Log warning if ServoMonitorCache size exceeds threshold.

Fixes gh-947

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/metrics/servo/ServoMetricsAutoConfiguration.java

@@ -71,8 +71,8 @@ public class ServoMetricsAutoConfiguration {
 	}
 
 	@Bean
-	public ServoMonitorCache monitorCache(MonitorRegistry monitorRegistry) {
-		return new ServoMonitorCache(monitorRegistry);
+	public ServoMonitorCache monitorCache(MonitorRegistry monitorRegistry, ServoMetricsConfigBean servoMetricsConfig) {
+		return new ServoMonitorCache(monitorRegistry, servoMetricsConfig);
 	}
 
 	@Bean

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/metrics/servo/ServoMetricsConfigBean.java

@@ -34,19 +34,33 @@ public class ServoMetricsConfigBean {
 	 */
 	String registryClass = "com.netflix.servo.BasicMonitorRegistry";
 
-	public String getRegistryClass() {
-		return this.registryClass;
-	}
+	/**
+	 * When the `ServoMonitorCache` reaches this size, a warning is logged.
+	 * This will be useful if you are using string concatenation in RestTemplate urls.
+	 */
+	int cacheWarningThreshold = 1000;
 
 	public boolean getEnabled() {
 		return this.enabled;
 	}
 
-	public void setEnabled(boolean enabled) {
+	public void isEnabled(boolean enabled) {
 		this.enabled = enabled;
 	}
 
+	public String getRegistryClass() {
+		return this.registryClass;
+	}
+
 	public void setRegistryClass(String registryClass) {
 		this.registryClass = registryClass;
 	}
+
+	public int getCacheWarningThreshold() {
+		return cacheWarningThreshold;
+	}
+
+	public void setCacheWarningThreshold(int cacheWarningThreshold) {
+		this.cacheWarningThreshold = cacheWarningThreshold;
+	}
 }

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/metrics/servo/ServoMonitorCache.java

@@ -20,17 +20,22 @@ import com.netflix.servo.MonitorRegistry;
 import com.netflix.servo.monitor.BasicTimer;
 import com.netflix.servo.monitor.MonitorConfig;
 
+import lombok.extern.apachecommons.CommonsLog;
+
 /**
  * Servo does not provide a mechanism to retrieve an existing monitor by name + tags.
  *
  * @author Jon Schneider
  */
+@CommonsLog
 public class ServoMonitorCache {
 	private final Map<MonitorConfig, BasicTimer> timerCache = new HashMap<>();
 	private final MonitorRegistry monitorRegistry;
+	private final ServoMetricsConfigBean config;
 
-	public ServoMonitorCache(MonitorRegistry monitorRegistry) {
+	public ServoMonitorCache(MonitorRegistry monitorRegistry, ServoMetricsConfigBean config) {
 		this.monitorRegistry = monitorRegistry;
+		this.config = config;
 	}
 
 	/**
@@ -39,13 +44,18 @@ public class ServoMonitorCache {
 	 * return it.
 	 */
 	public synchronized BasicTimer getTimer(MonitorConfig config) {
-		BasicTimer t = timerCache.get(config);
+		BasicTimer t = this.timerCache.get(config);
 		if (t != null)
 			return t;
 
 		t = new BasicTimer(config);
-		timerCache.put(config, t);
-		monitorRegistry.register(t);
+		this.timerCache.put(config, t);
+
+		if (this.timerCache.size() > this.config.getCacheWarningThreshold()) {
+			log.warn("timerCache is above the warning threshold of " + this.config.getCacheWarningThreshold() + " with size " + this.timerCache.size() + ".");
+		}
+
+		this.monitorRegistry.register(t);
 		return t;
 	}
 }

spring-cloud-netflix-core/src/test/java/org/springframework/cloud/netflix/metrics/servo/ServoMetricReaderTests.java

@@ -21,7 +21,7 @@ public class ServoMetricReaderTests {
 				new DimensionalServoMetricNaming());
 
 		MonitorConfig.Builder builder = new MonitorConfig.Builder("metricName");
-		ServoMonitorCache servoMonitorCache = new ServoMonitorCache(registry);
+		ServoMonitorCache servoMonitorCache = new ServoMonitorCache(registry, new ServoMetricsConfigBean());
 		servoMonitorCache.getTimer(builder.build());
 
