Avoid OOM-killing query if large result-level cache population fails …

…for query

Currently, result-level caching which attempts to allocate a large enough buffer to store query results will overflow the Integer.MAX_INT capacity. ByteArrayOutputStream materializes this case as an OutOfMemoryError, which is not caught and terminates the node. This limits the allocated buffer for storing query results to whatever is set in `CacheConfig.getResultLevelCacheLimit()`.

processing/src/main/java/org/apache/druid/io/LimitedOutputStream.java

@@ -28,7 +28,7 @@
 
 /**
  * An {@link OutputStream} that limits how many bytes can be written. Throws {@link IOException} if the limit
- * is exceeded.
+ * is exceeded. *Not* thread-safe.
  */
 public class LimitedOutputStream extends OutputStream
 {
@@ -88,6 +88,11 @@ public void close() throws IOException
     out.close();
   }
 
+  public OutputStream get()
+  {
+    return out;
+  }
+
   private void plus(final int n) throws IOException
   {
     written += n;

server/src/main/java/org/apache/druid/query/ResultLevelCachingQueryRunner.java

@@ -30,6 +30,7 @@
 import org.apache.druid.client.cache.Cache;
 import org.apache.druid.client.cache.Cache.NamedKey;
 import org.apache.druid.client.cache.CacheConfig;
+import org.apache.druid.io.LimitedOutputStream;
 import org.apache.druid.java.util.common.RE;
 import org.apache.druid.java.util.common.StringUtils;
 import org.apache.druid.java.util.common.guava.Sequence;
@@ -152,6 +153,8 @@ public void after(boolean isDone, Throwable thrown)
                   // The resultset identifier and its length is cached along with the resultset
                   resultLevelCachePopulator.populateResults();
                   log.debug("Cache population complete for query %s", query.getId());
+                } else { // thrown == null && !resultLevelCachePopulator.isShouldPopulate()
+                  log.error("Failed (gracefully) to populate result level cache for query %s", query.getId());
                 }
                 resultLevelCachePopulator.stopPopulating();
               }
@@ -233,8 +236,8 @@ private ResultLevelCachePopulator createResultLevelCachePopulator(
       try {
         //   Save the resultSetId and its length
         resultLevelCachePopulator.cacheObjectStream.write(ByteBuffer.allocate(Integer.BYTES)
-                                                                    .putInt(resultSetId.length())
-                                                                    .array());
+                                                              .putInt(resultSetId.length())
+                                                              .array());
         resultLevelCachePopulator.cacheObjectStream.write(StringUtils.toUtf8(resultSetId));
       }
       catch (IOException ioe) {
@@ -255,7 +258,7 @@ private class ResultLevelCachePopulator
     private final Cache.NamedKey key;
     private final CacheConfig cacheConfig;
     @Nullable
-    private ByteArrayOutputStream cacheObjectStream;
+    private LimitedOutputStream cacheObjectStream;
 
     private ResultLevelCachePopulator(
         Cache cache,
@@ -270,7 +273,14 @@ private ResultLevelCachePopulator(
       this.serialiers = mapper.getSerializerProviderInstance();
       this.key = key;
       this.cacheConfig = cacheConfig;
-      this.cacheObjectStream = shouldPopulate ? new ByteArrayOutputStream() : null;
+      this.cacheObjectStream = shouldPopulate ? new LimitedOutputStream(
+          new ByteArrayOutputStream(),
+          cacheConfig.getResultLevelCacheLimit(), limit -> StringUtils.format(
+          "resultLevelCacheLimit[%,d] exceeded. "
+          + "Max ResultLevelCacheLimit for cache exceeded. Result caching failed.",
+          limit
+      )
+      ) : null;
     }
 
     boolean isShouldPopulate()
@@ -289,12 +299,8 @@ private void cacheResultEntry(
     )
     {
       Preconditions.checkNotNull(cacheObjectStream, "cacheObjectStream");
-      int cacheLimit = cacheConfig.getResultLevelCacheLimit();
       try (JsonGenerator gen = mapper.getFactory().createGenerator(cacheObjectStream)) {
         JacksonUtils.writeObjectUsingSerializerProvider(gen, serialiers, cacheFn.apply(resultEntry));
-        if (cacheLimit > 0 && cacheObjectStream.size() > cacheLimit) {
-          stopPopulating();
-        }
       }
       catch (IOException ex) {
         log.error(ex, "Failed to retrieve entry to be cached. Result Level caching will not be performed!");
@@ -304,7 +310,8 @@ private void cacheResultEntry(
 
