rename evictImmediatelyOnHoldRelease to areWeakEntriesEphemeral (#18900)

Author: clintropolis

indexing-service/src/test/java/org/apache/druid/indexing/common/task/CompactionTaskRunTest.java

@@ -2073,7 +2073,7 @@ public boolean isVirtualStorage()
       }
 
       @Override
-      public boolean isVirtualStorageFabricEvictImmediatelyOnHoldRelease()
+      public boolean isVirtualStorageEphemeral()
       {
         return true;
       }

server/src/main/java/org/apache/druid/segment/loading/SegmentLoaderConfig.java

@@ -82,8 +82,8 @@ public class SegmentLoaderConfig
    * waiting for space pressure to trigger eviction. This setting is not intended to be configured directly by
    * administrators. Instead, it is expected to be set when appropriate via {@link #setVirtualStorage}.
    */
-  @JsonProperty("virtualStorageFabricEvictImmediatelyOnHoldRelease")
-  private boolean virtualStorageFabricEvictImmediatelyOnHoldRelease = false;
+  @JsonProperty("virtualStorageIsEphemeral")
+  private boolean virtualStorageIsEphemeral = false;
 
   private long combinedMaxSize = 0;
 
@@ -162,9 +162,9 @@ public int getVirtualStorageLoadThreads()
     return virtualStorageLoadThreads;
   }
 
-  public boolean isVirtualStorageFabricEvictImmediatelyOnHoldRelease()
+  public boolean isVirtualStorageEphemeral()
   {
-    return virtualStorageFabricEvictImmediatelyOnHoldRelease;
+    return virtualStorageIsEphemeral;
   }
 
   public SegmentLoaderConfig setLocations(List<StorageLocationConfig> locations)
@@ -174,15 +174,15 @@ public SegmentLoaderConfig setLocations(List<StorageLocationConfig> locations)
   }
 
   /**
-   * Sets {@link #virtualStorage} and {@link #virtualStorageFabricEvictImmediatelyOnHoldRelease}.
+   * Sets {@link #virtualStorage} and {@link #virtualStorageIsEphemeral}.
    */
   public SegmentLoaderConfig setVirtualStorage(
       boolean virtualStorage,
-      boolean virtualStorageFabricEvictImmediatelyOnHoldRelease
+      boolean virtualStorageFabricEphemeral
   )
   {
     this.virtualStorage = virtualStorage;
-    this.virtualStorageFabricEvictImmediatelyOnHoldRelease = virtualStorageFabricEvictImmediatelyOnHoldRelease;
+    this.virtualStorageIsEphemeral = virtualStorageFabricEphemeral;
     return this;
   }
 
@@ -216,9 +216,9 @@ public String toString()
            ", numThreadsToLoadSegmentsIntoPageCacheOnBootstrap=" + numThreadsToLoadSegmentsIntoPageCacheOnBootstrap +
            ", infoDir=" + infoDir +
            ", statusQueueMaxSize=" + statusQueueMaxSize +
-           ", useVirtualStorageFabric=" + virtualStorage +
-           ", virtualStorageFabricLoadThreads=" + virtualStorageLoadThreads +
-           ", virtualStorageFabricEvictImmediatelyOnHoldRelease=" + virtualStorageFabricEvictImmediatelyOnHoldRelease +
+           ", virtualStorage=" + virtualStorage +
+           ", virtualStorageLoadThreads=" + virtualStorageLoadThreads +
+           ", virtualStorageIsEphemeral=" + virtualStorageIsEphemeral +
            ", combinedMaxSize=" + combinedMaxSize +
            '}';
   }

server/src/main/java/org/apache/druid/segment/loading/SegmentLocalCacheManager.java

@@ -147,9 +147,9 @@ public SegmentLocalCacheManager(
       if (config.getNumThreadsToLoadSegmentsIntoPageCacheOnBootstrap() > 0) {
         throw DruidException.defensive("Invalid configuration: virtualStorage is incompatible with numThreadsToLoadSegmentsIntoPageCacheOnBootstrap");
       }
-      if (config.isVirtualStorageFabricEvictImmediatelyOnHoldRelease()) {
+      if (config.isVirtualStorageEphemeral()) {
         for (StorageLocation location : locations) {
-          location.setEvictImmediatelyOnHoldRelease(true);
+          location.setAreWeakEntriesEphemeral(true);
         }
       }
       virtualStorageLoadOnDemandExec =
@@ -533,9 +533,9 @@ private AcquireSegmentAction acquireExistingSegment(SegmentCacheEntryIdentifier
   public void load(final DataSegment dataSegment) throws SegmentLoadingException
   {
     if (config.isVirtualStorage()) {
-      if (config.isVirtualStorageFabricEvictImmediatelyOnHoldRelease()) {
+      if (config.isVirtualStorageEphemeral()) {
         throw DruidException.defensive(
-            "load() should not be called when virtualStorageFabricEvictImmediatelyOnHoldRelease is enabled"
+            "load() should not be called when virtualStorageIsEphemeral is true"
         );
       }
       // virtual storage doesn't do anything with loading immediately, but check to see if the segment is already cached
@@ -579,9 +579,9 @@ public void bootstrap(
   ) throws SegmentLoadingException
   {
     if (config.isVirtualStorage()) {
-      if (config.isVirtualStorageFabricEvictImmediatelyOnHoldRelease()) {
+      if (config.isVirtualStorageEphemeral()) {
         throw DruidException.defensive(
-            "bootstrap() should not be called when virtualStorageFabricEvictImmediatelyOnHoldRelease is enabled"
+            "bootstrap() should not be called when virtualStorageIsEphemeral is true"
         );
       }
       // during bootstrap, check if the segment exists in a location and mount it, getCachedSegments already
@@ -1083,7 +1083,7 @@ public void mount(StorageLocation mountLocation) throws SegmentLoadingException
           unmount();
         }
 
