Draft: Resolve "server has to remove ungracefully disconnected zombie clients"

[fraunhofer-iis-bot]

In GitLab by @vornkat-iis on May 8, 2023, 12:48

Closes #49

[fraunhofer-iis-bot]

In GitLab by @vornkat-iis on May 8, 2023, 14:23

added 1 commit

• a157d5d - Minimal keepalive settings

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[fraunhofer-iis-bot]

In GitLab by @vornkat-iis on May 8, 2023, 14:23

requested review from @Michael-M-Baron

[fraunhofer-iis-bot]

In GitLab by @vornkat-iis on May 8, 2023, 14:24

I pushed first version that should for the moment solve your issue. @Michael-M-Baron can you verify? The numbers should be tuned to your application.
I will add configuration options in next commits

[fraunhofer-iis-bot]

In GitLab by @vornkat-iis on May 8, 2023, 14:44

added 1 commit

• 166b24e - Move to extra function

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[fraunhofer-iis-bot]

In GitLab by @vornkat-iis on May 8, 2023, 15:21

added 1 commit

• e2a9f05 - Add docs

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[fraunhofer-iis-bot]

In GitLab by @vornkat-iis on May 26, 2023, 17:08

added 3 commits

• f7bd190 - Make keepalive configurable by libjapi user
• 1171bc2 - Extend docs
• 943311d - Add test and error handling for parameters

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[fraunhofer-iis-bot]

In GitLab by @vornkat-iis on May 26, 2023, 17:32

added 1 commit

• af593ac - fixup tests

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[fraunhofer-iis-bot]

In GitLab by @vornkat-iis on May 26, 2023, 17:36

Functionality tests are still missing. I have a draft locally but am not fully sure how to do this.

[vornkat-iis]

Added my draft here, maybe it helps one day to finish this issue. Tests pass right now because all relevant lines are commented out. Feel free to adapt

[Michael-M-Baron]

Had a look at the current state of this branch and it does not seem to fix the problem. What I did in my application:

• Set max allowed client to 1
• Enable TCP keep alive (japi_set_tcp_keepalive(ctx, 1, 60, 10, 3))
• Start server on different machine
• Connect to server with client
• Break down network connection on server side (ip link set eth0 down)
• Try doing something with still open client (After some timeouts client will not work anymore)
• Restart network on server side (ip link set eth0 up)

At this point, I can ping my server again but not connect with my client (wait for a couple of minutes and tried several times meanwhile).

My Suggestion:
Currently only the server socket is manipulated with the TCP-Probing. I think this has to be done with the clients and the server logic updated. I am going to test around.

[Michael-M-Baron]

Had a look at the current state of this branch and it does not seem to fix the problem. What I did in my application:

* Set max allowed client to 1

* Enable TCP keep alive (`japi_set_tcp_keepalive(ctx, 1, 60, 10, 3)`)

* Start server on different machine

* Connect to server with client

* Break down network connection on server side (`ip link set eth0 down`)

* Try doing something with still open client (After some timeouts client will not work anymore)

* Restart network on server side (`ip link set eth0 up`)

At this point, I can ping my server again but not connect with my client (wait for a couple of minutes and tried several times meanwhile).

My Suggestion: Currently only the server socket is manipulated with the TCP-Probing. I think this has to be done with the clients and the server logic updated. I am going to test around.

I figured out the problem:

• The current libjapi keep-alive mechanism was in fact already working.
• My application uses websockets which kept the connection alive although the ethernet connection was shut down

I added some more debug prints and updated the unit tests to cover the TCP keep alive mechanism. Breaking down the client socket connection for testing however cannot by simply done in the tests (May be with mocking), so the actual mechanism is not tested yet in the unit tests (I added TODO marks and going to open a separate ticket for that).