From 51b60168f7130621c6b6823e011e9c2aec02d93c Mon Sep 17 00:00:00 2001
From: Andrea Cavalli <andrea@cavallium.it>
Date: Mon, 6 Sep 2021 18:29:10 +0200
Subject: [PATCH] Implement phaser

---
 .../database/disk/CachedIndexSearcherManager.java    | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/src/main/java/it/cavallium/dbengine/database/disk/CachedIndexSearcherManager.java b/src/main/java/it/cavallium/dbengine/database/disk/CachedIndexSearcherManager.java
index 98aaa93..63881b0 100644
--- a/src/main/java/it/cavallium/dbengine/database/disk/CachedIndexSearcherManager.java
+++ b/src/main/java/it/cavallium/dbengine/database/disk/CachedIndexSearcherManager.java
@@ -6,6 +6,7 @@ import com.google.common.cache.LoadingCache;
 import it.cavallium.dbengine.database.LLSnapshot;
 import java.io.IOException;
 import java.time.Duration;
+import java.util.concurrent.Phaser;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.locks.LockSupport;
 import java.util.function.Function;
@@ -29,7 +30,7 @@ public class CachedIndexSearcherManager {
 	private final Similarity similarity;
 	private final SearcherManager searcherManager;
 	private final Duration queryRefreshDebounceTime;
-	private final AtomicInteger activeSearchers = new AtomicInteger(0);
+	private final Phaser activeSearchers = new Phaser(1);
 
 	private final LoadingCache<LLSnapshot, Mono<CachedIndexSearcher>> cachedSnapshotSearchers;
 	private final Mono<CachedIndexSearcher> cachedMainSearcher;
@@ -86,7 +87,7 @@ public class CachedIndexSearcherManager {
 						indexSearcher = snapshotsManager.resolveSnapshot(snapshot).getIndexSearcher();
 						associatedSearcherManager = null;
 					}
-					return new CachedIndexSearcher(indexSearcher, associatedSearcherManager, activeSearchers::decrementAndGet);
+					return new CachedIndexSearcher(indexSearcher, associatedSearcherManager, activeSearchers::arriveAndDeregister);
 				})
 				.cacheInvalidateWhen(indexSearcher -> Mono
 								.firstWithSignal(
@@ -152,7 +153,7 @@ public class CachedIndexSearcherManager {
 				.retrieveCachedIndexSearcher(snapshot)
 				// Increment reference count
 				.doOnNext(indexSearcher -> {
-					activeSearchers.incrementAndGet();
+					activeSearchers.register();
 					indexSearcher.incUsage();
 				});
 	}
@@ -181,10 +182,7 @@ public class CachedIndexSearcherManager {
 				.fromRunnable(this.closeRequested::tryEmitEmpty)
 				.then(refresherClosed.asMono())
 				.then(Mono.fromRunnable(() -> {
-					while (activeSearchers.get() > 0) {
-						// Park for 100ms
-						LockSupport.parkNanos(100000000L);
-					}
+					activeSearchers.arriveAndAwaitAdvance();
 					cachedSnapshotSearchers.invalidateAll();
 					cachedSnapshotSearchers.cleanUp();
 				}));