resolve: Add a Reset state #633
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The recovery layer needs to maintain its own cache for reconcilation (in addition to the other cache layers we keep). This caching can be eliminated by introducing a resolve::Update::Reset state that implicitly remotes all endpoints not present in the endpoint set.
hawkw
approved these changes
Aug 22, 2020
linkerd/proxy/resolve/src/recover.rs
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172
| let update = match initial { | ||
| Update::Add(eps) => Update::Reset(eps), | ||
| up => up, | ||
| }; |
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just to make sure i'm understanding correctly: if the last update was an Add, we send a Reset after reconnecting to nuke those endpoints. but what if the last update before the connection ended was not an Add? could it have been a Remove that only removed some previously sent endpoints? don't we need to do a complete reset regardless?
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Not quite.
If the first update was an add, we send a reset. I.e. we've been disconnected, so we could have missed removals. The first add, then, has the full state of the service. It doesn't make any sense to receive a Remove as the first update after a connect--we handle that state explicitly now.
I've tried to clarify this in the code.
hawkw
reviewed
Aug 24, 2020
Comment on lines
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| Some(Ok(Update::Remove(_))) => { | ||
| debug_assert!(false, "First update after connection must not be a Remove"); | ||
| // If we see this in production, just ignore and keep polling until an | ||
| // actionable update is received. | ||
| tracing::debug!("Ignoring removal after connect"); | ||
| continue; | ||
| } | ||
| Some(Ok(update)) => { | ||
| tracing::debug!("Connected"); | ||
| // If the first update is an Add; convert it to a Reset, indicating all | ||
| // other endpoints should be removed. | ||
| let update = match update { | ||
| Update::Add(eps) => Update::Reset(eps), | ||
| up => up, | ||
| }; |
olix0r
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to linkerd/linkerd2
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Aug 26, 2020
This release includes internal changes to the service discovery system, especially when discovering control plane components (like the destination and identity controllers). Now, the proxy attempts to balance requests across all pods in each control plane service. This requires control plane changes to use "headless" services so that SRV records are exposed. When the control plane services have a `clusterIP` set, the proxy falls back to using normal A-record lookups. --- * tracing: add richer verbose spans to http clients (linkerd/linkerd2-proxy#622) * trace: update tracing dependencies (linkerd/linkerd2-proxy#623) * Remove `Resolution` trait (linkerd/linkerd2-proxy#606) * Update proxy-identity to edge-20.8.2 (linkerd/linkerd2-proxy#627) * Add build arg for skipping identity wrapper (linkerd/linkerd2-proxy#624) * Wait for proxy thread to terminate in integration tests (linkerd/linkerd2-proxy#625) * Remove scrubbing for unused headers (linkerd/linkerd2-proxy#628) * Split orig-proto tests out of discovery tests (linkerd/linkerd2-proxy#629) * Re-enable outbound timeout test (linkerd/linkerd2-proxy#630) * profiles: perform profile resolution for IP addresses (linkerd/linkerd2-proxy#626) * Move resolve api to async-stream (linkerd/linkerd2-proxy#599) * Decouple discovery buffering from endpoint conversion (linkerd/linkerd2-proxy#631) * resolve: Add a Reset state (linkerd/linkerd2-proxy#633) * resolve: Eagerly fail resolutions (linkerd/linkerd2-proxy#634) * test: replace `net2` dependency with `socket2` (linkerd/linkerd2-proxy#635) * dns: Run DNS resolutions on the main runtime (linkerd/linkerd2-proxy#637) * Load balance requests to the control plane (linkerd/linkerd2-proxy#594) * Unify control plane client construction (linkerd/linkerd2-proxy#638)
olix0r
added a commit
to linkerd/linkerd2
that referenced
this pull request
Aug 26, 2020
This release includes internal changes to the service discovery system, especially when discovering control plane components (like the destination and identity controllers). Now, the proxy attempts to balance requests across all pods in each control plane service. This requires control plane changes to use "headless" services so that SRV records are exposed. When the control plane services have a `clusterIP` set, the proxy falls back to using normal A-record lookups. --- * tracing: add richer verbose spans to http clients (linkerd/linkerd2-proxy#622) * trace: update tracing dependencies (linkerd/linkerd2-proxy#623) * Remove `Resolution` trait (linkerd/linkerd2-proxy#606) * Update proxy-identity to edge-20.8.2 (linkerd/linkerd2-proxy#627) * Add build arg for skipping identity wrapper (linkerd/linkerd2-proxy#624) * Wait for proxy thread to terminate in integration tests (linkerd/linkerd2-proxy#625) * Remove scrubbing for unused headers (linkerd/linkerd2-proxy#628) * Split orig-proto tests out of discovery tests (linkerd/linkerd2-proxy#629) * Re-enable outbound timeout test (linkerd/linkerd2-proxy#630) * profiles: perform profile resolution for IP addresses (linkerd/linkerd2-proxy#626) * Move resolve api to async-stream (linkerd/linkerd2-proxy#599) * Decouple discovery buffering from endpoint conversion (linkerd/linkerd2-proxy#631) * resolve: Add a Reset state (linkerd/linkerd2-proxy#633) * resolve: Eagerly fail resolutions (linkerd/linkerd2-proxy#634) * test: replace `net2` dependency with `socket2` (linkerd/linkerd2-proxy#635) * dns: Run DNS resolutions on the main runtime (linkerd/linkerd2-proxy#637) * Load balance requests to the control plane (linkerd/linkerd2-proxy#594) * Unify control plane client construction (linkerd/linkerd2-proxy#638)
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The recovery layer needs to maintain its own cache for reconcilation (in
addition to the other cache layers we keep). This caching can be
eliminated by introducing a resolve::Update::Reset state that implicitly
remotes all endpoints not present in the endpoint set.