message in between the connection attempts: Give up sending metadata request since no node is available Yes, this log came for couple of times. Also, if you let it continue running, does it recover after the metadata.max.age.ms timeout? It does not reconnect. It is continuously trying to connect with dead node. -Manikumar -- Thanks, Ewen -- -Regards, Mayuresh R. Gharat (862) 250-7125 -- Thanks, Ewen
Re: New producer: metadata update problem on 2 Node cluster.
I agree that to find the least Loaded node the producer should fall back to the bootstrap nodes if its not able to connect to any nodes in the current metadata. That should resolve this. Rahul, I suppose the problem went off because the dead node in your case might have came back up and allowed for a metadata update. Can you confirm this? Thanks, Mayuresh On Tue, May 5, 2015 at 5:10 AM, Rahul Jain rahul...@gmail.com wrote: We observed the exact same error. Not very clear about the root cause although it appears to be related to leastLoadedNode implementation. Interestingly, the problem went away by increasing the value of reconnect.backoff.ms to 1000ms. On 29 Apr 2015 00:32, Ewen Cheslack-Postava e...@confluent.io wrote: Ok, all of that makes sense. The only way to possibly recover from that state is either for K2 to come back up allowing the metadata refresh to eventually succeed or to eventually try some other node in the cluster. Reusing the bootstrap nodes is one possibility. Another would be for the client to get more metadata than is required for the topics it needs in order to ensure it has more nodes to use as options when looking for a node to fetch metadata from. I added your description to KAFKA-1843, although it might also make sense as a separate bug since fixing it could be considered incremental progress towards resolving 1843. On Tue, Apr 28, 2015 at 9:18 AM, Manikumar Reddy ku...@nmsworks.co.in wrote: Hi Ewen, Thanks for the response. I agree with you, In some case we should use bootstrap servers. If you have logs at debug level, are you seeing this message in between the connection attempts: Give up sending metadata request since no node is available Yes, this log came for couple of times. Also, if you let it continue running, does it recover after the metadata.max.age.ms timeout? It does not reconnect. It is continuously trying to connect with dead node. -Manikumar -- Thanks, Ewen -- -Regards, Mayuresh R. Gharat (862) 250-7125
Re: New producer: metadata update problem on 2 Node cluster.
Mayuresh, I was testing this in a development environment and manually brought down a node to simulate this. So the dead node never came back up. My colleague and I were able to consistently see this behaviour several times during the testing. On 5 May 2015 20:32, Mayuresh Gharat gharatmayures...@gmail.com wrote: I agree that to find the least Loaded node the producer should fall back to the bootstrap nodes if its not able to connect to any nodes in the current metadata. That should resolve this. Rahul, I suppose the problem went off because the dead node in your case might have came back up and allowed for a metadata update. Can you confirm this? Thanks, Mayuresh On Tue, May 5, 2015 at 5:10 AM, Rahul Jain rahul...@gmail.com wrote: We observed the exact same error. Not very clear about the root cause although it appears to be related to leastLoadedNode implementation. Interestingly, the problem went away by increasing the value of reconnect.backoff.ms to 1000ms. On 29 Apr 2015 00:32, Ewen Cheslack-Postava e...@confluent.io wrote: Ok, all of that makes sense. The only way to possibly recover from that state is either for K2 to come back up allowing the metadata refresh to eventually succeed or to eventually try some other node in the cluster. Reusing the bootstrap nodes is one possibility. Another would be for the client to get more metadata than is required for the topics it needs in order to ensure it has more nodes to use as options when looking for a node to fetch metadata from. I added your description to KAFKA-1843, although it might also make sense as a separate bug since fixing it could be considered incremental progress towards resolving 1843. On Tue, Apr 28, 2015 at 9:18 AM, Manikumar Reddy ku...@nmsworks.co.in wrote: Hi Ewen, Thanks for the response. I agree with you, In some case we should use bootstrap servers. If you have logs at debug level, are you seeing this message in between the connection attempts: Give up sending metadata request since no node is available Yes, this log came for couple of times. Also, if you let it continue running, does it recover after the metadata.max.age.ms timeout? It does not reconnect. It is continuously trying to connect with dead node. -Manikumar -- Thanks, Ewen -- -Regards, Mayuresh R. Gharat (862) 250-7125
Re: New producer: metadata update problem on 2 Node cluster.
