There are several open source admin UI projects for MongoDB including web-based and native desktop applications. MongoHub is a native Mac OS application that allows CRUD operations, monitoring, and querying across multiple databases and collections. MongoDB includes monitoring and diagnostic tools like mongostat and mongosniff. Replication in MongoDB works by having a primary node that performs writes which are then replicated to other nodes, providing auto failover of the primary. Sharding in MongoDB distributes data across shards for improved performance, with the choice of shard key impacting load distribution. Map/reduce functions can be written for aggregation capabilities.

1. MongoDB
Part II

2. Admin UI
There are a number of open source projects that provide an
admin console to your MongoDB instances.
Some are web UI and some are native UI applications.
MongoHub is a native Mac OS app that has many great
bells and whistles (my personal fav)
MongoVUE is a native Windows .NET
Many Ruby web based apps that run using Sinatra and
MongoDB driver (Futon4Mongo, Mongo3, etc)

3. MongoHub details
Retail time CRUD operations monitoring
Multi-database views
Detailed collection views
Interactive querying
MySQL Import / Export

4. Monitoring and Diagnostics
The newer versions on MongoDB come with
mongostat
sudo mongosniff --source NET lo0
Could be straight forward to hook up custom Nagios
alerts and monitoring with this data

5. Replication
Old way < 1.6 New way >= 1.6

6. How it all works
MongoDB has a primary node who does the writes
The data is then replicated to the rest of the set
MongoDB has auto fail-over so if the current primary
pukes, then another node is "elected"
A write is theoretically complete when a "majority" of
the nodes in the set received the data
ma·jor·i·ty noun mə-ˈjor-ə-tē
In MongoDB terms it means there is at least 1
primary and at least 1 other node running
If only 1 node is left standing...well that sucks

7. The Ugly Truth
If a node fails-over during replication and all the nodes
haven't received it...
The data drops ;..(

8. MongoDB Make Believe Land
Node 2 Node 3

9. MongoDB Make Believe Land
Node 2 Node 3

10. MongoDB Make Believe Land
Node 2 Node 3

11. MongoDB Make Believe Land
Node 2 Node 3

12. How do I set that up?
Well, its super hard...
...NOT to do it right
I <3 MongoDB documentation
http://www.mongodb.
org/display/DOCS/Replica+Set+Tutorial
You can also do N nodes and 1 arbiter, where N % 2 == 0

13. "Shards are the secret sauce..."

14. I just shar(d|t)ed

15. Shards
Shard 2
Shard 1
Node 2 Node 3

16. Choose wisely!
> When sharding you must
choose your shard key wisely
for an even distribution of load
and data
> It's best to choose composite
shard keys and determine the
most common queries
> Helps ensure your query
targets a single shard vs.
querying ALL shards

17. Map / Reduce

18. Map / Reduce
> You can write map/reduce
functions in the shell and with
any of the supported MongoDB
drivers

19. Logging with MongoDB
Got this link from the MongoDB
meetup at Engine Yard this past
week.
Thanks to Robert Stewart for
the great presentation:
http://www.slideshare.
net/WombatNation/logging-
app-behavior-to-mongo-db