KTOR-7658: do not write unknown HTTP method names to metrics

ktor-server/ktor-server-plugins/ktor-server-metrics-micrometer/jvm/src/io/ktor/server/metrics/micrometer/MicrometerMetrics.kt

@@ -4,6 +4,7 @@
 
 package io.ktor.server.metrics.micrometer
 
+import io.ktor.http.HttpMethod.Companion.DefaultMethods
 import io.ktor.server.application.*
 import io.ktor.server.application.hooks.*
 import io.ktor.server.application.hooks.Metrics
@@ -146,19 +147,22 @@ public val MicrometerMetrics: ApplicationPlugin<MicrometerMetricsConfig> =
 
         @OptIn(InternalAPI::class)
         on(Metrics) { call ->
-            active?.incrementAndGet()
-            call.attributes.put(measureKey, CallMeasure(Timer.start(registry)))
+            if (call.request.httpMethod in DefaultMethods) {
+                active?.incrementAndGet()
+                call.attributes.put(measureKey, CallMeasure(Timer.start(registry)))
+            }
         }
 
         on(ResponseSent) { call ->
-            active?.decrementAndGet()
-            val measure = call.attributes[measureKey]
-            measure.timer.stop(
-                Timer.builder(metricName)
-                    .addDefaultTags(call, measure.throwable)
-                    .apply { pluginConfig.timerBuilder(this, call, measure.throwable) }
-                    .register(registry)
-            )
+            call.attributes.getOrNull(measureKey)?.let { measure ->
+                active?.decrementAndGet()
+                measure.timer.stop(
+                    Timer.builder(metricName)
+                        .addDefaultTags(call, measure.throwable)
+                        .apply { pluginConfig.timerBuilder(this, call, measure.throwable) }
+                        .register(registry)
+                )
+            }
         }
 
         on(CallFailed) { call, cause ->
@@ -167,7 +171,9 @@ public val MicrometerMetrics: ApplicationPlugin<MicrometerMetricsConfig> =
         }
 
         application.monitor.subscribe(RoutingRoot.RoutingCallStarted) { call ->
-            call.attributes[measureKey].route = call.route.parent.toString()
+            call.attributes.getOrNull(measureKey)?.let { measure ->
+                measure.route = call.route.parent.toString()
+            }
         }
     }
 

ktor-server/ktor-server-plugins/ktor-server-metrics-micrometer/jvm/test/io/ktor/server/metrics/micrometer/MicrometerMetricsTests.kt

@@ -67,6 +67,37 @@ class MicrometerMetricsTests {
         testRegistry.assertActive(0.0)
     }
 
+    @Test
+    fun `time is not measured for custom http requests`() = testApplication {
+        val testRegistry = SimpleMeterRegistry()
+        install(MicrometerMetrics) {
+            registry = testRegistry
+        }
+
+        routing {
+            get("/uri") {
+                call.respond("hello")
+            }
+        }
+
+        var timers = testRegistry.find(requestTimeTimerName).timers()
+        assertTrue(timers.isEmpty())
+
+        client.get("/uri")
+        timers = testRegistry.find(requestTimeTimerName).timers()
+        assertEquals(1, timers.size, "Metrics should be recorded for GET requests")
+
+        client.request("/uri") {
+            method = HttpMethod("CUSTOM")
+        }
+        timers = testRegistry.find(requestTimeTimerName).timers()
+        assertEquals(1, timers.size, "Metrics should not be recorded for custom requests")
+
+        client.put("/uri")
+        timers = testRegistry.find(requestTimeTimerName).timers()
+        assertEquals(2, timers.size, "Metrics should be recorded for PUT requests")
+    }
+
     @Test
     fun `errors are recorded`() = testApplication {
         val testRegistry = SimpleMeterRegistry()