Prefetcher, to read fast. by jean-philippe-martin · Pull Request #3054 · googleapis/google-cloud-java

jean-philippe-martin · 2018-03-16T22:06:55Z

The prefetcher can load data on another thread in between calls,
and it can intelligently use its existing buffer to deal with small
seeks without having to fetch again.

The prefetcher can load data on another thread in between calls, and it can intelligently use its existing buffer to deal with small seeks without having to fetch again.

jean-philippe-martin · 2018-03-26T21:26:32Z

@pongad, I understand the ball is in your camp? If it isn't then please let me know what you'd like me to do before you look at this PR.

pongad

@jean-philippe-martin Thank you for the PR! I made a few comments. @garrettjonesgoogle @jabubake Could you also take a look?

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@@ -0,0 +1,496 @@
+/*
+ * Copyright 2016 Google LLC


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+
+ // statistics, for profiling
+ // time spent blocking the user because we're waiting on the network
+ public long msWaitingForData;


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+ * @param bufSize buffer size in bytes
+ * @param chan channel to wrap in the prefetcher
+ */
+ public SeekableByteChannelPrefetcher(SeekableByteChannel chan, int bufSize) throws IOException {


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+ */
+ public SeekableByteChannelPrefetcher(SeekableByteChannel chan, int bufSize) throws IOException {
+ if (chan instanceof SeekableByteChannelPrefetcher) {
+ throw new IllegalArgumentException("Cannot put two prefetchers on the same channel.");


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+ // if we don't already have that block and the fetching thread is idle,
+ // make sure it now goes looking for that block index.
+ private void ensureFetching(long blockIndex) {
+ if (null != fetching) {


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+ this.bufSize = bufSize;
+ }
+ this.open = true;
+ int prefetcherIndex = prefetcherCount++;


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+ fetching = full.remove(0);
+ fetching.resetForIndex(blockIndex);
+ bytesRead += bufSize;
+ fetching.futureBuf = exec.submit(fetching);


jean-philippe-martin · 2018-03-27T04:48:53Z

In case you'd like extra eyes, @jart is familiar with this code and may be willing to help review.

jabubake · 2018-03-27T14:02:42Z

@frankyn FYI

pongad · 2018-03-28T02:45:16Z

I'm good with this. @jabubake Do you also want to take a look?

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@@ -0,0 +1,494 @@
+/*
+ * Copyright 2018 Google LLC


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+ exec = Executors.newFixedThreadPool(1, threadFactory);
+ }
+
+ public String getStatistics() {


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+ .setDaemon(true)
+ .build();
+ // Single thread to ensure no concurrent access to chan.
+ exec = Executors.newFixedThreadPool(1, threadFactory);


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+ // Make sure the prefetching thread's name indicate what it is and
+ // which prefetcher it belongs to (for debugging purposes only, naturally).
+ String nameFormat = "nio-prefetcher-" + prefetcherIndex + "-thread-%d";
+ ThreadFactory threadFactory = new ThreadFactoryBuilder()


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+ */
+ @Override
+ public SeekableByteChannel position(long newPosition) throws IOException {
+ if (!open) throw new ClosedChannelException();


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+ * the entity to grow to accommodate the new bytes; the values of any bytes
+ * between the previous end-of-file and the newly-written bytes are
+ * unspecified.
+ * <p>


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+ .build();
+ // Single thread to ensure no concurrent access to chan.
+ exec = Executors.newFixedThreadPool(1, threadFactory);
+ }


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+ * (Of course this is only worthwhile if the underlying SeekableByteChannel doesn't already
+ * implement prefetching).
+ */
+public final class SeekableByteChannelPrefetcher implements SeekableByteChannel {


* chore: manual update of update_generation_config.sh * chore: generate libraries at Thu Jul 24 18:09:38 UTC 2025 * Revert "chore: generate libraries at Thu Jul 24 18:09:38 UTC 2025" This reverts commit 9726a59d037322332a1fa0c097de6aefb663d68e. --------- Co-authored-by: cloud-java-bot <cloud-java-bot@google.com>

The prefetcher can load data on another thread in between calls, and it can intelligently use its existing buffer to deal with small seeks without having to fetch again.

Prefetcher, to read fast.
f1c4af4
The prefetcher can load data on another thread in between calls, and it can intelligently use its existing buffer to deal with small seeks without having to fetch again.

jean-philippe-martin requested a review from pongad as a code owner March 16, 2018 22:06

googlebot added the cla: yes This human has signed the Contributor License Agreement. label Mar 16, 2018

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pongad reviewed Mar 27, 2018
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jart reviewed Mar 28, 2018
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pongad reviewed Mar 28, 2018
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pongad merged commit 6bccbce into googleapis:masterApr 3, 2018

jean-philippe-martin deleted the jp_prefetcher branch April 16, 2018 18:04

jean-philippe-martin mentioned this pull request Oct 26, 2018
NIO channels could optimize buffer-invalidation on seeks #3041
Closed

suztomo pushed a commit that referenced this pull request Mar 9, 2026
test(deps): update dependency com.google.truth:truth to v1.2.0 (#3054)
fb4d0e5

suztomo pushed a commit that referenced this pull request Mar 30, 2026
Prefetcher, to read fast. (#3054)
1f564bc
The prefetcher can load data on another thread in between calls, and it can intelligently use its existing buffer to deal with small seeks without having to fetch again.

chingor13 pushed a commit that referenced this pull request Mar 30, 2026
chore: ensure grpc client thread pool is shutdown (#3054)
754a33e

lqiu96 pushed a commit that referenced this pull request Apr 1, 2026
Prefetcher, to read fast. (#3054)
6c172ec
The prefetcher can load data on another thread in between calls, and it can intelligently use its existing buffer to deal with small seeks without having to fetch again.

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