The document provides health tips for managing a MongoDB database, emphasizing the importance of keeping data in RAM and monitoring performance metrics such as slow queries, timeouts, and disk I/O spikes. It includes information on database statistics, connection management, and monitoring tools to ensure optimal database performance. Key recommendations include utilizing pre-allocation, logging, sharding, and regular checks on server status and connection pools.

1. MongoDB Health Tips

2. It’s a little different,
but not entirely new.

3. Keep it in RAM. Obviously.
www.flickr.com/photos/comedynose/4388430444/

4. How do you know?
> db.stats()
{
! "collections" : 3,
! "objects" : 379970142,
! "avgObjSize" : 146.4554114991488,
! "dataSize" : 55648683504, 51GB
! "storageSize" : 61795435008,
! "numExtents" : 64,
! "indexes" : 1,
! "indexSize" : 21354514128, 19GB
! "fileSize" : 100816388096,
! "ok" : 1
}
http://www.flickr.com/photos/comedynose/4388430444/

5. Where should it go?
Should it be in
What?
memory?
Indexes Always
Data If you can
http://www.flickr.com/photos/comedynose/4388430444/

6. How you’ll know
1) Slow queries
Thu Oct 14 17:01:11 [conn7410] update sd.apiLog
query: { c: "android/setDeviceToken", a: 1466, u:
"blah", ua: "Server Density Android" } 51926ms
www.flickr.com/photos/tonivc/2283676770/

7. How you’ll know
2) Timeouts
cursor timed out (20000 ms)

8. How you’ll know
3) Disk i/o spikes
www.flickr.com/photos/daddo83/3406962115/

9. Watch your storage
1) Pre-alloc

10. Watch your storage
2) Sharding maxSize

11. Watch your storage
3) Logging
--quiet
db.runCommand("logRotate");
killall -SIGUSR1 mongod

12. Watch your storage
4) Journaling
david@rs2b ~: ls -alh /mongodbdata/journal/
total 538M
drwxrwxr-x 2 david david 29 Mar 20 16:50 .
drwx------ 4 david david 4.0K Mar 13 09:50 ..
-rw------- 1 david david 538M Mar 20 17:00 j._862
-rw------- 1 david david 88 Mar 20 17:00 lsn

13. db.serverStatus()

14. db.serverStatus()
1) Used connections
www.flickr.com/photos/armchaircaver/2061231069/

