Hi, Mickael, Thanks for the KIP.
10. A common case is only one log dir per broker. Could we support sth like --add-config cordoned.log.dirs=* to make it more convenient for this case? 11. Since we changed the metadata record format, should we gate the new configuration based on a new metadata version? Jun On Wed, Jul 17, 2024 at 9:18 AM Mickael Maison <mickael.mai...@gmail.com> wrote: > Hi Kamal, > > Good spot, yes this is a typo. The flexibleVersions stays as "0+". Fixed > > Thanks, > Mickael > > On Wed, Jul 17, 2024 at 6:14 PM Mickael Maison <mickael.mai...@gmail.com> > wrote: > > > > Hi David, > > > > DA1: It's a point I considered, especially being able to cordon a > > whole broker. With the current proposal you just need to set > > cordoned.log.dirs to the same value as log.dirs. That does not seem > > excessively difficult. > > > > DA2: I did consider using a new metadata record like we do for > > fence/unfence. Since I don't expect cordoned log dirs to change very > > frequently, and the size should be small, I opted to reuse the > > BrokerRegistrationRecord metadata record. At the moment I guess it was > > mostly for the convenience while prototyping. Semantically it probably > > makes sense to have separate records. Your further point suggest > > design changes in the mechanism as a whole, so let's discuss these > > first and we can return to the exact metadata records after. > > I find the idea of having dedicated RPCs interesting. One of the > > reasons I piggybacked on the heartbeating process is for the mapping > > between log directory names and their UUIDs. Currently the mapping > > only exists on each broker instance. So if we wanted a dedicated RPC, > > we would first need to change how we manage the log directory to UUID > > mappings. I guess this could be done via the BrokerRegistration API. > > I'm not sure about storing additional metadata (reason, timestamp). We > > currently don't do that for any operations > > (AlterPartitionReassignments, UnregisterBroker). Typically these are > > stored in the tools used by the operators to drive these operations. > > You bring another interesting point about the ability to cordon > > brokers/log directories while they are offline. It's not something the > > current proposal supports. I'm not sure how useful this would turn out > > it practice. In experience is that brokers are mostly online, so I'd > > expect the need to do so relatively rare. This also kind of loops back > > to KAFKA-17094 [0] and the discussion Gantigmaa started on the dev > > list [1] about being able to identify the ids of offline (but still > > registered) brokers. > > > > DA3: With the current proposal, I don't see a reason why you would > > want to disable the new behavior. If you don't want to use it, you > > have nothing to do. It's opt-in as you need to set cordoned.log.dirs > > on some brokers to get the new behavior. If you don't want it anymore, > > you should unset cordoned.log.dirs. Can you explain why this would not > > work? > > > > DA4: Yes > > > > 0: https://issues.apache.org/jira/browse/KAFKA-17094 > > 1: https://lists.apache.org/thread/1rrgbhk43d85wobcp0dqz6mhpn93j9yo > > > > Thanks, > > Mickael > > > > > > On Sun, Jul 14, 2024 at 10:37 AM Kamal Chandraprakash > > <kamal.chandraprak...@gmail.com> wrote: > > > > > > Hi Mickael, > > > > > > In the BrokerHearbeatRequest.json, the flexibleVersions are bumped from > > > "0+" to "1+". Is it a typo? > > > > > > > > > On Fri, Jul 12, 2024 at 11:42 PM David Arthur <mum...@gmail.com> > wrote: > > > > > > > Mickael, thanks for the KIP! I think this could be quite a useful > feature. > > > > > > > > DA1: Having to know each of the log dirs for a broker seems a bit > > > > inconvenient for cases where we want to cordon off a whole broker. I > do > > > > think having the ability to cordon off a specific log dir is useful > for > > > > JBOD, but I imagine a common case might be to cordon off the whole > broker. > > > > > > > > DA2: Looks like the new "cordoned.log.dirs" can be configured > statically > > > > and updated dynamically per-broker. What do you think about a new > metadata > > > > record and RPC instead of using a config? From my understanding, the > > > > BrokerRegistration/Heartbeat is more about the lifecycle of a broker > > > > whereas cordoning a broker is an operator driven action. It might > make > > > > sense to have a separate record for this. We could include additional > > > > fields like a timestamp, a reason/comment field (e.g., > "decommissioning", > > > > "disk failure", "new broker" etc), stuff like that. > > > > > > > > This would also allow cordoning to be