     public void populateResults()
     {
-      byte[] cachedResults = Preconditions.checkNotNull(cacheObjectStream, "cacheObjectStream").toByteArray();
+      byte[] cachedResults = ((ByteArrayOutputStream) Preconditions.checkNotNull(cacheObjectStream, "cacheObjectStream")
+          .get()).toByteArray();
       cache.put(key, cachedResults);
     }
   }

server/src/test/java/org/apache/druid/query/ResultLevelCachingQueryRunnerTest.java

@@ -39,6 +39,7 @@
 public class ResultLevelCachingQueryRunnerTest extends QueryRunnerBasedOnClusteredClientTestBase
 {
   private Cache cache;
+  private static final int DEFAULT_CACHE_ENTRY_MAX_SIZE = Integer.MAX_VALUE;
 
   @Before
   public void setup()
@@ -58,7 +59,7 @@ public void testNotPopulateAndNotUse()
     prepareCluster(10);
     final Query<Result<TimeseriesResultValue>> query = timeseriesQuery(BASE_SCHEMA_INFO.getDataInterval());
     final ResultLevelCachingQueryRunner<Result<TimeseriesResultValue>> queryRunner1 = createQueryRunner(
-        newCacheConfig(false, false),
+        newCacheConfig(false, false, DEFAULT_CACHE_ENTRY_MAX_SIZE),
         query
     );
 
@@ -72,7 +73,7 @@ public void testNotPopulateAndNotUse()
     Assert.assertEquals(0, cache.getStats().getNumMisses());
 
     final ResultLevelCachingQueryRunner<Result<TimeseriesResultValue>> queryRunner2 = createQueryRunner(
-        newCacheConfig(false, false),
+        newCacheConfig(false, false, DEFAULT_CACHE_ENTRY_MAX_SIZE),
         query
     );
 
@@ -93,7 +94,7 @@ public void testPopulateAndNotUse()
     prepareCluster(10);
     final Query<Result<TimeseriesResultValue>> query = timeseriesQuery(BASE_SCHEMA_INFO.getDataInterval());
     final ResultLevelCachingQueryRunner<Result<TimeseriesResultValue>> queryRunner1 = createQueryRunner(
-        newCacheConfig(true, false),
+        newCacheConfig(true, false, DEFAULT_CACHE_ENTRY_MAX_SIZE),
         query
     );
 
@@ -107,7 +108,7 @@ public void testPopulateAndNotUse()
     Assert.assertEquals(0, cache.getStats().getNumMisses());
 
     final ResultLevelCachingQueryRunner<Result<TimeseriesResultValue>> queryRunner2 = createQueryRunner(
-        newCacheConfig(true, false),
+        newCacheConfig(true, false, DEFAULT_CACHE_ENTRY_MAX_SIZE),
         query
     );
 
@@ -128,7 +129,7 @@ public void testNotPopulateAndUse()
     prepareCluster(10);
     final Query<Result<TimeseriesResultValue>> query = timeseriesQuery(BASE_SCHEMA_INFO.getDataInterval());
     final ResultLevelCachingQueryRunner<Result<TimeseriesResultValue>> queryRunner1 = createQueryRunner(
-        newCacheConfig(false, false),
+        newCacheConfig(false, false, DEFAULT_CACHE_ENTRY_MAX_SIZE),
         query
     );
 
@@ -142,7 +143,7 @@ public void testNotPopulateAndUse()
     Assert.assertEquals(0, cache.getStats().getNumMisses());
 
     final ResultLevelCachingQueryRunner<Result<TimeseriesResultValue>> queryRunner2 = createQueryRunner(
-        newCacheConfig(false, true),
+        newCacheConfig(false, true, DEFAULT_CACHE_ENTRY_MAX_SIZE),
         query
     );
 
