[Libwebsockets] Problem of multiple persistent WebSocket connections

Andy Green andy at warmcat.com
Sat Sep 23 01:16:28 CEST 2017



On 09/22/2017 05:05 PM, Andy Green wrote:
> 
> 
> On 09/22/2017 04:40 PM, Zhang, Luis (Thin Client R&D) wrote:
>> We just created the connection, no data exchange.
>>
>> I developed a client simulator based on this lib, one process 
>> simulates 1000 webscoket connections. And then start one client 
>> simulator every 5 seconds.
> 
> What happens if you build lws with -DLWS_WITHOUT_EXTENSIONS=1 ? 
> Everything OK?

Assuming the answer is "yes", then this should be fixed on master.

-Andy

> -Andy
> 
>> Best Regards,
>> Luis
>>
>>
>> -----Original Message-----
>> From: Andy Green [mailto:andy at warmcat.com]
>> Sent: Friday, September 22, 2017 16:32
>> To: Zhang, Luis (Thin Client R&D) <xiaolu.zhang at hp.com>; 
>> libwebsockets at ml.libwebsockets.org
>> Subject: Re: [Libwebsockets] Problem of multiple persistent WebSocket 
>> connections
>>
>>
>>
>> On 09/22/2017 04:23 PM, Zhang, Luis (Thin Client R&D) wrote:
>>> Attached is the logs with Master and enabled LWS_WITH_STATS.
>>>
>>> Below are some configurations on server side in this test.
>>>     info.timeout_secs = 30
>>>     info.max_http_header_pool = 1024
>>>     info.ws_ping_pong_interval = 180
>>
>> Well, he is happy until ~35,000 connections
>>
>> [2017/09/22 16:14:14:9316] NOTICE:
>> Consuming message: request timed out
>> [2017/09/22 16:14:25:0909] NOTICE:
>> [2017/09/22 16:14:25:0909] NOTICE: LWS internal statistics dump ----->
>> [2017/09/22 16:14:25:0909] NOTICE: LWSSTATS_C_CONNECTIONS:
>>            35000
>> [2017/09/22 16:14:25:0909] NOTICE: LWSSTATS_C_API_CLOSE:
>>                0
>> [2017/09/22 16:14:25:0909] NOTICE: LWSSTATS_C_API_READ:
>>            70000
>> [2017/09/22 16:14:25:0909] NOTICE: LWSSTATS_C_API_LWS_WRITE:
>>            35000
>> [2017/09/22 16:14:25:0909] NOTICE: LWSSTATS_C_API_WRITE:
>>            35000
>> [2017/09/22 16:14:25:0909] NOTICE: LWSSTATS_C_WRITE_PARTIALS:
>>                0
>> [2017/09/22 16:14:25:0909] NOTICE: LWSSTATS_C_WRITEABLE_CB_REQ:
>>                0
>> [2017/09/22 16:14:25:0910] NOTICE: LWSSTATS_C_WRITEABLE_CB_EFF_REQ:
>>                0
>> [2017/09/22 16:14:25:0910] NOTICE: LWSSTATS_C_WRITEABLE_CB:
>>                0
>> [2017/09/22 16:14:25:0910] NOTICE: LWSSTATS_C_SSL_CONNECTIONS_FAILED:
>>                0
>> [2017/09/22 16:14:25:0910] NOTICE: LWSSTATS_C_SSL_CONNECTIONS_ACCEPTED:
>>                0
>> [2017/09/22 16:14:25:0910] NOTICE: LWSSTATS_C_SSL_CONNS_HAD_RX:
>>                0
>> [2017/09/22 16:14:25:0910] NOTICE: LWSSTATS_C_PEER_LIMIT_AH_DENIED:
>>                0
>> [2017/09/22 16:14:25:0910] NOTICE: LWSSTATS_C_PEER_LIMIT_WSI_DENIED:
>>                0
>> [2017/09/22 16:14:25:0910] NOTICE: LWSSTATS_C_TIMEOUTS:
>>                0
>> [2017/09/22 16:14:25:0910] NOTICE: LWSSTATS_C_SERVICE_ENTRY:
>>                0
>> [2017/09/22 16:14:25:0910] NOTICE: LWSSTATS_B_READ:
>>         25807460
>> [2017/09/22 16:14:25:0910] NOTICE: LWSSTATS_B_WRITE:
>>          6195000
>> [2017/09/22 16:14:25:0910] NOTICE: LWSSTATS_B_PARTIALS_ACCEPTED_PARTS:
>>                0
>> [2017/09/22 16:14:25:0910] NOTICE:
>> LWSSTATS_MS_SSL_CONNECTIONS_ACCEPTED_DELAY:        0ms
>> [2017/09/22 16:14:25:0910] NOTICE: LWSSTATS_MS_SSL_RX_DELAY:
>>                0ms
>> [2017/09/22 16:14:25:0910] NOTICE: LWSSTATS_MS_WRITABLE_DELAY:
>>                0us
>> [2017/09/22 16:14:25:0910] NOTICE: LWSSTATS_MS_WORST_WRITABLE_DELAY:
>>                0us
>> [2017/09/22 16:14:25:0910] NOTICE: Simultaneous SSL restriction:
