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From Murali Reddy <>
Subject Re: Run In memory event bus by default
Date Wed, 05 Feb 2014 06:23:35 GMT
On 05/02/14 6:14 AM, "Prachi Damle" <> wrote:

>Also we already have a MessageBus being used at couple of places to
>publish messages to other components about certain scenario.
>e.g: When reserved capacity for a VM that is stopped for time greater
>than configured threshold is freed up, CapacityManager publishes a
>message that is being subscribed to by the DeploymentPlanningManager.
>How do we differentiate between the MessageBus Vs EventBus usecases, when
>should we use one Vs the other?

Both are designed with different goals. Please see thread [1]. MessageBus
acts as generic transport abstraction to build IPC between the components.
Event bus has specific use case of enabling CloudStack components or
external system to publish-subscribe CloudStack events.

I guess which one to use depends on the use case. If some functionality
can be achieved just by consuming action/usage/sate change/alert events
generated then event bus should be good enough.


>-----Original Message-----
>From: Nitin Mehta []
>Sent: Tuesday, February 04, 2014 1:34 PM
>Cc: Murali Reddy
>Subject: Re: Run In memory event bus by default
>Please find my answers inline.
>On 04/02/14 11:04 AM, "Chiradeep Vittal" <>
>>Do you mean, "can we start it by default"?
>>Does it work for clustered management servers?
>Probably Murali who is the author can better answer this.
>But for my use case where I want to listen to the action events, its fine
>to subscribe in all the instances of MS and take appropriate action.
>>On 2/3/14 11:25 AM, "Nitin Mehta" <> wrote:
>>>I see that in memory event bus got checked in recently. I understand
>>>that its a plugin, but can we not start it by default ?
>>>It would help different components (for example - monitoring system,
>>>usage etc.) within CS to subscribe to events and take some useful
>>>action based on them if they could assume that some event bus were
>>>running by default.

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