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
