From: Mike McGrath <mmcgrath redhat com>
To: meghdoot bhattacharya <meghdoot_b yahoo com>
Cc: Luke Meyer <lmeyer redhat com>; "dev lists openshift redhat com" <dev lists openshift redhat com>
Sent: Wednesday, January 30, 2013 9:45 AM
Subject: Re: gear creation on nodes
On Wed, 30 Jan 2013, meghdoot bhattacharya wrote:
> I was talking to Operations and they like the concept of districts but they are interested in pinning a certain application in a certain district of nodes. In their minds, districts are logical pools
> that can come and go, they would use LBaaS to dynamically point to these districts for new applications or maybe new versions of applications pushed. They literally manage thousands of app [front, mid
> and back today]. But as per the discussion below looks like, an app can land in gears in different districts as longs as gear profiles are compatible. But what I think would be great is we have the
> option to create app X with gear profile Y and additionally with district Z. Validation check will be there if that district does not support Y. Future gear creations for the app in auto scale will be
> only within that district.
> Is this supported by any chance? One
way I think is to create a unique gear profile that only few apps want to use and be pinned into a district that is created with the unique gear profile. Then the
> algorithm will automatically pin the gear creation only within nodes in that district.
> Otherwise I guess we may have to add this as a feature ourselves.
Your operations team is correct that districts are logical pools that can
come and go but we've chosen not to expose that fact to the users.
Pinning to district is not something that is supported today.
Applications are spread across all available nodes, in the future there
will be better logical grouping via geography (which could be in the same
datacenter we're just calling it multi-geo support) which may do what
you're looking to do.
> From: Luke Meyer <lmeyer redhat com
> To: meghdoot bhattacharya <meghdoot_b yahoo com
> Cc: dev lists openshift redhat com
> Sent: Wednesday, January 30, 2013 6:17 AM
> Subject: Re: gear creation on nodes
> Other replies have talked about current developments in Origin. If you're looking at production usage, you will probably be considering OpenShift Enterprise, which for stability will generally be a
> little behind. The features in
discussion here won't be in OSE until version 1.2 at least.
> The existing OSE gear placement algorithm is described here:
> Krishna's pointer to the actual algorithm is good, but go back a few months if you want to see how it shipped in OSE.
> Note that there are options for enabling/disabling districts in /etc/openshift/plugins.d/openshift-origin-msg-broker-mcollective.conf as well as enabling/disabling non-district nodes when districts are
> enabled. The defaults
should usually be reasonable.
> As far as node host discovery - until Dan's change is complete, a node host is made discoverable by subscribing itself via mcollective. Gear placement requests are broadcast with a filter for node hosts
> to self-select according to their facts. With districts in play, one of the filters/facts is district. Other filters are for active_capacity and gear profile. So although with districts we have a
> registry of known nodes, that's not directly used yet. What really allows a node host to accept gears is its subscription to the broadcasts and the matching of its facts to the request filters.
> ----- Original Message -----
> From: "meghdoot bhattacharya" <meghdoot_b yahoo com
> To: dev lists openshift redhat com
> Sent: Monday, January 28, 2013 7:40:33 PM
> Subject: gear creation on nodes
> Given a set of nodes, when new gears are about to be created, what is the algorithm used to select the node?
> If brand new nodes/VM's are added later, how do those new nodes get discovered and made available to haproxy for future gear creation on those nodes? Does the mcollective in broker periodically send
> messages to discover new nodes or figure out if nodes are gone?
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