 		List<Metric<?>> metrics = Lists.newArrayList(reader.findAll());

spring-cloud-netflix-core/src/test/java/org/springframework/cloud/netflix/metrics/servo/ServoMonitorCacheTests.java

@@ -0,0 +1,46 @@
+package org.springframework.cloud.netflix.metrics.servo;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.springframework.boot.test.OutputCapture;
+
+import com.netflix.servo.MonitorRegistry;
+import com.netflix.servo.monitor.MonitorConfig;
+
+import static org.hamcrest.Matchers.*;
+import static org.junit.Assert.*;
+
+/**
+ * @author Spencer Gibb
+ */
+public class ServoMonitorCacheTests {
+
+	@Rule
+	public OutputCapture capture = new OutputCapture();
+
+	@Mock
+	MonitorRegistry monitorRegistry;
+
+	@Before
+	public void before() {
+		MockitoAnnotations.initMocks(this);
+	}
+
+	@Test
+	public void testCacheWarningLog() {
+		ServoMetricsConfigBean config = new ServoMetricsConfigBean();
+		config.setCacheWarningThreshold(1);
+		ServoMonitorCache cache = new ServoMonitorCache(monitorRegistry, config);
+
+		cache.getTimer(MonitorConfig.builder("monitorA").build());
+
+		assertThat(this.capture.toString(), not(containsString("timerCache is above the warning threshold")));
+
+		cache.getTimer(MonitorConfig.builder("monitorB").build());
+
+		assertThat(this.capture.toString(), containsString("timerCache is above the warning threshold"));
+	}
+}

spring-cloud-netflix-spectator/src/main/java/org/springframework/cloud/netflix/metrics/spectator/SpectatorMetricsAutoConfiguration.java

@@ -13,7 +13,6 @@
 
 package org.springframework.cloud.netflix.metrics.spectator;
 
-import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.actuate.autoconfigure.MetricRepositoryAutoConfiguration;
 import org.springframework.boot.actuate.endpoint.MetricReaderPublicMetrics;
 import org.springframework.boot.actuate.metrics.CounterService;
@@ -25,6 +24,7 @@ import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean
 import org.springframework.cloud.netflix.metrics.DefaultMetricsTagProvider;
 import org.springframework.cloud.netflix.metrics.MetricsInterceptorConfiguration;
 import org.springframework.cloud.netflix.metrics.MetricsTagProvider;
+import org.springframework.cloud.netflix.metrics.servo.ServoMetricsConfigBean;
 import org.springframework.cloud.netflix.metrics.servo.ServoMonitorCache;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -50,14 +50,18 @@ import com.netflix.spectator.servo.ServoRegistry;
 @ConditionalOnClass({ Registry.class, MetricReader.class })
 @Import(MetricsInterceptorConfiguration.class)
 public class SpectatorMetricsAutoConfiguration {
-	@Value("${netflix.metrics.servo.registryClass:com.netflix.servo.BasicMonitorRegistry}")
-	String servoRegistryClass;
 
 	@Bean
 	@ConditionalOnMissingBean
-	public MonitorRegistry monitorRegistry() {
+	public ServoMetricsConfigBean servoMetricsConfig() {
+		return new ServoMetricsConfigBean();
+	}
+
+	@Bean
+	@ConditionalOnMissingBean
+	public MonitorRegistry monitorRegistry(ServoMetricsConfigBean configBean) {
 		System.setProperty(DefaultMonitorRegistry.class.getCanonicalName()
-				+ ".registryClass", servoRegistryClass);
+				+ ".registryClass", configBean.getRegistryClass());
 		return DefaultMonitorRegistry.getInstance();
 	}
 
@@ -68,8 +72,8 @@ public class SpectatorMetricsAutoConfiguration {
 	}
 
 	@Bean
-	public ServoMonitorCache monitorCache() {
-		return new ServoMonitorCache(monitorRegistry());
+	public ServoMonitorCache monitorCache(MonitorRegistry monitorRegistry, ServoMetricsConfigBean configBean) {
+		return new ServoMonitorCache(monitorRegistry, configBean);
 	}
 
 	@Bean