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From Rafael Weingärtner <rafaelweingart...@gmail.com>
Subject Re: [Discuss] Management cluster / Zookeeper holding locks
Date Mon, 18 Dec 2017 09:43:31 GMT
so, how does that work?
I mean, instead of opening a transaction with the database and executing
locks, what do we need to do in the code?

On Mon, Dec 18, 2017 at 7:24 AM, Ivan Kudryavtsev <kudryavtsev_ia@bw-sw.com>
wrote:

> Rafael,
>
> - It's easy to configure and run ZK either in single node or cluster
> - zookeeper should replace mysql locking mechanism used inside ACS code
> (places where ACS locks tables or rows).
>
> I don't think from the other size, that moving from MySQL locks to ZK locks
> is easy and light and (even implemetable) way.
>
> 2017-12-18 16:20 GMT+07:00 Rafael Weingärtner <rafaelweingartner@gmail.com
> >:
>
> > How hard is it to configure Zookeeper and get everything up and running?
> > BTW: what zookeeper would be managing? CloudStack management servers or
> > MySQL nodes?
> >
> > On Mon, Dec 18, 2017 at 7:13 AM, Ivan Kudryavtsev <
> > kudryavtsev_ia@bw-sw.com>
> > wrote:
> >
> > > Hello, Marc-Aurele, I strongly believe that all mysql locks should be
> > > removed in favour of truly DLM solution like Zookeeper. The performance
> > of
> > > 3node ZK ensemble should be enough to hold up to 1000-2000 locks per
> > second
> > > and it helps to move to truly clustered MySQL like galera without
> single
> > > master server.
> > >
> > > 2017-12-18 15:33 GMT+07:00 Marc-Aurèle Brothier <marco@exoscale.ch>:
> > >
> > > > Hi everyone,
> > > >
> > > > I was wondering how many of you are running CloudStack with a cluster
> > of
> > > > management servers. I would think most of you, but it would be nice
> to
> > > hear
> > > > everyone voices. And do you get hosts going over their capacity
> limits?
> > > >
> > > > We discovered that during the VM allocation, if you get a lot of
> > parallel
> > > > requests to create new VMs, most notably with large profiles, the
> > > capacity
> > > > increase is done too far after the host capacity checks and results
> in
> > > > hosts going over their capacity limits. To detail the steps: the
> > > deployment
> > > > planner checks for cluster/host capacity and pick up one deployment
> > plan
> > > > (zone, cluster, host). The plan is stored in the database under a
> > VMwork
> > > > job and another thread picks that entry and starts the deployment,
> > > > increasing the host capacity and sending the commands. Here there's a
> > > time
> > > > gap between the host being picked up and the capacity increase for
> that
> > > > host of a couple of seconds, which is well enough to go over the
> > capacity
> > > > on one or more hosts. A few VMwork job can be added in the DB queue
> > > > targeting the same host before one gets picked up.
> > > >
> > > > To fix this issue, we're using Zookeeper to act as the multi JVM lock
> > > > manager thanks to their curator library (
> > > > https://curator.apache.org/curator-recipes/shared-lock.html). We
> also
> > > > changed the time when the capacity is increased, which occurs now
> > pretty
> > > > much after the deployment plan is found and inside the zookeeper
> lock.
> > > This
> > > > ensure we don't go over the capacity of any host, and it has been
> > proven
> > > > efficient since a month in our management server cluster.
> > > >
> > > > This adds another potential requirement which should be discuss
> before
> > > > proposing a PR. Today the code works seamlessly without ZK too, to
> > ensure
> > > > it's not a hard requirement, for example in a lab.
> > > >
> > > > Comments?
> > > >
> > > > Kind regards,
> > > > Marc-Aurèle
> > > >
> > >
> > >
> > >
> > > --
> > > With best regards, Ivan Kudryavtsev
> > > Bitworks Software, Ltd.
> > > Cell: +7-923-414-1515
> > > WWW: http://bitworks.software/ <http://bw-sw.com/>
> > >
> >
> >
> >
> > --
> > Rafael Weingärtner
> >
>
>
>
> --
> With best regards, Ivan Kudryavtsev
> Bitworks Software, Ltd.
> Cell: +7-923-414-1515
> WWW: http://bitworks.software/ <http://bw-sw.com/>
>



-- 
Rafael Weingärtner

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