Function aofCreatePipes

src/aof.cpp:1819–1846

Create the pipes used for parent - child process IPC during rewrite. * We have a data pipe used to send AOF incremental diffs to the child, * and two other pipes used by the children to signal it finished with * the rewrite so no more data should be written, and another for the * parent to acknowledge it understood this new condition. */

 * the rewrite so no more data should be written, and another for the
 * parent to acknowledge it understood this new condition. */
int aofCreatePipes(void) {
    int fds[6] = {-1, -1, -1, -1, -1, -1};
    int j;

    if (pipe(fds) == -1) goto error; /* parent -> children data. */
    if (pipe(fds+2) == -1) goto error; /* children -> parent ack. */
    if (pipe(fds+4) == -1) goto error; /* parent -> children ack. */
    /* Parent -> children data is non blocking. */
    if (anetNonBlock(NULL,fds[0]) != ANET_OK) goto error;
    if (anetNonBlock(NULL,fds[1]) != ANET_OK) goto error;
    if (aeCreateFileEvent(serverTL->el, fds[2], AE_READABLE, aofChildPipeReadable, NULL) == AE_ERR) goto error;

    g_pserver->aof_pipe_write_data_to_child = fds[1];
    g_pserver->aof_pipe_read_data_from_parent = fds[0];
    g_pserver->aof_pipe_write_ack_to_parent = fds[3];
    g_pserver->aof_pipe_read_ack_from_child = fds[2];
    g_pserver->el_alf_pip_read_ack_from_child = serverTL->el;
    g_pserver->aof_pipe_write_ack_to_child = fds[5];
    g_pserver->aof_pipe_read_ack_from_parent = fds[4];
    g_pserver->aof_stop_sending_diff = 0;
    return C_OK;

error:
    serverLog(LL_WARNING,"Error opening /setting AOF rewrite IPC pipes: %s",
        strerror(errno));
    for (j = 0; j < 6; j++) if(fds[j] != -1) close(fds[j]);
    return C_ERR;
}

void aofClosePipes(void) {
    int fdAofAckPipe = g_pserver->aof_pipe_read_ack_from_child;