>>                0/0/0
>> [2017/09/22 16:14:25:0910] NOTICE: Live wsi:
>>            35001
>> [2017/09/22 16:14:25:0910] NOTICE:   Listen port 7681 actual POLLIN:   1
>> [2017/09/22 16:14:25:0910] NOTICE: PT 1
>> [2017/09/22 16:14:25:0910] NOTICE:   AH in use / max:                  0
>> / 1024
>> [2017/09/22 16:14:25:0910] NOTICE:   AH wait list count / actual:      
>> 0 / 0
>> [2017/09/22 16:14:25:0910] NOTICE:
>> [2017/09/22 16:14:26:5866] NOTICE: Report count = 0
>> [2017/09/22 16:14:36:0051] NOTICE:
>> [2017/09/22 16:14:36:0052] NOTICE: LWS internal statistics dump ----->
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_C_CONNECTIONS:
>>            35258
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_C_API_CLOSE:
>>                0
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_C_API_READ:
>>            72265
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_C_API_LWS_WRITE:
>>            37129
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_C_API_WRITE:
>>            37129
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_C_WRITE_PARTIALS:
>>                0
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_C_WRITEABLE_CB_REQ:
>>             5000
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_C_WRITEABLE_CB_EFF_REQ:
>>             3966
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_C_WRITEABLE_CB:
>>             1966
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_C_SSL_CONNECTIONS_FAILED:
>>                0
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_C_SSL_CONNECTIONS_ACCEPTED:
>>                0
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_C_SSL_CONNS_HAD_RX:
>>                0
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_C_PEER_LIMIT_AH_DENIED:
>>                0
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_C_PEER_LIMIT_WSI_DENIED:
>>                0
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_C_TIMEOUTS:
>>                0
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_C_SERVICE_ENTRY:
>>                0
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_B_READ:
>>         25907970
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_B_WRITE:
>>          6217833
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_B_PARTIALS_ACCEPTED_PARTS:
>>                0
>> [2017/09/22 16:14:36:0052] NOTICE:
>> LWSSTATS_MS_SSL_CONNECTIONS_ACCEPTED_DELAY:        0ms
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_MS_SSL_RX_DELAY:
>>                0ms
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_MS_WRITABLE_DELAY:
>>         8163448955us
>> [2017/09/22 16:14:36:0052] NOTICE: LWSSTATS_MS_WORST_WRITABLE_DELAY:
>>          7244789us
>> [2017/09/22 16:14:36:0052] NOTICE:   Avg writable delay:
>>          4152313us
>> [2017/09/22 16:14:36:0052] NOTICE: Simultaneous SSL restriction:
>>                0/0/0
>> [2017/09/22 16:14:36:0052] NOTICE: Live wsi:
>>            35259
>> [2017/09/22 16:14:36:0052] NOTICE:   Listen port 7681 actual POLLIN:   1
>> [2017/09/22 16:14:36:0052] NOTICE: PT 1
>> [2017/09/22 16:14:36:0052] NOTICE:   AH in use / max:
>> 129 / 1024
>> [2017/09/22 16:14:36:0052] NOTICE:   AH wait list count / actual:      
>> 0 / 0
>>
>>
>> He starts to get connections around [2017/09/22 16:11:29:0440], he has 
>> 2K by then, and he starts to choke before 16:14:36, so it's around the 
>> 3m mark... ping-pong interval is very suspiously 180s, ie, 3m.  So I 
>> guess the number of connections is irrelevant, something happens when 
>> he starts to do the ping / pong.
