Updated Introduction to MongoDB

Introduction to MongoDB
A No-SQL Persistence Alternative
C E N T R A L - T E X A S - . N E T - U S E R - G R O U P

Chris Edwards

h t t p : / / c h r i s e d wa r d s . d r e a m h o s t e r s . c o m

About Me
Chris Edwards
Senior Developer at BancVue Ltd.
Email: ChrisEdwards357@gmail.com
Blog: http://chrisedwards.dreamhosters.com
Twitter: @cedwards
Github: http://github.com/chrisedwards
(Sample code for this talk is posted)

CENTRAL-TEXAS-.NET-USER-GROUP

MongoDB Session Roadmap
• What is the NoSQL Movement?
• What is MongoDB?
• Installing
• Using the Mongo Shell
• Accessing MongoDB via C#
- Basic Driver (mongodb-csharp driver)
- Using Linq
- Using NoRM for strong typing
• Accessing MongoDB via REST
• Replication
• Sharding


What is No-SQL?


What is No-SQL?

“Next Generation Databases mostly addressing some of the points:
being non-relational, distributed, open-source and horizontal
scalable. ... schema-free, easy replication support, simple API,
eventually consistent ...”
- nosql-database.org


What is No-SQL?

“Next Generation Databases mostly addressing some of the points:
being non-relational, distributed, open-source and horizontal
scalable. ... schema-free, easy replication support, simple API,
eventually consistent ...”
- nosql-database.org

• Non-Relational • Schema-Free
• Distributed • Replication Support
• Open-Source • Simple API
• Horizontally Scalable • Eventually Consistent


What is No-SQL?
It’s about using the right tool for the job.
• Not all systems have the same data needs.
• Sql is not the only option, nor is it always the best one.
• Consider all options carefully and choose wisely.


What is No-SQL?

Not Only SQL


What is No-SQL?

Not Only SQL
It’s not about flaming SQL.


What is No-SQL?

Not Only SQL
It’s not about flaming SQL.
Its about opening our minds to new technologies.

What is MongoDB?
• Document-oriented database
- Uses JSON (BSON actually)
• Schema-free
• Performant
- Written in C++
- Full index support
- No transactions (has atomic operations)
“Mongo only pawn in game of life”
- Memory-mapped files (delayed writes)
• Scalable
- Replication
- Auto-Sharding
• Commercially supported (10gen)
- Lots of documentation


Other Features of MongoDB
• Document-based queries
- Flexible document queries expressed in JSON/Javascript.
• Map Reduce
- Flexible aggregation and data processing.
- Queries run in parallel on all shards.
• GridFS
- Store files of any size easily.
• Geospatial Indexing
- Find object based on location. (i.e. find closest n items to x)
• Many Production Deployments


Other Features of MongoDB
• Supported Platforms
- OSX
- Linux
- Solaris
- Windows
- FreeBSD


MongoDB Basic Concepts
Document
- Analogous to a row in RDBMS
- Represented as JSON (BSON)
- Hierarchical
- Can reference other documents


Document Collection
- Analogous to a row in RDBMS - Analogous to a table in RDBMS
- Represented as JSON (BSON) - Collection of documents
- Hierarchical - Documents can be anything
- Can reference other documents - Advantageous if they are similar


Embedding
- Analogous to a foreign key
- Think “pre-joined relationship”.
- Clearer conceptual model.
- DDD Aggregate Root
- Can be
- Sub Objects
- Collections


Embedding
- Think “pre-joined relationship”
- Clearer conceptual model.
- DDD Aggregate Root
- Can be
- Sub Objects
- Collections

References
- Think “relationship”


MongoDB Basic Operations
Querying
All the following queries will find the document.


Querying

By property value


Querying

By property value

By embedded object property value


Querying

By property value


With comparison operators


Querying

By property value


With comparison operators

Values in collections (implicit “in”)


Indexing


Indexing
On property value


Indexing
On property value

On embedded object property


Indexing
On property value


On embedded collections


Indexing
On property value


On embedded collections

On multiple keys


Inserting


Updating
Using Query/Modify/Save


Updating
Using Query/Modify/Save

• Requires each object to be loaded in memory.
• Requires multiple hits to the database.
• Very inefficient.


