attilapiros commented on a change in pull request #29855:
URL: https://github.com/apache/spark/pull/29855#discussion_r498446110
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File path:
common/network-common/src/main/java/org/apache/spark/network/server/TransportRequestHandler.java
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@@ -181,6 +182,17 @@ public void onFailure(Throwable e) {
private void processStreamUpload(final UploadStream req) {
assert (req.body() == null);
try {
+ // Retain the original metadata buffer, since it will be used during the
invocation of
+ // this method. Will be released later.
+ req.meta.retain();
+ // Make a copy of the original metadata buffer. In benchmark, we noticed
that
+ // we cannot respond the original metadata buffer back to the client,
otherwise
+ // in cases where multiple concurrent shuffles are present, a wrong
metadata might
+ // be sent back to client. This is related to the eager release of the
metadata buffer,
+ // i.e., we always release the original buffer by the time the
invocation of this
+ // method ends, instead of by the time we respond it to the client. This
is necessary,
+ // otherwise we start seeing memory issues very quickly in benchmarks.
+ ByteBuffer meta = cloneBuffer(req.meta.nioByteBuffer());
Review comment:
I am sorry but I fail to see how concurrent shuffle is generating such
an error.
As `req` is final method argument I am sure this inner method cannot see
another instance, so is it possible the problem is just a an index change
within `req.meta` which can be solved by some duplicate methods?
Can we have a unit test for this method to investigate this a bit more?
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