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Don't expire keys when loading an RDB after a SYNC

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The cron is responsible for expiring keys. When keys are expired at
load time, it is possible that the snapshot of a master node gets
modified. This can in turn lead to inconsistencies in the data set.

A more concrete example of this behavior follows. A user reported a
slave that would show an monotonically increase input buffer length,
shortly after completing a SYNC. Also, `INFO` output showed a single
blocked client, which could only be the master link. Investigation
showed that indeed the `BRPOP` command was fed by the master. This
command can only end up in the stream of write operations when it did
NOT block, and effectively executed `RPOP`. However, when the key
involved in the `BRPOP` is expired BEFORE the command is executed, the
client executing it will block. The client in this case, is the master
link.
This commit is contained in:
Pieter Noordhuis 2012-01-13 17:49:16 -08:00 committed by antirez
parent d347348109
commit cb598cdd59
1 changed files with 6 additions and 2 deletions
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8
src/rdb.c
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@ -1026,8 +1026,12 @@ int rdbLoad(char *filename) {
if ((key = rdbLoadStringObject(&rdb)) == NULL) goto eoferr;
/* Read value */
if ((val = rdbLoadObject(type,&rdb)) == NULL) goto eoferr;
/* Check if the key already expired */
if (expiretime != -1 && expiretime < now) {
/* Check if the key already expired. This function is used when loading
* an RDB file from disk, either at startup, or when an RDB was
* received from the master. In the latter case, the master is
* responsible for key expiry. If we would expire keys here, the
* snapshot taken by the master may not be reflected on the slave. */
if (server.masterhost == NULL && expiretime != -1 && expiretime < now) {
decrRefCount(key);
decrRefCount(val);
continue;