LocationCache ConcurrentDict lock contention fix (#558)

* LocalCache ConcurrentDict lock contention fix * Documentation included * Release notes added * refreshing changelog
Azure · Jul 17, 2019 · 245e9bb · 245e9bb
1 parent f799c18
commit 245e9bb
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Showing 2 changed files with 7 additions and 7 deletions.
diff --git a/Microsoft.Azure.Cosmos/src/Routing/LocationCache.cs b/Microsoft.Azure.Cosmos/src/Routing/LocationCache.cs
@@ -79,8 +79,9 @@ public ReadOnlyCollection<Uri> ReadEndpoints
         {
             get
             {
-                if (this.locationUnavailablityInfoByEndpoint.Count > 0
-                    && DateTime.UtcNow - this.lastCacheUpdateTimestamp > this.unavailableLocationsExpirationTime)
+                // Hot-path: avoid ConcurrentDictionary methods which acquire locks
+                if (DateTime.UtcNow - this.lastCacheUpdateTimestamp > this.unavailableLocationsExpirationTime
+                    && this.locationUnavailablityInfoByEndpoint.Any())
                 {
                     this.UpdateLocationCache();
                 }
@@ -98,8 +99,9 @@ public ReadOnlyCollection<Uri> WriteEndpoints
         {
             get
             {
-                if (this.locationUnavailablityInfoByEndpoint.Count > 0
-                    && DateTime.UtcNow - this.lastCacheUpdateTimestamp > this.unavailableLocationsExpirationTime)
+                // Hot-path: avoid ConcurrentDictionary methods which acquire locks
+                if (DateTime.UtcNow - this.lastCacheUpdateTimestamp > this.unavailableLocationsExpirationTime
+                    && this.locationUnavailablityInfoByEndpoint.Any())
                 {
                     this.UpdateLocationCache();
                 }

diff --git a/changelog.md b/changelog.md
@@ -1,6 +1,3 @@
-# Changelog
-
-All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
@@ -14,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - [#548](https://github.com/Azure/azure-cosmos-dotnet-v3/pull/548) Fixed mis-typed message in CosmosException.ToString();
+- [#558](https://github.com/Azure/azure-cosmos-dotnet-v3/pull/558) LocationCache ConcurrentDict lock contention fix
 
 ## [3.0.0](https://www.nuget.org/packages/Microsoft.Azure.Cosmos/3.0.0) - 2019-07-15