done while a broker is offline > or > > > > before it has been provisioned. Not sure how likely that is, but > might be > > > > useful? > > > > > > > > DA3: Can we consider having a configuration to enable/disable the new > > > > replica placer behavior? This would be separate from the new > > > > MetadataVersion for the RPC/record changes. > > > > > > > > DA4: In the Motivation section, you mention the cluster expansion > scenario. > > > > For this scenario, is the expectation that the operator will cordon > off the > > > > existing full brokers so placements only happen on the new brokers? > > > > > > > > Cheers, > > > > David > > > > > > > > On Fri, Jul 12, 2024 at 8:53 AM Mickael Maison < > mickael.mai...@gmail.com> > > > > wrote: > > > > > > > > > Hi Kamal, > > > > > > > > > > Thanks for taking a look at the KIP! > > > > > > > > > > I briefly considered that option initially but I found it not very > > > > > practical once you have more than a few cordoned log directories. > > > > > I find your example is already not very easy to read, and it only > has > > > > > 2 entries. Also if the configuration is at the cluster level it'sis > > > > > not easy to see if a broker has all its log directories cordoned, > and > > > > > you still need to describe a specific broker's configuration to > find > > > > > the "name" of a log directory you want to cordon. > > > > > > > > > > I think an easy way to get an overall view of the cordoned log > > > > > directories/brokers will be via the kafka-log-dirs.sh tool. I am > also > > > > > considering adding metrics like we have today for > LogDirectoryOffline > > > > > to ease monitoring. > > > > > > > > > > Thanks, > > > > > Mickael > > > > > > > > > > On Thu, Jul 11, 2024 at 8:41 PM Kamal Chandraprakash > > > > > <kamal.chandraprak...@gmail.com> wrote: > > > > > > > > > > > > Hi Mickael, > > > > > > > > > > > > Thanks for the KIP! > > > > > > > > > > > > This is a useful feature which helps to decommission the nodes by > > > > > > essentially > > > > > > creating a new replica exclude broker list. > > > > > > > > > > > > To cordon a list of brokers, we have to apply the config on each > of the > > > > > > broker nodes > > > > > > and similarly to see the list of cordoned brokers, we have to > either > > > > > query > > > > > > individual broker > > > > > > config in the cluster or query each of the broker log directory. > > > > > > > > > > > > Can we move the configuration from the broker to cluster level? > (eg) > > > > > > > > > > > > bin/kafka-configs.sh --bootstrap-server localhost:9092 > > > > --broker-defaults > > > > > > --alter --add-config > > > > > > cordoned.log.dirs=[broker.id > .0]:[log.dir.0],[broker.id.1]:[log.dir.1] > > > > > > > > > > > > This will provide a consistent view of the list of cordoned > brokers in > > > > > the > > > > > > cluster. > > > > > > > > > > > > -- > > > > > > Kamal > > > > > > > > > > > > On Wed, Jul 10, 2024 at 7:53 PM Mickael Maison < > > > > mickael.mai...@gmail.com > > > > > > > > > > > > wrote: > > > > > > > > > > > > > Hi Luke, > > > > > > > > > > > > > > 4. You're right this scenario can happen. In this case I think > the > > > > > > > broker should enforce its new state and not create the replica > as all > > > > > > > its log directories are now cordoned. The replica will be > offline and > > > > > > > an administrator would need to reassign it to another broker. I > > > > expect > > > > > > > most users will rely on kafka-configs.sh to manage the > cordoned log > > > > > > > directories instead of updating the broker properties, so it > should > > > > > > > not be a common issue. > > > > > > > > > > > > > > 6. To resolve this issue, the user can uncordon a log > directory and > > > > > > > retry an operation that triggers the creation of the internal > topics. > > > > > > > For example start a consumer using a group should make the > broker > > > > > > > retry creating the __consumer_offsets topic. > > > > > > > > > > > > > > Thanks, > > > > > > > Mickael > > > > > > > > > > > > > > On Wed, Jul 10, 2024 at 4:14 PM Mickael Maison < > > > > > mickael.mai...