[
https://issues.apache.org/jira/browse/SSHD-901?focusedWorklogId=415983&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-415983
]
ASF GitHub Bot logged work on SSHD-901:
---------------------------------------
Author: ASF GitHub Bot
Created on: 04/Apr/20 15:54
Start Date: 04/Apr/20 15:54
Worklog Time Spent: 10m
Work Description: Arunapotti commented on issue #95: SSHD-901 Provide
'wantReply' option for client keep-alive heartbeat global request
URL: https://github.com/apache/mina-sshd/pull/95#issuecomment-609048804
Hi Goldstein,
OpenSSH has ClinetAliveInterval support that the servers can use to detect
and clean up dead/dangling clients besides for the keep-alive support.
ClientAliveInterval <http://man.openbsd.org/sshd_config#ClientAliveInterval>
Sets a timeout interval in seconds after which if no data has been received
from the client, sshd(8) <http://man.openbsd.org/sshd.8>will send a message
through the encrypted channel to request a response from the client. The
default is 0, indicating that these messages will not be sent to the client.
I am looking for an equivalent option with your SSHD.
Thanks
On Sat, Apr 4, 2020 at 8:02 AM Lyor Goldstein <notificati...@github.com>
wrote:
> to close any dangling client sessions from server due to network issues
>
> Please bear in mind that this mechanism is a *client side* one - i.e., it
> is used by the client in order to detect a non-responsive server sooner
> than the regular TCP/IP timeout would. AFAIK there is no server side
> mechanism to detect "dangling" client sessions. We do have an idle-timeout
> mechanism that closes a session if there is no traffic for the specified
> amount of time (current default=10 minutes). The purpose of the keepalive@
> mechanism (besides early detection) is also to generate some traffic so
> that the client does not time out if there is no traffic. By activating the
> wantReply option (default=disabled) we try to ensure that the server does
> not time out due to no traffic. Therefore, the keepalive@ mechanism is
> not likely to detect "dangling clients" on the server side.
>
> See
>
https://github.com/apache/mina-sshd/blob/master/docs/client-setup.md#keeping-the-session-alive-while-no-traffic
> on client heartbeat details, and the code for SessionHelper#getIdleTimeout
>
> There is a way to do this on the server side but it is rather
> *non-standard* (which we support) and it involves sending
> {{SSH_MSG_IGNORE}} messages from the server to the client thus maintaining
> some traffic on the session as well as detecting "dangling clients". See
> setSessionHeartbeat API with a {{HeartbeatType}} of IGNORE.
>
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Issue Time Tracking
-------------------
Worklog Id: (was: 415983)
Time Spent: 50m (was: 40m)
> InterruptedByTimeoutException occurring in client despite keepalive global
> request being sent
> ---------------------------------------------------------------------------------------------
>
> Key: SSHD-901
> URL: https://issues.apache.org/jira/browse/SSHD-901
> Project: MINA SSHD
> Issue Type: Bug
> Affects Versions: 2.2.0
> Environment: Windows 10
> Reporter: Jared Wiltshire
> Assignee: Lyor Goldstein
> Priority: Major
> Fix For: 2.3.0
>
> Time Spent: 50m
> Remaining Estimate: 0h
>
> This may be related to SSHD-891 but I couldn't follow that issue exactly.
> I was noticed that after exactly 10 minutes and 15 minutes a
> java.nio.channels.InterruptedByTimeoutException exception was being thrown by
> the client. After a little digging I discovered that this is the default
> value for NIO2_READ_TIMEOUT. This is the stack trace -
> {code:java}
> ERROR 2019-02-25T17:25:16,879
> (com.infiniteautomation.mango.cloudConnect.client.CloudConnectClient$ClientSessionListener.sessionException:83)
> - Session exception, session
> ClientSessionImpl[mango@localhost/127.0.0.1:9005]
> java.nio.channels.InterruptedByTimeoutException: null
> at
> sun.nio.ch.WindowsAsynchronousSocketChannelImpl$ReadTask.timeout(WindowsAsynchronousSocketChannelImpl.java:614)
> ~[?:1.8.0_144]
> at
> sun.nio.ch.WindowsAsynchronousSocketChannelImpl$2.run(WindowsAsynchronousSocketChannelImpl.java:649)
> ~[?:1.8.0_144]
> at
> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
> ~[?:1.8.0_144]
> at java.util.concurrent.FutureTask.run(FutureTask.java:266)
> ~[?:1.8.0_144]
> at
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
> ~[?:1.8.0_144]
> at
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
> ~[?:1.8.0_144]
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> ~[?:1.8.0_144]
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> ~[?:1.8.0_144]
> at java.lang.Thread.run(Thread.java:748) [?:1.8.0_144]
> {code}
> Now I have the heat beat interval (ClientFactoryManager.HEARTBEAT_INTERVAL)
> property set to less than 10 minutes and I verified that the global request
> is indeed being sent and received by the server.
> However I think that the issue is that the global request is sent with
> wantReply set to false. So the server does not reply with anything and the
> client does not read any data from the socket and hence times out.
> Does it not make sense for the server to reply? I believe this is a self
> defined global request (not in the SSH RFC) so we should be able change its
> behavior.
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