This class is only used by the blob store repository
and CCR and the abstractions didn't really make sense
with CCR ignoring the concrete `restoreFiles` method
completely and having a method used only by the blobstore
overriden as unsupported.
=> Moved to a more fitting set of abstractions
=> Dried up the stream wrapping in `BlobStoreRepository` a little
now that the `restoreFile` method could be simplified
Relates #48110 as it makes changing the API of `FileRestoreContext`
to what is needed for async restores simpler
The test testPauseAndResumeWithMultipleAutoFollowPatterns
failed multiple times, mostly because it creates too many leader
indices and the following cluster cannot cope with cluster state
updates generated by following indices creation and pause/
resume auto-followers changes.
This commit simplifies the test by creating at most 20 leader
indices and by waiting for any new leader index to be picked
up by the auto-follower before created another leader index.
It also pause and resume less auto-followers as previously.
closes#47917
The logic for handling empty segment files has been
unnecessary ever since #24021 which removes the support
for these files in 6.x -> we can safely remove the
support for restoring these from 7.x+ to simplify the code.
This commit adds two APIs that allow to pause and resume
CCR auto-follower patterns:
// pause auto-follower
POST /_ccr/auto_follow/my_pattern/pause
// resume auto-follower
POST /_ccr/auto_follow/my_pattern/resume
The ability to pause and resume auto-follow patterns can be
useful in some situations, including the rolling upgrades of
cluster using a bi-directional cross-cluster replication scheme
(see #46665).
This commit adds a new active flag to the AutoFollowPattern
and adapts the AutoCoordinator and AutoFollower classes so
that it stops to fetch remote's cluster state when all auto-follow
patterns associate to the remote cluster are paused.
When an auto-follower is paused, remote indices that match the
pattern are just ignored: they are not added to the pattern's
followed indices uids list that is maintained in the local cluster
state. This way, when the auto-follow pattern is resumed the
indices created in the remote cluster in the meantime will be
picked up again and added as new following indices. Indices
created and then deleted in the remote cluster will be ignored
as they won't be seen at all by the auto-follower pattern at
resume time.
Backport of #47510 for 7.x
Backport of (#47721) for 7.x.
Similarly to #47582, Auto-follow patterns creates following
indices as long as the remote index matches the pattern and
the remote primary shards are all started. But since 7.2 closed
indices are also replicated, and it does not play well with CCR
auto-follow patterns as they create following indices for closed
leader indices too.
This commit changes the getLeaderIndicesToFollow() so that closed
indices are excluded from auto-follow patterns.
Backport of (#47582)
Today when following a new leader index, we fetch the remote cluster state,
check the remote cluster license, check the user privileges, retrieve the
index shard stats before initiating a CCR restore session.
But if the leader index to follow is closed, we're executing a bunch of
operations that would inevitability fail at some point (on retrieving the
index shard stats, because this type of request forbid closed indices
when resolving indices). We could fail a Put Follow request at the first
step by checking the leader index state directly from the remote cluster
state.
This also helps the Resume Follow API to fail a bit earlier.
As a result of #45689 snapshot finalization started to
take significantly longer than before. This may be a
little unfortunate since it increases the likelihood
of failing to finalize after having written out all
the segment blobs.
This change parallelizes all the metadata writes that
can safely run in parallel in the finalization step to
speed the finalization step up again. Also, this will
generally speed up the snapshot process overall in case
of large number of indices.
This is also a nice to have for #46250 since we add yet
another step (deleting of old index- blobs in the shards
to the finalization.
Backport of #45794 to 7.x. Convert most `awaitBusy` calls to
`assertBusy`, and use asserts where possible. Follows on from #28548 by
@liketic.
There were a small number of places where it didn't make sense to me to
call `assertBusy`, so I kept the existing calls but renamed the method to
`waitUntil`. This was partly to better reflect its usage, and partly so
that anyone trying to add a new call to awaitBusy wouldn't be able to find
it.
I also didn't change the usage in `TransportStopRollupAction` as the
comments state that the local awaitBusy method is a temporary
copy-and-paste.
Other changes:
* Rework `waitForDocs` to scale its timeout. Instead of calling
`assertBusy` in a loop, work out a reasonable overall timeout and await
just once.
* Some tests failed after switching to `assertBusy` and had to be fixed.
