MongoDB 5.0+ Initial Sync Progress Monitoring

measureInitialSyncProgress.js

/*
* measureInitialSyncProgress
* @author Alex Bevilacqua <[email protected]>
* @updated 2021-02-23
*
* Can be run against a MongoDB 4.2.12+ mongod that is in STARTUP2 (intitial sync) state to gain some
* insight into how the sync is progressing based on the improvements introduced with SERVER-47863.
* For versions of MongoDB < 4.2.12, see https://www.alexbevi.com/blog/2020/02/13/mongodb-initial-sync-progress-monitoring
*
* usage:
*   mongo --quiet --eval "load('measureInitialSyncProgress.js'); measureInitialSyncProgress();"
*   // pass a value in milliseconds to measureInitialSyncProgress to override the refresh interval
*   // default: 5000 (5 seconds)
*   mongo --quiet --eval "load('measureInitialSyncProgress.js'); measureInitialSyncProgress(1000);"
*/
function msToTime(duration) {
  var milliseconds = parseInt((duration % 1000) / 100),
    seconds = Math.floor((duration / 1000) % 60),
    minutes = Math.floor((duration / (1000 * 60)) % 60),
    hours = Math.floor((duration / (1000 * 60 * 60)) % 24);

  hours = (hours < 10) ? "0" + hours : hours;
  minutes = (minutes < 10) ? "0" + minutes : minutes;
  seconds = (seconds < 10) ? "0" + seconds : seconds;

  return hours + ":" + minutes + ":" + seconds + "." + milliseconds;
}

var getReadableFileSizeString = function (fileSizeInBytes) {
  var i = -1;
  var byteUnits = [' kB', ' MB', ' GB', ' TB', 'PB', 'EB', 'ZB', 'YB'];
  do {
    fileSizeInBytes = fileSizeInBytes / 1024;
    i++;
  } while (fileSizeInBytes > 1024);
  return Math.max(fileSizeInBytes, 0.1).toFixed(1) + byteUnits[i];
};

function measureSyncProgress(previousResults) {
  var cmd = db.adminCommand({ replSetGetStatus: 1, initialSync: 1 });
  if (!cmd.hasOwnProperty("initialSyncStatus")) {
    print("Node not currently performing an initial sync");
    return { exit: true };
  }

  var status = cmd.initialSyncStatus;

  db.adminCommand({ replSetGetStatus: 1, initialSync: 1 }).initialSyncStatus.approxTotalBytesCopied

  var now = new Date();
  var started = status.initialSyncStart;

  var approxTotal = status.approxTotalDataSize;
  var approxCopied = status.approxTotalBytesCopied;

  var message = "Cloned " + getReadableFileSizeString(approxCopied) + " of " + getReadableFileSizeString(approxTotal) + " in " + msToTime(now - started);

  if (previousResults !== undefined && previousResults.hasOwnProperty("refreshIntervalMS") !== null && previousResults.hasOwnProperty("copied")) {
    var refreshInterval = previousResults.refreshIntervalMS / 1000;
    var intervalProgress = approxCopied - previousResults.copied;
    if (intervalProgress == 0) {
      message += " (No progress in past " + refreshInterval + " second(s))";
    } else {
      var rate = intervalProgress / refreshInterval;
      // We no longer have to calculate remaining ourselves as SERVER-53017 has fixed remainingInitialSyncEstimatedMillis
      // var remaining = msToTime(((approxTotal - approxCopied) / rate) * 1000);
      message += " (" + getReadableFileSizeString(intervalProgress) + " in past " + refreshInterval;
      message += " second(s)) at a rate of " + getReadableFileSizeString(rate) + "/second - ";
      message += msToTime(status.remainingInitialSyncEstimatedMillis) + " to go!";
    }
  }
  print(message);
  return { copied: approxCopied };
}

function measureInitialSyncProgress(refreshIntervalMS) {
  var dbver = db.version().split('-')[0];
  if (dbver < "4.2.12") {
    print("MongoDB 4.2.12 or greater required but found MongoDB " + dbver);
    print("For previous versions see https://www.alexbevi.com/blog/2020/02/13/mongodb-initial-sync-progress-monitoring/");
    return;
  }

  if (refreshIntervalMS === undefined || refreshIntervalMS === null) {
    refreshIntervalMS = 5000;
  }

  var result = measureSyncProgress(result);
  result["refreshIntervalMS"] = refreshIntervalMS;
  while (!result.exit) {
    sleep(refreshIntervalMS);
    result = measureSyncProgress(result);
    result["refreshIntervalMS"] = refreshIntervalMS;
  }
}