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Posted to github@beam.apache.org by "mutianf (via GitHub)" <gi...@apache.org> on 2023/08/23 15:37:29 UTC

[GitHub] [beam] mutianf opened a new pull request, #28122: fix: fix a race condition in BigtableService cache

mutianf opened a new pull request, #28122:
URL: https://github.com/apache/beam/pull/28122

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[GitHub] [beam] Abacn commented on a diff in pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "Abacn (via GitHub)" <gi...@apache.org>.
Abacn commented on code in PR #28122:
URL: https://github.com/apache/beam/pull/28122#discussion_r1303307732


##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigtable/BigtableServiceFactory.java:
##########
@@ -105,8 +106,12 @@ BigtableServiceEntry getServiceForReading(
       BigtableServiceEntry entry = entries.get(configId.id());
       if (entry != null) {
         // When entry is not null, refCount.get(configId.id()) should always exist.
-        // Do a getOrDefault to avoid unexpected NPEs.
-        refCounts.getOrDefault(configId.id(), new AtomicInteger(0)).getAndIncrement();
+        Preconditions.checkNotNull(
+            refCounts.get(configId.id()),

Review Comment:
   Though here is in synchronized block, assign a local variable to checkNotNull(refCounts.get(configId.id())) then call getAndIncrement on. this varaible. This is the canonical use of checkNotNull



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[GitHub] [beam] bvolpato commented on a diff in pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "bvolpato (via GitHub)" <gi...@apache.org>.
bvolpato commented on code in PR #28122:
URL: https://github.com/apache/beam/pull/28122#discussion_r1308904061


##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigtable/BigtableServiceFactory.java:
##########
@@ -105,8 +104,12 @@ BigtableServiceEntry getServiceForReading(
       BigtableServiceEntry entry = entries.get(configId.id());
       if (entry != null) {
         // When entry is not null, refCount.get(configId.id()) should always exist.
-        // Do a getOrDefault to avoid unexpected NPEs.
-        refCounts.getOrDefault(configId.id(), new AtomicInteger(0)).getAndIncrement();
+        // Doing a putIfAbsent to avoid NPE.
+        AtomicInteger count = refCounts.putIfAbsent(configId.id(), new AtomicInteger(0));
+        if (count == null) {
+          LOG.error("entry is not null but refCount of config Id " + configId.id() + " is null.");
+        }

Review Comment:
   Scratch that, putIfAbsent returns the old object, not the new (thanks for pointing out).



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[GitHub] [beam] Abacn commented on a diff in pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "Abacn (via GitHub)" <gi...@apache.org>.
Abacn commented on code in PR #28122:
URL: https://github.com/apache/beam/pull/28122#discussion_r1304869938


##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigtable/BigtableServiceFactory.java:
##########
@@ -105,8 +104,12 @@ BigtableServiceEntry getServiceForReading(
       BigtableServiceEntry entry = entries.get(configId.id());
       if (entry != null) {
         // When entry is not null, refCount.get(configId.id()) should always exist.
-        // Do a getOrDefault to avoid unexpected NPEs.
-        refCounts.getOrDefault(configId.id(), new AtomicInteger(0)).getAndIncrement();
+        // Doing a putIfAbsent to avoid NPE.
+        AtomicInteger count = refCounts.putIfAbsent(configId.id(), new AtomicInteger(0));

Review Comment:
   this will definitely fix symptom. Though I cannot see if it could cause any potential connection leak. Let's see if @bvolpato 's opinion.



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[GitHub] [beam] Abacn commented on a diff in pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "Abacn (via GitHub)" <gi...@apache.org>.
Abacn commented on code in PR #28122:
URL: https://github.com/apache/beam/pull/28122#discussion_r1303309112


##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigtable/BigtableServiceFactory.java:
##########
@@ -105,8 +106,12 @@ BigtableServiceEntry getServiceForReading(
       BigtableServiceEntry entry = entries.get(configId.id());
       if (entry != null) {
         // When entry is not null, refCount.get(configId.id()) should always exist.
-        // Do a getOrDefault to avoid unexpected NPEs.
-        refCounts.getOrDefault(configId.id(), new AtomicInteger(0)).getAndIncrement();
+        Preconditions.checkNotNull(
+            refCounts.get(configId.id()),

Review Comment:
   I see nullness error is suppressed in this file. Since NPE caused issue, would be nice to clean up nullness errorprone in this file and remove suppress(nullness) in the class decorator



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[GitHub] [beam] bvolpato commented on pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "bvolpato (via GitHub)" <gi...@apache.org>.
bvolpato commented on PR #28122:
URL: https://github.com/apache/beam/pull/28122#issuecomment-1697553320

