The document discusses various MongoDB command line tools and how to use them. It provides examples of using core tools like mongo, mongod, and mongostat to get database information and view performance metrics. Other tools covered include mongodump for backups, mongorestore for restores, mongoexport for data exports, and bsondump for document conversions. Third party tools like automongobackup and mongolog are also mentioned.

1. mongo*
Just what do those commands do?
By Russell Smith

2. /usr/bin/whoami
• Russell Smith
• Consultant for UKD1 Limited
• I Specialise in helping companies going through rapid growth;
• Code, architecture, infrastructure, devops, sysops, capacity planning, etc
• <3 MongoDB, Neo4j, MySQL, Riak, Gearman, Kohana, PHP, Debian, Puppet, etc...

3. Huh?
• MongoDB ships with a variety of CLI tools
• Some popular;
mongodump, mongorestore, mongostat, mongo
• Some less so;
mongosniff, mongoexport, mongoimport, bsondump, etc

4. Core

5. mongo
• Probably the most commonly used
• ‘Hidden’ gems;
• ~/.mongorc.js - will be executed by default
• --eval “some js” - evaluates Javascript and exits

6. mongo (cont.)
~ mongo test --eval "printjson(db.getCollectionNames())"
MongoDB shell version: 2.1.0-pre-
connecting to: test
[ "fs.chunks", "fs.files", "system.indexes", "system.profile", "test" ]
~ mongo test --quiet --eval "printjson(db.getCollectionNames())"
[ "fs.chunks", "fs.files", "system.indexes", "system.profile", "test" ]

7. ~/.mongorc.js
x = db.queue.count({state:4});
if (x > 0)
{
print('WARNING: ' + x + ' hung jobs');
}

8. ~/.mongorc.js
~ mongo
MongoDB shell version: 2.1.0-pre-
connecting to: test
WARNING: 2 hung jobs
>

9. mongod
• The server itself
• Useful:
• --fastsync - allows (much) faster starting of a replset member by
using a (recent) snapshot of a peer
• --keyFile - replset / sharding authentication file

10. mongos
• Sits in front of your shard servers and directs queries
• --keyFile

11. Common

12. mongodump
• Used to take backups
• Common options:
• --oplog
• -d
• -c

13. mongodump (cont.)
~ mongodump -d test -c queue -q "{state:4}"
connected to: 127.0.0.1
DATABASE: test
to
dump/test
test.queue to dump/test/queue.bson
2 objects

14. mongorestore
• Restores backups taken with mongodump
• Interesting options;
• --filter
• --oplogReplay
• Possible performance issues with custom (non ObjectId) _id

15. mongorestore (cont.)
mongorestore -d test -c queue --filter "{state:4}" dump/test/queue.bson
connected to: 127.0.0.1
Mon Sep 19 07:34:03 dump/test/queue.bson
Mon Sep 19 07:34:03
going into namespace [test.queue]
764 objects found
2 objects processed

16. mongostat
• Produces periodically updated stats
• Useful in watching server load & spotting general performance issues

17. Common Cursor Total
operations paging data size queues
fsync active
locked
flushes clients

18. mongostat (cont’d)
• Watch for;
• faults (page faults)
• idx miss (index btree page misses)
• locked (percentage of time globally locked)
• repl (it should normally be M or SEC)

19. Others

20. mongoexport
• Useful to export data for use with another database or program
• You may specify down to the field level using a filter if needed
• Can export as;
• JSON (default)
• CSV

21. mongoimport
• Imports data in to mongodb
• Currently supports importing;
• JSON
• CSV
• TSV

22. mongoimport (cont’d)
• Useful options include;
• --upsert - allows updating objects that exist already
(see --upsertFields)
• --headerline - if your CSV / TSV contains headers
• -f / --fields - specify field names

23. bsondump
bsondump test.bson --type json
{ "_id" :
ObjectId( "4e72f51414345f302b0eea2e" ),
• Convert bson -> json
"test" : 1 }
1 objects found

24. bsondump (cont.)
bsondump test.bson --type debug
--- new object ---
size : 36
_id
• Debug info:
type: 7 size: 17
test
type: 1 size: 14
etc

25. mongofiles
~ mongofiles put test.txt
connected to: 127.0.0.1
added file: { _id: ObjectId('4e761b07c21062d06b349819'), filename:
"test.txt", chunkSize: 262144, uploadDate: new Date(1316363015625),
md5: "d41d8cd98f00b204e9800998ecf8427e", length: 12256 }
done!

26. mongofiles (cont.)
~ mongofiles list
connected to: 127.0.0.1
test.txt
12256

27. mongotop
• New in 1.9
• Collection level load stats

28. mongosniff
• Used for sniffing the traffic between client / server
• Can forward traffic
• Only really useful for debugging...

30. mongo-perf
• Does not ship with mongodb
See : https://github.com/mongodb/mongo-perf
• I can’t compile it, but it probably works

31. Useful third party tools

32. tungsten replicator
mysql> create table foo(id int primary key, msg varchar(35));
Query OK, 0 rows affected (0.05 sec)
mysql> insert into foo values(1, 'hello from MySQL!');
Query OK, 1 row affected (0.00 sec)
> db.foo.find()
{ "_id" : ObjectId("4dc77bacad9092bd1aef046d"), "id" : "1", "data" :
"hello from MySQL!" }
• http://code.google.com/p/tungsten-replicator/
• http://code.google.com/p/tungsten-replicator/wiki/

33. automongobackup
• A port of the popular AutoMySQLBackup
• Rotates & compresses backups
• https://github.com/micahwedemeyer/automongobackup

34. mongolog
• Full query logging
• Uses mongosniff
• Will be on github soon

35. Other interesting projects
• Eliots Munin plugins : https://github.com/erh/mongo-munin
• gridfs-fuse : https://github.com/mikejs/gridfs-fuse

36. Further reading
• Tungsten with Mongo details
http://scale-out-blog.blogspot.com/2011/05/introducing-mysql-to-mongodb.html
• Javascript shell API
http://api.mongodb.org/js/current/
• Admin UI’s
http://www.mongodb.org/display/DOCS/Admin+UIs
• Hacking the shell
http://bit.ly/r2vghH

37. Questions?