Koushik Das created CLOUDSTACK-4855:
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Summary: Throttle based on the # of outstanding requests to the
directly managed HV host (direct agents)
Key: CLOUDSTACK-4855
URL: https://issues.apache.org/jira/browse/CLOUDSTACK-4855
Project: CloudStack
Issue Type: Bug
Security Level: Public (Anyone can view this level - this is the default.)
Components: Management Server
Affects Versions: 4.1.0, pre-4.0.0, 4.2.0
Reporter: Koushik Das
Fix For: 4.3.0
Currently requests to all direct managed HV hosts (direct agents) are handled
by the direct agent thread pool. The size of the pool is determined by global
config direct.agent.pool.size defaulted to 500.
Currently there is no restriction on the number of requests that can be sent to
a given HV host. The down side is if a lot commands are getting generated for
some specific hosts (may be there is some issue with the host, the host is slow
in responding and there is a pile up of outstanding requests), it may
essentially starve the requests going to other hosts due to unavailability of
direct agent threads as most of them will be serving a very few hosts.
The problem being addressed is that a few bad hosts should not affect the
entire management server. The solution is to localize the impact of the bad
hosts.
One such way is to throttle based on the # of outstanding requests on per host
basis. The outstanding requests will be a % of the direct agent pool size.
This will ensure that the impacted host will be bound by a upper cap on the
number of threads it can use to process request and not the entire pool.
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