[JSch-users] Concurrency with JSch

Discussion:

Lahiru Gunathilake

2014-10-07 18:18:24 UTC

Hi All,

I have extended the JCraft library to authenticate my servers with a token
and everything works fine when I use in the serial mode. But when I moved
to a thread pool and try to share the JCraftSession and try to create
multiple channels in large number of threads (I have already increased my
maxSessionCount in sshd_config) I get the following error and I am not sure
what is really going on.

Every 20-30 request I get the below error.

"com.jcraft.jsch.JSchException: channel is not opened."

Anybody using the sessions and creating channels concurrently ? I am not
synchronizing the session in each thread ? Should I synchronize the session
object if I am using in multi-threaded mode ?

Regards
Lahiru

--
Research Assistant
Science Gateways Group
Indiana University

Lahiru Gunathilake

2014-10-07 18:34:54 UTC

Permalink

Hi Users,

And when I remove the threadpool an still submit a very large load I can
see I am getting the following error intermittently,

com.jcraft.jsch.JSchException: Packet corrupt

at com.jcraft.jsch.Session.start_discard(Session.java:1049)

at com.jcraft.jsch.Session.read(Session.java:956)

at com.jcraft.jsch.UserAuthNone.start(UserAuthNone.java:56)

at com.jcraft.jsch.Session.connect(Session.java:389)

at com.jcraft.jsch.Session.connect(Session.java:183)

Regards

Lahiru

Post by Lahiru Gunathilake
Hi All,
I have extended the JCraft library to authenticate my servers with a token
and everything works fine when I use in the serial mode. But when I moved
to a thread pool and try to share the JCraftSession and try to create
multiple channels in large number of threads (I have already increased my
maxSessionCount in sshd_config) I get the following error and I am not sure
what is really going on.
Every 20-30 request I get the below error.
"com.jcraft.jsch.JSchException: channel is not opened."
Anybody using the sessions and creating channels concurrently ? I am not
synchronizing the session in each thread ? Should I synchronize the session
object if I am using in multi-threaded mode ?
Regards
Lahiru
--
Research Assistant
Science Gateways Group
Indiana University

--
Research Assistant
Science Gateways Group
Indiana University

guillaume cornet

2014-11-17 16:22:19 UTC

Permalink

Hi Lahiru !

I'm creating many SftpChannel in multiple Session and I'm facing the same
issue (e.g. 'Packet corrupt' or 'connection is closed by foreign host').

In order to solve this issue, I've introduce an retry mechanism in my code,
so that a new Session is created an openend when such error are detected.

I know it is not the best solution, but it was easier to do this rather
than modifying JCraft source code to make it thread safe.

Does anybody encounter such concurrency issue ?

G.

Post by Lahiru Gunathilake
Hi Users,
And when I remove the threadpool an still submit a very large load I can
see I am getting the following error intermittently,
com.jcraft.jsch.JSchException: Packet corrupt
at com.jcraft.jsch.Session.start_discard(Session.java:1049)
at com.jcraft.jsch.Session.read(Session.java:956)
at com.jcraft.jsch.UserAuthNone.start(UserAuthNone.java:56)
at com.jcraft.jsch.Session.connect(Session.java:389)
at com.jcraft.jsch.Session.connect(Session.java:183)
Regards
Lahiru

Post by Lahiru Gunathilake
Hi All,
I have extended the JCraft library to authenticate my servers with a
token and everything works fine when I use in the serial mode. But when I
moved to a thread pool and try to share the JCraftSession and try to create
multiple channels in large number of threads (I have already increased my
maxSessionCount in sshd_config) I get the following error and I am not sure
what is really going on.
Every 20-30 request I get the below error.
"com.jcraft.jsch.JSchException: channel is not opened."
Anybody using the sessions and creating channels concurrently ? I am not
synchronizing the session in each thread ? Should I synchronize the session
object if I am using in multi-threaded mode ?
Regards
Lahiru
--
Research Assistant
Science Gateways Group
Indiana University

--
Research Assistant
Science Gateways Group
Indiana University
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Lahiru Gunathilake

2014-11-17 17:45:26 UTC

Permalink

Hi guillaume,

I was able tohandle it in my code level by synchronizing the code.
Everything works fine, I share sessions but synchronized the methods.

Lahiru

On Mon, Nov 17, 2014 at 11:22 AM, guillaume cornet <

Post by guillaume cornet
Hi Lahiru !
I'm creating many SftpChannel in multiple Session and I'm facing the same
issue (e.g. 'Packet corrupt' or 'connection is closed by foreign host').
In order to solve this issue, I've introduce an retry mechanism in my
code, so that a new Session is created an openend when such error are
detected.
I know it is not the best solution, but it was easier to do this rather
than modifying JCraft source code to make it thread safe.
Does anybody encounter such concurrency issue ?
G.

Post by Lahiru Gunathilake
Hi All,
I have extended the JCraft library to authenticate my servers with a
token and everything works fine when I use in the serial mode. But when I
moved to a thread pool and try to share the JCraftSession and try to create
multiple channels in large number of threads (I have already increased my
maxSessionCount in sshd_config) I get the following error and I am not sure
what is really going on.
Every 20-30 request I get the below error.
"com.jcraft.jsch.JSchException: channel is not opened."
Anybody using the sessions and creating channels concurrently ? I am not
synchronizing the session in each thread ? Should I synchronize the session
object if I am using in multi-threaded mode ?
Regards
Lahiru
--
Research Assistant
Science Gateways Group
Indiana University

--
Research Assistant
Science Gateways Group
Indiana University

Bogdan SOLGA

2014-11-18 08:14:45 UTC

Permalink

Hello, Guillaume!

I had the same issues with JSCH, and still haven't figured out a proper way
to handle the thread safety, besides executing in multiple threads and
using a retry mechanism.

I would also be interested to find a better way, though.

Kind regards,
Bogdan

On Mon, Nov 17, 2014 at 6:22 PM, guillaume cornet <

Post by Lahiru Gunathilake
Hi All,
I have extended the JCraft library to authenticate my servers with a
token and everything works fine when I use in the serial mode. But when I
moved to a thread pool and try to share the JCraftSession and try to create
multiple channels in large number of threads (I have already increased my
maxSessionCount in sshd_config) I get the following error and I am not sure
what is really going on.
Every 20-30 request I get the below error.
"com.jcraft.jsch.JSchException: channel is not opened."
Anybody using the sessions and creating channels concurrently ? I am not
synchronizing the session in each thread ? Should I synchronize the session
object if I am using in multi-threaded mode ?
Regards
Lahiru
--
Research Assistant
Science Gateways Group
Indiana University

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