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From Pavel Kovalenko <jokse...@gmail.com>
Subject Re: Exchange stucks while node restoring state from WAL
Date Tue, 28 Aug 2018 14:59:23 GMT
Hello Maxim,

I think you're going in the right direction, but why you perform binary
recovery only in the case when a node in the baseline?
I think that node can also perform binary recovery before the first
exchange is started in case of
1) First activation
2) Baseline change

In all of these cases, you need just local available CacheDescriptors to
restore binary state from WAL.
I would like also see a test when Ignite is stopped in the middle of a
checkpoint and binary recovery succeed before PME in that case also.


ср, 22 авг. 2018 г. в 15:31, Pavel Kovalenko <jokserfn@gmail.com>:

> Hello Maxim,
>
> Thank you for your work. I will review your changes within the next
> several days.
>
> 2018-08-22 11:12 GMT+03:00 Maxim Muzafarov <maxmuzaf@gmail.com>:
>
>> Pavel,
>>
>> Thank you for so detailed introduction into the root of the problem of
>> ticket IGNITE-7196.
>> As you mentioned before, we can divide this ticket into two sub-tasks. So,
>> I will
>> file new issue for `Logical consistency recovery`. I think it's more
>> convenient way
>> for reviewing and merging each of these high level Steps (PRs).
>>
>> Currently, let's focus on `Physical(binary) consistency recovery` as the
>> most critical
>> part of this issue and synchronize our vision and vision of other
>> community
>> members
>> on implementation details of Step 1. From this point everything what I'm
>> saying is about
>> only binary recovery.
>>
>>
>> I think PR is almost ready (I need to check TC carefully).
>> Can you look at my changes? Am I going the right way?
>>
>> PR: https://github.com/apache/ignite/pull/4520
>> Upsource: https://reviews.ignite.apache.org/ignite/review/IGNT-CR-727
>> JIRA: https://issues.apache.org/jira/browse/IGNITE-7196
>>
>>
>> These are my milestones which I've tried to solve:
>> 1. On first time cluster activation no changes required. We should keep
>> this behavior.
>>
>> 2. `startMemoryPolicies` earlier if need.
>> Now at the master branch data regions starts at onActivate method called.
>> If we are  trying
>> to restore binary state on node reconnects to cluster we should start
>> regions earlier.
>>
>> 3. `suspendLogging` method added to switch off handlers.
>> Keep fast PDS cleanup when joining is not in BLT (or belongs to another
>> BLT).
>> Restore memory and metastorage initialization required `WALWriter` and
>> `FileWriteHandle`
>> to be started. They can lock directory\files and block cleanups.
>>
>> 4. `isBaselineNode` check before resumming logging.
>> The same as point 3. Local node gets discovery data and determines
>> #isLocalNodeNotInBaseline.
>> If node not in current baseline it performs cleanup local PDS and we
>> should
>> reset state of
>> previously initialized at startup metastorage instance.
>>
>> 5. `cacheProcessorStarted` callback added to restore memory at startup.
>> We can restore memory only after having info about all
>> `CacheGroupDescriptor`. To achieve this
>> we should do restoring at the moment `GridCacheProcessor` started.
>>
>> 6. Move `fsync` for `MemoryRecoveryRecord` at node startup.
>> We are fsync'ing it inside running PME. Suppose, it used for recovery
>> actions and\or control
>> cluster state outside Ignite project (methods `nodeStart` and
>> `nodeStartedPointers` of this
>> are not used at Ignite project code). I've moved them at the node startup,
>> but may be we should
>> dumping timestamp only at the time of node activation. Not sure.
>>
>> 7. `testBinaryRecoverBeforeExchange` test added to check restore before
>> PME.
>> Not sure that we should repeat wal reading logic as it was in
>> `testApplyDeltaRecords` test for
>> checking memory restoring. Suppose, minimally necessary condition is to
>> check `lastRestored` and
>> `checkpointHistory` states of database manager's (they should happend
>> before node joins to cluster).
>>
>> I will create separate ticket and refactor these minor issues after we
>> will
>> finish with 7196:
>> - simlify registerMBeans methods for
>> `Ignite\GridCacheDatabaseSharedManager`
>> - add @Override annotations if missed
>> - fix abbreviations regarding IdeaAbbrPlugin
>> - createDataRegionConfiguration method can be removed and simplified
>> - startMemoryPolicies rename to startDataRegion
>> - output messages format fix code style needed
>> - fix format javadoc's
>> - make inner classes private
>> - missed logging for cleanupCheckpointDirectory,
>> cleanupCheckpointDirectory, cleanupWalDirectories
>>
>> On Fri, 3 Aug 2018 at 18:20 Pavel Kovalenko <jokserfn@gmail.com> wrote:
>>
>> > Maxim,
>> >
>> > In the addition to my answer, I propose to divide the whole task into 2
>> > steps:
>> > 1) Physical consistency recovery before PME.
>> > 2) Logical consistency recovery before PME.
>> >
>> > The first step can be done before the discovery manager start, as it no
>> > needs any information about caches, it operates only with pages binary