>>
>> Can you describe what the connections are doing, if I wanted to 
>> reproduce this test?  They are upgrading to ws and just sitting there 
>> idle, or something else?
>>
>> -Andy
>>
>>> Best Regards,
>>> Luis
>>>
>>> -----Original Message-----
>>> From: Andy Green [mailto:andy at warmcat.com]
>>> Sent: Tuesday, September 19, 2017 16:38
>>> To: Zhang, Luis (Thin Client R&D) <xiaolu.zhang at hp.com>;
>>> libwebsockets at ml.libwebsockets.org
>>> Subject: Re: [Libwebsockets] Problem of multiple persistent WebSocket
>>> connections
>>>
>>>
>>>
>>> On 09/19/2017 04:23 PM, Zhang, Luis (Thin Client R&D) wrote:
>>>> Thank you.
>>>>
>>>> In my project, the value of info.max_http_header_pool is 16. I will 
>>>> set it to 256 and try again.
>>>>
>>>> Besides, I enabled the ping/pong and set ws_ping_pong_interval to 
>>>> 180s in my project. I just disabled ping/pong and tested again, 
>>>> there is no problem for 100K connections.
>>>>
>>>> So does the ping/pong impact the performance and connections of the 
>>>> server side?
>>>
>>> Well, it will generate a lot of traffic if you have 100K synthetic ws 
>>> connections created all at once.  Because they will want to send 
>>> pings and get pongs all at once.
>>>
>>> It may be related, but stuff that times out on ping / pong has a
>>> different timeout code, either PENDING_TIMEOUT_WS_PONG_CHECK_SEND_PING
>>> (16) or PENDING_TIMEOUT_WS_PONG_CHECK_GET_PONG (17).
>>>
>>> As I said the timeout code you reported getting (3) is because an 
>>> accepted connection did not process http headers.  That really looks 
>>> like ah starvation ("pfd events 0").
>>>
>>> I suggest you test things on lws master until we know what's
>>> happening... also enabling LWS_WITH_STATS at cmake on master will get
>>> you helpful logging dumps every 10s like this
>>>
>>> [2017/09/19 15:08:01:2053] NOTICE: LWS internal statistics dump ----->
>>> [2017/09/19 15:08:01:2053] NOTICE: LWSSTATS_C_CONNECTIONS:
>>>                 1
>>> [2017/09/19 15:08:01:2053] NOTICE: LWSSTATS_C_API_CLOSE:
>>>                 0
>>> [2017/09/19 15:08:01:2053] NOTICE: LWSSTATS_C_API_READ:
>>>                27
>>> [2017/09/19 15:08:01:2053] NOTICE: LWSSTATS_C_API_LWS_WRITE:
>>>                13
>>> [2017/09/19 15:08:01:2054] NOTICE: LWSSTATS_C_API_WRITE:
>>>                13
>>> [2017/09/19 15:08:01:2054] NOTICE: LWSSTATS_C_WRITE_PARTIALS:
>>>                 0
>>> [2017/09/19 15:08:01:2054] NOTICE: LWSSTATS_C_WRITEABLE_CB_REQ:
>>>                17
>>> [2017/09/19 15:08:01:2054] NOTICE: LWSSTATS_C_WRITEABLE_CB_EFF_REQ:
>>>                13
