Fix memory leak in SnapBuildSerialize.

The memory for the snapshot was leaked while serializing it to disk during
logical decoding. This memory will be freed only once walsender stops
streaming the changes. This can lead to a huge memory increase when master
logs Standby Snapshot too frequently say when the user is trying to create
many replication slots.

Reported-by: [email protected]
Diagnosed-by: [email protected]
Author: Amit Kapila
Backpatch-through: 9.5
Discussion: https://postgr.es/m/033ab54c-6393-42ee-8ec9-2b399b5d8cde[email protected]

diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index 3089f0d5ddcd8db53bb04eceb426b05396b701c9..76c674ba8a1a13ea9a508f780cd568197f9f789c 100644 (file)
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -1480,7 +1480,7 @@ static void
 SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
 {
    Size        needed_length;
-   SnapBuildOnDisk *ondisk;
+   SnapBuildOnDisk *ondisk = NULL;
    char       *ondisk_c;
    int         fd;
    char        tmppath[MAXPGPATH];
@@ -1679,6 +1679,9 @@ SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
 out:
    ReorderBufferSetRestartPoint(builder->reorder,
                                 builder->last_serialized_snapshot);
+   /* be tidy */
+   if (ondisk)
+       pfree(ondisk);
 }
 
 /*