Cloudstack already have a well-defined set of events, currently being used by the Usage module. We can extend this to publish the events to registered listeners/subscribers.
Nitin, We should evaluate the google guava package for this purpose. -abhi >-----Original Message----- >From: Chiradeep Vittal [mailto:chiradeep.vit...@citrix.com] >Sent: Saturday, May 12, 2012 3:48 AM >To: cloudstack-dev@incubator.apache.org >Cc: Dean >Subject: Re: Event Publish and Subscribe ( was perhaps Re: Cloudstack >Questions ) > >+1. >This could also be used for example to update DNS records on a DNS server >whenever a VM is started / stopped in a network. >A subscriber to the event bus can do this, and potentially things like >updating a >CMDB or an LDAP server. > >The important caveat is that this will be asynchronous to the stuff happening >inside the management server: it has limited utility for doing stuff that is >required to succeed before an API operation can succeed. >For example, if a VM start requires a NAT rule to be programmed on the >firewall before the start can be considered successful. You could write a event >bus subscriber that does this, but the management server would not know if >it was successful or not. > >There's at least a couple of entry points: >1. com.cloud.utils.fsm.StateListener. Classes that implement this listener get >notified on finite state event transitions. Examples include VM start / stop 2. >com.cloud.network.element.NetworkElement. Classes that implement this >get notified of network state transitions. Examples include adding nics and >removing nics to/from a network. > >I think the first question regarding monitoring VMs on the isolated VLAN had a >different origin though. >The intention there was to have a monitoring service (e.g., Nagios) reach into >the VM and monitor stuff like CPU, IO, or even applications. >The issue there was around network reachability. > >-- >Chiradeep > > > >On 5/11/12 2:09 PM, "Adrian Cole" <adr...@jclouds.org> wrote: > >>+1 >> >>Makes sense to have pubsub. Inside the java codebase, we could >>consider a clean and idiomatic lib like guava which is easy to unit test. >> >>http://codingjunkie.net/guava-eventbus/ >> >>Then, expose out-of-JVM hooks for any of the popular services people use. >> >>-A >>On May 11, 2012 1:58 PM, "Dean" <cl...@tizatron.com> wrote: >> >>> Cross reference to: >>> >>> >>> >>>http://mail-archives.apache.org/mod_mbox/incubator-cloudstack- >dev/201204. >>>mbox/browser >>> >>> [ from: Marlon Davids ] >>> < munch > >>> > 2) How do we monitor VM's that are in Cloudstack when they are in >>> > an >>> isolated VLAN does >>> > anyone have a clever workaround? >>> > 3) Has anyone developed a script for parsing and alerting on >>> > warning >>> events in the >>> > management Log yet? >>> >>> I would like to propose cloudstack consider a pub/sub model for event >>> handling to complement API calls like listEvents. >>> >>> Polling can be problematic and sensitive to scaling. >>> >>> A simple example would be state change on a physical device. The >>>admin server can simply publish a message on a network socket >>>indicating that the device has changed it's state. >>> >>> If a subscriber was interested in that device, it could make an api >>>call to the admin server for state change information for that device only. >>>The >>> admin server may choose to validate that physical device against the >>>current state table in the database. >>> >>> The API would reply that this node changed it's state from >>>Operational to Prep For Maintenance. (or whatever the transition >>>state would be) >>> >>> The message exchange could be wrapped around vm states, resource >>> additions/removals etc. >>> >>> Using a library like zeromq, a developer can write any number of >>>consumers in any language they wanted to subscribe to the Event Bus. >>> >>> Comments? >>> >>> -- >>> -Dean
