Refactor HttpJsonMetricHandler to be BufferedHttpMetricHandler

This makes it easier for derived implementations to be created that don't necessarily use JSON. This commit adds the ability to specify a media type when sending data which means derived implementations only need to handle serialization.

Author: Dean Ward

src/StackExchange.Metrics/Handlers/BosunMetricHandler.cs

@@ -15,7 +15,7 @@ namespace StackExchange.Metrics.Handlers
     /// <summary>
     /// Implements <see cref="BufferedMetricHandler" /> by sending data to a Bosun endpoint.
     /// </summary>
-    public class BosunMetricHandler : HttpJsonMetricHandler
+    public class BosunMetricHandler : BufferedHttpMetricHandler
     {
         static readonly byte[] s_comma;
         static readonly byte[] s_startArray;
@@ -94,7 +94,7 @@ public Uri BaseUri
         public bool EnableExternalCounters { get; set; } = true;
 
         /// <inheritdoc />
-        protected override ValueTask SendCounterAsync(ReadOnlySequence<byte> sequence) => SendAsync(_metricUri, HttpMethod.Post, PayloadType.Counter, sequence);
+        protected override ValueTask SendCounterAsync(ReadOnlySequence<byte> sequence) => SendAsync(_metricUri, HttpMethod.Post, PayloadType.Counter, MediaTypes.Json, sequence);
 
         /// <inheritdoc />
         protected override ValueTask SendCumulativeCounterAsync(ReadOnlySequence<byte> sequence)
@@ -104,14 +104,14 @@ protected override ValueTask SendCumulativeCounterAsync(ReadOnlySequence<byte> s
                 return default;
             }
 
-            return SendAsync(_counterUri, HttpMethod.Post, PayloadType.CumulativeCounter, sequence);
+            return SendAsync(_counterUri, HttpMethod.Post, PayloadType.CumulativeCounter, MediaTypes.Json, sequence);
         }
 
         /// <inheritdoc />
-        protected override ValueTask SendGaugeAsync(ReadOnlySequence<byte> sequence) => SendAsync(_metricUri, HttpMethod.Post, PayloadType.Gauge, sequence);
+        protected override ValueTask SendGaugeAsync(ReadOnlySequence<byte> sequence) => SendAsync(_metricUri, HttpMethod.Post, PayloadType.Gauge, MediaTypes.Json, sequence);
 
         /// <inheritdoc />
-        protected override ValueTask SendMetadataAsync(ReadOnlySequence<byte> sequence) => SendAsync(_metadataUri, HttpMethod.Post, PayloadType.Metadata, sequence, gzip: false);
+        protected override ValueTask SendMetadataAsync(ReadOnlySequence<byte> sequence) => SendAsync(_metadataUri, HttpMethod.Post, PayloadType.Metadata, MediaTypes.Json, sequence, gzip: false);
 
         /// <inheritdoc />
         protected override void SerializeMetric(IBufferWriter<byte> writer, in MetricReading reading)

src/StackExchange.Metrics/Handlers/SignalFxMetricHandler.cs

@@ -139,9 +139,9 @@ private IMetricHandler GetHandler()
         }
 
         /// <summary>
-        /// Implements <see cref="HttpJsonMetricHandler" /> by sending data to the SignalFX REST API.
+        /// Implements <see cref="BufferedHttpMetricHandler" /> by sending data to the SignalFX REST API.
         /// </summary>
-        private class JsonMetricHandler : HttpJsonMetricHandler
+        private class JsonMetricHandler : BufferedHttpMetricHandler
         {
             Uri _baseUri;
             Uri _metricUri;
@@ -255,13 +255,13 @@ protected override void SerializeMetadata(IBufferWriter<byte> writer, IEnumerabl
             }
 
             /// <inheritdoc />
-            protected override ValueTask SendCounterAsync(ReadOnlySequence<byte> sequence) => SendAsync(_metricUri, HttpMethod.Post, PayloadType.Counter, sequence);
+            protected override ValueTask SendCounterAsync(ReadOnlySequence<byte> sequence) => SendAsync(_metricUri, HttpMethod.Post, PayloadType.Counter, MediaTypes.Json, sequence);
 
             /// <inheritdoc />
-            protected override ValueTask SendCumulativeCounterAsync(ReadOnlySequence<byte> sequence) => SendAsync(_metricUri, HttpMethod.Post, PayloadType.CumulativeCounter, sequence);
+            protected override ValueTask SendCumulativeCounterAsync(ReadOnlySequence<byte> sequence) => SendAsync(_metricUri, HttpMethod.Post, PayloadType.CumulativeCounter, MediaTypes.Json, sequence);
 
             /// <inheritdoc />
-            protected override ValueTask SendGaugeAsync(ReadOnlySequence<byte> sequence) => SendAsync(_metricUri, HttpMethod.Post, PayloadType.Gauge, sequence);
+            protected override ValueTask SendGaugeAsync(ReadOnlySequence<byte> sequence) => SendAsync(_metricUri, HttpMethod.Post, PayloadType.Gauge, MediaTypes.Json, sequence);
 
