Re:PATCH: standby crashed when replay block which truncated in standby but failed to truncate in master node

Is this an issue?
Can we fix like this?
Thanks!

At 2019-09-22 00:38:03, "Thunder" <thunder1(at)126(dot)com> wrote:

The step to reproduce this issue.
1. Create a table
create table gist_point_tbl(id int4, p point);
create index gist_pointidx on gist_point_tbl using gist(p);
2. Insert data
insert into gist_point_tbl (id, p) select g, point(g*10, g*10) from generate_series(1, 1000000) g;
3. Delete data
delete from gist_point_bl;
4. Vacuum table
vacuum gist_point_tbl;
-- Send SIGINT to vacuum process after WAL-log of the truncation is flushed and the truncation is not finished
-- We will receive error message "ERROR: canceling statement due to user request"
5. Vacuum table again
vacuum gist_point tbl;
-- The standby node crashed and the PANIC log is "PANIC: WAL contains references to invalid pages"

The standby node succeed to replay truncate log but master node doesn't truncate the file, it will be crashed if master node writes to these blocks which truncated in standby node.
I try to fix issue to prevent query cancel interrupts during truncating.

diff --git a/src/backend/catalog/storage.c b/src/backend/catalog/storage.c
index 5df4382b7e..04b696ae01 100644
--- a/src/backend/catalog/storage.c
+++ b/src/backend/catalog/storage.c
@@ -26,6 +26,7 @@
#include "access/xlogutils.h"
#include "catalog/storage.h"
#include "catalog/storage_xlog.h"
+#include "miscadmin.h"
#include "storage/freespace.h"
#include "storage/smgr.h"
#include "utils/memutils.h"
@@ -248,6 +249,14 @@ RelationTruncate(Relation rel, BlockNumber nblocks)
if (vm)
visibilitymap_truncate(rel, nblocks);

+ /*
+ * When master node flush WAL-log of the truncation and then receive SIGINT signal to cancel
+ * this transaction before the truncation, if standby receive this WAL-log and do the truncation,
+ * standby node will crash when master node writes to these blocks which are truncated in standby node.
+ * So we prevent query cancel interrupts.
+ */
+ HOLD_CANCEL_INTERRUPTS();
+
/*
* We WAL-log the truncation before actually truncating, which means
* trouble if the truncation fails. If we then crash, the WAL replay
@@ -288,6 +297,8 @@ RelationTruncate(Relation rel, BlockNumber nblocks)

/* Do the real work */
smgrtruncate(rel->rd_smgr, MAIN_FORKNUM, nblocks);
+
+ RESUME_CANCEL_INTERRUPTS();
}