@gmail.com> > > > > > > > wrote: > > > > > > > > > > > > > > > > Hi Chia-Ping, > > > > > > > > > > > > > > > > Question 1) Yes that's a good summary. I'd also add that > managing > > > > > > > > cordoned log directories is intended to be done by cluster > > > > > > > > administrators who also know about operations in-progress or > > > > planned > > > > > > > > such as scaling or adding/removing log directories. In > practice you > > > > > > > > can't expect users to provide "good" explicit partition > assignments > > > > > as > > > > > > > > they are not aware of the cluster operations. > > > > > > > > > > > > > > > > Question 2) I don't see an actual question :) > > > > > > > > > > > > > > > > Question 3) My current proposal is that in that case, > brokers will > > > > > > > > ignore the preferred log directory and place the new replica > on a > > > > log > > > > > > > > directory that is not cordoned. To use AlterReplicaLogDirs > you need > > > > > > > > ALTER permission on the CLUSTER resource. In most > environments > > > > users > > > > > > > > don't have permissions to use that API. Or if they do, I'd > expect > > > > > them > > > > > > > > to also have ALTER_CONFIGS on the BROKER resource and be > able to > > > > > > > > change the cordoned log directories configuration. > > > > > > > > > > > > > > > > Question 4) If we don't include the CordonedLogDirs field in > > > > > > > > BrokerRegistrationRequest as you said there's a small window > when > > > > the > > > > > > > > controller would not know if a broker can be used for > assignments. > > > > If > > > > > > > > all log directories are cordoned the controller should not > use that > > > > > > > > broker for assignments. > > > > > > > > > > > > > > > > Question 5) In KRaft mode offline brokers are still > registered, and > > > > > > > > can be used for partition assignment. So we need to persist > the > > > > > > > > cordoned log directories too to exclude brokers that don't > have > > > > > > > > uncordoned log directories. > > > > > > > > > > > > > > > > Thanks, > > > > > > > > Mickael > > > > > > > > > > > > > > > > > > > > > > > > On Wed, Jul 10, 2024 at 12:25 PM Luke Chen < > show...@gmail.com> > > > > > wrote: > > > > > > > > > > > > > > > > > > Hi Mickael, > > > > > > > > > > > > > > > > > > Thanks for the response. > > > > > > > > > > > > > > > > > > > 4. Cordoned log directories are persisted to the > metadata log > > > > > via the > > > > > > > > > RegisterBrokerRecord, BrokerRegistrationChangeRecord > records. If > > > > a > > > > > > > > > broker is offline, the controller will use the latest > known state > > > > > of > > > > > > > > > the broker to determine the broker's cordoned log > directories. > > > > I've > > > > > > > > > added a sentence clarifying this point. > > > > > > > > > > > > > > > > > > OK, so if the broker A goes offline, and the controller is > in > > > > > "fenced" > > > > > > > > > state, without any cordoned log dirs, then some topic > created and > > > > > > > assigned > > > > > > > > > to broker A. Later, broker A starts up with all its log > dirs > > > > > cordoned > > > > > > > > > configured. At this situation, will the broker A create the > > > > > partitions? > > > > > > > > > > > > > > > > > > > 6. I'm leaning towards considering that scenario a > > > > configuration > > > > > > > > > error. If all log directories are cordoned before the > internal > > > > > topics > > > > > > > > > are created, then the broker will not be able to create > them. > > > > This > > > > > > > > > seems like a pretty strange scenario, where it's the first > time > > > > you > > > > > > > > > start a broker, you've cordoned all its log directory, and > the > > > > > > > > > internal topics (offsets and transactions) have not yet > been > > > > > created > > > > > > > > > in the rest of the cluster. > > > > > > > > > > > > > > > > > > Yes, I agree that this should be a configuration error. > > > > > > > > > So the follow-up question is: Suppose users encounter this > issue, > > > > > and > > > > > > > how > > > > > > > > > could they resolve it? > > > > > > > > > Uncordon the log dir dynamically using kafka-configs.sh? > Will the > > > > > > > > > uncordoning config change recreate the partitions we didn't > > > > create > > > > > > > earlier > > > > > > > > > because of log dir cordoned? > > > > > > > > > > > > > > > > > > > The metadata log is different (not managed by > LogManager), so I > > > > > think > > > > > > > > > it should always be created regardless if its log > directory is > > > > > > > > > cordoned or not. > > > > > > > > > > > > > > > > > > I agree we should treat "__cluster_metadata" differently. > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks. > > > > > > > > > Luke > > > > > > > > > > > > > > > > > > > > > > > > > > > On Wed, Jul 10, 2024 at 12:42 AM Mickael Maison < > > > > > > > mickael.mai...