Add metrics to track count, size of deleted logfiles

logback-core/pom.xml

@@ -60,6 +60,11 @@
       <optional>true</optional>
     </dependency>
 
+    <dependency>
+      <groupId>com.yammer.metrics</groupId>
+      <artifactId>metrics-core</artifactId>
+      <version>1.0-hubspot-SNAPSHOT</version>
+    </dependency>
 
     <dependency>
       <groupId>org.mockito</groupId>

logback-core/src/main/java/ch/qos/logback/core/LogbackMetrics.java

@@ -0,0 +1,29 @@
+package ch.qos.logback.core;
+
+import ch.qos.logback.core.rolling.helper.ArchiveRemoverReason;
+import ch.qos.logback.core.rolling.helper.FileNamePattern;
+import com.google.common.collect.ImmutableMap;
+import com.yammer.metrics.Metrics;
+import com.yammer.metrics.core.Counter;
+import com.yammer.metrics.core.Histogram;
+import com.yammer.metrics.core.MetricName;
+
+public class LogbackMetrics {
+  public static Counter getDeletedLogFilesCounter(ArchiveRemoverReason reason, FileNamePattern fileNamePattern) {
+    return Metrics.newCounter(
+        new MetricName(
+            LogbackMetrics.class,
+            "log-files-deleted",
+            ImmutableMap.of("reason", reason.name(), "fileNamePattern", fileNamePattern.getPattern())
+        )
+    );
+  }
+  public static Histogram getDeletedLogFileSizeHistogram(ArchiveRemoverReason reason, FileNamePattern fileNamePattern) {
+    return Metrics.newHistogram(
+        new MetricName(
+            LogbackMetrics.class,
+            "deleted-log-file-size",
+            ImmutableMap.of("reason", reason.name(), "fileNamePattern", fileNamePattern.getPattern())
+        ));
+  }
+}

logback-core/src/main/java/ch/qos/logback/core/rolling/helper/ArchiveRemoverReason.java

@@ -0,0 +1,6 @@
+package ch.qos.logback.core.rolling.helper;
+
+public enum ArchiveRemoverReason {
+  MAX_HISTORY, // Exceeded max age for an archived file
+  TOTAL_SIZE_CAP, // Exceeded total size of all archived files
+}

logback-core/src/main/java/ch/qos/logback/core/rolling/helper/TimeBasedArchiveRemover.java

@@ -12,13 +12,16 @@
 package ch.qos.logback.core.rolling.helper;
 
 import static ch.qos.logback.core.CoreConstants.UNBOUNDED_TOTAL_SIZE_CAP;
+import static ch.qos.logback.core.rolling.helper.ArchiveRemoverReason.MAX_HISTORY;
+import static ch.qos.logback.core.rolling.helper.ArchiveRemoverReason.TOTAL_SIZE_CAP;
 
 import java.io.File;
 import java.time.Instant;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Future;
 
 import ch.qos.logback.core.CoreConstants;
+import ch.qos.logback.core.LogbackMetrics;
 import ch.qos.logback.core.pattern.Converter;
 import ch.qos.logback.core.pattern.LiteralConverter;
 import ch.qos.logback.core.spi.ContextAwareBase;
@@ -114,6 +117,9 @@ private boolean checkAndDeleteFile(File f) {
             addWarn("Cannot delete non existent file");
             return false;
         }
+
+        LogbackMetrics.getDeletedLogFilesCounter(MAX_HISTORY, fileNamePattern).inc();
+        LogbackMetrics.getDeletedLogFileSizeHistogram(MAX_HISTORY, fileNamePattern).update(f.length());
 
         boolean result = f.delete();
         if (!result) {
@@ -136,6 +142,11 @@ void capTotalSize(Instant now) {
                     // assume that deletion attempt will succeed.
                     totalRemoved += size;
 
+                    LogbackMetrics.getDeletedLogFilesCounter(TOTAL_SIZE_CAP,
+                        fileNamePattern).inc();
+                    LogbackMetrics.getDeletedLogFileSizeHistogram(TOTAL_SIZE_CAP,
+                        fileNamePattern).update(f.length());
+
                     checkAndDeleteFile(f);
                 }
                 totalSize += size;

logback-core/src/main/java/module-info.java

@@ -17,6 +17,8 @@
 
     // optionally require jansi
     requires static org.fusesource.jansi;
+    requires com.google.common;
+    requires metrics.core;
 
     exports ch.qos.logback.core;
     exports ch.qos.logback.core.boolex;