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fix: address more concurrency concerns in caching client #114

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Merged
merged 2 commits into from
Jul 21, 2021
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fix: address more concurrency concerns in caching client #114

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fix: address more concurrency concerns in caching client
aaron-steinfeld Jul 21, 2021
7cc0def
chore: remove redundant cache put
aaron-steinfeld Jul 21, 2021
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14 changes: 6 additions & 8 deletions ...nt/src/main/java/org/hypertrace/entity/data/service/rxclient/EntityDataCachingClient.java
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,6 @@
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import javax.annotation.Nonnull;
import org.hypertrace.entity.data.service.v1.Entity;
import org.hypertrace.entity.data.service.v1.EntityDataServiceGrpc;
Expand All @@ -38,8 +37,8 @@ class EntityDataCachingClient implements EntityDataClient {
private final LoadingCache<EntityKey, Single<Entity>> cache;
private final ConcurrentMap<EntityKey, PendingEntityUpdate> pendingEntityUpdates =
new ConcurrentHashMap<>();
private final Striped<ReadWriteLock> pendingUpdateStripedLock =
Striped.lazyWeakReadWriteLock(PENDING_UPDATE_MAX_LOCK_COUNT);
private final Striped<Lock> pendingUpdateStripedLock =
Striped.lazyWeakLock(PENDING_UPDATE_MAX_LOCK_COUNT);
private final Clock clock;

EntityDataCachingClient(
Expand Down Expand Up @@ -69,8 +68,8 @@ public Single<Entity> createOrUpdateEntityEventually(
SingleSubject<Entity> singleSubject = SingleSubject.create();
EntityKey entityKey = EntityKey.entityInCurrentContext(entity);

// Acquire lock allowing multiple concurrent update adds, but only if no update executions
Lock lock = this.pendingUpdateStripedLock.get(entityKey).readLock();
// Don't allow other update processing until finished
Lock lock = this.pendingUpdateStripedLock.get(entityKey);
try {
lock.lock();
this.pendingEntityUpdates
Expand Down Expand Up @@ -121,8 +120,8 @@ private class PendingEntityUpdate {
private UpsertCondition condition;

private void executeUpdate() {
// Acquire write lock to ensure no more modification of this update
Lock lock = pendingUpdateStripedLock.get(entityKey).writeLock();
// Make sure no current additions
Lock lock = pendingUpdateStripedLock.get(entityKey);
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@satish-mittal satish-mittal Jul 21, 2021

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L133 seems redundant since cache update is already done within L132. Can be removed.

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@aaron-steinfeld aaron-steinfeld Jul 21, 2021 •
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two different uses of the word cache.

Single<Entity> updateResult =
          EntityDataCachingClient.this.createOrUpdateEntity(entityKey, condition).cache();

Caches in the Single - that is, all subscribers will share a result rather than re-executing
( http://reactivex.io/RxJava/3.x/javadoc/io/reactivex/rxjava3/core/Single.html#cache-- )

EntityDataCachingClient.this.cache.put(entityKey, updateResult);

puts the single itself into the guava cache for future callers

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@satish-mittal satish-mittal Jul 21, 2021

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Yes, but if we go inside:

private Single<Entity> createOrUpdateEntity(
      EntityKey entityKey, UpsertCondition upsertCondition) {
    Single<Entity> updateResult =
        this.upsertEntityWithoutCaching(entityKey, upsertCondition).cache();
    EntityDataCachingClient.this.cache.put(entityKey, updateResult);
    return updateResult;
  }

that is already adding the single within the guava cache, right?

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@aaron-steinfeld aaron-steinfeld Jul 21, 2021

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Thanks for following up on this, my mind is clearly all over the place 🙁 - addressed.

try {
lock.lock();
EntityDataCachingClient.this.pendingEntityUpdates.remove(entityKey);
Expand All @@ -131,7 +130,6 @@ private void executeUpdate() {
}
Single<Entity> updateResult =
EntityDataCachingClient.this.createOrUpdateEntity(entityKey, condition).cache();
EntityDataCachingClient.this.cache.put(entityKey, updateResult);

responseObservers.forEach(updateResult::subscribe);
}
Expand Down