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https://issues.apache.org/jira/browse/SSHD-812?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16429898#comment-16429898
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Guillaume Nodet edited comment on SSHD-812 at 4/8/18 9:23 PM:
--------------------------------------------------------------
This would not solve the initial problem, as the reads from a single handle
would still be synchronized, so this would give no benefit as to reading
multiple parts of a single file concurrently.
An optimization to consider, and maybe more important, would be to have the
subsystem implement {{AsyncCommand}} instead of the simple {{Command}} and make
sure we're using the async capability of the output stream.
{code:title=main}
Buffer cmd = readCommand(in);
process(cmd);
{code}
{code:title=doRead}
Handle h = handles.get(handle);
FileHandle fh = validateHandle(handle, h, FileHandle.class);
getExecutor(fh).execute(() -> {
fh.read(...)
asyncOut.writeBuffer(buffer);
});
{code}
This way, if the executor is designed correctly, we'd have a single thread
processing all the read operations sequentially on a given file, and
asynchronously writing the output, thus avoiding the cost of writing to the
socket to slow down the reads, as {{writeBuffer}} returns immediately, without
waiting for the write to be finished.
was (Author: gnt):
This would not solve the initial problem, as the reads from a single handle
would still be synchronized, so this would give no benefit as to reading
multiple parts of a single file concurrently.
An optimization to consider, and maybe more important, would be to have the
subsystem implement {{AsyncCommand}} instead of the simple {{Command}} and make
sure we're using the async capability of the output stream.
{code:title=main}
Buffer cmd = readCommand(in);
process(cmd);
{code}
{code:title=doRead}
Handle h = handles.get(handle);
FileHandle fh = validateHandle(handle, h, FileHandle.class);
getExecutor(fh).execute(() -> {
fh.read(...)
asyncOut.writeBuffer(buffer);
});
{code}
This way, if the executor is designed correctly, we'd have a single thread
processing all the read operations sequentially on a given file, and
asynchronously writing the output, thus avoiding the cost of writing to the
socket to slow down the reads.
> 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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