Add an InstrumentedAppender constructor that allows passing a CollectorRegistry

simpleclient_logback/src/main/java/io/prometheus/client/logback/InstrumentedAppender.java

@@ -3,38 +3,46 @@
 import ch.qos.logback.classic.Level;
 import ch.qos.logback.classic.spi.ILoggingEvent;
 import ch.qos.logback.core.UnsynchronizedAppenderBase;
+import io.prometheus.client.CollectorRegistry;
 import io.prometheus.client.Counter;
 
 public class InstrumentedAppender extends UnsynchronizedAppenderBase<ILoggingEvent> {
-
   public static final String COUNTER_NAME = "logback_appender_total";
 
-  private static final Counter COUNTER;
-  private static final Counter.Child TRACE_LABEL;
-  private static final Counter.Child DEBUG_LABEL;
-  private static final Counter.Child INFO_LABEL;
-  private static final Counter.Child WARN_LABEL;
-  private static final Counter.Child ERROR_LABEL;
-
-  static {
-    COUNTER = Counter.build().name(COUNTER_NAME)
-            .help("Logback log statements at various log levels")
-            .labelNames("level")
-            .register();
-
-    TRACE_LABEL = COUNTER.labels("trace");
-    DEBUG_LABEL = COUNTER.labels("debug");
-    INFO_LABEL = COUNTER.labels("info");
-    WARN_LABEL = COUNTER.labels("warn");
-    ERROR_LABEL = COUNTER.labels("error");
-  }
+  private static final Counter defaultCounter = Counter.build().name(COUNTER_NAME)
+          .help("Logback log statements at various log levels")
+          .labelNames("level")
+          .register();
+  private final Counter.Child traceCounter;
+  private final Counter.Child debugCounter;
+  private final Counter.Child infoCounter;
+  private final Counter.Child warnCounter;
+  private final Counter.Child errorCounter;
 
   /**
    * Create a new instrumented appender using the default registry.
    */
   public InstrumentedAppender() {
+    this(defaultCounter);
   }
 
+  /**
+   * Create a new instrumented appender using the supplied registry.
+   */
+  public InstrumentedAppender(CollectorRegistry registry) {
+    this(Counter.build().name(COUNTER_NAME)
+            .help("Logback log statements at various log levels")
+            .labelNames("level")
+            .register(registry));
+  }
+
+  private InstrumentedAppender(Counter counter) {
+    this.traceCounter = counter.labels("trace");
+    this.debugCounter = counter.labels("debug");
+    this.infoCounter = counter.labels("info");
+    this.warnCounter = counter.labels("warn");
+    this.errorCounter = counter.labels("error");
+  }
 
   @Override
   public void start() {
@@ -45,19 +53,19 @@ public void start() {
   protected void append(ILoggingEvent event) {
     switch (event.getLevel().toInt()) {
       case Level.TRACE_INT:
-        TRACE_LABEL.inc();
+        this.traceCounter.inc();
         break;
       case Level.DEBUG_INT:
-        DEBUG_LABEL.inc();
+        this.debugCounter.inc();
         break;
       case Level.INFO_INT:
-        INFO_LABEL.inc();
+        this.infoCounter.inc();
         break;
       case Level.WARN_INT:
-        WARN_LABEL.inc();
+        this.warnCounter.inc();
         break;
       case Level.ERROR_INT:
-        ERROR_LABEL.inc();
+        this.errorCounter.inc();
         break;
       default:
         break;

simpleclient_logback/src/test/java/io/prometheus/client/logback/InstrumentedAppenderTest.java

@@ -12,15 +12,21 @@
 import org.junit.Test;
 
 public class InstrumentedAppenderTest {
-
+  private CollectorRegistry registry;
   private InstrumentedAppender appender;
+  private InstrumentedAppender defaultAppender;
   private ILoggingEvent event;
 
   @Before
   public void setUp() throws Exception {
-    appender = new InstrumentedAppender();
+    registry = new CollectorRegistry();
+
+    appender = new InstrumentedAppender(registry);
     appender.start();
-
+
+    defaultAppender = new InstrumentedAppender();
+    defaultAppender.start();
+
     event = mock(ILoggingEvent.class);
   }
 
@@ -29,48 +35,63 @@ public void metersTraceEvents() throws Exception {
     when(event.getLevel()).thenReturn(Level.TRACE);
 
     appender.doAppend(event);
-
     assertEquals(1, getLogLevelCount("trace"));
+
+    defaultAppender.doAppend(event);
+    assertEquals(1, getDefaultLogLevelCount("trace"));
   }
 
   @Test
   public void metersDebugEvents() throws Exception {
     when(event.getLevel()).thenReturn(Level.DEBUG);
 
     appender.doAppend(event);
-
     assertEquals(1, getLogLevelCount("debug"));
+
+    defaultAppender.doAppend(event);
+    assertEquals(1, getDefaultLogLevelCount("debug"));
   }
 
   @Test
   public void metersInfoEvents() throws Exception {
     when(event.getLevel()).thenReturn(Level.INFO);
 
     appender.doAppend(event);
-
     assertEquals(1, getLogLevelCount("info"));
+
+    defaultAppender.doAppend(event);
+    assertEquals(1, getDefaultLogLevelCount("info"));
   }
 
   @Test
   public void metersWarnEvents() throws Exception {
     when(event.getLevel()).thenReturn(Level.WARN);
 
     appender.doAppend(event);
-
     assertEquals(1, getLogLevelCount("warn"));
+
+    defaultAppender.doAppend(event);
+    assertEquals(1, getDefaultLogLevelCount("warn"));
   }
 
   @Test
   public void metersErrorEvents() throws Exception {
     when(event.getLevel()).thenReturn(Level.ERROR);
 
     appender.doAppend(event);
-
     assertEquals(1, getLogLevelCount("error"));
+
+    defaultAppender.doAppend(event);
+    assertEquals(1, getDefaultLogLevelCount("error"));
   }
 
   private int getLogLevelCount(String level) {
-    return CollectorRegistry.defaultRegistry.getSampleValue(COUNTER_NAME, 
-            new String[]{"level"}, new String[]{level}).intValue();
+    return registry.getSampleValue(COUNTER_NAME, new String[]{"level"}, new String[]{level}).intValue();
+  }
+
+  private int getDefaultLogLevelCount(String level) {
+    return CollectorRegistry.defaultRegistry
+            .getSampleValue(COUNTER_NAME, new String[]{"level"}, new String[]{level})
+            .intValue();
   }
 }