[Building Sakai] Maximum simultaneous users

[Matthew Jones]

The "load balanced thin client" idea is what most schools in production run
on, it's in this diagram here.

https://confluence.sakaiproject.org/display/DOC/Sakai+Admin+Guide+-+Load+Balancing+and+Scaling

Basically you get a load balancer: hardware (like Cisco ACE, f5 big-ip,
Citrix Netscaler) or software (pound, ha-proxy) out in front distributing
the load to identical servers with sticky sessions. The servers each run one
(or multiple) tomcats and often are setup with Apache (or something faster
like lighttpd/nginx) in front to serve up the static content (or other
content tomcat can't support). Michigan uses Apache because we need some
modules only available in Apache and it's reliable.

The servers all have to be setup with a shared filesystem (NFS/AFS/SMB) and
connect to a shared database (which may be one machine or also clustered).
There isn't much information shared between the machines, and users sessions
remain on each node in the cluster. Events are passed with the *
ClusterEventTrackingService *(currently) and it looks like 2.9 will support
cluster chat with jgroups multicast (which would probably be great to get
rid of some of the events). All of the nodes maintain their own cache unless
you setup a cluster wide ehcache [1] (which we haven't done at Michigan) and
there's no session failover that's "easy" to setup, as it requires a
terracotta server (documented in [2])

Anyway, there's a lot of possibilities here. The easiest is to get a few
identical servers (virtual machines?) setup on a shared file system with a
load balancer in front of them and see where it goes from there. ;)

[1]
https://confluence.sakaiproject.org/display/SAKDEV/Sakai+Cluster-wide+Caching
[2]
https://confluence.sakaiproject.org/display/TERRA/Manual+Testing+of+Terracotta+Clustering+with+the+Wiley+Worksite+Setup+Tool

On Fri, Aug 19, 2011 at 2:13 PM, Claudia Roberta <claudia.icmc at gmail.com>wrote:

> Thank for answers!
>
> Please... I want to know the instructions to install the Sakai in Cluster
> and what features should respect the tools to make it work well in the
> cluster.
>
> Tks,
>
> Claudia
>
>
> 2011/8/19 Matthew Jones <jonespm at umich.edu>
>
>> We're running across a 5 node cluster though, where each node only takes
>> on 1/5 of the users. Putting all 9K users all on 1 system could cause
>> connection unresponsiveness if existing tomcat connections were still busy
>> when new requests came in, and couldn't complete fast enough to handle new
>> requests. There also are issues with database pool exhaustion which can be
>> improved by having multiple nodes.
>>
>> There's no limit in Sakai for sure, but tomcat has limits, as does a
>> database, and you need to cluster both of these (or run it on faster
>> hardware with higher limits) to handle more users.
>>
>> On Fri, Aug 19, 2011 at 12:15 PM, Sean DeMonner <demonner at umich.edu>wrote:
>>
>>> I'm not aware of any hard limit. We routinely run with 10,000+ concurrent
>>> users in Production. The error you've mentioned sounds more like a malformed
>>> request from your load testing software (missing or bad site ID, for
>>> example).
>>>
>>> SMD.
>>>
>>>
>>>
>>> On Aug 19, 2011, at 9:40 AM, Claudia Roberta wrote:
>>>
>>> Hi guys,
>>>
>>> The Sakai has simultaneous user limit?
>>>
>>> We conducted a test with 9,000 concurrent users and the following error
>>> message was displayed:
>>> *“The site you requested is not available.” *
>>>
>>> Tks,
>>>
>>> Claudia _______________________________________________
>>> sakai-dev mailing list
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>>>
>>>
>>>
>>>
>>>
>>> ====================================================
>>> Sean DeMonner, Director, Teaching & Learning, ITS
>>> 3350 Duderstadt Center, University of Michigan, (734) 615-9765
>>>
>>>
>>>
>>>
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>>
>>
>
>
> --
> Claudia Roberta
> Intermídia - ICMC/USP - São Carlos, SP - Brasil
>
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