Check your ec2 network settings. OS and varnish settings look okay, your varnishstat shows that varnish is coasting along fine.
It's not threads. You have 800 available, according to the varnishstat; it's running with 800 threads, handling 12,000+ connections, and there is no thread creation failure. Therefore it does not need to add threads. What does something like firebug show when you request during the load test? The delay may be anything from DNS to the ec2 network. Stefan Caunter Operations Torstar Digital m: (416) 561-4871 From: [email protected] [mailto:[email protected]] On Behalf Of Tejaswi Nadahalli Sent: March-04-11 1:09 AM To: [email protected] Subject: Under Load: Server Unavailable/Connection Dropped/Delayed Reponse Hi Everyone, I am seeing a situation similar to : http://www.varnish-cache.org/lists/pipermail/varnish-misc/2011-January/0 05351.html (Connections Dropped Under Load) http://www.varnish-cache.org/lists/pipermail/varnish-misc/2010-December/ 005258.html (Hanging Connections) I have httperf loading a varnish cache with never-expire content. While the load is on, other browser/wget requests to the varnish server get delayed to 10+ seconds. Any ideas what could be happening? ssh doesn't seem to be impacted. So, is it some kind of thread problem? In production, I see a similar situation with around 1000 req/second load. I am running varnishd with the following command line options (as per http://kristianlyng.wordpress.com/2009/10/19/high-end-varnish-tuning/): sudo varnishd -f /etc/varnish/default.vcl -s malloc,5G -T 127.0.0.1:2000 -a 0.0.0.0:80 -p thread_pools=8 -p thread_pool_min=100 -p thread_pool_max=5000 -p thread_pool_add_delay=2 -p cli_timeout=25 -p session_linger=100 -p lru_interval=20 -t 31536000 I am on Ubuntu Lucid 64 bit Amazon EC2 C1.XLarge with 8 processing units. My network sysctl parameters are tuned according to: http://varnish-cache.org/trac/wiki/Performance fs.file-max = 360000 net.ipv4.ip_local_port_range = 1024 65536 net.core.rmem_max = 16777216 net.core.wmem_max = 16777216 net.ipv4.tcp_rmem = 4096 87380 16777216 net.ipv4.tcp_wmem = 4096 65536 16777216 net.ipv4.tcp_fin_timeout = 3 net.core.netdev_max_backlog = 30000 net.ipv4.tcp_no_metrics_save = 1 net.core.somaxconn = 262144 net.ipv4.tcp_syncookies = 0 net.ipv4.tcp_max_orphans = 262144 net.ipv4.tcp_max_syn_backlog = 262144 net.ipv4.tcp_synack_retries = 2 net.ipv4.tcp_syn_retries = 2 Any help would be greatly appreciated
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