@@ -163,7 +164,7 @@ public void testPopulateAndUse()
     prepareCluster(10);
     final Query<Result<TimeseriesResultValue>> query = timeseriesQuery(BASE_SCHEMA_INFO.getDataInterval());
     final ResultLevelCachingQueryRunner<Result<TimeseriesResultValue>> queryRunner1 = createQueryRunner(
-        newCacheConfig(true, true),
+        newCacheConfig(true, true, DEFAULT_CACHE_ENTRY_MAX_SIZE),
         query
     );
 
@@ -177,7 +178,7 @@ public void testPopulateAndUse()
     Assert.assertEquals(1, cache.getStats().getNumMisses());
 
     final ResultLevelCachingQueryRunner<Result<TimeseriesResultValue>> queryRunner2 = createQueryRunner(
-        newCacheConfig(true, true),
+        newCacheConfig(true, true, DEFAULT_CACHE_ENTRY_MAX_SIZE),
         query
     );
 
@@ -192,6 +193,41 @@ public void testPopulateAndUse()
     Assert.assertEquals(1, cache.getStats().getNumMisses());
   }
 
+  @Test
+  public void testNoPopulateIfEntrySizeExceedsMaximum()
+  {
+    prepareCluster(10);
+    final Query<Result<TimeseriesResultValue>> query = timeseriesQuery(BASE_SCHEMA_INFO.getDataInterval());
+    final ResultLevelCachingQueryRunner<Result<TimeseriesResultValue>> queryRunner1 = createQueryRunner(
+        newCacheConfig(true, true, 128),
+        query
+    );
+
+    final Sequence<Result<TimeseriesResultValue>> sequence1 = queryRunner1.run(
+        QueryPlus.wrap(query),
+        responseContext()
+    );
+    final List<Result<TimeseriesResultValue>> results1 = sequence1.toList();
+    Assert.assertEquals(0, cache.getStats().getNumHits());
+    Assert.assertEquals(0, cache.getStats().getNumEntries());
+    Assert.assertEquals(1, cache.getStats().getNumMisses());
+
+    final ResultLevelCachingQueryRunner<Result<TimeseriesResultValue>> queryRunner2 = createQueryRunner(
+        newCacheConfig(true, true, DEFAULT_CACHE_ENTRY_MAX_SIZE),
+        query
+    );
+
+    final Sequence<Result<TimeseriesResultValue>> sequence2 = queryRunner2.run(
+        QueryPlus.wrap(query),
+        responseContext()
+    );
+    final List<Result<TimeseriesResultValue>> results2 = sequence2.toList();
+    Assert.assertEquals(results1, results2);
+    Assert.assertEquals(0, cache.getStats().getNumHits());
+    Assert.assertEquals(1, cache.getStats().getNumEntries());
+    Assert.assertEquals(2, cache.getStats().getNumMisses());
+  }
+
   @Test
   public void testPopulateCacheWhenQueryThrowExceptionShouldNotCache()
   {
@@ -206,7 +242,7 @@ public void testPopulateCacheWhenQueryThrowExceptionShouldNotCache()
 
     final Query<Result<TimeseriesResultValue>> query = timeseriesQuery(BASE_SCHEMA_INFO.getDataInterval());
     final ResultLevelCachingQueryRunner<Result<TimeseriesResultValue>> queryRunner = createQueryRunner(
-        newCacheConfig(true, false),
+        newCacheConfig(true, false, DEFAULT_CACHE_ENTRY_MAX_SIZE),
         query
     );
 
@@ -249,7 +285,11 @@ private <T> ResultLevelCachingQueryRunner<T> createQueryRunner(
     );
   }
 
-  private CacheConfig newCacheConfig(boolean populateResultLevelCache, boolean useResultLevelCache)
+  private CacheConfig newCacheConfig(
+      boolean populateResultLevelCache,
+      boolean useResultLevelCache,
+      int resultLevelCacheLimit
+  )
   {
     return new CacheConfig()
     {
@@ -264,6 +304,12 @@ public boolean isUseResultLevelCache()
       {
         return useResultLevelCache;
       }
+
+      @Override
+      public int getResultLevelCacheLimit()
+      {
+        return resultLevelCacheLimit;
+      }
     };
   }
 }