Allow proxy to be specified (#2127) (#2128)

Co-authored-by: David Martin <[email protected]>
Co-authored-by: David Martin <[email protected]>

Author: emasab

src/Confluent.SchemaRegistry/CachedSchemaRegistryClient.cs

@@ -23,6 +23,7 @@
 using System.Threading.Tasks;
 using System.Linq;
 using System;
+using System.Net;
 using System.Threading;
 using System.Security.Cryptography.X509Certificates;
 using Confluent.Kafka;
@@ -166,8 +167,12 @@ private static SubjectNameStrategyDelegate GetValueSubjectNameStrategy(
         /// <param name="authenticationHeaderValueProvider">
         ///     The authentication header value provider
         /// </param>
+        /// <param name="proxy">
+        ///     The proxy server to use for connections
+        /// </param>
         public CachedSchemaRegistryClient(IEnumerable<KeyValuePair<string, string>> config,
-            IAuthenticationHeaderValueProvider authenticationHeaderValueProvider)
+            IAuthenticationHeaderValueProvider authenticationHeaderValueProvider,
+            IWebProxy proxy = null)
         {
             if (config == null)
             {
@@ -352,13 +357,8 @@ public CachedSchemaRegistryClient(IEnumerable<KeyValuePair<string, string>> conf
             }
 
             var sslCaLocation = config.FirstOrDefault(prop => prop.Key.ToLower() == SchemaRegistryConfig.PropertyNames.SslCaLocation).Value;
-            if (string.IsNullOrEmpty(sslCaLocation))
-            {
-                this.restService = new RestService(schemaRegistryUris, timeoutMs, authenticationHeaderValueProvider, SetSslConfig(config), sslVerify);
-            } else
-            {
-                this.restService = new RestService(schemaRegistryUris, timeoutMs, authenticationHeaderValueProvider, SetSslConfig(config), sslVerify, new X509Certificate2(sslCaLocation));
-            }
+            var sslCaCertificate = string.IsNullOrEmpty(sslCaLocation) ? null : new X509Certificate2(sslCaLocation);
+            this.restService = new RestService(schemaRegistryUris, timeoutMs, authenticationHeaderValueProvider, SetSslConfig(config), sslVerify, sslCaCertificate, proxy);
         }
 
         /// <summary>
@@ -372,6 +372,20 @@ public CachedSchemaRegistryClient(IEnumerable<KeyValuePair<string, string>> conf
         {
         }
 
+        /// <summary>
+        ///     Initialize a new instance of the SchemaRegistryClient class.
+        /// </summary>
+        /// <param name="config">
+        ///     Configuration properties.
+        /// </param>
+        /// <param name="proxy">
+        ///     The proxy server to use for connections
+        /// </param>
+        public CachedSchemaRegistryClient(IEnumerable<KeyValuePair<string, string>> config, IWebProxy proxy)
+            : this(config, null, proxy)
+        {
+
+        }
 
         /// <remarks>
         ///     This is to make sure memory doesn't explode in the case of incorrect usage.

src/Confluent.SchemaRegistry/Rest/RestService.cs

@@ -58,14 +58,14 @@ public class RestService : IRestService
         /// </summary>
         public RestService(string schemaRegistryUrl, int timeoutMs,
             IAuthenticationHeaderValueProvider authenticationHeaderValueProvider, List<X509Certificate2> certificates,
-            bool enableSslCertificateVerification, X509Certificate2 sslCaCertificate = null)
+            bool enableSslCertificateVerification, X509Certificate2 sslCaCertificate = null, IWebProxy proxy = null)
         {
             this.authenticationHeaderValueProvider = authenticationHeaderValueProvider;
 
             this.clients = schemaRegistryUrl
                 .Split(',')
                 .Select(SanitizeUri) // need http or https - use http if not present.
-                .Select(uri => new HttpClient(CreateHandler(certificates, enableSslCertificateVerification, sslCaCertificate))
+                .Select(uri => new HttpClient(CreateHandler(certificates, enableSslCertificateVerification, sslCaCertificate, proxy))
                 {
                     BaseAddress = new Uri(uri, UriKind.Absolute), Timeout = TimeSpan.FromMilliseconds(timeoutMs)
                 })
@@ -79,10 +79,16 @@ private static string SanitizeUri(string uri)
         }
 
         private static HttpClientHandler CreateHandler(List<X509Certificate2> certificates,
-            bool enableSslCertificateVerification, X509Certificate2 sslCaCertificate)
+            bool enableSslCertificateVerification, X509Certificate2 sslCaCertificate,
+            IWebProxy proxy)
         {
             var handler = new HttpClientHandler();
 
+            if (proxy != null)
+            {
+                handler.Proxy = proxy;
+            }
+
             if (!enableSslCertificateVerification)
             {
                 handler.ServerCertificateCustomValidationCallback = (_, __, ___, ____) => { return true; };