Help needed on AWS Lex Plugin/Lex status code

[Daniel Ng]

Dear all,

Just wondered if anyone has encountered "Stream [x] closed with status [7]"?

i.e. does anyone know what a status [7] code means?

This is using the UMS Lex plugin with the SDK log-level set to 6 and UMSLEX log-level set to debug.

The relevant unimrcp server log snippet is (as you can see, it creates the stream and then more or less comes back straight-away with the status 7 that then causes Unimrcp to stop input and close the channels):

2022-05-09 14:35:44:485278 [DEBUG]  Check connection [https://runtime-v2-lex.eu-west-2.amazonaws.com:443] state [2] pending streams [0] active streams [0] max streams [1] <edc17efe960444b2>

2022-05-09 14:35:44:485304 [DEBUG]  Submit [/bots/M3PVMFHP4I/botAliases/TSTALIASID/botLocales/en_GB/sessions/ebc486b581214e2c/conversation] headers [12] <edc17efe960444b2>

2022-05-09 14:35:44:485346 [DEBUG]  Store stream [9] <edc17efe960444b2>

2022-05-09 14:35:44:485377 [DEBUG]  Send H2 data [303 bytes] <edc17efe960444b2>

2022-05-09 14:35:44:493396 [DEBUG]  Receive H2 data [13 bytes] <edc17efe960444b2>

2022-05-09 14:35:44:493435 [DEBUG]  Process H2 frame [3] <edc17efe960444b2>

2022-05-09 14:35:44:493445 [DEBUG]  Stream [9] closed with status [7] <edc17efe960444b2>

2022-05-09 14:35:44:493514 [DEBUG]  Stop Input <ebc486b581214e2c@lex>

Thanks in advance.

Kind Regards,

Daniel

[Arsen Chaloyan]

Hi Daniel,

This is an error raised by the underlying nghttp library which stands for "REFUSED STREAM".

https://nghttp2.org/documentation/enums.html#c.nghttp2_error_code.NGHTTP2_REFUSED_STREAM

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Arsen Chaloyan
Author of UniMRCP
http://www.unimrcp.org

[Ed Houston]

Hi Arsen,

Thanks for the reply.

I'm not sure if this would make sense, but can I ask if you could automatically do one retry when you get the "Refused Stream" response?

The reasoning for suggesting this is that it appears to be intermittent and that the same credentials/network work ok for another call/request/stream, so without knowing more and delving deep its potentially an easy way to fix something that could be quite complicated to unpick.

Also we don't really get this level of error granularity at in CVP/MRCP, so at the CVP app level we don't know that this has happened and therefore can't initiate the retry.
What do you think?

Cheers,

Ed.

[Arsen Chaloyan]

Hi Ed,

I agree that re-attempting would make sense when the original request fails with an intermittent error. And the reattempt would need to be implemented by the plugin to be transparent to the client for various reasons. I've logged this issue to be implemented in future versions of the plugin. It would be interesting to understand where this error originates, though. Maybe you can share the logs with a few such failures to possibly find a common pattern. I'd guess this must be an issue related to a specific environment.

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