>>> [2017/09/19 15:08:01:2054] NOTICE: LWSSTATS_C_WRITEABLE_CB:
>>>                13
>>> [2017/09/19 15:08:01:2054] NOTICE: LWSSTATS_C_SSL_CONNECTIONS_FAILED:
>>>                 0
>>> [2017/09/19 15:08:01:2054] NOTICE: LWSSTATS_C_SSL_CONNECTIONS_ACCEPTED:
>>>                 0
>>> [2017/09/19 15:08:01:2054] NOTICE: LWSSTATS_C_SSL_CONNS_HAD_RX:
>>>                 0
>>> [2017/09/19 15:08:01:2054] NOTICE: LWSSTATS_C_PEER_LIMIT_AH_DENIED:
>>>                 0
>>> [2017/09/19 15:08:01:2054] NOTICE: LWSSTATS_C_PEER_LIMIT_WSI_DENIED:
>>>                 0
>>> [2017/09/19 15:08:01:2054] NOTICE: LWSSTATS_C_TIMEOUTS:
>>>                 0
>>> [2017/09/19 15:08:01:2054] NOTICE: LWSSTATS_C_SERVICE_ENTRY:
>>>              1243
>>> [2017/09/19 15:08:01:2055] NOTICE: LWSSTATS_B_READ:
>>>              4485
>>> [2017/09/19 15:08:01:2055] NOTICE: LWSSTATS_B_WRITE:
>>>              1435
>>> [2017/09/19 15:08:01:2055] NOTICE: LWSSTATS_B_PARTIALS_ACCEPTED_PARTS:
>>>                 0
>>> [2017/09/19 15:08:01:2055] NOTICE:
>>> LWSSTATS_MS_SSL_CONNECTIONS_ACCEPTED_DELAY:        0ms
>>> [2017/09/19 15:08:01:2055] NOTICE: LWSSTATS_MS_SSL_RX_DELAY:
>>>                 0ms
>>> [2017/09/19 15:08:01:2055] NOTICE: LWSSTATS_MS_WRITABLE_DELAY:
>>>              1314us
>>> [2017/09/19 15:08:01:2055] NOTICE: LWSSTATS_MS_WORST_WRITABLE_DELAY:
>>>              1063us
>>> [2017/09/19 15:08:01:2055] NOTICE:   Avg writable delay:
>>>               101us
>>> [2017/09/19 15:08:01:2055] NOTICE: Simultaneous SSL restriction:
>>>                 0/0/0
>>> [2017/09/19 15:08:01:2055] NOTICE: Live wsi:
>>>                 5
>>> [2017/09/19 15:08:01:2055] NOTICE:   Listen port 2200 actual POLLIN:   1
>>> [2017/09/19 15:08:01:2056] NOTICE: PT 1
>>> [2017/09/19 15:08:01:2056] NOTICE:   AH in use / 
>>> max:                  0 / 4
>>> [2017/09/19 15:08:01:2056] NOTICE:   AH wait list count / 
>>> actual:      0 / 0
>>> [2017/09/19 15:08:01:2056] NOTICE:  Peers: total active 1
>>> [2017/09/19 15:08:01:2056] NOTICE:   peer 127.0.0.1: count wsi: 1, count
>>> ah: 0
>>> [2017/09/19 15:08:01:2056] NOTICE:
>>> [2017/09/19 15:08:12:2181] NOTICE:
>>>
>>> -Andy
>>>
>>>> Best Regards,
>>>> Luis
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: Andy Green [mailto:andy at warmcat.com]
>>>> Sent: Tuesday, September 19, 2017 15:49
>>>> To: Zhang, Luis (Thin Client R&D) <xiaolu.zhang at hp.com>;
>>>> libwebsockets at ml.libwebsockets.org
>>>> Subject: Re: [Libwebsockets] Problem of multiple persistent WebSocket
>>>> connections
>>>>
>>>>
>>>>
>>>> On 09/19/2017 03:32 PM, Zhang, Luis (Thin Client R&D) wrote:
>>>>> Attached is the log file.
