展开查看详情
2 .Agenda
● What is MongoDB?
● Single Instances
● Replica-set architecture
● Shard architecture
● Q&A
4 .MongoDB
MongoDB is a free and open-source, cross-platform, document-oriented
database program. Classified as a NoSQL database program, MongoDB uses
JSON-like documents with schemata. MongoDB is developed by MongoDB
Inc.,
5 .MongoDB
● Open source document-oriented database
● Made to run in the cloud, easily scalable
● Quick installation and configuration
● Fast deployment, schema-free
7 .Single Instance
Single Instance
● Commonly used for development/tests
● Embedded systems
8 .Single Instance
MongoDB mobile is currently in Beta
IoT, Android, TV, IOS
10 .Replica-set
● Way to scale out
● Ability to elect a new primary in case of failure (auto HA)
● Data are the same in the replicas, asynchronous replication.
● Single master - PRIMARY
11 .Replica-set
How does a replica-set work?
Main collection when running PRIMARY
replica-set is oplog.rs;
Secondary
Secondary
12 .Replica-set - oplogs
How does a replica-set work?
Secondaries -
Pull oplog and
apply locally
13 .Replica-set
Replica-set
● Heartbeat
● Votes
● Priority
● Arbiter
● Hidden
14 .Replica-set
How does a replica-set work?
Chained replication
Secondaries -
Pull oplog and
apply locally
15 .Replica-set
How does a replica-set work?
Delayed Secondary
Secondaries -
Pull oplog and
apply locally
16 .Replica-set
What if a heartbeat fails?
An election process will promote a secondary to primary when the primary is no
longer available.
The most up to date instance has preference to become a primary, although it is
not always true.
17 .Replica-set
What if a heartbeat fails?
Each instance can have different priorities, in sum the higher the priority, the
greater the probability of the instance becoming a primary.
Arbiters do not hold data, they're only used to
break ties in elections.
Use an arbiter if a replica set has an even
number of members.
18 .Replica-set
● Tweaking the consistency
- readPreference
- writeConcern
19 .Replica-set - writeConcern
The default write concern value is "1", which means that once the primary receives
the operation, it is considered complete.
If an election is triggered, we can lose this operation as it might not be replicated.
It is possible to specify a different writeConcern per query or per connection.
The possible values are:
1, 2, 3, N / "majority" / "tag_name"
20 .Replica-set - readPreference
Read Preference is primary.
Every single read will come from the primary if we don't specify a parameter for the
driver to read from secondaries.
Important! Reading from secondaries may return outdated, stall data.. However,
this is a very common way to scale out read intensive applications.
22 .Sharded Cluster
Config Servers
mongos
Shard1 Shard2
23 .Sharded Cluster architecture
Mongos
Config
Shards
24 .Sharded Cluster - chunks
shard1 shard2
A database can have multiple collections, each
collection can be sharded differently. Each shard has
chunks and their documents.
25 .Sharded Cluster
Primary Shard
Data are split among shards in small chunks by the shard key.
Each chunk has 64MB data (default).
Chunks are distributed among the shards but can also live in a single one.
26 .Sharded Cluster - Shard key
Shard key:
Field(s) that will be used to distribute the data among the shards. Once data is
partitioned there is no way to change the shard key.
(No other key except _id/not part of shard key columns could be unique - you can
explain about this)
A shard key can be used to distribute data in:
● Hashed
● Range
● Zones
27 .Sharded Cluster
Hashed Shard key:
28 .Sharded Cluster
Range Shard key:
29 .Sharded Cluster
TAG Shard key:
热门城市
