stefan-egli commented on code in PR #12:
URL:
https://github.com/apache/sling-org-apache-sling-discovery-base/pull/12#discussion_r2063865052
##########
src/main/java/org/apache/sling/discovery/base/commons/BaseDiscoveryService.java:
##########
@@ -93,6 +97,12 @@ public TopologyView getTopology() {
.listInstances(localClusterView);
topology.addInstances(attachedInstances);
+ // Check if topology changes should be delayed
+ if (topologyReadinessHandler != null &&
topologyReadinessHandler.shouldDelayTopologyChange()) {
+ logger.debug("getTopology: topology changes are delayed, returning
old view");
+ return oldView;
+ }
+
Review Comment:
This only covers the startup case. For shutdown returning the `oldView` here
doesn't result in sending `TOPOLOGY_CHANGING` events, which is what should
happen. So this section needs to distinguish between startup and shutdown - and
in the shutdown case it should call `oldView.setNotCurrent();` (would probably
be good to have a test case for exactly this).
PS: calling also `handleIsolatedFromTopology();` (as is done in the above
try/catch block) would be an interesting addition. But I fear that would result
in the entire cluster noticing the change (and a `TOPOLOGY_CHANGING` for
everybody) - plus then it would stall the entire cluster, as it would expect a
stable (`current`) topology again - which the local instance wouldn't do, as it
now behaves differently when terminating. So doing
`handleIsolatedFromTopology()` would be risky (might be good to have a test
case that ensures only the local instance gets a `TOPOLOGY_CHANGING` and none
of the other cluster members).
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