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Posted to dev@brooklyn.apache.org by Aled Sage <al...@gmail.com> on 2017/03/22 17:11:11 UTC
UsageListener: notified of promotion to master?
Hi all,
I'm writing a UsageListener [1] that is going to record the Brooklyn
instance's apps in an external inventory. This is mostly
straight-forward (except needing the fix at [2]).
The tricky bit is when a Brooklyn standby instance is promoted to master
- I want my listener to be notified so it can record the identity of the
new master Brooklyn for each of the pre-existing app.
I don't see anywhere I can get a notification of this. Is there?
---
Possible solutions include:
1. Add an additional application event (e.g. state
"MANAGEMENT_CHANGED") - the UsageListener would receive this event
for every app when it successfully rebinds.
2. Register a new kind of listener, to be notified of the management
context's state - on becoming "master", my listener could iterate
over all the apps.
I don't particularly like either of those options.
For (1), it isn't really to do with app "Usage" like the other events.
For (2), my listener code would be fiddly - I'd need to worry about
receiving concurrent notifications via the normal UsageListener while
I'm iterating over the pre-existing apps (assuming the new listener is
called asynchronously, rather than blocking the management context's
startup).
It feels like (2) is a more generally useful feature to add (for
programmatic support, at least). Does it sound useful for things beyond
my use-case?
Thoughts?
Aled
[1]
https://github.com/apache/brooklyn-server/blob/master/core/src/main/java/org/apache/brooklyn/core/mgmt/usage/UsageListener.java
[2] https://github.com/apache/brooklyn-server/pull/606
Re: UsageListener: notified of promotion to master?
Posted by Aled Sage <al...@gmail.com>.
Hi all,
I finally got round to implementing this! See PR at
https://github.com/apache/brooklyn-server/pull/832
Aled
On 22/03/2017 19:52, Svetoslav Neykov wrote:
>> It feels like (2) is a more generally useful feature to add (for programmatic support, at least). Does it sound useful for things beyond my use-case?
> Yes. I needed this exact functionality last week - for a piece of code shared between all applications. I ended up writing a poller thread that monitors the state.
> I think it will be a useful thing to add.
>
> Svet.
>
>
>> On 22.03.2017 г., at 19:11, Aled Sage <al...@gmail.com> wrote:
>>
>> Hi all,
>>
>> I'm writing a UsageListener [1] that is going to record the Brooklyn instance's apps in an external inventory. This is mostly straight-forward (except needing the fix at [2]).
>>
>> The tricky bit is when a Brooklyn standby instance is promoted to master - I want my listener to be notified so it can record the identity of the new master Brooklyn for each of the pre-existing app.
>>
>> I don't see anywhere I can get a notification of this. Is there?
>>
>> ---
>>
>> Possible solutions include:
>>
>> 1. Add an additional application event (e.g. state
>> "MANAGEMENT_CHANGED") - the UsageListener would receive this event
>> for every app when it successfully rebinds.
>> 2. Register a new kind of listener, to be notified of the management
>> context's state - on becoming "master", my listener could iterate
>> over all the apps.
>>
>> I don't particularly like either of those options.
>>
>> For (1), it isn't really to do with app "Usage" like the other events.
>>
>> For (2), my listener code would be fiddly - I'd need to worry about receiving concurrent notifications via the normal UsageListener while I'm iterating over the pre-existing apps (assuming the new listener is called asynchronously, rather than blocking the management context's startup).
>>
>> It feels like (2) is a more generally useful feature to add (for programmatic support, at least). Does it sound useful for things beyond my use-case?
>>
>> Thoughts?
>>
>> Aled
>>
>> [1] https://github.com/apache/brooklyn-server/blob/master/core/src/main/java/org/apache/brooklyn/core/mgmt/usage/UsageListener.java
>> [2] https://github.com/apache/brooklyn-server/pull/606
>>
>>
Re: UsageListener: notified of promotion to master?
Posted by Svetoslav Neykov <sv...@cloudsoftcorp.com>.
> It feels like (2) is a more generally useful feature to add (for programmatic support, at least). Does it sound useful for things beyond my use-case?
Yes. I needed this exact functionality last week - for a piece of code shared between all applications. I ended up writing a poller thread that monitors the state.
I think it will be a useful thing to add.
Svet.
> On 22.03.2017 г., at 19:11, Aled Sage <al...@gmail.com> wrote:
>
> Hi all,
>
> I'm writing a UsageListener [1] that is going to record the Brooklyn instance's apps in an external inventory. This is mostly straight-forward (except needing the fix at [2]).
>
> The tricky bit is when a Brooklyn standby instance is promoted to master - I want my listener to be notified so it can record the identity of the new master Brooklyn for each of the pre-existing app.
>
> I don't see anywhere I can get a notification of this. Is there?
>
> ---
>
> Possible solutions include:
>
> 1. Add an additional application event (e.g. state
> "MANAGEMENT_CHANGED") - the UsageListener would receive this event
> for every app when it successfully rebinds.
> 2. Register a new kind of listener, to be notified of the management
> context's state - on becoming "master", my listener could iterate
> over all the apps.
>
> I don't particularly like either of those options.
>
> For (1), it isn't really to do with app "Usage" like the other events.
>
> For (2), my listener code would be fiddly - I'd need to worry about receiving concurrent notifications via the normal UsageListener while I'm iterating over the pre-existing apps (assuming the new listener is called asynchronously, rather than blocking the management context's startup).
>
> It feels like (2) is a more generally useful feature to add (for programmatic support, at least). Does it sound useful for things beyond my use-case?
>
> Thoughts?
>
> Aled
>
> [1] https://github.com/apache/brooklyn-server/blob/master/core/src/main/java/org/apache/brooklyn/core/mgmt/usage/UsageListener.java
> [2] https://github.com/apache/brooklyn-server/pull/606
>
>