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Allow non-constant endpoints to opt-in to timings #2366

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Allow non-constant endpoints to opt-in to timings #2366

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3 changes: 2 additions & 1 deletion dialogue-core/src/main/java/com/palantir/dialogue/core/DialogueChannel.java
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Original file line number Diff line number Diff line change
Expand Up @@ -253,7 +253,8 @@ private static EndpointChannelFactory createEndpointChannelFactory(Channel multi
channel = new RangeAcceptsIdentityEncodingChannel(channel);
channel = ContentEncodingChannel.of(channel, endpoint);
channel = TracedChannel.create(cf, channel, endpoint);
if (ChannelToEndpointChannel.isConstant(endpoint)) {
if (ChannelToEndpointChannel.isConstant(endpoint)
|| endpoint.tags().contains("dialogue-enable-endpoint-timing")) {
Comment on lines +256 to +257
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I suppose we could probably update ChannelToEndpointChannel to use a caffeine cache with weak keys, and get rid of the isConstant check altogether once the feign client implementation reuses endpoint values -- worst case is weakref churn and metric fanout, but we don't expect these things to be entirely unbounded. When Endpoints aren't reused, this method is called for every request, so looking up the timers in a large TaggedMetricRegistry can be nontrivial, but code that expects decent performance shouldn't stray far from the standard path.

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I think I'm in favor of this proposal for a couple reasons:

  • Even in the current implementation, a poorly implemented client with unbounded service/endpoint names could blow up this ChannelToEndpointChannel cache. Using a Caffeine cache would allow to avoid this by use weak keys and/or bounding the cache.
  • ChannelToEndpointChannel assumes that non-constant endpoints are uniquely identified by (service, endpoint), but this isn't correct, for the reasons mentioned in Cache Feign endpoints conjure-java-runtime#2973 (comment). It would probably be good to switch to a cache for this reason alone.

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I've put up #2367. Let me know if this isn't what you were imagining.

// Avoid producing metrics for non-constant endpoints which may produce
// high cardinality.
channel = TimingEndpointChannel.create(cf, channel, endpoint);
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