Backport of Avoid blocking child type updates on parent ack into release/1.12.x #15501
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When providing updates to Envoy it is safest to follow the update order of: Clusters, Endpoints, Listeners, Routes. This order is encoded in our delta xDS response generation code. Another noteworthy attribute of these resources is that there are parent->child relationships between: Cluster->Endpoints and Listener->Routes. Envoy couples the storage of a parent and a child type such that whenever a control plane sends an update for a parent type, it MUST also send fresh data for the child type, even if Envoy previously had the latest data for the child type. A wrinkle that isn't accounted for currently is that Envoy does not actually ACK parent types until after attempting to receive data for the child types. This behavior also actually differs between Clusters and Listeners: - When a cluster is sent, Envoy will wait up to a 15s timeout for endpoints to arrive before sending the cluster ACK. - When a listener is sent, and it specifies RDS routes, Envoy will wait until those routes arrive before ACKing the listener. Though it's not clear to me what the timeout is for this, it exceeds a minute from my tests. However, a behavior encoded in our xDS update order is that we avoid sending ANY data if we are waiting on ACKs for ANY resource. Meaning that when we first send a cluster to Envoy and it requests endpoints for that cluster, the endpoints do not actually get sent for at least 15. This is because the endpoint update is paused by Consul until the cluster ACK, which Envoy pauses until it gets endpoints or times out. This commit changes the xDS order gating such that we only block listener/route updates if there are cluster/endpoin updates pending. This is to avoid routing to an invalid destination.
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@freddygv Would be open to learning how to test this manually by pairing. |
freddygv
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Nov 21, 2022
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Backport
This PR is auto-generated from #15083 to be assessed for backporting due to the inclusion of the label backport/1.12.
WARNING automatic cherry-pick of commits failed. Commits will require human attention.
The below text is copied from the body of the original PR.
Description
When providing updates to Envoy it is safest to follow the update order of: Clusters, Endpoints, Listeners, Routes. This order is encoded in our delta xDS response generation code.
Another noteworthy attribute of these resources is that there are parent->child relationships between: Cluster->Endpoints and Listener->Routes. Envoy couples the storage of a parent and a child type such that whenever a control plane sends an update for a parent type, it MUST also send fresh data for the child type, even if Envoy previously had the latest data for the child type.
A wrinkle that isn't accounted for currently is that Envoy does not actually ACK parent types until after attempting to receive data for the child types. This behavior also actually differs between Clusters and Listeners:
However, a behavior encoded in our xDS update order is that we avoid sending ANY data if we are waiting on ACKs for ANY resource. Meaning that when we first send a cluster to Envoy and it requests endpoints for that cluster, the endpoints do not actually get sent for at least 15s. This is because the endpoint update is paused by Consul until the cluster ACK, which Envoy pauses until it gets endpoints or times out.
This commit changes the xDS order gating such that we only block listener/route updates if there are cluster/endpoin updates pending. This is to avoid routing to an invalid destination.
Testing & Reproduction steps
Links
Likely related to: envoyproxy/envoy#5887
PR Checklist
Overview of commits