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https://issues.apache.org/jira/browse/HBASE-22686?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16884296#comment-16884296
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Hudson commented on HBASE-22686:
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Results for branch branch-1.3
[build #865 on
builds.a.o|https://builds.apache.org/job/HBase%20Nightly/job/branch-1.3/865/]:
(/) *{color:green}+1 overall{color}*
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details (if available):
(/) {color:green}+1 general checks{color}
-- For more information [see general
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(/) {color:green}+1 jdk7 checks{color}
-- For more information [see jdk7
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(/) {color:green}+1 jdk8 hadoop2 checks{color}
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(/) {color:green}+1 source release artifact{color}
-- See build output for details.
> ZkSplitLogWorkerCoordination doesn't allow a regionserver to pick up all of
> the split work it is capable of
> -----------------------------------------------------------------------------------------------------------
>
> Key: HBASE-22686
> URL: https://issues.apache.org/jira/browse/HBASE-22686
> Project: HBase
> Issue Type: Bug
> Reporter: Andrew Purtell
> Assignee: Andrew Purtell
> Priority: Major
> Fix For: 3.0.0, 1.5.0, 2.3.0, 2.2.1, 1.3.6, 1.4.11, 2.1.7
>
> Attachments: HBASE-22686-branch-1.3.patch,
> HBASE-22686-branch-1.3.patch, HBASE-22686-branch-1.patch,
> HBASE-22686-branch-1.patch, HBASE-22686-branch-1.patch, HBASE-22686.patch,
> HBASE-22686.patch, HBASE-22686.patch
>
>
> A region hosted by a crashed regionserver cannot be reassigned until the
> crashed regionserver's write-ahead logs have been processed and split into
> per-region recovered edits files. Reassignment of a region from a crashed
> server will be held up by the distributed split work backlog. Every
> regionserver runs a background daemon thread that manages the acquisition and
> execution of distributed log split tasks. This thread registers a watcher on
> a znode managed by the master. When the master is processing a server
> shutdown or crash or cluster restart when it detects the presence of
> unprocessed WAL files it will register the WAL files for processing under the
> znode. One or more live regionservers will attempt to get an exclusive lock
> on an entry. One of them wins, splits the WAL file, deletes the entry, then
> will acquire more work or go back to sleep if the worklist is empty. A
> regionserver can acquire at most a fixed number of log split tasks determined
> by configuration, hbase.regionserver.wal.max.splitters (default 2). If the
> number of entries/logs to process exceeds the number of available split
> workers in the cluster, perhaps due to the correlated failure of a
> significant subset of the fleet, then splitting work will fall behind.
> Regions may remain in RIT until the backlog is cleared.
> However, the regionserver side coordination logic -
> ZkSplitLogWorkerCoordination - only allows a regionserver to grab one task
> one at a time. Nearby javadoc says "This policy puts an upper-limit on the
> number of simultaneous log splitting that could be happening in a cluster."
> That upper limit will be the number of currently live regionservers. I don't
> feel I understand exactly why this is necessary or appropriate because a
> regionserver can handle more than one task at once and in fact the max number
> of concurrent split tasks it can accept is configurable.
> {code:java}
> /**
> * This function calculates how many splitters it could create based on
> expected average tasks per
> * RS and the hard limit upper bound(maxConcurrentTasks) set by
> configuration. <br>
> * At any given time, a RS allows spawn MIN(Expected Tasks/RS, Hard Upper
> Bound)
> * @param numTasks current total number of available tasks
> */
> private int calculateAvailableSplitters(int numTasks) {
> // at lease one RS(itself) available
> int availableRSs = 1;
> try {
> List<String> regionServers =
> ZKUtil.listChildrenNoWatch(watcher, watcher.rsZNode);
> availableRSs = Math.max(availableRSs, (regionServers == null) ? 0 :
> regionServers.size());
> } catch (KeeperException e) {
> // do nothing
> LOG.debug("getAvailableRegionServers got ZooKeeper exception", e);
> }
> int expectedTasksPerRS = (numTasks / availableRSs) + ((numTasks %
> availableRSs == 0) ? 0 : 1);
> expectedTasksPerRS = Math.max(1, expectedTasksPerRS); // at least be one
> // calculate how many more splitters we could spawn
> return Math.min(expectedTasksPerRS, maxConcurrentTasks)
> - this.tasksInProgress.get();
> {code}
> Shouldn't this simply be:
> {code:java}
> private int calculateAvailableSplitters() {
> return maxConcurrentTasks - tasksInProgress.get();
> }
> {code}
> ?
> This is branch-1.
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