>>>>>
>>>>> There are a lot of TIMEDOUT messages likes below. I modified the 
>>>>> timeout from 5 seconds to 15 seconds, the issue occurred too.
>>>>>
>>>>> [2017/09/19 15:16:22:0048] NOTICE: wsi 0x7fd624162660: TIMEDOUT
>>>>> WAITING on 3 (did hdr 0, ah (nil), wl 611, pfd events 0)
>>>>> [2017/09/19 15:16:22:0048] NOTICE: wsi 0x7fd624142bb0: TIMEDOUT
>>>>> WAITING on 3 (did hdr 0, ah (nil), wl 611, pfd events 0)
>>>>> [2017/09/19 15:16:22:0048] NOTICE: wsi 0x7fd624142900: TIMEDOUT
>>>>> WAITING on 3 (did hdr 0, ah (nil), wl 611, pfd events 0)
>>>>> [2017/09/19 15:16:22:0048] NOTICE: wsi 0x7fd624142650: TIMEDOUT
>>>>> WAITING on 3 (did hdr 0, ah (nil), wl 611, pfd events 0)
>>>>> [2017/09/19 15:16:22:0048] NOTICE: wsi 0x7fd6241303a0: TIMEDOUT
>>>>> WAITING on 3 (did hdr 0, ah (nil), wl 611, pfd events 0)
>>>>> [2017/09/19 15:16:22:0048] NOTICE: wsi 0x7fd6241300f0: TIMEDOUT
>>>>> WAITING on 3 (did hdr 0, ah (nil), wl 611, pfd events 0)
>>>>> [2017/09/19 15:16:22:0048] NOTICE: wsi 0x7fd62412fe40: TIMEDOUT
>>>>> WAITING on 3 (did hdr 0, ah (nil), wl 611, pfd events 0)
>>>>
>>>> Timeout reason 3 is "PENDING_TIMEOUT_ESTABLISH_WITH_SERVER"... this 
>>>> starts when we accept the incoming connection and is cleared when we 
>>>> deal with his headers.
>>>>
>>>> Since an ah is required to deal with the headers, I guess these are 
>>>> getting tied up.
>>>>
>>>> When you create the context, what do you set 
>>>> info.max_http_header_pool to?  The default is just 4... if you have 
>>>> 100,000 connections you probably want to scale this up to 256 or 
>>>> more.  This sets how many connections can simultaneously process 
>>>> http headers.
>>>>
>>>> -Andy
>>>>
>>>>> Best Regards,
>>>>> Luis
>>>>>
>>>>>
>>>>> -----Original Message-----
>>>>> From: Libwebsockets
>>>>> [mailto:libwebsockets-bounces at ml.libwebsockets.org] On Behalf Of
>>>>> Zhang, Luis (Thin Client R&D)
>>>>> Sent: Monday, September 18, 2017 9:47
>>>>> To: Andy Green <andy at warmcat.com>;
>>>>> libwebsockets at ml.libwebsockets.org
>>>>> Subject: Re: [Libwebsockets] Problem of multiple persistent
>>>>> WebSocket connections
>>>>>
>>>>> I will reproduce it and get more detailed logs later.
>>>>>
>>>>> Best Regards,
>>>>> Luis
>>>>>
>>>>>
>>>>> -----Original Message-----
>>>>> From: Andy Green [mailto:andy at warmcat.com]
>>>>> Sent: Monday, September 18, 2017 9:33
>>>>> To: Zhang, Luis (Thin Client R&D) <xiaolu.zhang at hp.com>;
>>>>> libwebsockets at ml.libwebsockets.org
>>>>> Subject: RE: [Libwebsockets] Problem of multiple persistent
>>>>> WebSocket connections
>>>>>
>>>>>
>>>>>
>>>>> On September 18, 2017 9:12:35 AM GMT+08:00, "Zhang, Luis (Thin 
>>>>> Client R&D)" <xiaolu.zhang at hp.com> wrote:
>>>>>> Thanks.