@gmail.com> > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > Hi Luke, > > > > > > > > > > > > > > > > > > > > 2. isCordoned() is a new method on LogDirDescription. It > does > > > > not > > > > > > > take > > > > > > > > > > any arguments. It just returns true if this log > directory the > > > > > > > > > > LogDirDescription represents is cordoned. > > > > > > > > > > > > > > > > > > > > 3. Sorry that was a typo. This method will only return a > log > > > > > > > directory > > > > > > > > > > that is not cordoned. Fixed > > > > > > > > > > > > > > > > > > > > 4. Cordoned log directories are persisted to the > metadata log > > > > > via the > > > > > > > > > > RegisterBrokerRecord, BrokerRegistrationChangeRecord > records. > > > > If > > > > > a > > > > > > > > > > broker is offline, the controller will use the latest > known > > > > > state of > > > > > > > > > > the broker to determine the broker's cordoned log > directories. > > > > > I've > > > > > > > > > > added a sentence clarifying this point. > > > > > > > > > > > > > > > > > > > > 5. Yes a log directory can be uncordoned. You can either > update > > > > > the > > > > > > > > > > properties file and restart the broker or dynamically > change > > > > the > > > > > > > value > > > > > > > > > > at runtime using kafka-configs. I've added a paragraph > about it > > > > > in > > > > > > > the > > > > > > > > > > KIP. > > > > > > > > > > > > > > > > > > > > 6. I'm leaning towards considering that scenario a > > > > configuration > > > > > > > > > > error. If all log directories are cordoned before the > internal > > > > > topics > > > > > > > > > > are created, then the broker will not be able to create > them. > > > > > This > > > > > > > > > > seems like a pretty strange scenario, where it's the > first time > > > > > you > > > > > > > > > > start a broker, you've cordoned all its log directory, > and the > > > > > > > > > > internal topics (offsets and transactions) have not yet > been > > > > > created > > > > > > > > > > in the rest of the cluster. > > > > > > > > > > The metadata log is different (not managed by > LogManager), so I > > > > > think > > > > > > > > > > it should always be created regardless if its log > directory is > > > > > > > > > > cordoned or not. > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > Mickael > > > > > > > > > > > > > > > > > > > > On Tue, Jul 9, 2024 at 3:48 PM Chia-Ping Tsai < > > > > > chia7...@gmail.com> > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > hi Mickael > > > > > > > > > > > > > > > > > > > > > > That is totally a good idea, but I have a question > about the > > > > > > > > > > implementation > > > > > > > > > > > > > > > > > > > > > > Do we consider making pluggable ReplicaPlacer > (KIP-660) first > > > > > and > > > > > > > then > > > > > > > > > > add > > > > > > > > > > > another impl of ReplicaPlacer to offer cordon > mechanism? > > > > Noted > > > > > that > > > > > > > > > > > `ReplicaPlacer` can implement Reconfigurable to get > updated > > > > at > > > > > > > runtime. > > > > > > > > > > > That is similar to KIP-1066 - change cordoned.log.dirs > > > > through > > > > > > > configs > > > > > > > > > > > update. > > > > > > > > > > > > > > > > > > > > > > The benefit is to let users have their optimized > policy for > > > > > > > specific > > > > > > > > > > > scenario. Also, it can avoid that we add more and more > > > > > mechanism > > > > > > > to our > > > > > > > > > > > code base. Of course we can merge the mechanism which > can be > > > > > used > > > > > > > by 99% > > > > > > > > > > > users :smile > > > > > > > > > > > > > > > > > > > > > > Best, > > > > > > > > > > > Chia-Ping > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Luke Chen <show...@gmail.com> 於 2024年7月9日 週二 下午9:07寫道： > > > > > > > > > > > > > > > > > > > > > > > Hi Mickael, > > > > > > > > > > > > > > > > > > > > > > > > Thanks for the KIP! > > > > > > > > > > > > This is a long waiting feature for many users! > > > > > > > > > > > > > > > > > > > > > > > > Questions: > > > > > > > > > > > > 1. I think piggyback the "BrokerHeartbeatRequest" to > > > > forward > > > > > the > > > > > > > > > > corden log > > > > > > > > > > > > dir to controller makes sense to me. > > > > > > > > > > > > We already did similar things for fence, controller > > > > shutdown, > > > > > > > failed > > > > > > > > > > log > > > > > > > > > > > > dir...etc. > > > > > > > > > > > > > > > > > > > > > > > > 2. In the admin API, what parameters will the new > added > > > > > > > isCordoned() > > > > > > > > > > method > > > > > > > > > > > > take? > > > > > > > > > > > > > > > > > > > > > > > > 3. In the KIP, we said: > > > > > > > > > > > > "defaultDir(): This method will not return the Uuid > of a > > > > log > > > > > > > directory > > > > > > > > > > that > > > > > > > > > > > > is not cordoned." > > > > > > > > > > > > --> It's hard to understand. Does that mean we will > only > > > > > return > > > > > > > > > > cordoned > > > > > > > > > > > > log dir? > > > > > > > > > > > > From the current java doc of the interface, it > doesn't look > > > > > > > right: > > > > > > > > > > > > "Get the default directory for new partitions placed > in a > > > > > given > > > > > > > > > > broker." > > > > > > > > > > > > > > > > > > > > > > > > 4. Currently, if a broker is registered and then go > > > > offline. > > > > > In > > > > > > > this > > > > > > > > > > state, > > > > > > > > > > > > the controller will still distribute partitions to > this > > > > > broker. > > > > > > > > > > > > So, if now, the broker get startup with > "cordoned.log.dirs" > > > > > set, > > > > > > > what > > > > > > > > > > will > > > > > > > > > > > > happen? > > > > > > > > > > > > Will the newly assigned partitions be created > successfully > > > > or > > > > > > > not? > > > > > > > > > > > > > > > > > > > > > > > > 5. I think after a log dir get cordoned, we can > always > > > > > uncordon > > > > > > > it, > > > > > > > > > > right? > > > > > > > > > > > > I think we should mention it in the KIP. > > > > > > > > > > > > > > > > > > > > > > > > 6. If a broker is startup with "cordoned.log.dirs" > set, and > > > > > does > > > > > > > that > > > > > > > > > > mean > > > > > > > > > > > > the internal topics partitions (ex: > __consumer_offsets) > > > > > cannot be > > > > > > > > > > created, > > > > > > > > > > > > either? > > > > > > > > > > > > Also, if this log dir is happen to be the metadata > log dir, > > > > > what > > > > > > > will > > > > > > > > > > > > happen to the metadata topic creation? > > > > > > > > > > > > > > > > > > > > > > > > Thanks. > > > > > > > > > > > > Luke > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Tue, Jul 9, 2024 at 12:12 AM Mickael Maison < > > > > > > > > > > mickael.mai...@gmail.com> > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > Hi, > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks for taking a look. > > > > > > > > > > > > > > > > > > > > > > > > > > - Yes you're right, I meant > AlterPartitionReassignments. > > > > > Fixed. > > > > > > > > > > > > > - That's a good idea. I was expecting users to > discover > > > > > > > cordoned log > > > > > > > > > > > > > directories by describing broker configurations. > But > > > > being > > > > > > > able to > > > > > > > > > > > > > also get this information when describing log > directories > > > > > makes > > > > > > > > > > sense. > > > > > > > > > > > > > I've added that to the KIP. > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > > Mickael > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Fri, Jul 5, 2024 at 8:05 AM Haruki Okada < > > > > > > > ocadar...@gmail.com> > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > Hi, > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thank you for the KIP. > > > > > > > > > > > > > > The motivation sounds make sense to me. > > > > > > > > > > > > > > > > > > > > > > > > > > > > I have a few questions: > > > > > > > > > > > > > > > > > > > > > > > > > > > > - [nits] "AlterPartitions request" in Error > handling > > > > > section > > > > > > > is > > > > > > > > > > > > > > "AlterPartitionReassignments request" actually, > right? > > > > > > > > > > > > > > - Don't we need to include cordoned information > in > > > > > > > DescribeLogDirs > > > > > > > > > > > > > response > > > > > > > > > > > > > > too? Some tools (e.g. CruiseControl) need to > have a way > > > > > to > > > > > > > know > > > > > > > > > > which > > > > > > > > > > > > > > broker/log-dirs are cordoned to generate > partition > > > > > > > reassignment > > > > > > > > > > > > proposal. > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > > > > > > > > > > > > > > > > > 2024年7月4日(木) 22:57 Mickael Maison < > > > > > mickael.mai...@gmail.com > > > > > > > >: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Hi, > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > I'd like to start a discussion on KIP-1066 that > > > > > introduces > > > > > > > a > > > > > > > > > > > > mechanism > > > > > > > > > > > > > > > to cordon log directories and brokers. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-1066%3A+Mechanism+to+cordon+brokers+and+log+directories > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > > > > Mickael > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > > > > > > > > ======================== > > > > > > > > > > > > > > Okada Haruki > > > > > > > > > > > > > > ocadar...@gmail.com > > > > > > > > > > > > > > ======================== > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > David Arthur > > > > >
