Function propagateExpire

app/redis-6.2.6/src/db.c:1465–1482

Propagate expires into slaves and the AOF file. * When a key expires in the master, a DEL operation for this key is sent * to all the slaves and the AOF file if enabled. * * This way the key expiry is centralized in one place, and since both * AOF and the master->slave link guarantee operation ordering, everything * will be consistent even if we allow write operations against expiring * key

 * will be consistent even if we allow write operations against expiring
 * keys. */
void propagateExpire(redisDb *db, robj *key, int lazy) {
    robj *argv[2];

    argv[0] = lazy ? shared.unlink : shared.del;
    argv[1] = key;
    incrRefCount(argv[0]);
    incrRefCount(argv[1]);

    /* If the master decided to expire a key we must propagate it to replicas no matter what..
     * Even if module executed a command without asking for propagation. */
    int prev_replication_allowed = server.replication_allowed;
    server.replication_allowed = 1;
    propagate(server.delCommand,db->id,argv,2,PROPAGATE_AOF|PROPAGATE_REPL);
    server.replication_allowed = prev_replication_allowed;

    decrRefCount(argv[0]);
    decrRefCount(argv[1]);
}

/* Check if the key is expired. */
int keyIsExpired(redisDb *db, robj *key) {