* Correct the expect templates in AbstractUpgradeTestCase. The ES
Security team confirmed that they don't use templates any more, so
remove this from the expected templates. Also rewrite how the setup
code checks for templates, in order to give more information.
* Remove an expected ML template from XPackRestTestConstants The ML team
advised that the ML tests shouldn't be waiting for any
`.ml-notifications*` templates, since such checks should happen in the
production code instead.
* Also rework the template checking code in `XPackRestTestHelper` to give
more helpful failure messages.
* Fix issue in `DataFrameSurvivesUpgradeIT` when upgrading from < 7.4
We disable MSU optimization if the local checkpoint is smaller than
max_seq_no_of_updates. Hence, we need to relax the MSU assertion in
FollowingEngine for that scenario. Suppose the leader has three
operations: index-0, delete-1, and index-2 for the same doc Id. MSU on
the leader is 1 as index-2 is an append. If the follower applies index-0
then index-2, then the assertion is violated.
Closes#47137
This commit adds the ability to require an ingest pipeline on an
index. Today we can have a default pipeline, but that could be
overridden by a request pipeline parameter. This commit introduces a new
index setting index.required_pipeline that acts similarly to
index.default_pipeline, except that it can not be overridden by a
request pipeline parameter. Additionally, a default pipeline and a
request pipeline can not both be set. The required pipeline can be set
to _none to ensure that no pipeline ever runs for index requests on that
index.
* Write metadata during snapshot finalization after segment files to prevent outdated metadata in case of dynamic mapping updates as explained in #41581
* Keep the old behavior of writing the metadata beforehand in the case of mixed version clusters for BwC reasons
* Still overwrite the metadata in the end, so even a mixed version cluster is fixed by this change if a newer version master does the finalization
* Fixes#41581
We renew the CCR retention lease at a fixed interval, therefore it's
possible to have more than one in-flight renewal requests at the same
time. If requests arrive out of order, then the assertion is violated.
Closes#46416Closes#46013
* More Efficient Ordering of Shard Upload Execution (#42791)
* Change the upload order of of snapshots to work file by file in parallel on the snapshot pool instead of merely shard-by-shard
* Inspired by #39657
* Cleanup BlobStoreRepository Abort and Failure Handling (#46208)
Today we might carry on a big merge uncommitted and therefore
occupy a significant amount of diskspace for quite a long time
if for instance indexing load goes down and we are not quickly
reaching the translog size threshold. This change will cause a
flush if we hit a significant merge (512MB by default) which
frees diskspace sooner.
If a CCR lease is disappeared while we are renewing it, then we will
issue asyncAddRetentionLease to add that lease. And if
asyncAddRetentionLease takes longer than retentionLeaseRenewInterval,
then we can issue another asyncAddRetentionLease request. One of
asyncAddRetentionLease requests will fail with
RetentionLeaseAlreadyExistsException, hence trip the assertion.
Closes#45192
The setting index.soft_deletes.retention.operations is no longer needed
nor recommended in CCR. We, therefore, should hint users about the
retention leases period setting instead when operations are no longer
available for replicating.
* Restrict which tasks can use testclusters
This PR fixes a problem between the interaction of test-clusters and
build cache.
Before this any task could have used a cluster without tracking it as
input.
With this change a new interface is introduced to track the tasks that
can use clusters and we do consider the cluster as input for all of
them.
Today we recover a replica by copying operations from the primary's translog.
However we also retain some historical operations in the index itself, as long
as soft-deletes are enabled. This commit adjusts peer recovery to use the
operations in the index for recovery rather than those in the translog, and
ensures that the replication group retains enough history for use in peer
recovery by means of retention leases.
Reverts #38904 and #42211
Relates #41536
Backport of #45136 to 7.x.
We keep adding the current primary term to operations for which we do not assign a sequence
number. This does not make sense anymore as all operations which we care about have
sequence numbers now. The goal of this commit is to clean things up in InternalEngine and
reduce the complexity.
The problem is that RemoteClusterConnection closes the connection manager asynchronously, which races with the threadpool being shutdown at the end of the test.
Closes#44339Closes#44610
Deleting a follower index does not delete its ShardFollowTasks, potentially
leaving many persistent tasks in the cluster that cannot be allocated on
nodes and unnecessary fill the logs. This commit adds a cluster state listener
(ShardFollowTaskCleaner) that completes (with a failure) any persistent task
that refers to a non existent follower index.
