refactor(metrics): make Monitors self-contained; MetricsCollector becomes a registry wiring bean (#1059)

* refactor(metrics): Monitors owns its CompositeMeterRegistry; MetricsCollector wires registries in

Previously Monitors pulled its registry from MetricsCollector, creating an
awkward dependency from conductor-core → conductor-metrics. Now Monitors
owns the CompositeMeterRegistry directly and exposes addMeterRegistry() /
getRegistry(). MetricsCollector (contribs) becomes a thin Spring wiring
component that calls Monitors.addMeterRegistry() on startup.

- Removes conductor-core → conductor-metrics build dependency (cycle-free)
- Adds conductor-metrics → conductor-core build dependency
- Adds getGauge() / getDistributionSummary() aliases for callers using the
  'get' naming convention
- Deprecates MetricsCollector.getMeterRegistry() in favour of
  Monitors.getRegistry()

* Applied spotless

* test(metrics): add MonitorsTest covering registry ownership and meter APIs

Verifies addMeterRegistry(), getRegistry(), counter/timer/gauge identity
caching, getGauge/getDistributionSummary aliases, and tag isolation.

* test(metrics): add Spring integration test verifying MetricsCollector wires registries into Monitors

Boots a minimal Spring context with a SimpleMeterRegistry, confirms that
counters/timers/gauges recorded via Monitors are visible in the
Spring-wired registry after MetricsCollector initialises.

* Applied spotless

* refactor(metrics): retire conductor-metrics module, move classes to core/server

MetricsCollector moves to core alongside Monitors — they are companion classes
(Monitors owns the registry, MetricsCollector wires Spring-managed registries in).
Registry-specific configs (Logging, CloudWatch, AzureMonitor) move to server where
they belong as deployment-level concerns. No Java code imported from the old
contribs.metrics package, so this is a pure relocation with no call-site changes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* refactor(metrics): delete retired conductor-metrics module directory

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(metrics): add micrometer-registry-prometheus to server and server-lite

Without this dependency Spring Boot cannot create PrometheusMeterRegistry,
so /actuator/prometheus silently returns 404 even though
conductor.metrics-prometheus.enabled=true is set in all default configs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* chore: simplify metrics comment in server build files

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(build): remove stale :conductor-metrics dep from scheduler-core

The scheduler module (merged from main via #1064) still referenced
:conductor-metrics, which this branch retired. Monitors is already
provided by :conductor-core.

---------

core/build.gradle

@@ -14,7 +14,6 @@ apply plugin: 'groovy'
 
 dependencies {
     implementation project(':conductor-common')
-    implementation project(':conductor-metrics')
 
     compileOnly 'org.springframework.boot:spring-boot-starter'
     compileOnly 'org.springframework.boot:spring-boot-starter-validation'

core/src/main/java/com/netflix/conductor/metrics/MetricsCollector.java

@@ -10,38 +10,39 @@
  * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
  * specific language governing permissions and limitations under the License.
  */
-package com.netflix.conductor.contribs.metrics;
+package com.netflix.conductor.metrics;
 
 import org.springframework.stereotype.Component;
 
 import io.micrometer.core.instrument.MeterRegistry;
-import io.micrometer.core.instrument.composite.CompositeMeterRegistry;
-import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
 import lombok.extern.slf4j.Slf4j;
 
+/**
+ * Spring component that registers all available {@link MeterRegistry} instances with {@link
+ * Monitors} at startup. Monitors owns the composite registry; this class is purely a wiring point
+ * between Spring-managed registries and the static Monitors API.
+ */
 @Slf4j
 @Component
 public class MetricsCollector {
 