   @Abacn thanks for the double check, this should be good to go


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[GitHub] [beam] Abacn commented on a diff in pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "Abacn (via GitHub)" <gi...@apache.org>.
Abacn commented on code in PR #28122:
URL: https://github.com/apache/beam/pull/28122#discussion_r1303305418


##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigtable/BigtableServiceFactory.java:
##########
@@ -75,15 +76,15 @@ static BigtableServiceEntry create(ConfigId configId, BigtableService service) {
 
     @Override
     public void close() {
-      int refCount =
-          refCounts.getOrDefault(getConfigId().id(), new AtomicInteger(0)).decrementAndGet();
-      if (refCount < 0) {
-        LOG.error(
-            "close() Ref count is < 0, configId=" + getConfigId().id() + " refCount=" + refCount);
-      }
-      LOG.debug("close() for config id " + getConfigId().id() + ", ref count is " + refCount);
-      if (refCount == 0) {
-        synchronized (lock) {
+      synchronized (lock) {
+        int refCount =
+            refCounts.getOrDefault(getConfigId().id(), new AtomicInteger(0)).decrementAndGet();
+        if (refCount < 0) {
+          LOG.error(
+              "close() Ref count is < 0, configId=" + getConfigId().id() + " refCount=" + refCount);
+        }
+        LOG.debug("close() for config id " + getConfigId().id() + ", ref count is " + refCount);
+        if (refCount == 0) {

Review Comment:
   concurrent programming can be tricky. It makes sense to me that move the lock here could resolve the race condition. However, is there any harm if make the entire close() function synchronized?



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[GitHub] [beam] bvolpato commented on a diff in pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "bvolpato (via GitHub)" <gi...@apache.org>.
bvolpato commented on code in PR #28122:
URL: https://github.com/apache/beam/pull/28122#discussion_r1303312575


##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigtable/BigtableServiceFactory.java:
##########
@@ -75,15 +76,15 @@ static BigtableServiceEntry create(ConfigId configId, BigtableService service) {
 
     @Override
     public void close() {
-      int refCount =
-          refCounts.getOrDefault(getConfigId().id(), new AtomicInteger(0)).decrementAndGet();
-      if (refCount < 0) {
-        LOG.error(
-            "close() Ref count is < 0, configId=" + getConfigId().id() + " refCount=" + refCount);
-      }
-      LOG.debug("close() for config id " + getConfigId().id() + ", ref count is " + refCount);
-      if (refCount == 0) {
-        synchronized (lock) {
+      synchronized (lock) {
+        int refCount =
+            refCounts.getOrDefault(getConfigId().id(), new AtomicInteger(0)).decrementAndGet();
+        if (refCount < 0) {
+          LOG.error(
+              "close() Ref count is < 0, configId=" + getConfigId().id() + " refCount=" + refCount);
+        }
+        LOG.debug("close() for config id " + getConfigId().id() + ", ref count is " + refCount);
+        if (refCount == 0) {

Review Comment:
    decrementAndCount is thread safe, so I wonder what's the actual underlying issue here.
   
   I also understand why `< 0` is logging an error, but shouldn't we trigger `.remove()` in that case too? Instead of doing `== 0` in the next if



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[GitHub] [beam] bvolpato commented on a diff in pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "bvolpato (via GitHub)" <gi...@apache.org>.
bvolpato commented on code in PR #28122:
URL: https://github.com/apache/beam/pull/28122#discussion_r1306601260


##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigtable/BigtableServiceFactory.java:
##########
@@ -105,8 +104,12 @@ BigtableServiceEntry getServiceForReading(
       BigtableServiceEntry entry = entries.get(configId.id());
       if (entry != null) {
         // When entry is not null, refCount.get(configId.id()) should always exist.
-        // Do a getOrDefault to avoid unexpected NPEs.
-        refCounts.getOrDefault(configId.id(), new AtomicInteger(0)).getAndIncrement();
+        // Doing a putIfAbsent to avoid NPE.
+        AtomicInteger count = refCounts.putIfAbsent(configId.id(), new AtomicInteger(0));
+        if (count == null) {
+          LOG.error("entry is not null but refCount of config Id " + configId.id() + " is null.");
+        }

Review Comment:
   I believe you've experienced the racing and there was a reason to add it, though, so this should be fine -- but it appears that this branch is spurious / never reachable.
   
   It seems that what the previous code could simply be fixed by using putIfAbsent?
   
