Add a caching channel factory.

src/Lib/CachedChannelFactory.cs

@@ -0,0 +1,97 @@
+// Copyright 2019 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+using Google.Ads.GoogleAds.Config;
+using Grpc.Auth;
+using Grpc.Core;
+using System;
+using System.Collections.Generic;
+
+namespace Google.Ads.GoogleAds.Lib
+{
+ /// <summary>
+ /// A channel factory that uses internal caching when possible.
+ /// </summary>
+ internal class CachedChannelFactory
+ {
+ /// <summary>
+ /// The cache to store existing channels.
+ /// </summary>
+ private static Dictionary<string, Channel> cache = new Dictionary<string, Channel>();
+
+
+ /// <summary>
+ /// Gets the channel for the specified configuration.
+ /// </summary>
+ /// <param name="config">The configuration.</param>
+ /// <returns>The channel.</returns>
+ internal static Channel GetChannel(GoogleAdsConfig config)
+ {
+ Channel retval = null;
+
+ // Channels with unique (credentials, Url) combination should be unique.
+ string key = string.Join("~", new object[] {
+ config.OAuth2Mode,
+ config.OAuth2ClientId,
+ config.OAuth2ClientSecret,
+ config.OAuth2RefreshToken,
+ config.OAuth2PrivateKey,
+ config.OAuth2PrnEmail,
+ config.ServerUrl
+ });
+
+ lock (cache)
+ {
+ if (cache.ContainsKey(key))
+ {
+ retval = cache[key];
+ if (retval.State == ChannelState.Shutdown)
+ {
+ // If the channel is shut down, then remove it from cache.
+ lock (cache)
+ {
+ cache.Remove(key);
+ retval = null;
+ }
+ }
+ }
+
+ if (retval == null)
+ {
+ // Create a new channel.
+ lock (cache)
+ {
+ retval = CreateChannel(config);
+ cache[key] = retval;
+ }
+ }
+ }
+
+ return retval;
+ }
+
+ /// <summary>
+ /// Creates the channel.
+ /// </summary>
+ /// <param name="config">The configuration.</param>
+ /// <returns>The channel.</returns>
+ private static Channel CreateChannel(GoogleAdsConfig config)
+ {
+ ChannelCredentials channelCredentials =
+ GoogleGrpcCredentials.ToChannelCredentials(config.Credentials);
+ Uri uri = new Uri(config.ServerUrl);
+ return new Channel(uri.Host, uri.Port, channelCredentials);
+ }
+ }
+}