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https://issues.apache.org/jira/browse/HDFS-9108?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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James Clampffer updated HDFS-9108:
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Attachment: 9108-async-repro.patch
Simple reproducer using async api. If using gcc you'll probably get hit with
the weak_ptr exception due to remote_block_reader::async_read calling
this->make_shared_from_this(). Switch it to make_shared<decltype>(this)(this)
to reproduce the underlying issue. Will submit another patch for the shared
pointer issue.
> Pointer to read buffer isn't being passed to kernel
> ---------------------------------------------------
>
> Key: HDFS-9108
> URL: https://issues.apache.org/jira/browse/HDFS-9108
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: hdfs-client
> Environment: Ubuntu x86_64, gcc 4.8.2
> Reporter: James Clampffer
> Assignee: James Clampffer
> Attachments: 9108-async-repro.patch
>
>
> Somewhere between InputStream->PositionRead and the asio code the pointer to
> the destination buffer gets lost. PositionRead will correctly return the
> number of bytes read but the buffer won't be filled.
> This only seems to effect the remote_block_reader, RPC calls are working.
> Valgrind error:
> Syscall param recvmsg(msg.msg_iov) points to uninitialised byte(s)
> msg.msg_iov[0] should equal the buffer pointer passed to PositionRead
> Hit when using a promise to make the async call block until completion.
> auto stat = std::make_shared<std::promise<Status>>();
> std::future<Status> future(stat->get_future());
> size_t readCount = 0;
> auto h = [stat, &readCount,buf](const Status &s, size_t bytes) {
> stat->set_value(s);
> readCount = bytes;
> };
> char buf[50];
> inputStream->PositionRead(buf, 50, 0, h);
>
> //wait for async to finish
> future.get();
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