Function replicationCreateMasterClient

app/redis-6.2.6/src/replication.c:1454–1483

Once we have a link with the master and the synchronization was * performed, this function materializes the master client we store * at server.master, starting from the specified file descriptor. */

 * performed, this function materializes the master client we store
 * at server.master, starting from the specified file descriptor. */
void replicationCreateMasterClient(connection *conn, int dbid) {
    server.master = createClient(conn);
    if (conn)
        connSetReadHandler(server.master->conn, readQueryFromClient);

    /**
     * Important note:
     * The CLIENT_DENY_BLOCKING flag is not, and should not, be set here.
     * For commands like BLPOP, it makes no sense to block the master
     * connection, and such blocking attempt will probably cause deadlock and
     * break the replication. We consider such a thing as a bug because
     * commands as BLPOP should never be sent on the replication link.
     * A possible use-case for blocking the replication link is if a module wants
     * to pass the execution to a background thread and unblock after the
     * execution is done. This is the reason why we allow blocking the replication
     * connection. */
    server.master->flags |= CLIENT_MASTER;

    server.master->authenticated = 1;
    server.master->reploff = server.master_initial_offset;
    server.master->read_reploff = server.master->reploff;
    server.master->user = NULL; /* This client can do everything. */
    memcpy(server.master->replid, server.master_replid,
        sizeof(server.master_replid));
    /* If master offset is set to -1, this master is old and is not
     * PSYNC capable, so we flag it accordingly. */
    if (server.master->reploff == -1)
        server.master->flags |= CLIENT_PRE_PSYNC;
    if (dbid != -1) selectDb(server.master,dbid);
}

/* This function will try to re-enable the AOF file after the
 * master-replica synchronization: if it fails after multiple attempts