josh-mckenzie commented on code in PR #1954:
URL: https://github.com/apache/cassandra/pull/1954#discussion_r1041237457
##########
src/java/org/apache/cassandra/db/Mutation.java:
##########
@@ -393,34 +411,115 @@ public static class MutationSerializer implements
IVersionedSerializer<Mutation>
{
public void serialize(Mutation mutation, DataOutputPlus out, int
version) throws IOException
{
+ serialization(mutation,
version).serialize(PartitionUpdate.serializer, mutation, out, version);
+ }
+
+ /**
+ * Called early during request processing to prevent that {@link
#serialization(Mutation, int)} is
+ * called concurrently.
+ * See {@link
org.apache.cassandra.service.StorageProxy#sendToHintedReplicas(Mutation,
ReplicaPlan.ForWrite, AbstractWriteResponseHandler, String, Stage)}
+ */
+ @SuppressWarnings("JavadocReference")
+ public void prepareSerializedBuffer(Mutation mutation, int version)
+ {
+ serialization(mutation, version);
+ }
+
+ /**
+ * Retrieve the cached serialization of this mutation, or compute and
cache said serialization if it doesn't
+ * exist yet. Note that this method is _not_ synchronized even though
it may (and will often) be called
+ * concurrently. Concurrent calls are still safe however, the only
risk is that the value is not cached yet,
+ * multiple concurrent calls may compute it multiple times instead of
just once. This is ok as in practice
+ * as we make sure this doesn't happen in the hot path by forcing the
initial caching in
+ * {@link
org.apache.cassandra.service.StorageProxy#sendToHintedReplicas(Mutation,
ReplicaPlan.ForWrite, AbstractWriteResponseHandler, String, Stage)}
+ * via {@link #prepareSerializedBuffer(Mutation)}, which is the only
caller that passes
+ * {@code isPrepare==true}.
+ */
+ @SuppressWarnings("JavadocReference")
+ private Serialization serialization(Mutation mutation, int version)
+ {
+ int versionOrdinal = MessagingService.getVersionOrdinal(version);
+ // Retrieves the cached version, or build+cache it if it's not
cached already.
+ Serialization serialization =
mutation.cachedSerializations[versionOrdinal];
+ if (serialization == null)
+ {
+ serialization = new SizeOnlyCacheableSerialization();
+ long sertializedSize =
serialization.serializedSize(PartitionUpdate.serializer, mutation, version);
+
+ // Exessively large mutation objects cause GC pressure and
huge allocations when serialized.
Review Comment:
nit: Excessively
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