>> > data. On this step, we can do points a) and b) from answer 3) and fsync
>> the
>> > state of the page memory.
>> > The second step is much harder to implement as it requires major
>> changes in
>> > Discovery SPI. Discovery node join event is triggered on coordinator
>> after
>> > node successfully joins to the cluster. To avoid it, we should
>> introduce a
>> > new state of node and fire discovery event only after logical recovery
>> has
>> > finished. I doubt that logical recovery consumes a lot of time of
>> exchange,
>> > but physical recovery does, as it performs fsync on disk after restore.
>> >
>> >
>> >
>> >
>> > 2018-08-03 17:46 GMT+03:00 Pavel Kovalenko <jokserfn@gmail.com>:
>> >
>> > > Hello Maxim,
>> > >
>> > > 1) Yes, Discovery Manager is starting after GridCacheProcessor, which
>> > > starts GridCacheDatabaseSharedManager which invokes readMetastorage on
>> > > start.
>> > >
>> > > 2) Before we complete the local join future, we create and add
>> Exchange
>> > > future on local node join to ExchangeManager. So, when local join
>> future
>> > > completes, first PME on that node should be already run or at least
>> there
>> > > will be first Exchange future in Exchange worker queue.
>> > >
>> > > 3) I don't exactly understand what do you mean saying "update obsolete
>> > > partition counter", but the process is the following:
>> > >     a) We restore page memory state (which contain partition update
>> > > counters) from the last checkpoint.
>> > >     b) We repair page memory state using physical delta records from
>> WAL.
>> > >     c) We apply logical records since last checkpoint finish marker.
>> > > During this iteration, if we meet DataRecord we increment update
>> counter
>> > on
>> > > appropriate partition. NOTE: This phase currently happens during
>> > exchange.
>> > >     After that partition exchange starts and information about actual
>> > > update counters will be collected from FullMessage. If partition
>> counters
>> > > are outdated, rebalance will start after PME end.
>> > >
>> > > 4) I think yes because everything that you need is cache descriptors
>> of
>> > > currently started caches on the grid. Some information can be
>> retrieved
>> > > from the static configuration. Information about dynamically started
>> > caches
>> > > can be retrieved from Discovery Data Bag received when a node joins to
>> > > ring. See
>> org.apache.ignite.internal.processors.cache.ClusterCachesInfo#
>> > > onGridDataReceived
>> > >
>> > > 5) I think the main problem is that metastorage and page memory share
>> one
>> > > WAL. But If this phase will happen before PME is started on all
>> cluster
>> > > nodes, I think it's acceptable that they will use 2 WAL iterations.
>> > >
>> > > 2018-08-03 10:28 GMT+03:00 Nikolay Izhikov <nizhikov@apache.org>:
>> > >
>> > >> Hello, Maxim.
>> > >>
>> > >> > 1) Is it correct that readMetastore() happens after node starts>
>> but
>> > >> before including node into the ring?>
>> > >>
>> > >> I think yes.
>> > >> You can have some kind of metainformation required on node join.
>> > >>
>> > >> > 5) Does in our final solution for new joined node readMetastore>
>> and
>> > >> restoreMemory should be performed in one step?
>> > >>
>> > >> I think, no.
>> > >>
>> > >> Meta Information can be required to perform restore memory.
>> > >> So we have to restore metainformation in first step and restore whole
>> > >> memory as a second step.
>> > >>
>> > >> В Пт, 03/08/2018 в 09:44 +0300, Maxim Muzafarov пишет:
>> > >> > Hi Igniters,
>> > >> >
>> > >> >
>> > >> > I'm working on bug [1] and have some questions about the final
>> > >> > implementation. Probably, I've already found answers on some of
>> > >> > them but I want to be sure. Please, help me to clarify details.
>> > >> >
>> > >> >
>> > >> > The key problem here is that we are reading WAL and restoring
>> > >> > memory state of new joined node inside PME. Reading WAL can
>> > >> > consume huge amount of time, so the whole cluster stucks and
>> > >> > waits for the single node.
>> > >> >
>> > >> >
>> > >> > 1) Is it correct that readMetastore() happens after node starts
>> > >> > but before including node into the ring?
>> > >> >
>> > >> > 2) Is after onDone() method called for LocalJoinFuture on local
>> > >> > node happend we can proceed with initiating PME on local node?
>> > >> >
>> > >> > 3) After reading checkpoint and restore memory for new joined
>> > >> > node how and when we are updating obsolete partitions update
>> > >> > counter? At historical rebalance, right?
>> > >> >
>> > >> > 4) Should we restoreMemory for new joined node before PME
>> > >> > initiates on the other nodes in cluster?
>> > >> >
>> > >> > 5) Does in our final solution for new joined node readMetastore
>> > >> > and restoreMemory should be performed in one step?
>> > >> >
>> > >> >
>> > >> > [1] https://issues.apache.org/jira/browse/IGNITE-7196
>> > >>
>> > >
>> > >
>> >
>> --
>> --
>> Maxim Muzafarov
>>
>
>

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