Updating
Using Atomic Updates


Updating
Using Atomic Updates

• Analogous to transactions.
• Requires only one trip to the database.
• Operations are atomic.
• Can perform multiple operations at once.


MongoDB System Components



mongod.exe
The database server



mongod.exe mongo.exe
The database server The interactive shell



mongod.exe mongo.exe
The database server The interactive shell

mongos.exe
The sharding router


Installing MongoDB
1. Download MongoDB. www.mongodb.com/downloads

2. Extract it.
3. Create the data folder. usually /data/db -or- C:datadb

4. Run mongod.exe


Installing MongoDB
1. Download MongoDB. www.mongodb.com/downloads

2. Extract it.
3. Create the data folder. usually /data/db -or- C:datadb

4. Run mongod.exe

That’s it!


Accessing MongoDB via the Shell
• Inserting a document into a collection.
• Querying a collection.
• Modifying a document.
• Deleting a document.


Accessing MongoDB via the Shell
• Inserting a document into a collection.
• Querying a collection.
• Modifying a document.
• Deleting a document.

Lets do it!


Accessing MongoDB via C#
• mongo-csharp-driver
- 10gen-supported driver
• mongodb-csharp driver
- Most mature driver for C#.
- Includes LINQ support
• NoRM driver
- Using NoRM for strongly typed access.
- Also has LINQ support


• mongo-csharp-driver
- 10gen-supported driver
• mongodb-csharp driver
- Most mature driver for C#.
- Includes LINQ support
• NoRM driver
- Using NoRM for strongly typed access.
- Also has LINQ support

For more information and/or drivers for other languages, check out www.mongodb.org



Demo


Accessing MongoDB via REST
• To enable basic REST interface, use --rest command line.
- mongod.exe --rest
• REST interface uses port +1000.
- http://127.0.0.1:28017/database/collection/
- http://127.0.0.1:28017/database/collection/?filter&Field=Value

• Full REST support is provided by the Sleepy.Mongoose lib.
- http://github.com/kchodorow/sleepy.mongoose


MongoDB Replication
• Master-Slave
- Master - mongod.exe --master
- Slave - mongod.exe --source <master url>:<master port>
- Slave can use --slavedelay <delay in seconds> to have a rolling backup.

• Replica Pairs (obsolete)
• Replica Sets (Suggested Approach)
- Full Failover support
- Supports more than 2 servers in a replica cluster
- Data center and rack aware
- Can have passive set members (slaves) that are never primary
• Master-Master (limited)
- Both masters are also configured as slaves
- Safe for insert, delete by id, and any queries
- Unsafe for concurrent updates of single object


MongoDB Auto-Sharding: Features


• Based on a defined shard key.


• Auto-balances as shard servers are added or removed.
- Can go from single master to sharded system with zero downtime.


• Failover handled through replica sets. (each shard replicated)


• Failover handled through replica sets. (each shard replicated)
• Map Reduce queries are run in parallel across shards.


MongoDB Auto-Sharding: Architecture
• Shard Servers
- Instance of mongod.exe --shardsvr
- Optionally configured with a replication set for failover.
• Config Servers
- Instance of mongod.exe --configsvr
- Usually a group of 3. System is up so long as 1 config server is running.
• Shard Routers
- Instance of mongos.exe --configdb <config server>:<config port>
- Acts like mongod.exe to clients.
- Can be on the same box as a shard server.
- Can run on appserver to reduce traffic.


Sample Logical Architecture


Sample Physical Architecture


MongoDB Auto-Sharding: Configuration
Startup Servers
• Startup Shard Servers
- mongod.exe --shardsvr

• Startup Config Servers
- mongod.exe --configsvr

• Startup Shard Routers
- mongos.exe --configdb <config server>:<config port>

Configure Cluster
• Add Shards to the Cluster
- Execute the following command for each shard using either the driver or shell.
- db.runcommand( { addshard : “<shard server>:<shard server port>” } );

• Enable Sharding on the Databases to Shard
- db.runcommand( { enablesharding : “<dbname>” } );

• Specify Collections to Shard
- db.runcommand( { shardCollection : “<collection>”, key : <key pattern> } );


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