attilapiros commented on a change in pull request #29855:
URL: https://github.com/apache/spark/pull/29855#discussion_r499217716
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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 tried to delay the release of req.meta until the stream callback
finishes processing the stream, however that can lead to memory issues on the
shuffle service side when there are many blocks to be transferred.
I still do not see how a cloned buffer which should live also until the
stream callback finishes processing the stream would help on this. The
`ByteBuf` is reference counted so with a retain & release the same time period
could be covered without the duplication. The duplication even increases the
memory footprint for the time when both instances are alive.
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