Expose remaining auto resizes free metric Expose the number of times the cache can automatically expand its capacity. Feature: Issue 13940 Change-Id: Id0ca170b1c3e80fbf875fd6d1b8fb76974a72c88

diff --git a/metrics.md b/metrics.md
index aeb6679..85e2745 100644
--- a/metrics.md
+++ b/metrics.md

@@ -9,4 +9,10 @@
   : the amount of free space left in the cache as a percentage.
 
   See the [official documentation](https://javadoc.io/static/net.openhft/chronicle-map/3.20.83/net/openhft/chronicle/map/ChronicleMap.html#percentageFreeSpace--)
+  for more information.
+
+* cache/chroniclemap/remaining_autoresizes_<cache-name>
+  : the number of times the cache can automatically expand its capacity.
+
+  See the [official documentation](https://javadoc.io/static/net.openhft/chronicle-map/3.20.83/net/openhft/chronicle/map/ChronicleMap.html#remainingAutoResizes--)
   for more information.
\ No newline at end of file

diff --git a/src/main/java/com/googlesource/gerrit/modules/cache/chroniclemap/ChronicleMapCacheImpl.java b/src/main/java/com/googlesource/gerrit/modules/cache/chroniclemap/ChronicleMapCacheImpl.java
index a7a5589..6b95702 100644
--- a/src/main/java/com/googlesource/gerrit/modules/cache/chroniclemap/ChronicleMapCacheImpl.java
+++ b/src/main/java/com/googlesource/gerrit/modules/cache/chroniclemap/ChronicleMapCacheImpl.java

@@ -122,6 +122,7 @@
 
     <K, V> void registerCallBackMetrics(String name, ChronicleMap<K, TimedValue<V>> store) {
       String PERCENTAGE_FREE_SPACE_METRIC = "cache/chroniclemap/percentage_free_space_" + name;
+      String REMAINING_AUTORESIZES_METRIC = "cache/chroniclemap/remaining_autoresizes_" + name;
 
       metricMaker.newCallbackMetric(
           PERCENTAGE_FREE_SPACE_METRIC,
@@ -129,6 +130,14 @@
           new Description(
               String.format("The amount of free space in the %s cache as a percentage", name)),
           () -> (long) store.percentageFreeSpace());
+
+      metricMaker.newCallbackMetric(
+          REMAINING_AUTORESIZES_METRIC,
+          Integer.class,
+          new Description(
+              String.format(
+                  "The number of times the %s cache can automatically expand its capacity", name)),
+          store::remainingAutoResizes);
     }
   }
 

diff --git a/src/test/java/com/googlesource/gerrit/modules/cache/chroniclemap/ChronicleMapCacheTest.java b/src/test/java/com/googlesource/gerrit/modules/cache/chroniclemap/ChronicleMapCacheTest.java
index e8f8e7d..459e2f2 100644
--- a/src/test/java/com/googlesource/gerrit/modules/cache/chroniclemap/ChronicleMapCacheTest.java
+++ b/src/test/java/com/googlesource/gerrit/modules/cache/chroniclemap/ChronicleMapCacheTest.java

@@ -370,6 +370,27 @@
         () -> (long) getMetric(freeSpaceMetricName).getValue() < 100, Duration.ofSeconds(2));
   }
 
+  @Test
+  public void shouldTriggerRemainingAutoResizeMetric() throws Exception {
+    String cachedValue = UUID.randomUUID().toString();
+    String autoResizeMetricName = "cache/chroniclemap/remaining_autoresizes_" + cachedValue;
+    gerritConfig.setInt("cache", cachedValue, "maxEntries", 2);
+    gerritConfig.setInt("cache", cachedValue, "avgKeySize", cachedValue.getBytes().length);
+    gerritConfig.setInt("cache", cachedValue, "avgValueSize", valueSize(cachedValue));
+    gerritConfig.save();
+
+    ChronicleMapCacheImpl<String, String> cache = newCacheWithMetrics(cachedValue);
+
+    assertThat(getMetric(autoResizeMetricName).getValue()).isEqualTo(1);
+
+    cache.put(cachedValue + "1", cachedValue);
+    cache.put(cachedValue + "2", cachedValue);
+    cache.put(cachedValue + "3", cachedValue);
+
+    WaitUtil.waitUntil(
+        () -> (int) getMetric(autoResizeMetricName).getValue() == 0, Duration.ofSeconds(2));
+  }
+
   private int valueSize(String value) {
     final TimedValueMarshaller<String> marshaller =
         new TimedValueMarshaller<>(StringCacheSerializer.INSTANCE);