min yun law created SSHD-1078:
---------------------------------
Summary: SCP/SFTP failed for big file upload
Key: SSHD-1078
URL: https://issues.apache.org/jira/browse/SSHD-1078
Project: MINA SSHD
Issue Type: Bug
Affects Versions: 2.5.1
Reporter: min yun law
Trying to merge product from jsch to mina sshd that keep the same SSH
architecture (lets call SessionPool) which for each remote node, there is only
one session object and limited channels (<=8) for executing commands and file
operations. The SessionPool manages the session/channels for nodes and make
sure only 8 threads(ssh channels) per node that can be run concurrently. This
architecture works for Jsch for many years, but when using mina sshd, this
architecture wont work when with upload big file, we always see following
exception:
{code:java}
java.io.EOFException: Channel is being closed
at
org.apache.sshd.common.channel.AbstractChannel$2.<init>(AbstractChannel.java:794)
at
org.apache.sshd.common.channel.AbstractChannel.writePacket(AbstractChannel.java:792)
at
org.apache.sshd.common.channel.ChannelAsyncOutputStream.doWriteIfPossible(ChannelAsyncOutputStream.java:168)
at
org.apache.sshd.common.channel.ChannelAsyncOutputStream.writePacket(ChannelAsyncOutputStream.java:70)
at
org.apache.sshd.client.subsystem.sftp.impl.DefaultSftpClient.send(DefaultSftpClient.java:292)
at
org.apache.sshd.client.subsystem.sftp.impl.SftpOutputStreamAsync.flush(SftpOutputStreamAsync.java:210)
at
org.apache.sshd.client.subsystem.sftp.impl.SftpOutputStreamAsync.write(SftpOutputStreamAsync.java:141)
{code}
>From SSH server log, we see follow error:
{code:java}
Aug 19 15:56:38 xxxx sftp-server[202217]: error: Unknown message 0
Aug 19 15:56:38 xxxx sftp-server[202217]: error: msg_len 0 < consumed 1
{code}
other client side exceptions by mina sshd as:
org.apache.sshd.common.channel.WindowClosedException: Already closed:
Window[client/remote](ChannelExec[id=79, recipient=1]-ClientSessionImp
----
After many tries, finally I found that for big file upload/download, I have to
give its own SshClient/ClientSession objects and then there will no such
channel closing exception during file upload.
That means we cannot share the same SshClient and ClientSession object per
remote node to execute commands and file operations, and there may has bug in
ClientSession when handle channels in this situation.
the reason that we like to share the same SshClient/ClientSession for the same
remote node is to manage the session/channels and close them when no usage,
also to reduce the cost to allocate those objects.
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