-    static final CompositeMeterRegistry compositeRegistry = new CompositeMeterRegistry();
-    private static final MeterRegistry simpleRegistry = new SimpleMeterRegistry();
-
     public MetricsCollector(MeterRegistry... registries) {
         log.info("=========");
         log.info("Conductor configured with {} metrics registries", registries.length);
         for (MeterRegistry registry : registries) {
             log.info("Metrics registry: {}", registry);
+            Monitors.addMeterRegistry(registry);
         }
         log.info(
                 "check https://docs.micrometer.io/micrometer/reference/ for configuration options");
         log.info("=========");
-        compositeRegistry.add(simpleRegistry);
-        for (MeterRegistry meterRegistry : registries) {
-            compositeRegistry.add(meterRegistry);
-        }
     }
 
+    /**
+     * @deprecated Use {@link Monitors#getRegistry()} directly.
+     */
+    @Deprecated
     public static MeterRegistry getMeterRegistry() {
-        return compositeRegistry;
+        return Monitors.getRegistry();
     }
 }

core/src/main/java/com/netflix/conductor/metrics/Monitors.java

@@ -21,7 +21,6 @@ import java.util.concurrent.TimeUnit;
 
 import org.apache.commons.lang3.StringUtils;
 
-import com.netflix.conductor.contribs.metrics.MetricsCollector;
 import com.netflix.conductor.model.TaskModel;
 import com.netflix.conductor.model.WorkflowModel;
 
@@ -33,13 +32,34 @@ import io.micrometer.core.instrument.ImmutableTag;
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.Tag;
 import io.micrometer.core.instrument.Timer;
+import io.micrometer.core.instrument.composite.CompositeMeterRegistry;
+import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
 import lombok.extern.slf4j.Slf4j;
 
 @Slf4j
 public class Monitors {
     public static final String NO_DOMAIN = "NO_DOMAIN";
 
-    private static final MeterRegistry registry = MetricsCollector.getMeterRegistry();
+    private static final CompositeMeterRegistry registry = new CompositeMeterRegistry();
+
+    static {
+        // Always include an in-process registry so meters are never dropped
+        // before a real registry is wired in by MetricsCollector.
+        registry.add(new SimpleMeterRegistry());
+    }
+
+    /**
+     * Returns the shared composite registry. Callers may add common tags via {@code
+     * getRegistry().config()}.
+     */
+    public static MeterRegistry getRegistry() {
+        return registry;
+    }
+
+    /** Register an additional {@link MeterRegistry}. Called by MetricsCollector on startup. */
+    public static void addMeterRegistry(MeterRegistry meterRegistry) {
+        registry.add(meterRegistry);
+    }
 
     private static final double[] percentiles = new double[] {0.5, 0.75, 0.90, 0.95, 0.99};
     private static final Map<String, AtomicDouble> gauges = new ConcurrentHashMap<>();
@@ -90,6 +110,19 @@ public class Monitors {
                 });
     }
 
+    /** Alias for {@link #gauge(String, String...)} — preferred name for new call sites. */
+    public static AtomicDouble getGauge(String name, String... tags) {
+        return gauge(name, tags);
+    }
+
+    /**
+     * Alias for {@link #distributionSummary(String, String...)} — preferred name for new call
+     * sites.
+     */
+    public static DistributionSummary getDistributionSummary(String name, String... tags) {
+        return distributionSummary(name, tags);
+    }
+
     private static Iterable<Tag> toTags(String... kv) {
         List<Tag> tags = new ArrayList<>();
         for (int i = 0; i < kv.length - 1; i += 2) {

core/src/test/java/com/netflix/conductor/metrics/MetricsCollectorTest.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2025 Conductor Authors.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package com.netflix.conductor.metrics;
+
+import org.junit.Test;
+
+import io.micrometer.core.instrument.Counter;
+import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
+
+import static org.junit.Assert.*;
+
+public class MetricsCollectorTest {
+
+    @Test
+    public void constructor_wiresRegistryIntoMonitors() {
+        SimpleMeterRegistry registry = new SimpleMeterRegistry();
+        new MetricsCollector(registry);
+
+        Monitors.getCounter("mc_test_counter", "source", "test").increment(7);
+
+        Counter counter = registry.find("mc_test_counter").counter();
+        assertNotNull("Counter should be visible in the wired registry", counter);
+        assertEquals(7.0, counter.count(), 0.001);
+    }
+
+    @Test
+    public void getMeterRegistry_delegatesToMonitors() {
+        assertSame(Monitors.getRegistry(), MetricsCollector.getMeterRegistry());
+    }
+}