15. db.serverStatus()
2) Available connections

16. Fri Nov 19 17:24:32 [mongosMain] Listener: accept() returns -1 errno:24 Too many open files
Fri Nov 19 17:24:32 [mongosMain] Listener: accept() returns -1 errno:24 Too many open files
Fri Nov 19 17:24:32 [mongosMain] Listener: accept() returns -1 errno:24 Too many open files
Fri Nov 19 17:24:32 [mongosMain] Listener: accept() returns -1 errno:24 Too many open files
Fri Nov 19 17:24:32 [mongosMain] Listener: accept() returns -1 errno:24 Too many open files
Fri Nov 19 17:24:32 [mongosMain] Listener: accept() returns -1 errno:24 Too many open files
Fri Nov 19 17:24:32 [mongosMain] Listener: accept() returns -1 errno:24 Too many open files
Fri Nov 19 17:24:32 [mongosMain] Listener: accept() returns -1 errno:24 Too many open files
Fri Nov 19 17:24:32 [mongosMain] Listener: accept() returns -1 errno:24 Too many open files
Fri Nov 19 17:24:32 [mongosMain] Listener: accept() returns -1 errno:24 Too many open files
Fri Nov 19 17:24:32 [mongosMain] Listener: accept() returns -1 errno:24 Too many open files
Fri Nov 19 17:24:32 [mongosMain] Listener: accept() returns -1 errno:24 Too many open files
Fri Nov 19 17:24:32 [mongosMain] Listener: accept() returns -1 errno:24 Too many open files
Fri Nov 19 17:24:32 [conn2335] getaddrinfo("rs1b") failed: No address associated with hostname
Fri Nov 19 17:24:32 [conn2335] getaddrinfo("rs1d") failed: No address associated with hostname
Fri Nov 19 17:24:32 [conn2335] getaddrinfo("rs1c") failed: No address associated with hostname
Fri Nov 19 17:24:32 [conn2335] getaddrinfo("rs2b") failed: No address associated with hostname
Fri Nov 19 17:24:32 [conn2335] getaddrinfo("rs2d") failed: No address associated with hostname
Fri Nov 19 17:24:32 [conn2335] getaddrinfo("rs2c") failed: No address associated with hostname
Fri Nov 19 17:24:32 [conn2335] getaddrinfo("rs2a") failed: No address associated with hostname
Fri Nov 19 17:24:32 [conn2268] checkmaster: rs2b:27018 { setName: "set2", ismaster: false, secondary: true, hosts: [ "rs2b:27018", "rs2d:27018", "rs2c:27018", "rs2a:27018" ], arbiters:
[ "rs2arbiter:27018" ], primary: "rs2a:27018", maxBsonObjectSize: 8388608, ok: 1.0 }
MessagingPort say send() errno:9 Bad file descriptor (NONE)
Fri Nov 19 17:24:32 [conn2268] checkmaster: caught exception rs2d:27018 socket exception
Fri Nov 19 17:24:32 [conn2268] MessagingPort say send() errno:9 Bad file descriptor (NONE)
Fri Nov 19 17:24:32 [conn2268] checkmaster: caught exception rs2c:27018 socket exception
Fri Nov 19 17:24:32 [conn2268] MessagingPort say send() errno:9 Bad file descriptor (NONE)
Fri Nov 19 17:24:32 [conn2268] checkmaster: caught exception rs2a:27018 socket exception
Fri Nov 19 17:24:33 [conn2330] getaddrinfo("rs1a") failed: No address associated with hostname
Fri Nov 19 17:24:33 [conn2330] getaddrinfo("rs1b") failed: No address associated with hostname
Fri Nov 19 17:24:33 [conn2330] getaddrinfo("rs1d") failed: No address associated with hostname
Fri Nov 19 17:24:33 [conn2330] getaddrinfo("rs1c") failed: No address associated with hostname
Fri Nov 19 17:24:33 [conn2327] getaddrinfo("rs2b") failed: No address associated with hostname
Fri Nov 19 17:24:33 [conn2327] getaddrinfo("rs2d") failed: No address associated with hostname
Fri Nov 19 17:24:33 [conn2327] getaddrinfo("rs2c") failed: No address associated with hostname
Fri Nov 19 17:24:33 [conn2327] getaddrinfo("rs2a") failed: No address associated with hostname
Fri Nov 19 17:24:33 [conn2126] getaddrinfo("rs2b") failed: No address associated with hostname
Fri Nov 19 17:24:33 [conn2126] getaddrinfo("rs2d") failed: No address associated with hostname
Fri Nov 19 17:24:33 [conn2126] getaddrinfo("rs2c") failed: No address associated with hostname
Fri Nov 19 17:24:33 [conn2126] getaddrinfo("rs2a") failed: No address associated with hostname
Fri Nov 19 17:24:33 [conn2343] getaddrinfo("rs1b") failed: No address associated with hostname
Fri Nov 19 17:24:33 [conn2343] getaddrinfo("rs1d") failed: No address associated with hostname
Fri Nov 19 17:24:33 [conn2343] getaddrinfo("rs1c") failed: No address associated with hostname
Fri Nov 19 17:24:34 [conn2332] getaddrinfo("rs1b") failed: No address associated with hostname
Fri Nov 19 17:24:34 [conn2332] getaddrinfo("rs1d") failed: No address associated with hostname
Fri Nov 19 17:24:34 [conn2332] getaddrinfo("rs1c") failed: No address associated with hostname
Fri Nov 19 17:24:34 [conn2332] getaddrinfo("rs2b") failed: No address associated with hostname
Fri Nov 19 17:24:34 [conn2332] getaddrinfo("rs2d") failed: No address associated with hostname
Fri Nov 19 17:24:34 [conn2332] getaddrinfo("rs2c") failed: No address associated with hostname
Fri Nov 19 17:24:34 [conn2332] getaddrinfo("rs2a") failed: No address associated with hostname
Fri Nov 19 17:24:34 [conn2343] getaddrinfo("rs2d") failed: No address associated with hostname
Fri Nov 19 17:24:34 [conn2343] getaddrinfo("rs2c") failed: No address associated with hostname
Fri Nov 19 17:24:34 [conn2343] getaddrinfo("rs2a") failed: No address associated with hostname
Fri Nov 19 17:24:34 [conn2343] trying reconnect to rs2d:27018

