Function trimReplicationBacklog

src/replication.cpp:5766–5778

If we automatically grew the backlog we need to trim it back to the config setting when possible

// If we automatically grew the backlog we need to trim it back to
//  the config setting when possible
void trimReplicationBacklog() {
    serverAssert(GlobalLocksAcquired());
    serverAssert(g_pserver->repl_batch_offStart < 0);   // we shouldn't be in a batch
    if (g_pserver->repl_backlog_size <= g_pserver->repl_backlog_config_size)
        return; // We're already a good size
    if (g_pserver->repl_lowest_off > 0 && (g_pserver->master_repl_offset - g_pserver->repl_lowest_off + 1) > g_pserver->repl_backlog_config_size)
        return; // There is untransmitted data we can't truncate
    if (cserver.force_backlog_disk && g_pserver->repl_backlog == g_pserver->repl_backlog_disk)
        return; // We're already in the disk backlog and we're told to stay there

    serverLog(LL_NOTICE, "Reclaiming %lld replication backlog bytes", g_pserver->repl_backlog_size - g_pserver->repl_backlog_config_size);
    resizeReplicationBacklog(g_pserver->repl_backlog_config_size);
}