I think that this bug has been introduced by #34404: before this change the
task would have been completed as failed and removed from the cluster state.
Backport of #44702 and #44801 on 7.x
* Mute failing test
tracked in #44552
* mute EvilSecurityTests
tracking in #44558
* Fix line endings in ESJsonLayoutTests
* Mute failing ForecastIT test on windows
Tracking in #44609
* mute BasicRenormalizationIT.testDefaultRenormalization
tracked in #44613
* fix mute testDefaultRenormalization
* Increase busyWait timeout windows is slow
* Mute failure unconfigured node name
* mute x-pack internal cluster test windows
tracking #44610
* Mute JvmErgonomicsTests on windows
Tracking #44669
* mute SharedClusterSnapshotRestoreIT testParallelRestoreOperationsFromSingleSnapshot
Tracking #44671
* Mute NodeTests on Windows
Tracking #44256
If the setting on the follower and the leader are identical after
filtering out private and internal settings, then we should not call
update setting (on the follower) as there's nothing to change. Moreover,
this makes the ShardFollowTask abort as it considers
ActionRequestValidationException (caused by an empty update setting
request) as a fatal error.
Closes#44521
this commit removes usage of the deprecated
constructor with a single argument and no Writeable.Reader.
The purpose of this is to reduce the boilerplate necessary for
properly implementing a new action, as well as reducing the
chances of using the incorrect super constructor while classes
are being migrated to Writeable
relates #34389.
This commit avoids a situation where we might stack overflow in the
auto-follower coordinator. In the face of repeated failures to get the
remote cluster state, we would previously be called back on the same
thread and then recurse to try again. If this failure persists, the
repeated callbacks on the same thread would lead to a stack
overflow. The repeated failures can occur, for example, if the connect
queue is full when we attempt to make a connection to the remote
cluster. This commit avoids this by truncating the call stack if we are
called back on the same thread as the initial request was made on.
This commit avoids an NPE when checking for privileges to follow
indices. The problem here is that in some cases we might not be able to
read the authentication info from the thread context. In that case, a
null user would be returned and we were not guarding against this.
Test clusters currently has its own set of logic for dealing with
finding different versions of Elasticsearch, downloading them, and
extracting them. This commit converts testclusters to use the
DistributionDownloadPlugin.
This commit creates new base classes for master node actions whose
response types still implement Streamable. This simplifies both finding
remaining classes to convert, as well as creating new master node
actions that use Writeable for their responses.
relates #34389
* The incompatible snapshots logic was created to track 1.x snapshots that
became incompatible with 2.x
* It serves no purpose at this point
* It adds an additional GET request to every loading of
RepositoryData (from loading the incompatible snapshots blob)
The base classes for transport requests and responses currently
implement Streamable and Writeable. The writeTo method on these base
classes is implemented with an empty implementation. Not only does this
complicate subclasses to think they need to call super.writeTo, but it
also can lead to not implementing writeTo when it should have been
implemented, or extendiong one of these classes when not necessary,
since there is nothing to actually implement.
This commit removes the empty writeTo from these base classes, and fixes
subclasses to not call super and in some cases implement an empty
writeTo themselves.
relates #34389
This PR enables the indexing optimization using sequence numbers on
replicas. With this optimization, indexing on replicas should be faster
and use less memory as it can forgo the version lookup when possible.
This change also deactivates the append-only optimization on replicas.
Relates #34099
Action is a class that encapsulates meta information about an action
that allows it to be called remotely, specifically the action name and
response type. With recent refactoring, the action class can now be
constructed as a static constant, instead of needing to create a
subclass. This makes the old pattern of creating a singleton INSTANCE
both misnamed and lacking a common placement.
This commit renames Action to ActionType, thus allowing the old INSTANCE
naming pattern to be TYPE on the transport action itself. ActionType
also conveys that this class is also not the action itself, although
this change does not rename any concrete classes as those will be
removed organically as they are converted to TYPE constants.
relates #34389
The Action base class currently works for both Streamable and Writeable
response types. This commit intorduces StreamableResponseAction, for
which only the legacy Action implementions which provide newResponse()
will extend. This eliminates the need for overriding newResponse() with
an UnsupportedOperationException.
relates #34389
This commit replaces usages of Streamable with Writeable for the
AcknowledgedResponse and its subclasses, plus associated actions.
Note that where possible response fields were made final and default
constructors were removed.
