Breaking Varnish

[Tim Kientzle]

We're evaluating Varnish as a possible replacement for our
installed Squid servers.  Performance-wise, Varnish is very
impressive, and we're pretty pleased with the configuration
flexibility.

But...

Under heavy load, we're seeing a lot of segfaults and
assertion failures.  I've pasted an excerpt below of
two of the issues we've seen using Varnish 2.0.2 on Linux
2.6.21 kernel with the default VCL (using command-line options
to set the listen address and the addresses of the two back-end
servers).

We're going to repeat these tests and see if we can get
more detail, possibly including core dumps.  What other
information would be useful in diagnosing and fixing
these issues?

Cheers,

Tim Kientzle

==========================================================

1) Varnish repeatedly died due to SIGSEGV:

child (2816) Started
Child (2816) said Closed fds: 4 7 8 10 11
Child (2816) said Child starts
Child (2816) said managed to mmap 49392648192 bytes of 49392648192
Child (2816) said Ready
Child (2816) died signal=11
Child cleanup complete

2) Varnish repeatedly died due to SIGABRT:

child (3017) Started
Child (3017) said Closed fds: 4 7 8 10 11
Child (3017) said Child starts
Child (3017) said managed to mmap 49392648192 bytes of 49392648192
Child (3017) said Ready
Child (3017) died signal=6
Child (3017) Panic message: Assert error in cnt_lookup(),  
cache_center.c line 625:
   Condition(sp->objhead != NULL) not true. thread = (cache-worker)sp  
= 0x2afee0fb3008 {
   fd = -1, id = 15, xid = 0,
   client = 10.2.8.27:45430,
   step = STP_DONE,
   handling = DELIVER,
   ws = 0x2afee0fb3078 {
     id = "sess",
     {s,f,r,e} = {0x2afee0fb37b0,,+587,(nil),+8192},
   },
},