Hi guys,
So sometimes are backend is really slow in returning a response. So
slow that it looks like it
is causing varnish to timeout before the backend does and so varnish
seems to eventually give up
and returns a 503.
Ther are 4 curl requests
* the first 2 timeout and give a 503
* the 3rd one is a hit miss but gives a 200
* the 4th one is a cache hit and gives a 200
https://gist.github.com/0452c374ee21dbba138d
Here's the varnishlog filtered for client requests
http://gist.github.com/279254e0f2452814bf46
Here's varnishstat
https://gist.github.com/219534d51a503b546070
Here's are current startup run time parameters options right now:
https://gist.github.com/219534d51a503b546070
So, Im pretty certain what is happening is that our backend takes too
long and varnish times
out. How can I set the time out higher... is it sess_timeout?
Thanks guys,
Tung
On Wed, Mar 25, 2009 at 10:37 AM, Tung Nguyen tngu...@bleacherreport.comwrote:
Kristian, thank you.
Im glad to hear that most defaults are good.
Yup, the default thread_pool_min = 1 seems kinda funny. We'll set it to at
least 100.
I didnt even know about the cli_timeout and will set it to a base line of
10 seconds to test.
Im wondering how you are testing, Im using ab, apachebench, to see how
things behave with -c 10 -n 1000, on the varnished pages.
Here's more specific questions more run time parameters. The general
question I have is what to look for during testing, should I be looking at
your varnishstat and are the most important things to look for in that
output.
Our varnish stack will look like this:
LB - Varnish x 2 - Nginx x 6 - Mongrel x 60
Some questions about how best to decide how to configure them best to
configure the run time parameters.
-p obj_workspace=4096
Cant find obj_workspace in the man page but found it in the twitter email
post
http://projects.linpro.no/pipermail/varnish-dev/2009-February/000968.html
Is obj_workspace how much space preallocated to be used for the obj that
gets returned from the backend? So, if my nginx backend returns a web page
that is over 4MB than -p obj_workspace is not enough, would that crash
varnish, or log the error somewhere.
-p sess_workspace=262144
Same deal here with the man page and twitter post.
What is the sess_workspace?
http_workspace
How does sess_workspace and obj_workspace relate to http_workspace?
If we use obj_workspace=4096 and sess_workspace=262144, does the default
http_workspace=8192 make sense?
-p lru_interval=60
Shows up on the twitter post again, but no man notes yet. Whats the
default for this?
-p sess_timeout=10 \
Default for this is 5. If the requests from the backend takes longer than
5 seconds, what happens? Sometimes we have really slow response from the
backend..
-p shm_workspace=32768 \
Is this the same as setting the command line flag -l shmlogsize. The
default is 80MB. So dont know twitter did both setting it to less..
-p thread_pools=4 \
-p thread_pool_min=100 \
thread_pool_max
The defaults are 1,1,1000 respectively. Im wondering how best to determine
this or just leave as default.
##
# output of varnishstat, what is best to look at here?
##
0+07:11:24
Hitrate ratio:44
4
Hitrate avg:nan nan nan
400 0.00 0.02 Client connections accepted
400 0.00 0.02 Client requests received
1 0.00 0.00 Cache hits
5 0.00 0.00 Cache misses
399 0.00 0.02 Backend connections success
399 0.00 0.02 Backend connections failures
1 0.00 0.00 Backend connections reuses
5 0.00 0.00 Backend connections recycles
6 .. N struct srcaddr
21 .. N struct sess_mem
1 .. N struct sess
1 .. N struct object
1 .. N struct objecthead
3 .. N struct smf
1 .. N small free smf
1 .. N large free smf
1 .. N struct vbe_conn
2 .. N struct bereq
10 .. N worker threads
23 0.00 0.00 N worker threads created
76 0.00 0.00 N overflowed work requests
2 .. N backends
5 .. N expired objects
6 0.00 0.00 Objects sent with write
400 0.00 0.02 Total Sessions