This is a large PR, but the change is mostly mechanical.
Relates to #34389
Backport of #43414
Local and global checkpoints currently do not correctly reflect what's persisted to disk. The issue is
that the local checkpoint is adapted as soon as an operation is processed (but not fsynced yet). This
leaves room for the history below the global checkpoint to still change in case of a crash. As we rely
on global checkpoints for CCR as well as operation-based recoveries, this has the risk of shard
copies / follower clusters going out of sync.
This commit required changing some core classes in the system:
- The LocalCheckpointTracker keeps track now not only of the information whether an operation has
been processed, but also whether that operation has been persisted to disk.
- TranslogWriter now keeps track of the sequence numbers that have not been fsynced yet. Once
they are fsynced, TranslogWriter notifies LocalCheckpointTracker of this.
- ReplicationTracker now keeps track of the persisted local and persisted global checkpoints of all
shard copies when in primary mode. The computed global checkpoint (which represents the
minimum of all persisted local checkpoints of all in-sync shard copies), which was previously stored
in the checkpoint entry for the local shard copy, has been moved to an extra field.
- The periodic global checkpoint sync now also takes async durability into account, where the local
checkpoints on shards only advance when the translog is asynchronously fsynced. This means that
the previous condition to detect inactivity (max sequence number is equal to global checkpoint) is
not sufficient anymore.
- The new index closing API does not work when combined with async durability. The shard
verification step is now requires an additional pre-flight step to fsync the translog, so that the main
verify shard step has the most up-to-date global checkpoint at disposition.
This commit removes some very old test logging annotations that appeared
to be added to investigate test failures that are long since closed. If
these are needed, they can be added back on a case-by-case basis with a
comment associating them to a test failure.
Backport of: https://github.com/elastic/elasticsearch/pull/43222
This commit replaces usages of Streamable with Writeable for the
SingleShardRequest / TransportSingleShardAction classes and subclasses of
these classes.
Note that where possible response fields were made final and default
constructors were removed.
Relates to #34389
With this change, we will rebuild the live version map and local
checkpoint using documents (including soft-deleted) from the safe commit
when opening an internal engine. This allows us to safely prune away _id
of all soft-deleted documents as the version map is always in-sync with
the Lucene index.
Relates #40741
Supersedes #42979
In these tests, we sleep for a small multiple of the renew interval,
then check that the retention leases are not changed. If a renewal
request takes longer than that interval because of GC or slow CI, then
the retention leases are not the same as before sleep. With this change,
we relax to assert that we eventually stop the renewable process.
Closes#39509
The retention leases stats is null if the processing shard copy is being
closed. In this the case, we should check against null then retry to
avoid failing a test.
Closes#41237
This commit refactors put mapping request validation for reuse. The
concrete case that we are after here is the ability to apply effectively
the same framework to indices aliases requests. This commit refactors
the put mapping request validation framework to allow for that.
Adds a metadata field to snapshots which can be used to store arbitrary
key-value information. This may be useful for attaching a description of
why a snapshot was taken, tagging snapshots to make categorization
easier, or identifying the source of automatically-created snapshots.
This commit adds functionality so that aliases that are manipulated on
leader indices are replicated by the shard follow tasks to the follower
indices. Note that we ignore write indices. This is due to the fact that
follower indices do not receive direct writes so the concept is not
useful.
Relates #41815
testRetentionLeaseIsAddedIfItDisappearsWhileFollowing does not reset the
mock transport service after test. Surviving transport interceptors from
that test can sneaky remove retention leases and make other tests fail.
Closes#39331Closes#39509Closes#41428Closes#41679Closes#41737Closes#41756
We need more information to understand why CcrRetentionLeaseIT is
failing. This commit adds some debug log to retention leases and enables
them in CcrRetentionLeaseIT.
ShardId already implements Writeable so there is no need for it to implement Streamable too. Also the readShardId static method can be
easily replaced with direct usages of the constructor that takes a
StreamInput as argument.
* Remove IndexShard dependency from Repository
In order to simplify repository testing especially for BlobStoreRepository
it's important to remove the dependency on IndexShard and reduce it to
Store and MapperService (in the snapshot case). This significantly reduces
the dependcy footprint for Repository and allows unittesting without starting
nodes or instantiate entire shard instances. This change deprecates the old
method signatures and adds a unittest for FileRepository to show the advantage
of this change.