>>>>>>
>>>>>> The platform is Debian 8.5 and I used libuv.
>>>>>
>>>>> OK... so what happens when it seems to go wrong?
>>>>>
>>>>> Can you reproduce this with the libuv test server?  Can you let me 
>>>>> know how to reproduce?
>>>>>
>>>>> LWS_WITH_STATS is on master, it logs a bunch of interesting stats 
>>>>> every 10s.
>>>>>
>>>>> -Andy
>>>>>
>>>>>> Best Regards,
>>>>>> Luis
>>>>>>
>>>>>>
>>>>>> -----Original Message-----
>>>>>> From: Andy Green [mailto:andy at warmcat.com]
>>>>>> Sent: Monday, September 18, 2017 9:11
>>>>>> To: Zhang, Luis (Thin Client R&D) <xiaolu.zhang at hp.com>;
>>>>>> libwebsockets at ml.libwebsockets.org
>>>>>> Subject: Re: [Libwebsockets] Problem of multiple persistent
>>>>>> WebSocket connections
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 09/18/2017 09:07 AM, Andy Green wrote:
>>>>>>>
>>>>>>>
>>>>>>> On 09/18/2017 08:51 AM, Zhang, Luis (Thin Client R&D) wrote:
>>>>>>>> I'm working on developing a WebSocket Server that supports for
>>>>>>>> multiple persistent WebSocket connections. Our goal is supporting
>>>>>> for
>>>>>>>> 100K connections concurrently. As mentioned in
>>>>>>>> https://libwebsockets.org/ that per thread can support 250K
>>>>>>>> connections. So I think that there is no problem for supporting
>>>>>>>> 100K
>>>>>>
>>>>>>>> persistent WebSocket connections. And I verified it with v2.0.0,
>>>>>>>> it works well.
>>>>>>>>
>>>>>>>> But, when I upgraded the libwebsockets lib to v2.1, the server
>>>>>> cannot
>>>>>>>> accepted so many connections. It only can accepted about 40K
>>>>>>>> connections. When about 40K connections were established, I
>>>>>>>> cannot establish websocket connection any more. I also test it
>>>>>>>> with v2.2
>>>>>> and
>>>>>>>> v2.3, I got the same result.
>>>>>>>>
>>>>>>>> The test environment of all test case are same, just the version
>>>>>>>> of libwesocket lib are different.
>>>>>>>
>>>>>>>       - what is the platform?
>>>>>>>
>>>>>>>       - what *exactly* happens when you "cannot establish websocket
>>>>>>> connection any more"?  Logs?
>>>>>>
>>>>>> ... and...
>>>>>>
>>>>>>      - what event loop?  Default, using libuv / ev / event?
>>>>>>
>>>>>>>
>>>>>>> There's no intention to reduce the max clients the server can
>>>>>>> serve, on the contrary...
>>>>>>>
>>>>>>> -Andy
>>>>>>>
>>>>>>>> Any thoughts? Thank you.
>>>>>>>>
>>>>>>>> Best Regards,
>>>>>>>>
>>>>>>>> Luis
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>>> Libwebsockets mailing list
>>>>>>>> Libwebsockets at ml.libwebsockets.org
>>>>>>>> https://libwebsockets.org/mailman/listinfo/libwebsockets
>>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> Libwebsockets mailing list
>>>>>>> Libwebsockets at ml.libwebsockets.org
>>>>>>> https://libwebsockets.org/mailman/listinfo/libwebsockets
>>>>> _______________________________________________
>>>>> Libwebsockets mailing list
>>>>> Libwebsockets at ml.libwebsockets.org
>>>>> https://libwebsockets.org/mailman/listinfo/libwebsockets
>>>>>
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