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https://issues.apache.org/jira/browse/SOLR-12338?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16494162#comment-16494162
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David Smiley commented on SOLR-12338:
-------------------------------------
Please consider this alternative utility class:
{code:java}
/** A set of locks by a key {@code T}, kind of like Google Striped but the keys
are sparse/lazy. */
private static class SparseStripedLock<T> {
private final Semaphore sizeSemaphore;
private ConcurrentHashMap<T, CountDownLatch> map = new ConcurrentHashMap<>();
SparseStripedLock(int maxSize) {
this.sizeSemaphore = new Semaphore(maxSize);
}
void add(T t) throws InterruptedException {
if (t != null) {
CountDownLatch myLock = new CountDownLatch(1);
while (true) {
CountDownLatch existingLock = map.putIfAbsent(t, myLock); // returns
null if no existing
if (existingLock == null) {
break;// myLock was successfully inserted (and is pre-locked) already
locked, was successfully inserted
}
existingLock.await();// wait for existing lock/permit to become
available (see remove() below)
// we will most likely exit in next loop, though if contended then
possibly not
}
}
// won the lock
sizeSemaphore.acquire(); //nocommit do at start of add()?
}
void remove(T t) {
if (t != null) {
map.remove(t).countDown(); // remove and signal to any "await"-ers
}
sizeSemaphore.release();
}
}
{code}
Notice the comments, the loop, the new name, use of CountDownLatch, and the one
nocommit/question.
> Replay buffering tlog in parallel
> ---------------------------------
>
> Key: SOLR-12338
> URL: https://issues.apache.org/jira/browse/SOLR-12338
> Project: Solr
> Issue Type: Improvement
> Security Level: Public(Default Security Level. Issues are Public)
> Reporter: Cao Manh Dat
> Assignee: Cao Manh Dat
> Priority: Major
> Attachments: SOLR-12338.patch, SOLR-12338.patch, SOLR-12338.patch,
> SOLR-12338.patch, SOLR-12338.patch
>
>
> Since updates with different id are independent, therefore it is safe to
> replay them in parallel. This will significantly reduce recovering time of
> replicas in high load indexing environment.
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