GitHub user ruffle1986 opened a pull request:
https://github.com/apache/metron/pull/1208
METRON-1790: Unsubscribe from every observable in the pcap panel UI
component
## Contributor Comments
Original Jira ticket: https://issues.apache.org/jira/browse/METRON-1790
**Motivation:**
There are a lot of http requests performed in the pcap panel ui component
and we just unsubscribe from some of them when the component is no longer
rendered on the screen. It could cause memory consumption issues. Because of
the active subscriptions, the garbage collector is not able to remove these
objects from the memory, however they're not needed anymore.
There's another benefit of unsubscribing from these http calls. If the user
leaves the pcap tab but there are pending requests, the unsubscribe method
cancels the active xhrs immediately so it won't wait for fulfilment
unnecessarily.
I would also refactor that part when we convert an observable to a promise.
I would keep it as an observable. By doing this, we would be able to
unsubscribe from it as well in the destructor method. Promises are not
cancelable.
https://github.com/apache/metron/blob/master/metron-interface/metron-alerts/src/app/pcap/pcap-panel/pcap-panel.component.ts#L70
Resources:
https://angular.io/guide/lifecycle-hooks#ondestroy
> This is the place to free resources that won't be garbage collected
automatically. Unsubscribe from Observables and DOM events. Stop interval
timers.
**Changes**
- Collect every subscription in an object and unsubscribe from them by
going through the object.
- Keep the `getPackets` observable as is. Remove `toPromise()`
**Testing**
Go to the PCAP tab and start querying or just let the component figure if
there are any running jobs (The latter starts an http request immediately when
the component is rendered). But before making any http requests, open up the
network tab and make sure you throttled the traffic by setting the connection
to "Slow 3G" (top right corner) to let the request be in pending state for a
while before it fulfils. By this, you get some extra time to change between the
PCAP and the Alerts tab. If you change between the tabs and there are any http
requests in pending state, they're going to be cancelled and highlighted in red
color.
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You can merge this pull request into a Git repository by running:
$ git pull https://github.com/ruffle1986/metron METRON-1790
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/metron/pull/1208.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #1208
----
commit e1bfcabccf0780c6725d1c5fcbb100e869e267ce
Author: ruffle1986 <ftamas.mail@...>
Date: 2018-09-21T11:48:53Z
feat(pcap panel): unsubscribe from every observable.
----
---
