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Use dynamicMetadata to construct metadataMatchCriteria() #3254

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merged 9 commits into from
May 4, 2018
Merged

Use dynamicMetadata to construct metadataMatchCriteria() #3254

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bde0c9c
Use dynamicMetadata to construct metadataMatchCriteria()
Apr 30, 2018
1747131
Fix formatting issues
Apr 30, 2018
be4fe35
Fix more tests
Apr 30, 2018
f1f12e0
Add a test for overriding metadata matcha via dynamic metadata
Apr 30, 2018
b261a23
Handle route_entry_->metadataMatchCriteria() == nullptr
May 1, 2018
663c922
Fix formatting
May 1, 2018
b24da82
Improve method docs.
May 3, 2018
d29a4a5
Return the cached result of metadataMatchCriteria()
May 3, 2018
8b7bb04
More tests
May 3, 2018
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Return the cached result of metadataMatchCriteria() 
Signed-off-by: Raul Gutierrez Segales <[email protected]>
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Raul Gutierrez Segales committed May 3, 2018
commit d29a4a5d3f47cd9c12bb759821262d619a513665
7 changes: 7 additions & 0 deletions source/common/router/router.h
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Expand Up @@ -165,6 +165,13 @@ class Filter : Logger::Loggable<Logger::Id::router>,
}
const Router::MetadataMatchCriteria* metadataMatchCriteria() override {
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In the retry case you may end up calling this method multiple times. Is it worth checking to see if metadata_match_ is not nullptr and returning if not? Is there any chance that doing the merge multiple times could have strange effects? If not to both of these, I would still add a comment about how this can happen multiple times for a single request.

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I think checking for nullptr and returning early is worth it. Multiple calls to merge should yield the same result, but we can avoid the computation and creating new objects.

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@mattklein123 hold on -- can the route_entry_ for a request change (e.g.: someone called clearRouteCache() and then metadataMatchCriteria() gets called again)? In that case, caching the result for metadataMatchCriteria() would be wrong... we'd want to recompute.

cc: @zuercher @htuch

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I think it's ok, as long as metadataMatchCriteria() isn't invoked until LoadBalancer::chooseHost, which happens during Router::Filter::getConnPool in Filter::decodeHeaders and again in Filter::doRetry. The route_ and route_entry_ get set in decodeHeaders before load balancing, and I believe that once that happens they do not change.

clearRouteCache operates on the Http::ConnectionManagerImpl::ActiveStreamFilterBase which ends up being the source of the route_ and therefore route_entry_ via its implementation of StreamFilterCallbacks::route().

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This seems right, can we add an ASSERT to this effect (i.e. if we get called twice, the route entry is the same)?

if (route_entry_) {
// Have we been called before? If so, there's no need to recompute because
// by the time this method is called for the first time, route_entry_ should
// not change anymore.
if (metadata_match_ != nullptr) {
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Can you add a test for this as well? Thanks.

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@htuch done — plus two bonus tests:

  • using > 1 key/value pair in dynamicMetadata()
  • mixing a key that overrides the route entry with one that doesn't

thanks for the review!

return metadata_match_.get();
}

// The request's metadata, if present, takes precedence over the route's.
const auto& request_metadata = callbacks_->requestInfo().dynamicMetadata().filter_metadata();
const auto filter_it = request_metadata.find(Envoy::Config::MetadataFilters::get().ENVOY_LB);
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