xds: Fix XdsDepManager aggregate cluster child ordering and loop detection #12129
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…ction The children of aggregate clusters have a priority order, so we can't ever throw them in an ordinary set for later iteration. This now detects recusion limits only after subscribing, but that matches our existing behavior in CdsLoadBalancer2. We don't get much value detecting the limit before subscribing and doing so makes watcher types more different. Loops are still a bit broken as they won't be unwatched when orphaned, as they will form a reference loop. In CdsLoadBalancer2, duplicate clusters had duplicate watchers so there was single-ownership and reference cycles couldn't form. Fixing that is a bigger change. Intermediate aggregate clusters are now included in XdsConfig, just for simplicity. It doesn't hurt anything whether they are present or missing. but it required updates to some tests.
| if (!config.hasValue()) { | ||
| clusters.put(clusterName, StatusOr.fromStatus(Status.INTERNAL.withDescription( | ||
| "Unable to get leaves for " + clusterName + ": " | ||
| + config.getStatus().getDescription()))); |
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Shall we include the childCluster name as well in the error status?
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config.getStatus().getDescription() includes the child's name. XdsWatcherBase's onError/onDoesNotExist formats an error message including toContextString(), which propagates that important error information.
I do suspect I will want to change this at some point to leave a reference to the broken cluster, as it appears we previously just discarded such failures. But I'll figure that out in later work as I rewrite CdsLB2, and check the gRFCs to see if they dictated the bahavior.
kannanjgithub
approved these changes
Jun 5, 2025
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The children of aggregate clusters have a priority order, so we can't ever throw them in an ordinary set for later iteration.
This now detects recusion limits only after subscribing, but that matches our existing behavior in CdsLoadBalancer2. We don't get much value detecting the limit before subscribing and doing so makes watcher types more different.
Loops are still a bit broken as they won't be unwatched when orphaned, as they will form a reference loop. In CdsLoadBalancer2, duplicate clusters had duplicate watchers so there was single-ownership and reference cycles couldn't form. Fixing that is a bigger change.
Intermediate aggregate clusters are now included in XdsConfig, just for simplicity. It doesn't hurt anything whether they are present or missing. but it required updates to some tests.