17. connPoolStats
> db.runCommand("connPoolStats")
{
! "hosts" : {
! ! "config1:27019" : {
! ! ! "available" : 2,
! ! ! "created" : 6
! ! },
! ! "set1/rs1a:27018,rs1b:27018" : {
! ! ! "available" : 1,
! ! ! "created" : 249
! ! },
...
! },
! "totalAvailable" : 5,
! "totalCreated" : 1002,
! "numDBClientConnection" : 3490,
! "numAScopedConnection" : 3,
}

18. db.serverStatus()
3) Index counters
"indexCounters" : {
! ! "btree" : {
! ! ! "accesses" : 15180175,
! ! ! "hits" : 15178725,
! ! ! "misses" : 1450,
! ! ! "resets" : 0,
! ! ! "missRatio" : 0.00009551932
! ! }
! },

19. db.serverStatus()
4) Op counters
www.flickr.com/photos/cosmic_bandita/2395369614/

20. db.serverStatus()
5) Background flushing
Picture is unrelated! Mmm, ice cream.

21. db.serverStatus()
6) Dur

22. rs.status()
{
! "_id" : 1,
! "name" : "rs3b:27018",
! "health" : 1,
! "state" : 2,
! "stateStr" : "SECONDARY",
! "uptime" : 1886098,
! "optime" : {
! ! "t" : 1291252178000,
! ! "i" : 13
! },
! "optimeDate" : ISODate("2010-12-02T01:09:38Z"),
"lastHeartbeat" : ISODate("2010-12-02T01:09:38Z")
},
www.ex-astris-scientia.org/inconsistencies/ent_vs_tng.htm (yes it’s a replicator from Star Trek)

23. rs.status()
1) myState
Value Meaning
0 Starting up (phase 1)
1 Primary
2 Secondary
3 Recovering
4 Fatal error
5 Starting up (phase 2)
6 Unknown state
7 Arbiter
8 Down
en.wikipedia.org/wiki/State_of_matter

24. rs.status()
2) Optime
"optimeDate" : ISODate("2010-12-02T01:09:38Z")
www.flickr.com/photos/robbie73/4244846566/

25. rs.status()
3) Heartbeat
"lastHeartbeat" : ISODate("2010-12-02T01:09:38Z")
www.flickr.com/photos/drawblindfaith/3400981091/

26. mongostat

27. mongostat
1) faults
Picture is unrelated! Snowmobile in Norway.

28. mongostat
2) locked
www.flickr.com/photos/bbusschots/4541573665/

29. mongostat
3) index miss
www.flickr.com/photos/gareandkitty/276471187/

30. mongostat
4) queues

31. mongostat
5) Diagnostics

32. Current operations
db.currentOp();
{
! ! ! "opid" : "shard1:299939199",
! ! ! "active" : true,
! ! ! "lockType" : "write",
! ! ! "waitingForLock" : false,
! ! ! "secs_running" : 15419,
! ! ! "op" : "remove",
! ! ! "ns" : "sd.metrics",
! ! ! "query" : {
! ! ! ! "accId" : 1391,
! ! ! ! "tA" : {
! ! ! ! ! "$lte" : ISODate("2010-11-24T19:53:00Z")
! ! ! ! }
! ! ! },
! ! ! "client" : "10.121.12.228:44426",
! ! ! "desc" : "conn"
! ! },
www.flickr.com/photos/jeffhester/2784666811/

33. Monitoring tools
Run yourself
Ganglia

34. Monitoring tools
Server Density

38. Monitoring tools
www.mongomonitor.com

39. Recap

40. Recap
Keep it in RAM

41. Recap
Keep it in RAM
Watch your storage

42. Recap
Keep it in RAM
Watch your storage
db.serverStatus()
rs.status()

43. David Mytton
@davidmytton
david@boxedice.com
www.mongomonitor.com
Woop Japan!