Verification after data migration between MongoDB clusters

dbHashVerifier.js

/*
Author: Katkam Nitin Reddy < redknitin [at] gmail [dot] com >
Date: September 26, 2022
Description: This script uses the dbHash command to compare the source and destination clusters

Using the Mongo shell, connect to the source cluster and run this script
This script needs write access to the target cluster to write the log
*/

//Commented this out - We are no longer writing to a log; console output only
//verificationDbName = 'verifyLog'

otherMongoUri = 'mongodb://username_here:[email protected]:27017,cluster0-shard-00-01.fdu3e.mongodb.net:27017,cluster0-shard-00-02.fdu3e.mongodb.net:27017/?tls=true&replicaSet=atlas-jusd5q-shard-0'  //this is the target's URI
otherMongo = new Mongo(otherMongoUri)

dbList = db.adminCommand({listDatabases: 1}).databases.map(i => i.name)
for (i=0; i<dbList.length; i++) {	
	//Skipping system DBs
	if (dbList[i]=="admin" || dbList[i]=="config" || dbList[i]=="local") continue;

	collList = db.getSiblingDB(dbList[i]).getCollectionNames()
	hashes = db.getSiblingDB(dbList[i]).runCommand({dbHash: 1}).collections
	otherHashes = otherMongo.getDB(dbList[i]).runCommand({dbHash: 1}).collections
	for (j=0; j<collList.length; j++) {
		isMatched = false
		if (hashes[collList[j]] == otherHashes[collList[j]]) {
			print("YES: " + dbList[i] + "-" + collList[j])
			isMatched = true
		} else {
			print("NO: " + dbList[i] + "-" + collList[j])
		}

		//Commented this out to prevent writes
		//otherMongo.getDB(verificationDbName).hashMatch.insertOne({_id: {db: dbList[i], coll: collList[j]}, matched: isMatched})
	}
}

//Commented this out - We are no longer writing to a log; console output only
//List mismatched collections
//otherMongo.getDB(verificationDbName).hashMatch.find({matched: false, "_id.db": {$nin: ["admin", "local", "config"]}})