Metrics exposure (#334)

* Added ability to observe http connection metrics.

Author: JonathanHenson

include/aws/http/connection.h

@@ -105,6 +105,14 @@ typedef void(aws_http2_on_remote_settings_change_fn)(
     size_t num_settings,
     void *user_data);
 
+/**
+ * Callback invoked on each statistics sample.
+ *
+ * connection_nonce is unique to each connection for disambiguation of each callback per connection.
+ */
+typedef void(
+    aws_http_statistics_observer_fn)(size_t connection_nonce, const struct aws_array_list *stats_list, void *user_data);
+
 /**
  * Configuration options for connection monitoring
  */
@@ -121,6 +129,17 @@ struct aws_http_connection_monitoring_options {
      * as unhealthy.
      */
     uint32_t allowable_throughput_failure_interval_seconds;
+
+    /**
+     * invoked on each statistics publish by the underlying IO channel. Install this callback to receive the statistics
+     * for observation. This field is optional.
+     */
+    aws_http_statistics_observer_fn *statistics_observer_fn;
+
+    /**
+     * user_data to be passed to statistics_observer_fn.
+     */
+    void *statistics_observer_user_data;
 };
 
 /**

source/connection_monitor.c

@@ -69,6 +69,11 @@ static void s_process_statistics(
         }
     }
 
+    if (impl->options.statistics_observer_fn) {
+        impl->options.statistics_observer_fn(
+            (size_t)(uintptr_t)(context), stats_list, impl->options.statistics_observer_user_data);
+    }
+
     struct aws_channel *channel = context;
 
     uint64_t bytes_per_second = 0;

tests/test_connection_monitor.c

@@ -284,12 +284,52 @@ static struct http_monitor_test_stats_event s_test_rw_above_events[] = {
         .expected_throughput = 1000,
     },
 };
+
+struct observer_cb_data {
+    bool invoked;
+    size_t nonce;
+    size_t number_of_stats;
+    struct aws_crt_statistics_socket socket_stats;
+    struct aws_crt_statistics_http1_channel http_stats;
+};
+static void s_observer_cb(size_t connection_nonce, const struct aws_array_list *stats, void *user_data) {
+    struct observer_cb_data *cb_data = user_data;
+    cb_data->invoked = true;
+    cb_data->nonce = connection_nonce;
+    cb_data->number_of_stats = aws_array_list_length(stats);
+
+    for (size_t i = 0; i < cb_data->number_of_stats; ++i) {
+        struct aws_crt_statistics_base *base_ptr = NULL;
+        aws_array_list_get_at(stats, (void **)&base_ptr, i);
+
+        if (base_ptr->category == AWSCRT_STAT_CAT_SOCKET) {
+            cb_data->socket_stats = *(struct aws_crt_statistics_socket *)base_ptr;
+        }
+
+        if (base_ptr->category == AWSCRT_STAT_CAT_HTTP1_CHANNEL) {
+            cb_data->http_stats = *(struct aws_crt_statistics_http1_channel *)base_ptr;
+        }
+    }
+}
 static int s_test_http_connection_monitor_rw_above(struct aws_allocator *allocator, void *ctx) {
     (void)ctx;
 
+    struct observer_cb_data cb_data;
+    AWS_ZERO_STRUCT(cb_data);
+    s_test_options.statistics_observer_fn = s_observer_cb;
+    s_test_options.statistics_observer_user_data = &cb_data;
     int result = s_do_http_monitoring_test(
         allocator, &s_test_options, s_test_rw_above_events, AWS_ARRAY_SIZE(s_test_rw_above_events));
     ASSERT_TRUE(result == AWS_OP_SUCCESS);
+    ASSERT_TRUE(cb_data.invoked);
+    ASSERT_TRUE(cb_data.nonce > 0);
+    ASSERT_UINT_EQUALS(2U, cb_data.number_of_stats);
+    ASSERT_UINT_EQUALS(s_test_rw_above_events[0].socket_stats.bytes_written, cb_data.socket_stats.bytes_written);
+    ASSERT_UINT_EQUALS(s_test_rw_above_events[0].socket_stats.bytes_read, cb_data.socket_stats.bytes_read);
+    ASSERT_UINT_EQUALS(
+        s_test_rw_above_events[0].http_stats.current_outgoing_stream_id, cb_data.http_stats.current_outgoing_stream_id);
+    ASSERT_UINT_EQUALS(
+        s_test_rw_above_events[0].http_stats.current_incoming_stream_id, cb_data.http_stats.current_incoming_stream_id);
 
     return AWS_OP_SUCCESS;
 }