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Posted to issues@fluss.apache.org by "swuferhong (via GitHub)" <gi...@apache.org> on 2025/08/01 05:48:17 UTC
[PR] [client] Fix the RemoteLogDownloader cannot perform concurrent downloads error [fluss]
swuferhong opened a new pull request, #1443:
URL: https://github.com/apache/fluss/pull/1443
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### Purpose
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Linked issue: close #1442
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This pr is aims to fix the RemoteLogDownloader cannot perform concurrent downloads error
### Brief change log
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### Tests
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Re: [PR] [client] Fix the RemoteLogDownloader cannot perform concurrent downloads error [fluss]
Posted by "loserwang1024 (via GitHub)" <gi...@apache.org>.
loserwang1024 commented on code in PR #1443:
URL: https://github.com/apache/fluss/pull/1443#discussion_r2247030051
##########
fluss-client/src/main/java/com/alibaba/fluss/client/table/scanner/log/RemoteLogDownloader.java:
##########
@@ -140,44 +137,55 @@ void recycleRemoteLog(RemoteLogSegment segment) {
* to fetch.
*/
void fetchOnce() throws Exception {
- // wait until there is a remote fetch request
- RemoteLogDownloadRequest request = segmentsToFetch.poll(pollTimeout, TimeUnit.MILLISECONDS);
- if (request == null) {
+ int availablePermits = prefetchSemaphore.availablePermits();
+ List<RemoteLogDownloadRequest> requests = new ArrayList<>(availablePermits);
+ segmentsToFetch.drainTo(requests, availablePermits);
+ if (requests.size() <= 0) {
+ Thread.sleep(pollSleepTimeout);
return;
}
- // blocks until there is capacity (the fetched file is consumed)
- prefetchSemaphore.acquire();
+
+ prefetchSemaphore.acquire(requests.size());
Review Comment:
If the remoteLogDownloader is just a single thread, maybe a `Semaphore` is no need? Maybe a simple `EMPTY` condition is enough.
What is availablePermits is 8 while segmentsToFetch is just 4, then the thread will be blocked here.
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Re: [PR] [client] Fix the RemoteLogDownloader cannot perform concurrent downloads error [fluss]
Posted by "loserwang1024 (via GitHub)" <gi...@apache.org>.
loserwang1024 commented on code in PR #1443:
URL: https://github.com/apache/fluss/pull/1443#discussion_r2247030051
##########
fluss-client/src/main/java/com/alibaba/fluss/client/table/scanner/log/RemoteLogDownloader.java:
##########
@@ -140,44 +137,55 @@ void recycleRemoteLog(RemoteLogSegment segment) {
* to fetch.
*/
void fetchOnce() throws Exception {
- // wait until there is a remote fetch request
- RemoteLogDownloadRequest request = segmentsToFetch.poll(pollTimeout, TimeUnit.MILLISECONDS);
- if (request == null) {
+ int availablePermits = prefetchSemaphore.availablePermits();
+ List<RemoteLogDownloadRequest> requests = new ArrayList<>(availablePermits);
+ segmentsToFetch.drainTo(requests, availablePermits);
+ if (requests.size() <= 0) {
+ Thread.sleep(pollSleepTimeout);
return;
}
- // blocks until there is capacity (the fetched file is consumed)
- prefetchSemaphore.acquire();
+
+ prefetchSemaphore.acquire(requests.size());
Review Comment:
If the remoteLogDownloader is just a single thread, maybe a `Semaphore` is no need? Maybe a simple `EMPTY` condition is enough.
What is availablePermits is 8 while segmentsToFetch is just 4?
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Re: [PR] [client] Fix the RemoteLogDownloader cannot perform concurrent downloads error [fluss]
Posted by "swuferhong (via GitHub)" <gi...@apache.org>.
swuferhong commented on code in PR #1443:
URL: https://github.com/apache/fluss/pull/1443#discussion_r2255777485
##########
fluss-client/src/main/java/com/alibaba/fluss/client/table/scanner/log/RemoteLogDownloader.java:
##########
@@ -140,44 +137,55 @@ void recycleRemoteLog(RemoteLogSegment segment) {
* to fetch.
*/
void fetchOnce() throws Exception {
- // wait until there is a remote fetch request
- RemoteLogDownloadRequest request = segmentsToFetch.poll(pollTimeout, TimeUnit.MILLISECONDS);
- if (request == null) {
+ int availablePermits = prefetchSemaphore.availablePermits();
+ List<RemoteLogDownloadRequest> requests = new ArrayList<>(availablePermits);
+ segmentsToFetch.drainTo(requests, availablePermits);
+ if (requests.size() <= 0) {
+ Thread.sleep(pollSleepTimeout);
return;
}
- // blocks until there is capacity (the fetched file is consumed)
- prefetchSemaphore.acquire();
+
+ prefetchSemaphore.acquire(requests.size());
Review Comment:
After offline discussion, this case will not happen.
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Re: [PR] [client] Fix the RemoteLogDownloader cannot perform concurrent downloads error [fluss]
Posted by "wuchong (via GitHub)" <gi...@apache.org>.
wuchong commented on PR #1443:
URL: https://github.com/apache/fluss/pull/1443#issuecomment-3216234920
I opened a new PR for this issue https://github.com/apache/fluss/pull/1579
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Re: [PR] [client] Fix the RemoteLogDownloader cannot perform concurrent downloads error [fluss]
Posted by "wuchong (via GitHub)" <gi...@apache.org>.
wuchong closed pull request #1443: [client] Fix the RemoteLogDownloader cannot perform concurrent downloads error
URL: https://github.com/apache/fluss/pull/1443
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Re: [PR] [client] Fix the RemoteLogDownloader cannot perform concurrent downloads error [fluss]
Posted by "loserwang1024 (via GitHub)" <gi...@apache.org>.
loserwang1024 commented on code in PR #1443:
URL: https://github.com/apache/fluss/pull/1443#discussion_r2247030051
##########
fluss-client/src/main/java/com/alibaba/fluss/client/table/scanner/log/RemoteLogDownloader.java:
##########
@@ -140,44 +137,55 @@ void recycleRemoteLog(RemoteLogSegment segment) {
* to fetch.
*/
void fetchOnce() throws Exception {
- // wait until there is a remote fetch request
- RemoteLogDownloadRequest request = segmentsToFetch.poll(pollTimeout, TimeUnit.MILLISECONDS);
- if (request == null) {
+ int availablePermits = prefetchSemaphore.availablePermits();
+ List<RemoteLogDownloadRequest> requests = new ArrayList<>(availablePermits);
+ segmentsToFetch.drainTo(requests, availablePermits);
+ if (requests.size() <= 0) {
+ Thread.sleep(pollSleepTimeout);
return;
}
- // blocks until there is capacity (the fetched file is consumed)
- prefetchSemaphore.acquire();
+
+ prefetchSemaphore.acquire(requests.size());
Review Comment:
If the remoteLogDownloader is just a single thread, maybe a `Semaphore` is no need? Maybe a simple `EMPTY` condition is enough.
What if availablePermits is 8 while segmentsToFetch is just 4?
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