In addition, the unittesting surfaced a bug where the internal file names that
are private to the repository were used in the recovery stats instead of the
target file names which makes it impossible to relate to the actual lucene files
in the recovery stats.
* don't delegate deprecated methods
* apply comments
* test
Moves the test infrastructure away from using node.max_local_storage_nodes, allowing us in a
follow-up PR to deprecate this setting in 7.x and to remove it in 8.0.
This also changes the behavior of InternalTestCluster so that starting up nodes will not automatically
reuse data folders of previously stopped nodes. If this behavior is desired, it needs to be explicitly
done by passing the data path from the stopped node to the new node that is started.
Previously, TransportSingleShardAction required constructing a new
empty response object. This response object's Streamable readFrom
was used. As part of the migration to Writeable, the interface here
was updated to leverage Writeable.Reader.
relates to #34389.
These tests are failing somewhat mysteriously, indicating that when we
renew retention leaess during a restore that our retention leases that
we added before starting the restore suddenly do not exist. To make
sense of this, this commit enables trace logging.
The run task is supposed to run elasticsearch with the given plugin or
module. However, for modules, this is most realistic if using the full
distribution. This commit changes the run setup to use the default or
oss as appropriate.
With this change, we will verify the consistency of version and source
(besides id, seq_no, and term) of live documents between shard copies
at the end of disruption tests.
Today we choose to initialize max_seq_no_of_updates on primaries only so
we can deal with a situation where a primary is on an old node (before
6.5) which does not have MUS while replicas on new nodes (6.5+).
However, this strategy is quite complex and can lead to bugs (for
example #40249) since we have to assign a correct value (not too low) to
MSU in all possible situations (before recovering from translog,
restoring history on promotion, and handing off relocation).
Fortunately, we don't have to deal with this BWC in 7.0+ since all nodes
in the cluster should have MSU. This change simplifies the
initialization of MSU by always assigning it a correct value in the
constructor of Engine regardless of whether it's a replica or primary.
Relates #33842
Motivated by slow snapshot deletes reported in e.g. #39656 and the fact that these likely are a contributing factor to repositories accumulating stale files over time when deletes fail to finish in time and are interrupted before they can complete.
* Makes snapshot deletion async and parallelizes some steps of the delete process that can be safely run concurrently via the snapshot thread poll
* I did not take the biggest potential speedup step here and parallelize the shard file deletion because that's probably better handled by moving to bulk deletes where possible (and can still be parallelized via the snapshot pool where it isn't). Also, I wanted to keep the size of the PR manageable.
* See https://github.com/elastic/elasticsearch/pull/39656#issuecomment-470492106
* Also, as a side effect this gives the `SnapshotResiliencyTests` a little more coverage for master failover scenarios (since parallel access to a blob store repository during deletes is now possible since a delete isn't a single task anymore).
* By adding a `ThreadPool` reference to the repository this also lays the groundwork to parallelizing shard snapshot uploads to improve the situation reported in #39657
* Introduce Delegating ActionListener Wrappers
* Dry up use cases of ActionListener that simply pass through the response or exception to another listener
It looks like these permissions were copy/pasted from another plugin yet
almost none of these permissions are needed for the CCR plugin. This
commit removes all these unneeded permissions from the CCR plugin.
This is a dependency of #39504
Motivation:
By refactoring `TransportShardBulkAction#shardOperationOnPrimary` to async, we enable using `DeterministicTaskQueue` based tests to run indexing operations. This was previously impossible since we were blocking on the `write` thread until the `update` thread finished the mapping update.
With this change, the mapping update will trigger a new task in the `write` queue instead.
This change significantly enhances the amount of coverage we get from `SnapshotResiliencyTests` (and other potential future tests) when it comes to tracking down concurrency issues with distributed state machines.
The logical change is effectively all in `TransportShardBulkAction`, the rest of the changes is then simply mechanically moving the caller code and tests to being async and passing the `ActionListener` down.
Since the move to async would've added more parameters to the `private static` steps in this logic, I decided to inline and dry up (between delete and update) the logic as much as I could instead of passing the listener + wait-consumer down through all of them.
* Replace usages RandomizedTestingTask with built-in Gradle Test (#40978)
This commit replaces the existing RandomizedTestingTask and supporting code with Gradle's built-in JUnit support via the Test task type. Additionally, the previous workaround to disable all tasks named "test" and create new unit testing tasks named "unitTest" has been removed such that the "test" task now runs unit tests as per the normal Gradle Java plugin conventions.