   ```
   refCounts.putIfAbsent(configId.id(), new AtomicInteger(0)).getAndIncrement();
   ```
   
   You may not even need `refCounts.put(configId.id(), new AtomicInteger(1));` which is done later, so you have only 1 AtomicInteger per config id
   
   



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[GitHub] [beam] bvolpato commented on a diff in pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "bvolpato (via GitHub)" <gi...@apache.org>.
bvolpato commented on code in PR #28122:
URL: https://github.com/apache/beam/pull/28122#discussion_r1308904061


##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigtable/BigtableServiceFactory.java:
##########
@@ -105,8 +104,12 @@ BigtableServiceEntry getServiceForReading(
       BigtableServiceEntry entry = entries.get(configId.id());
       if (entry != null) {
         // When entry is not null, refCount.get(configId.id()) should always exist.
-        // Do a getOrDefault to avoid unexpected NPEs.
-        refCounts.getOrDefault(configId.id(), new AtomicInteger(0)).getAndIncrement();
+        // Doing a putIfAbsent to avoid NPE.
+        AtomicInteger count = refCounts.putIfAbsent(configId.id(), new AtomicInteger(0));
+        if (count == null) {
+          LOG.error("entry is not null but refCount of config Id " + configId.id() + " is null.");
+        }

Review Comment:
   Scratch that, putIfAbsent returns the old object, not the new.



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[GitHub] [beam] bvolpato commented on a diff in pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "bvolpato (via GitHub)" <gi...@apache.org>.
bvolpato commented on code in PR #28122:
URL: https://github.com/apache/beam/pull/28122#discussion_r1303312575


##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigtable/BigtableServiceFactory.java:
##########
@@ -75,15 +76,15 @@ static BigtableServiceEntry create(ConfigId configId, BigtableService service) {
 
     @Override
     public void close() {
-      int refCount =
-          refCounts.getOrDefault(getConfigId().id(), new AtomicInteger(0)).decrementAndGet();
-      if (refCount < 0) {
-        LOG.error(
-            "close() Ref count is < 0, configId=" + getConfigId().id() + " refCount=" + refCount);
-      }
-      LOG.debug("close() for config id " + getConfigId().id() + ", ref count is " + refCount);
-      if (refCount == 0) {
-        synchronized (lock) {
+      synchronized (lock) {
+        int refCount =
+            refCounts.getOrDefault(getConfigId().id(), new AtomicInteger(0)).decrementAndGet();
+        if (refCount < 0) {
+          LOG.error(
+              "close() Ref count is < 0, configId=" + getConfigId().id() + " refCount=" + refCount);
+        }
+        LOG.debug("close() for config id " + getConfigId().id() + ", ref count is " + refCount);
+        if (refCount == 0) {

Review Comment:
    decrementAndCount is thread safe, so I wonder what's the actual underlying issue here.
   
   I also understand why < 0 is logging an error, but shouldn't we `.remove()` in that case too? Instead of doing `== 0` in the next if



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[GitHub] [beam] github-actions[bot] commented on pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] commented on PR #28122:
URL: https://github.com/apache/beam/pull/28122#issuecomment-1690282344

   Assigning reviewers. If you would like to opt out of this review, comment `assign to next reviewer`:
   
   R: @bvolpato for label java.
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[GitHub] [beam] Abacn merged pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "Abacn (via GitHub)" <gi...@apache.org>.
Abacn merged PR #28122:
URL: https://github.com/apache/beam/pull/28122


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[GitHub] [beam] mutianf commented on a diff in pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "mutianf (via GitHub)" <gi...@apache.org>.
mutianf commented on code in PR #28122:
URL: https://github.com/apache/beam/pull/28122#discussion_r1304671705


##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigtable/BigtableServiceFactory.java:
##########
@@ -75,15 +76,15 @@ static BigtableServiceEntry create(ConfigId configId, BigtableService service) {
 
     @Override
     public void close() {
-      int refCount =
-          refCounts.getOrDefault(getConfigId().id(), new AtomicInteger(0)).decrementAndGet();
-      if (refCount < 0) {
-        LOG.error(
-            "close() Ref count is < 0, configId=" + getConfigId().id() + " refCount=" + refCount);
-      }
-      LOG.debug("close() for config id " + getConfigId().id() + ", ref count is " + refCount);
-      if (refCount == 0) {
-        synchronized (lock) {
+      synchronized (lock) {
+        int refCount =
+            refCounts.getOrDefault(getConfigId().id(), new AtomicInteger(0)).decrementAndGet();
+        if (refCount < 0) {
+          LOG.error(
+              "close() Ref count is < 0, configId=" + getConfigId().id() + " refCount=" + refCount);
+        }
+        LOG.debug("close() for config id " + getConfigId().id() + ", ref count is " + refCount);
+        if (refCount == 0) {

Review Comment:
   I think it's fine, originally the part that's outside of the lock was also just getting the ref count.



