Change conflicting meter names in ServerMetrics (#5804)

Motivation:

`MetricCollectingService` uses `.active.requests` to track the number of the current requests. If `armeria.server` is used as the prefix of the meter name, the name conflicts with "armeria.server.active.requests" in `ServerMetrics`.

`ServerMetrics.activeRequests()` counts all requests including `TransientService` which is excluded by `MetricCollectingService` with no `TransientServiceOption`. So, semantically, it would be better to use `.all` to the meter name to indicate that it counts all requests.

Modifications:

- Rename "armeria.server.active.requests" in `ServerMetrics` to "armeria.server.all.requests{state=active}".
- Rename "armeria.server.pending.requests" in `ServerMetrics` to "armeria.server.all.requests{state=pending}".

Result:

The meter names in `ServerMetrics` no longer conflict with `MetricCollectingService`.

core/src/main/java/com/linecorp/armeria/server/ServerMetrics.java

@@ -157,17 +157,22 @@ void decreaseActiveConnections() {
     public void bindTo(MeterRegistry meterRegistry) {
         meterRegistry.gauge("armeria.server.connections", activeConnections);
         // pending requests
-        meterRegistry.gauge("armeria.server.pending.requests",
-                            ImmutableList.of(Tag.of("protocol", "http1")), pendingHttp1Requests);
-        meterRegistry.gauge("armeria.server.pending.requests",
-                            ImmutableList.of(Tag.of("protocol", "http2")), pendingHttp2Requests);
+        final String allRequestsMeterName = "armeria.server.all.requests";
+        meterRegistry.gauge(allRequestsMeterName,
+                            ImmutableList.of(Tag.of("protocol", "http1"), Tag.of("state", "pending")),
+                            pendingHttp1Requests);
+        meterRegistry.gauge(allRequestsMeterName,
+                            ImmutableList.of(Tag.of("protocol", "http2"), Tag.of("state", "pending")),
+                            pendingHttp2Requests);
         // Active requests
-        meterRegistry.gauge("armeria.server.active.requests", ImmutableList.of(Tag.of("protocol", "http1")),
+        meterRegistry.gauge(allRequestsMeterName,
+                            ImmutableList.of(Tag.of("protocol", "http1"), Tag.of("state", "active")),
                             activeHttp1Requests);
-        meterRegistry.gauge("armeria.server.active.requests", ImmutableList.of(Tag.of("protocol", "http2")),
+        meterRegistry.gauge(allRequestsMeterName,
+                            ImmutableList.of(Tag.of("protocol", "http2"), Tag.of("state", "active")),
                             activeHttp2Requests);
-        meterRegistry.gauge("armeria.server.active.requests",
-                            ImmutableList.of(Tag.of("protocol", "http1.websocket")),
+        meterRegistry.gauge(allRequestsMeterName,
+                            ImmutableList.of(Tag.of("protocol", "http1.websocket"), Tag.of("state", "active")),
                             activeHttp1WebSocketRequests);
     }
 

core/src/test/java/com/linecorp/armeria/server/ServerMetricsTest.java

@@ -19,13 +19,16 @@
 import static org.awaitility.Awaitility.await;
 
 import java.time.Duration;
+import java.util.Map;
 import java.util.concurrent.CompletableFuture;
 
+import org.assertj.core.api.Condition;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.RegisterExtension;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.CsvSource;
 
+import com.linecorp.armeria.client.BlockingWebClient;
 import com.linecorp.armeria.client.ClientFactory;
 import com.linecorp.armeria.client.ClientOptions;
 import com.linecorp.armeria.client.WebClient;
@@ -37,14 +40,31 @@
 import com.linecorp.armeria.common.HttpResponse;
 import com.linecorp.armeria.common.HttpStatus;
 import com.linecorp.armeria.common.SessionProtocol;
+import com.linecorp.armeria.common.metric.MeterIdPrefixFunction;
+import com.linecorp.armeria.common.metric.MoreMeters;
+import com.linecorp.armeria.common.prometheus.PrometheusMeterRegistries;
+import com.linecorp.armeria.server.metric.MetricCollectingService;
 import com.linecorp.armeria.testing.junit5.server.ServerExtension;
 
+import io.micrometer.prometheusmetrics.PrometheusMeterRegistry;
+
 class ServerMetricsTest {
 
     @RegisterExtension
-    private static final ServerExtension server = new ServerExtension() {
+    final ServerExtension server = new ServerExtension() {
+        @Override
+        protected boolean runForEachTest() {
+            return true;
+        }
+
         @Override
         protected void configure(ServerBuilder sb) throws Exception {
+            final PrometheusMeterRegistry prometheusMeterRegistry = PrometheusMeterRegistries.newRegistry();
+            sb.meterRegistry(prometheusMeterRegistry);
+            // Use 'armeria.server' to make sure that the metric names are not conflicted with `ServerMetrics`.
+            sb.decorator(MetricCollectingService.newDecorator(
+                    MeterIdPrefixFunction.ofDefault("armeria.server")));
+
             sb.requestTimeoutMillis(0)
               .requestAutoAbortDelayMillis(0)
               .service("/ok/http", new HttpService() {
@@ -257,4 +277,29 @@ void checkWhenRequestTimeout(SessionProtocol sessionProtocol, long expectedPendi
             await().until(() -> serverMetrics.activeConnections() == 0);
         }
     }
+
+    @CsvSource({ "H1C", "H2C" })
+    @ParameterizedTest
+    void meterNames(SessionProtocol protocol) {
+        final BlockingWebClient client = BlockingWebClient.of(server.uri(protocol));
+        assertThat(client.get("/ok/http").status()).isEqualTo(HttpStatus.OK);
+
+        await().untilAsserted(() -> {
+            final Map<String, Double> meters = MoreMeters.measureAll(server.server().meterRegistry());
+            // armeria.server.active.requests#value is measured by MetricCollectingService
+            assertThat(meters).hasKeySatisfying(new Condition<String>("armeria.server.active.requests#value") {
+                @Override
+                public boolean matches(String key) {
+                    return key.startsWith("armeria.server.active.requests#value{hostname.pattern=");
+                }
+            });
+
+            final String protocolName = protocol == SessionProtocol.H1C ? "http1" : "http2";
+            // armeria.server.active.requests.all#value is measured by ServerMetrics
+            assertThat(meters).containsKey("armeria.server.all.requests#value{protocol=" + protocolName +
+                                           ",state=active}");
+            assertThat(meters).containsKey("armeria.server.all.requests#value{protocol=" + protocolName +
+                                           ",state=pending}");
+        });
+    }
 }