core/src/test/java/com/netflix/conductor/metrics/MonitorsTest.java

@@ -0,0 +1,111 @@
+/*
+ * Copyright 2025 Conductor Authors.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package com.netflix.conductor.metrics;
+
+import java.util.concurrent.TimeUnit;
+
+import org.junit.Test;
+
+import io.micrometer.core.instrument.Counter;
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.Timer;
+import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
+
+import static org.junit.Assert.*;
+
+public class MonitorsTest {
+
+    @Test
+    public void getRegistry_returnsNonNull() {
+        assertNotNull(Monitors.getRegistry());
+    }
+
+    @Test
+    public void addMeterRegistry_metersAreVisibleInAddedRegistry() {
+        SimpleMeterRegistry extra = new SimpleMeterRegistry();
+        Monitors.addMeterRegistry(extra);
+
+        // Record something after adding the registry
+        Monitors.getCounter("test_add_registry_counter", "tag", "value").increment(3);
+
+        Counter counter = extra.find("test_add_registry_counter").counter();
+        assertNotNull("Counter should be visible in newly added registry", counter);
+        assertEquals(3.0, counter.count(), 0.001);
+    }
+
+    @Test
+    public void getCounter_sameKeyReturnsSameInstance() {
+        Counter c1 = Monitors.getCounter("test_counter_identity", "k", "v");
+        Counter c2 = Monitors.getCounter("test_counter_identity", "k", "v");
+        assertSame(c1, c2);
+    }
+
+    @Test
+    public void getTimer_sameKeyReturnsSameInstance() {
+        Timer t1 = Monitors.getTimer("test_timer_identity", "k", "v");
+        Timer t2 = Monitors.getTimer("test_timer_identity", "k", "v");
+        assertSame(t1, t2);
+    }
+
+    @Test
+    public void getGauge_aliasMatchesGauge() {
+        // getGauge and gauge should return the same AtomicDouble for the same key
+        assertSame(
+                Monitors.gauge("test_gauge_alias", "k", "v"),
+                Monitors.getGauge("test_gauge_alias", "k", "v"));
+    }
+
+    @Test
+    public void getDistributionSummary_aliasMatchesDistributionSummary() {
+        assertSame(
+                Monitors.distributionSummary("test_dist_alias", "k", "v"),
+                Monitors.getDistributionSummary("test_dist_alias", "k", "v"));
+    }
+
+    @Test
+    public void recordGauge_valueIsReflectedInRegistry() {
+        SimpleMeterRegistry probe = new SimpleMeterRegistry();
+        Monitors.addMeterRegistry(probe);
+
+        Monitors.recordGauge("test_gauge_value", 42L);
+
+        // gauge() in Monitors uses an AtomicDouble — the value set should be reflected
+        assertNotNull(probe.find("test_gauge_value").gauge());
+        assertEquals(42.0, probe.find("test_gauge_value").gauge().value(), 0.001);
+    }
+
+    @Test
+    public void timerRecordsTime() {
+        SimpleMeterRegistry probe = new SimpleMeterRegistry();
+        Monitors.addMeterRegistry(probe);
+
+        Monitors.getTimer("test_timer_record", "op", "read").record(100, TimeUnit.MILLISECONDS);
+
+        Timer timer = probe.find("test_timer_record").timer();
+        assertNotNull(timer);
+        assertEquals(1, timer.count());
+    }
+
+    @Test
+    public void metersWithDifferentTagsAreDistinct() {
+        MeterRegistry registry = Monitors.getRegistry();
+
+        Monitors.getCounter("test_tag_distinct", "env", "prod").increment(1);
+        Monitors.getCounter("test_tag_distinct", "env", "staging").increment(2);
+
+        // Two separate meters, not the same object
+        assertNotSame(
+                Monitors.getCounter("test_tag_distinct", "env", "prod"),
+                Monitors.getCounter("test_tag_distinct", "env", "staging"));
+    }
+}

