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From "Andrew Bayer (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CLOUDSTACK-3163) Virtual Router startup time is painfully long
Date Mon, 24 Jun 2013 18:58:19 GMT
Andrew Bayer created CLOUDSTACK-3163:
----------------------------------------

             Summary: Virtual Router startup time is painfully long
                 Key: CLOUDSTACK-3163
                 URL: https://issues.apache.org/jira/browse/CLOUDSTACK-3163
             Project: CloudStack
          Issue Type: Bug
      Security Level: Public (Anyone can view this level - this is the default.)
    Affects Versions: pre-4.0.0
         Environment: CloudPlatform 3.0.3, but I don't see any changes to the relevant code
(I think) on master
            Reporter: Andrew Bayer
            Priority: Critical


When you've got a couple thousand instances, spread across 10 or so pods, virtual router startup
time is near crippling - actually, if you don't enable the option to have virtual routers
only populated with instances in their pod, it *is* crippling, in that the virtual routers
don't finish starting before the management server decides they've timed out and tries to
start a new one.

This seems to be the result of a few painful inefficiencies:

- The same codepath is followed whether you're adding a new instance to an already running
VR, or adding two hundred already running instances to a new VR. So each ssh/scp/sed/cp/chmod/etc
command is replicated for each instance, rather than finding efficiencies by doing things
across the whole set of instances. 
- But what really eats up the time is the population of vm data - for each piece of vm data
(which, from a rough look at the code, seems to be something like 10 or 11 data files), there
are something like 7 ssh calls and an scp call. So that means that per instance, we have somewhere
around 80 to 90 ssh/scp calls, plus the single ssh call for dhcp_entry.sh. So with 200 instances,
that's 1600 to 1800 ssh/scp calls on a single VR, with all the overhead entailed in opening
that many ssh connections, starting bash, etc, etc... Given that in my experience, a VR with
~200 instances takes ~90 minutes to start up (I may be misremembering slightly - it could
be ~200 instances takes closer to 60 minutes, and ~300 takes closer to 90), that works out
to 3 seconds or so per ssh/scp, which doesn't seem implausible to me. 

So, this shouldn't be this way. At a minimum, there's no reason not to offload the whole process
from a script run on the host making repeated ssh calls to the VR to a script on the VR that
gets called from the host, albeit possibly a temporary one that's generated on the fly and
copied over to the VR. That alone would probably save most of the VR startup time, just by
dropping the number of ssh/scp connections per instance from 80-90 to 3 (dhcp_entry.sh call,
scp of temporary script, execution of temporary script).

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