-        if (config.isVirtualStorageFabricEvictImmediatelyOnHoldRelease()) {
+        if (config.isVirtualStorageEphemeral()) {
           setDeleteInfoFileOnUnmount();
         }
       }

server/src/main/java/org/apache/druid/segment/loading/StorageLocation.java

@@ -80,6 +80,11 @@
  * is repeated until either a sufficient amount of space has been reclaimed, or no additional space is able to be
  * reclaimed, in which case the new reservation fails.
  * <p>
+ * There is an auxilary mode for weak references when {@link #areWeakEntriesEphemeral} is set to true. In this mode, weak
+ * entries are short-lived entries that only exist while one or more reservation hold are active, and are unmounted when
+ * the holds are released. This is useful in cases where entries are unlikely to be re-used such as in asynchronous
+ * tasks.
+ * <p>
  * This class is thread-safe, so that multiple threads can update its state at the same time.
  * One example usage is that a historical server can use multiple threads to load different segments in parallel
  * from deep storage.
@@ -106,7 +111,7 @@ public class StorageLocation
   @GuardedBy("lock")
   private WeakCacheEntry hand;
 
-  private volatile boolean evictImmediatelyOnHoldRelease = false;
+  private volatile boolean areWeakEntriesEphemeral = false;
 
   /**
    * Current total size of files in bytes, including weak entries.
@@ -170,11 +175,12 @@ public File getPath()
   }
 
   /**
-   * Sets whether weak cache entries should be immediately evicted once all holds are released.
+   * Sets whether weak cache entries should be retained after all holds are released. If true, weak references are
+   * removed and unmounted immediately after all holds are released
    */
-  public void setEvictImmediatelyOnHoldRelease(final boolean evictImmediatelyOnHoldRelease)
+  public void setAreWeakEntriesEphemeral(final boolean areWeakEntriesEphemeral)
   {
-    this.evictImmediatelyOnHoldRelease = evictImmediatelyOnHoldRelease;
+    this.areWeakEntriesEphemeral = areWeakEntriesEphemeral;
   }
 
   public <T extends CacheEntry> T getStaticCacheEntry(CacheEntryIdentifier entryId)
@@ -448,7 +454,7 @@ private Runnable createWeakEntryReleaseRunnable(
     return () -> {
       weakEntry.release();
 
-      if (!isNewEntry && !evictImmediatelyOnHoldRelease) {
+      if (!isNewEntry && !areWeakEntriesEphemeral) {
         // No need to consider removal from weakCacheEntries on hold release.
         return;
       }
@@ -462,7 +468,7 @@ private Runnable createWeakEntryReleaseRunnable(
               // Furthermore, if evictImmediatelyOnHoldRelease is set, evict on release if all holds are gone.
               final boolean isMounted = weakCacheEntry.cacheEntry.isMounted();
               if ((isNewEntry && !isMounted)
-                  || (evictImmediatelyOnHoldRelease && !weakCacheEntry.isHeld())) {
+                  || (areWeakEntriesEphemeral && !weakCacheEntry.isHeld())) {
                 unlinkWeakEntry(weakCacheEntry);
                 weakCacheEntry.unmount(); // call even if never mounted, to terminate the phaser
                 if (isMounted) {

server/src/test/java/org/apache/druid/segment/loading/SegmentLoaderConfigTest.java

@@ -31,13 +31,13 @@ public void testSetVirtualStorage()
 
     // Verify default values
     Assert.assertFalse(config.isVirtualStorage());
-    Assert.assertFalse(config.isVirtualStorageFabricEvictImmediatelyOnHoldRelease());
+    Assert.assertFalse(config.isVirtualStorageEphemeral());
 
     // Set both to true
     config.setVirtualStorage(true, true);
 
     // Verify both fields are set
     Assert.assertTrue(config.isVirtualStorage());
-    Assert.assertTrue(config.isVirtualStorageFabricEvictImmediatelyOnHoldRelease());
+    Assert.assertTrue(config.isVirtualStorageEphemeral());
   }
 }

server/src/test/java/org/apache/druid/segment/loading/SegmentLocalCacheManagerTest.java

@@ -1197,7 +1197,7 @@ public boolean isVirtualStorage()
       }
 
       @Override
-      public boolean isVirtualStorageFabricEvictImmediatelyOnHoldRelease()
+      public boolean isVirtualStorageEphemeral()
       {
         return true;
       }