metrics/README.md

@@ -1,31 +0,0 @@
-# Metrics
-Conductor publishes detailed metrics for the server. 
-For the list of metrics published by server, see:
-
-https://netflix.github.io/conductor/metrics/server/
-
-Conductor supports plugging in metrics collectors, the following are currently supported by this module:
-1. Datadog
-2. Prometheus
-3. Logging (dumps all the metrics to Slf4J logger)
-
-## Published Artifacts
-
-Group: `com.netflix.conductor`
-
-| Published Artifact | Description |
-| ----------- | ----------- | 
-| conductor-metrics | Metrics configuration  |
-
-**Note**: If you are using `condutor-contribs` as a dependency, the metrics module is already included, you do not need to include it separately.
-
-#### Configuration
-* Logging Metrics
-
-    `conductor.metrics-logger.enabled=true`
-* Prometheus
-
-    `conductor.metrics-prometheus.enabled=true`
-* Datadog
-
-    `conductor.metrics-datadog.enabled=true`

metrics/build.gradle

@@ -1,37 +0,0 @@
-dependencies {
-
-    implementation project(':conductor-common')
-
-    compileOnly 'org.springframework.boot:spring-boot-starter'
-    compileOnly 'org.springframework.boot:spring-boot-starter-web'
-
-    implementation "org.apache.commons:commons-lang3:"
-
-    implementation "com.google.guava:guava:${revGuava}"
-
-    implementation "javax.ws.rs:jsr311-api:${revJsr311Api}"
-
-    implementation "io.reactivex:rxjava:${revRxJava}"
-
-    // Metrics
-    implementation "io.micrometer:micrometer-core:${revMicrometer}"
-    implementation "io.micrometer:micrometer-registry-atlas:${revMicrometer}"
-    implementation "io.micrometer:micrometer-registry-prometheus:${revMicrometer}"
-    implementation "io.micrometer:micrometer-registry-datadog:${revMicrometer}"
-    implementation "io.micrometer:micrometer-registry-jmx:${revMicrometer}"
-    implementation "io.micrometer:micrometer-registry-otlp:${revMicrometer}"
-    implementation "io.micrometer:micrometer-registry-dynatrace:${revMicrometer}"
-    implementation "io.micrometer:micrometer-registry-elastic:${revMicrometer}"
-    implementation "io.micrometer:micrometer-registry-new-relic:${revMicrometer}"
-    implementation "io.micrometer:micrometer-registry-stackdriver:${revMicrometer}"
-    implementation "io.micrometer:micrometer-registry-statsd:${revMicrometer}"
-    implementation "io.micrometer:micrometer-registry-cloudwatch2:${revMicrometer}"
-    implementation "io.micrometer:micrometer-registry-azure-monitor:${revMicrometer}"
-    implementation "io.micrometer:micrometer-registry-influx:${revMicrometer}"
-
-    testImplementation 'org.springframework.boot:spring-boot-starter-web'
-    testImplementation "org.testcontainers:mockserver:${revTestContainer}"
-    testImplementation "org.mock-server:mockserver-client-java:${revMockServerClient}"
-
-
-}

redis-configuration/build.gradle

@@ -1,6 +1,5 @@
 dependencies {
     implementation project(':conductor-core')
-    implementation project(':conductor-metrics')
 
     implementation 'org.springframework.boot:spring-boot-starter'
     implementation 'org.springframework.boot:spring-boot-autoconfigure'

scheduler/core/build.gradle

@@ -5,7 +5,6 @@ plugins {
 
 dependencies {
     implementation project(':conductor-common')
-    implementation project(':conductor-metrics')
     implementation project(':conductor-core')
 
     implementation 'org.springframework.retry:spring-retry'

server-lite/build.gradle

@@ -46,7 +46,9 @@ dependencies {
     implementation project(':conductor-kafka')
 