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[GitHub] [beam] mutianf commented on a diff in pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "mutianf (via GitHub)" <gi...@apache.org>.
mutianf commented on code in PR #28122:
URL: https://github.com/apache/beam/pull/28122#discussion_r1304672738


##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigtable/BigtableServiceFactory.java:
##########
@@ -105,8 +106,12 @@ BigtableServiceEntry getServiceForReading(
       BigtableServiceEntry entry = entries.get(configId.id());
       if (entry != null) {
         // When entry is not null, refCount.get(configId.id()) should always exist.
-        // Do a getOrDefault to avoid unexpected NPEs.
-        refCounts.getOrDefault(configId.id(), new AtomicInteger(0)).getAndIncrement();
+        Preconditions.checkNotNull(
+            refCounts.get(configId.id()),

Review Comment:
   I don't thnk i'm able to remove the suppress(nullness) annotation on the class. If I removed it doing:
   
   ```
         BigtableServiceEntry entry = entries.get(configId.id());
         if (entry != null) {
   ```
   
   Won't build



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[GitHub] [beam] mutianf commented on a diff in pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "mutianf (via GitHub)" <gi...@apache.org>.
mutianf commented on code in PR #28122:
URL: https://github.com/apache/beam/pull/28122#discussion_r1303444386


##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigtable/BigtableServiceFactory.java:
##########
@@ -75,15 +76,15 @@ static BigtableServiceEntry create(ConfigId configId, BigtableService service) {
 
     @Override
     public void close() {
-      int refCount =
-          refCounts.getOrDefault(getConfigId().id(), new AtomicInteger(0)).decrementAndGet();
-      if (refCount < 0) {
-        LOG.error(
-            "close() Ref count is < 0, configId=" + getConfigId().id() + " refCount=" + refCount);
-      }
-      LOG.debug("close() for config id " + getConfigId().id() + ", ref count is " + refCount);
-      if (refCount == 0) {
-        synchronized (lock) {
+      synchronized (lock) {
+        int refCount =
+            refCounts.getOrDefault(getConfigId().id(), new AtomicInteger(0)).decrementAndGet();
+        if (refCount < 0) {
+          LOG.error(
+              "close() Ref count is < 0, configId=" + getConfigId().id() + " refCount=" + refCount);
+        }
+        LOG.debug("close() for config id " + getConfigId().id() + ", ref count is " + refCount);
+        if (refCount == 0) {

Review Comment:
   I think the underlying issue is the race between:
    - close() decrementing the counter and
    - getServiceForReading() incrementing the counter
   Since decrementing the counter is outside of the lock, and we're getting the refCount number and do something with it, there could be a race. 
   
   When `<0`, that means refCounts doesn't has a reference to configId, so we're not triggering the remove there. 



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[GitHub] [beam] bvolpato commented on a diff in pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "bvolpato (via GitHub)" <gi...@apache.org>.
bvolpato commented on code in PR #28122:
URL: https://github.com/apache/beam/pull/28122#discussion_r1306601326


##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigtable/BigtableServiceFactory.java:
##########
@@ -150,8 +153,12 @@ BigtableServiceEntry getServiceForWriting(
       LOG.debug("getServiceForWriting(), config id: " + configId.id());
       if (entry != null) {
         // When entry is not null, refCount.get(configId.id()) should always exist.
-        // Do a getOrDefault to avoid unexpected NPEs.
-        refCounts.getOrDefault(configId.id(), new AtomicInteger(0)).getAndIncrement();
+        // Doing a putIfAbsent to avoid NPE.
+        AtomicInteger count = refCounts.putIfAbsent(configId.id(), new AtomicInteger(0));

Review Comment:
   Same here



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[GitHub] [beam] bvolpato commented on a diff in pull request #28122: fix: fix a race condition in BigtableService cache

Posted by "bvolpato (via GitHub)" <gi...@apache.org>.
bvolpato commented on code in PR #28122:
URL: https://github.com/apache/beam/pull/28122#discussion_r1306601260


##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigtable/BigtableServiceFactory.java:
##########
@@ -105,8 +104,12 @@ BigtableServiceEntry getServiceForReading(
       BigtableServiceEntry entry = entries.get(configId.id());
       if (entry != null) {
         // When entry is not null, refCount.get(configId.id()) should always exist.
-        // Do a getOrDefault to avoid unexpected NPEs.
-        refCounts.getOrDefault(configId.id(), new AtomicInteger(0)).getAndIncrement();
+        // Doing a putIfAbsent to avoid NPE.
+        AtomicInteger count = refCounts.putIfAbsent(configId.id(), new AtomicInteger(0));
+        if (count == null) {
+          LOG.error("entry is not null but refCount of config Id " + configId.id() + " is null.");
+        }

Review Comment:
   I believe you've experienced the racing and there was a reason to add it, though, so this should be fine -- but it appears that this branch is spurious / never reachable.
   
   It appears that what the previous code could simply be fixed by using putIfAbsent?
   
   ```
   refCounts.putIfAbsent(configId.id(), new AtomicInteger(0)).getAndIncrement();
   ```
   
   You may not even need `refCounts.put(configId.id(), new AtomicInteger(1));` which is done later, so you have only 1 AtomicInteger per config id
   
   



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