(cherry picked from commit 323f312bbc829a63056a79ebe45adced5099f6e6)
* Fix forking JVM runner
* Don't bump shadow plugin version
Many gradle projects specifically use the -try exclude flag, because
there are many cases where auto-closeable resource ignore is never
referenced in body of corresponding try statement. Suppressing this
warning specifically in each case that it happens using
`@SuppressWarnings("try")` would be very verbose.
This change removes `-try` from any gradle project and adds it to the
build plugin. Also this change removes exclude flags from gradle projects
that is already specified in build plugin (for example -deprecation).
Relates to #40366
It is important that resync actions are not rejected on the primary even if its
`write` threadpool is overloaded. Today we do this by exposing
`registerRequestHandlers` to subclasses and overriding it in
`TransportResyncReplicationAction`. This isn't ideal because it obscures the
difference between this action and other replication actions, and also might
allow subclasses to try and use some state before they are properly
initialised. This change replaces this override with a constructor parameter to
solve these issues.
Relates #40706
Currently the TransportMessageListener is applied and used in the
Transport class. However, local requests and responses never make it to
this class. This PR moves the listener add/remove methods to the
TransportService. After this change the Transport can only have one
listener set with it. This one listener is the TransportService, which
will then propogate the events to the external listeners.
Additionally this commit back ports #40237
Remove Tracer from MockTransportService
Currently the TransportMessageListener is applied and used in the
Transport class. However, local requests and responses never make it to
this class. This PR moves the listener add/remove methods to the
TransportService. After this change the Transport can only have one
listener set with it. This one listener is the TransportService, which
will then propogate the events to the external listeners.
In some cases, a request to perform a retention lease action can arrive
on a primary shard before it is active. In this case, the primary shard
would not yet be in primary mode, tripping an assertion in the
replication tracker. Instead, we should not attempt to perform such
actions on an initializing shard. This commit addresses this by not
returning the primary shard in the single shard iterator if the primary
shard is not yet active.
If there's a failover on the follower, then its max_seq_no_of_updates is
bootstrapped from its max_seq_no which might be higher than the
max_seq_no_of_updates of the leader. We need to relax this check.
Relates #40249
This commit adjusts the frequency with which CCR renews retention leases
and with which primaries sync retention leases to replicas. This helps
Lucene reclaim soft-deleted documents more aggressively, which we have
found in some use-cases can help improve performance, and either way
will help keep disk space under more control.
Currently, we cannot update index setting index.translog.sync_interval if index is open, because it's
not dynamic which can be updated for closed index only.
Closes#32763
If a replica were first reset due to one primary failover and then
promoted (before resync completes), its MSU would not include changes
since global checkpoint, leading to errors during translog replay.
Fixed by re-initializing MSU before restoring local history.
This named writable was never registered, so it means that we could not
read auto-follow patterns that were registered in the cluster
state. This causes them to be lost on restarts, a bad bug. This commit
addresses this by registering this named writable, and we add a basic
CCR restart test to ensure that CCR keeps functioning properly when the
follower is restarted.
We introduced WAIT_CLUSTERSTATE action in #19287 (5.0), but then stopped
using it since #25692 (6.0). This change removes that action and related
code in 7.x and 8.0.
Relates #19287
Relates #25692
We were leaking a reference to an AutoFollowCoordinator during
construction, violating safe publication according to the JLS
specification. This commit addresses this by waiting to register
AutoFollowCoordinator with the ClusterApplierService after the
AutoFollowCoordinator is fully constructed. We also remove ourselves as
a listener when stopping.
When shutting down a node, auto-followers will keep trying to run. This
is happening even as transport services and other components are being
closed. In some cases, this can lead to a stack overflow as we rapidly
try to check the license state of the remote cluster, can not because
the transport service is shutdown, and then immeidately retry
again. This can happen faster than the shutdown, and we die with stack
overflow. This commit adds a stop command to auto-followers so that this
retry loop occurs at most once on shutdown.
When an auto-follower coordinator times out waiting for the remote
cluster state, we do not log any indication of this. While this is
expected behavior in quiet deployments, it is still useful to see this
information for tracing the behavior of the auto-follow
coordinator. This commit adds a trace log message indicating that the
timeout.