     //Metrics
-    implementation project(':conductor-metrics')
+    implementation "io.micrometer:micrometer-registry-cloudwatch2:${revMicrometer}"
+    implementation "io.micrometer:micrometer-registry-azure-monitor:${revMicrometer}"
+    implementation "io.micrometer:micrometer-registry-prometheus:${revMicrometer}"
 
     //Event Listener
     implementation project(':conductor-workflow-event-listener')

server/build.gradle

@@ -76,7 +76,9 @@ dependencies {
     implementation project(':conductor-scheduler-sqlite-persistence')
 
     //Metrics
-    implementation project(':conductor-metrics')
+    implementation "io.micrometer:micrometer-registry-cloudwatch2:${revMicrometer}"
+    implementation "io.micrometer:micrometer-registry-azure-monitor:${revMicrometer}"
+    implementation "io.micrometer:micrometer-registry-prometheus:${revMicrometer}"
 
     //Event Listener
     implementation project(':conductor-workflow-event-listener')

server/src/main/java/com/netflix/conductor/server/config/AzureMonitorMetricsConfiguration.java

@@ -10,7 +10,7 @@
  * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
  * specific language governing permissions and limitations under the License.
  */
-package com.netflix.conductor.contribs.metrics;
+package com.netflix.conductor.server.config;
 
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
@@ -34,7 +34,7 @@ public class AzureMonitorMetricsConfiguration {
     public MeterRegistry getAzureMonitorMeterRegistry(
             @Value("${management.azuremonitor.metrics.export.instrumentationKey:null}")
                     String instrumentationKey) {
-        AzureMonitorConfig cloudWatchConfig =
+        AzureMonitorConfig azureMonitorConfig =
                 new AzureMonitorConfig() {
                     @Override
                     public String instrumentationKey() {
@@ -46,6 +46,6 @@ public class AzureMonitorMetricsConfiguration {
                         return null;
                     }
                 };
-        return new AzureMonitorMeterRegistry(cloudWatchConfig, Clock.SYSTEM);
+        return new AzureMonitorMeterRegistry(azureMonitorConfig, Clock.SYSTEM);
     }
 }

server/src/main/java/com/netflix/conductor/server/config/CloudWatchMetricsConfiguration.java

@@ -10,7 +10,7 @@
  * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
  * specific language governing permissions and limitations under the License.
  */
-package com.netflix.conductor.contribs.metrics;
+package com.netflix.conductor.server.config;
 
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;

server/src/main/java/com/netflix/conductor/server/config/LoggingMetricsConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023 Conductor Authors.
+ * Copyright 2022 Conductor Authors.
  * <p>
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
  * the License. You may obtain a copy of the License at
@@ -10,7 +10,7 @@
  * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
  * specific language governing permissions and limitations under the License.
  */
-package com.netflix.conductor.contribs.metrics;
+package com.netflix.conductor.server.config;
 
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.context.annotation.Bean;

settings.gradle

@@ -53,7 +53,6 @@ include 'common-persistence'
 include 'mysql-persistence'
 include 'postgres-persistence'
 include 'sqlite-persistence'
-include 'metrics'
 include 'es7-persistence'
 include 'es8-persistence'
 include 'os-persistence'

test-util/build.gradle

@@ -11,7 +11,6 @@ dependencies {
     implementation project(':conductor-grpc-server')
     implementation project(':conductor-grpc-client')
     implementation project(':conductor-redis-persistence')
-    implementation project(':conductor-metrics')
 
 
     implementation "com.fasterxml.jackson.core:jackson-databind"