Bug 57380

  the webservers use poll() as there fd-event-source and are designed as a
  non-blocking, single process webserver.

  'ab' is called on a remote machine the test the performance of the servers
  under some load. grisu is used as the test machine. doubleheart is running
  a thttpd 2.20c at port 1027 and a lighttpd 
  (http://jan.kneschke.de/projects/lighttpd/) at port 1025. 

  After handling about 4000 connections the webserver doesn't receive 
  any new POLLIN events at all for the next 10-15 seconds. Any 
  connection-attempt within the period is, as you can see in the tcpdump 
  output, accepted by the kernel and the received data is thrown away as 
  the kernel sends a RST.
  After those 10-15 seconds the application gets a POLLIN event for the
  server socket and the normal data-transfer takes place for the next 4000
  requests.

  This behaviour is reproducable with thttpd 2.20c and the current lighttpd.

Fix: 

no fix nor workaround is known yet.





    Jan
  
-- 
Jan Kneschke                                     http://jan.kneschke.de/
Perhaps you want to say 'thank you, jan':    http://jk.123.org/wishlist/
How-To-Repeat:    
  Calling 'ab' (apachebench) at grisu with the following paramters:

  /usr/sbin/ab -n 10000 -c 10 http://192.168.2.38:1025/index.html

  results in the following output:

  ...
  Time taken for tests:   40.610 seconds
  Complete requests:      10000
  Failed requests:        5980
     (Connect: 0, Length: 5980, Exceptions: 0)
  ...


  This is reproducable and the number of failed requests is always
  5980 +/- 50 requests. In other words: after 4000 requests tcpdump shows
  the following output: 

  00:53:48.923029 192.168.2.10.39774 > 192.168.2.38.1025: S [tcp sum ok]
    1013737315:1013737315(0) win 5840 <mss 1460,sackOK,timestamp 5208461
    0,nop,wscale0> (DF) (ttl 64, id 7918, len 60)
0x0000   4500 003c 1eee 4000 4006 964d c0a8 020a        E..<..@.@..M....
0x0010   c0a8 0226 9b5e 0401 3c6c 6763 0000 0000        ...&.^..<lgc....
0x0020   a002 16d0 eeaa 0000 0204 05b4 0402 080a        ................
0x0030   004f 798d 0000 0000 0103 0300                  .Oy.........

  00:53:48.923330 192.168.2.38.1025 > 192.168.2.10.39774: S [tcp sum ok]
    1803860672:1803860672(0) ack 1013737316 win 65535 <mss 1460,nop,wscale
    1,nop,nop,timestamp 4459794 5208461> (DF) (ttl 64, id 6821, len 60)
0x0000   4500 003c 1aa5 4000 4006 9a96 c0a8 0226        E..<..@.@......&
0x0010   c0a8 020a 0401 9b5e 6b84 bac0 3c6c 6764        .......^k...<lgd
0x0020   a012 ffff d4ce 0000 0204 05b4 0103 0301        ................
0x0030   0101 080a 0044 0d12 004f 798d                  .....D...Oy.

  00:53:48.924009 192.168.2.10.39774 > 192.168.2.38.1025: . [tcp sum ok] ack 1
    win 5840 <nop,nop,timestamp 5208461 4459794> (DF)
    (ttl 64, id 7919, len 52)
0x0000   4500 0034 1eef 4000 4006 9654 c0a8 020a        E..4..@.@..T....
0x0010   c0a8 0226 9b5e 0401 3c6c 6764 6b84 bac1        ...&.^..<lgdk...
0x0020   8010 16d0 e9c3 0000 0101 080a 004f 798d        .............Oy.
0x0030   0044 0d12

  00:53:48.924150 192.168.2.10.39774 > 192.168.2.38.1025: P [tcp sum ok]
    1:29(28) ack 1 win 5840 <nop,nop,timestamp 5208461 4459794> (DF)
    (ttl 64, id 7920, len 80)
 0x0000   4500 0050 1ef0 4000 4006 9637 c0a8 020a        E..P..@.@..7....
 0x0010   c0a8 0226 9b5e 0401 3c6c 6764 6b84 bac1        ...&.^..<lgdk...
 0x0020   8018 16d0 27e4 0000 0101 080a 004f 798d        ....'........Oy.
 0x0030   0044 0d12 4745 5420 2f69 6e64 6578 2e68        .D..GET./index.h
 0x0040   746d 6c20 4854 5450 2f31 2e30 0d0a 0d0a        tml.HTTP/1.0....

  00:53:48.924728 192.168.2.38.1025 > 192.168.2.10.39774: R [tcp sum ok]
    1803860673:1803860673(0) win 0 (ttl 64, id 6831, len 40)
0x0000   4500 0028 1aaf 0000 4006 daa0 c0a8 0226        E..(....@......&
0x0010   c0a8 020a 0401 9b5e 6b84 bac1 0000 0000        .......^k.......
0x0020   5004 0000 64ba 0000

  This is SYN, SYN+ACK, ACK, DATA, RST.

  strace shows that no connection attempt has been reported to the
  application which is poll()'ing the server socket.

  /* the common loop without any block attempts */

  accept(3, {sa_family=AF_UNSPEC, sa_data="\0\0\0\0\0\0\0\0\0\0\0\0\0\0"}, [0]) = 5
  fcntl(5, F_SETFL, O_RDWR|O_NONBLOCK)    = 0
  read(5, "GET /index.html HTTP/1.0\r\n\r\n", 4095) = 28
  stat("/home/jan/lighttpd-0.1.0/servers/", {st_mode=S_IFDIR|0755, st_size=512, ...}) = 0
  fstat(6, {st_mode=S_IFREG|0644, st_size=4348, ...}) = 0
  write(5, "HTTP/1.0 200 OK\r\nConnection: clo"..., 235) = 235
  write(2, "1064875136: (network.c.210) 235 "..., 33) = 33
  syscall_393(0x6, 0x5, 0, 0, 0x10fc, 0, 0xbfbff2c0, 0) = 0
  close(5)                                = 0

  /* no futher waiting connections */

  accept(3, 0xbfbff700, [1852702730])     = -1 EAGAIN (Resource temporarily unavailable)

  /* enter the main-loop */

  gettimeofday({1769235301, 1663069807}, NULL) = 0
  poll([{fd=3, events=POLLIN}], 1, 1000)  = 0
  gettimeofday({4294967295, 65537}, NULL) = 0
  poll([{fd=3, events=POLLIN}], 1, 1000)  = 0
  gettimeofday({4294967295, 65537}, NULL) = 0
  poll([{fd=3, events=POLLIN}], 1, 1000)  = 0
  ...

  (strace is broken for accept() and gettimeofday(), syscall_393() is sendfile())