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https://issues.apache.org/jira/browse/SSHD-812?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16416766#comment-16416766
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Goldstein Lyor commented on SSHD-812:
-------------------------------------
The way to do this would be:
{code:java}
@Override
public void start(Environment env) throws IOException {
this.env = env;
try {
ExecutorService executor = getExecutorService();
====> start several threads here <====
pendingFuture = executor.submit(this);
} catch (RuntimeException e) { // e.g., RejectedExecutionException
log.error("Failed (" + e.getClass().getSimpleName() + ") to start
command: " + e.toString(), e);
throw new IOException(e);
}
}
{code}
and then modify the _run()_ method so that all threads somehow wait on some
lock to read a command packet. Once read, the thread that succeeded
relinquishes the lock (thus letting some other thread read a packet), processes
the request and then goes back to waiting to its turn to read again. The code
{{SftpSubsystem}} code though now not only has to be *multi-thread safe*, but
also raises some *race conditions*:
* What if the session is closed while a thread is processing a request but has
not generated a response
* What if a file handle is closed by a command from one thread while another
thread is reading/writing to it
* Ditto for files being removed, renamed, symlink-ed, concurrently etc...
One could say it is the client's problem, but we need to make the server able
to tolerate such behavior
> support asynchronization mode for sftp subsystem
> ------------------------------------------------
>
> Key: SSHD-812
> URL: https://issues.apache.org/jira/browse/SSHD-812
> Project: MINA SSHD
> Issue Type: New Feature
> Affects Versions: 1.7.0
> Environment: java1.8, linux
> Reporter: Zhenliang Su
> Assignee: Goldstein Lyor
> Priority: Minor
> Labels: asynchronous, sftp
> Attachments: Main.java, doRead.png
>
>
> I used SSHD as a middleman between client and target sftp server.
> I found that, when filezilla client directly connect to the target sftp
> server, it transfers fast. When filezilla client connect to the middleman, it
> transfers slow.
> I analyzed the source code of
> org.apache.sshd.server.subsystem.sftp.SftpSubsystem#doRead, and I found it
> behaves like block mode, and client's other SSH_FXP_READ request blocked in
> the same thread.
>
> my middleman code:
> [^Main.java]
>
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