Hi Ewen, Thanks for the response. I agree with you, In some case we should use bootstrap servers. If you have logs at debug level, are you seeing this message in between the connection attempts: Give up sending metadata request since no node is available Yes, this log came for couple of times. Also, if you let it continue running, does it recover after the metadata.max.age.ms timeout? It does not reconnect. It is continuously trying to connect with dead node. -Manikumar
Re: New producer: metadata update problem on 2 Node cluster.
Ok, all of that makes sense. The only way to possibly recover from that state is either for K2 to come back up allowing the metadata refresh to eventually succeed or to eventually try some other node in the cluster. Reusing the bootstrap nodes is one possibility. Another would be for the client to get more metadata than is required for the topics it needs in order to ensure it has more nodes to use as options when looking for a node to fetch metadata from. I added your description to KAFKA-1843, although it might also make sense as a separate bug since fixing it could be considered incremental progress towards resolving 1843. On Tue, Apr 28, 2015 at 9:18 AM, Manikumar Reddy ku...@nmsworks.co.in wrote: Hi Ewen, Thanks for the response. I agree with you, In some case we should use bootstrap servers. If you have logs at debug level, are you seeing this message in between the connection attempts: Give up sending metadata request since no node is available Yes, this log came for couple of times. Also, if you let it continue running, does it recover after the metadata.max.age.ms timeout? It does not reconnect. It is continuously trying to connect with dead node. -Manikumar -- Thanks, Ewen
Re: New producer: metadata update problem on 2 Node cluster.
Any comments on this issue? On Apr 24, 2015 8:05 PM, Manikumar Reddy ku...@nmsworks.co.in wrote: We are testing new producer on a 2 node cluster. Under some node failure scenarios, producer is not able to update metadata. Steps to reproduce 1. form a 2 node cluster (K1, K2) 2. create a topic with single partition, replication factor = 2 3. start producing data (producer metadata : K1,K2) 2. Kill leader node (say K1) 3. K2 becomes the leader (producer metadata : K2) 4. Bring back K1 and Kill K2 before metadata.max.age.ms 5. K1 becomes the Leader (producer metadata still contains : K2) After this point, producer is not able to update the metadata. producer continuously trying to connect with dead node (K2). This looks like a bug to me. Am I missing anything?
Re: New producer: metadata update problem on 2 Node cluster.
Maybe add this to the description of https://issues.apache.org/jira/browse/KAFKA-1843 ? I can't find it now, but I think there was another bug where I described a similar problem -- in some cases it makes sense to fall back to the list of bootstrap nodes because you've gotten into a bad state and can't make any progress without a metadata update but can't connect to any nodes. The leastLoadedNode method only considers nodes in the current metadata, so in your example K1 is not considered an option after seeing the producer metadata update that only includes K2. In KAFKA-1501 I also found another obscure edge case where you can run into this problem if your broker hostnames/ports aren't consistent across restarts. Yours is obviously much more likely to occur, and may not even be that uncommon for producers that are only sending data to one topi. If you have logs at debug level, are you seeing this message in between the connection attempts: Give up sending metadata request since no node is available Also, if you let it continue running, does it recover after the metadata.max.age.ms timeout? If so, I think that would definitely confirm the issue and might suggest a fix -- preserve the bootstrap metadata and fall back to choosing a node from it when leastLoadedNode would otherwise return null. -Ewen On Mon, Apr 27, 2015 at 5:40 AM, Manikumar Reddy manikumar.re...@gmail.com wrote: Any comments on this issue? On Apr 24, 2015 8:05 PM, Manikumar Reddy ku...@nmsworks.co.in wrote: We are testing new producer on a 2 node cluster. Under some node failure scenarios, producer is not able to update metadata. Steps to reproduce 1. form a 2 node cluster (K1, K2) 2. create a topic with single partition, replication factor = 2 3. start producing data (producer metadata : K1,K2) 2. Kill leader node (say K1) 3. K2 becomes the leader (producer metadata : K2) 4. Bring back K1 and Kill K2 before metadata.max.age.ms 5. K1 becomes the Leader (producer metadata still contains : K2) After this point, producer is not able to update the metadata. producer continuously trying to connect with dead node (K2). This looks like a bug to me. Am I missing anything? -- Thanks, Ewen