             /// <inheritdoc />
             protected override ValueTask SendMetadataAsync(ReadOnlySequence<byte> sequence)

…/Infrastructure/HttpJsonMetricHandler.cs …rastructure/BufferedHttpMetricHandler.cssrc/StackExchange.Metrics/Infrastructure/HttpJsonMetricHandler.cs renamed to src/StackExchange.Metrics/Infrastructure/BufferedHttpMetricHandler.cs src/StackExchange.Metrics/Infrastructure/HttpJsonMetricHandler.cs renamed to src/StackExchange.Metrics/Infrastructure/BufferedHttpMetricHandler.cs

@@ -9,18 +9,19 @@
 
 namespace StackExchange.Metrics.Infrastructure
 {
+
+
     /// <summary>
-    /// Abstract implementation of <see cref="BufferedMetricHandler" /> that posts JSON
-    /// to an HTTP endpoint.
+    /// Abstract implementation of <see cref="BufferedMetricHandler" /> that posts content to an HTTP endpoint.
     /// </summary>
-    public abstract class HttpJsonMetricHandler : BufferedMetricHandler
+    public abstract class BufferedHttpMetricHandler : BufferedMetricHandler
     {
         private readonly Lazy<HttpClient> _httpClientFactory;
 
         /// <summary>
-        /// Constructs an instance of <see cref="HttpJsonMetricHandler" /> that sends metric data using an <see cref="HttpClient" />.
+        /// Constructs an instance of <see cref="BufferedHttpMetricHandler" /> that sends metric data using an <see cref="HttpClient" />.
         /// </summary>
-        protected HttpJsonMetricHandler()
+        protected BufferedHttpMetricHandler()
         {
             _httpClientFactory = new Lazy<HttpClient>(CreateHttpClient);
         }
@@ -124,7 +125,7 @@ protected override ValueTask SendAsync(PayloadType payloadType, ReadOnlySequence
         protected virtual HttpClient CreateHttpClient() => new HttpClient();
 
         /// <inheritdoc />
-        protected async ValueTask SendAsync(Uri uri, HttpMethod method, PayloadType payloadType, ReadOnlySequence<byte> sequence, bool gzip = true)
+        protected async ValueTask SendAsync(Uri uri, HttpMethod method, PayloadType payloadType, MediaTypeHeaderValue mediaType, ReadOnlySequence<byte> sequence, bool gzip = true)
         {
             if (uri == null)
             {
@@ -135,7 +136,7 @@ protected async ValueTask SendAsync(Uri uri, HttpMethod method, PayloadType payl
             var postambleLength = GetPostambleLength(payloadType);
             var request = new HttpRequestMessage(method, uri)
             {
-                Content = new ReadOnlySequenceContent(gzip, payloadType, sequence, preambleLength, WritePreambleAsync, postambleLength, WritePostambleAsync)
+                Content = new ReadOnlySequenceContent(gzip, payloadType, mediaType, sequence, preambleLength, WritePreambleAsync, postambleLength, WritePostambleAsync)
             };
 
             var response = await _httpClientFactory.Value.SendAsync(request);
@@ -176,6 +177,7 @@ private class ReadOnlySequenceContent : HttpContent
             public ReadOnlySequenceContent(
                 bool gzip,
                 PayloadType type,
+                MediaTypeHeaderValue mediaType,
                 in ReadOnlySequence<byte> sequence, 
                 int preambleLength,
                 Func<Stream, PayloadType, Task> writePreamble, 
@@ -190,15 +192,13 @@ Func<Stream, PayloadType, Task> writePostamble
                 _writePreamble = writePreamble;
                 _writePostamble = writePostamble;
 
-                Headers.ContentType = s_jsonHeader;
+                Headers.ContentType = mediaType;
                 if (gzip)
                 {
                     Headers.ContentEncoding.Add("gzip");
                 }
             }
 
-            static readonly MediaTypeHeaderValue s_jsonHeader = new MediaTypeHeaderValue("application/json");
-
             protected override async Task SerializeToStreamAsync(Stream stream, TransportContext context)
             {
                 IDisposable toDispose = null;

src/StackExchange.Metrics/Infrastructure/MediaTypes.cs

@@ -0,0 +1,15 @@
+using System.Net.Http.Headers;
+
+namespace StackExchange.Metrics.Infrastructure
+{
+    /// <summary>
+    /// Common media types used by the <see cref="BufferedHttpMetricHandler"/>.
+    /// </summary>
+    public static class MediaTypes
+    {
+        /// <summary>
+        /// Media type used for JSON payloads: application/json
+        /// </summary>
+        public static readonly MediaTypeHeaderValue Json = new MediaTypeHeaderValue("application/json");
+    }
+}