Creating a sharded cluster

Example on GitHub: sharded_cluster_crud

In this tutorial, you get a sharded cluster up and running on your local machine and learn how to manage the cluster using the tt utility. This cluster uses the following external modules:

vshard enables sharding in the cluster.
crud allows you to manipulate data in the sharded cluster.

The cluster created in this tutorial includes 5 instances: one router and 4 storages, which constitute two replica sets.

Prerequisites

Before starting this tutorial:

Install the tt utility.
Install tarantool.

Примечание

The tt utility provides the ability to install Tarantool software using the tt install command.

Creating a cluster application

The tt create command can be used to create an application from a predefined or custom template. For example, the built-in vshard_cluster template enables you to create a ready-to-run sharded cluster application.

In this tutorial, the application layout is prepared manually:

Create a tt environment in the current directory by executing the tt init command.
Inside the empty instances.enabled directory of the created tt environment, create the sharded_cluster_crud directory.
Inside instances.enabled/sharded_cluster_crud, create the following files:
- instances.yml specifies instances to run in the current environment.
- config.yaml specifies the cluster configuration.
- storage.lua contains code specific for storages.
- router.lua contains code specific for a router.
- sharded_cluster_crud-scm-1.rockspec specifies external dependencies required by the application.
The next Developing the application section shows how to configure the cluster and write code for routing read and write requests to different storages.

Developing the application

Configuring instances to run

Open the instances.yml file and add the following content:

storage-a-001:
storage-a-002:
storage-b-001:
storage-b-002:
router-a-001:

This file specifies instances to run in the current environment.

Configuring the cluster

This section describes how to configure the cluster in the config.yaml file.

Step 1: Configuring credentials

Add the credentials configuration section:

credentials:
  users:
    replicator:
      password: 'topsecret'
      roles: [ replication ]
    storage:
      password: 'secret'
      roles: [ sharding ]

In this section, two users with the specified passwords are created:

The replicator user with the replication role.
The storage user with the sharding role.

These users are intended to maintain replication and sharding in the cluster.

Важно

It is not recommended to store passwords as plain text in a YAML configuration. Learn how to load passwords from safe storage such as external files or environment variables from Loading secrets from safe storage.

Step 2: Specifying advertise URIs

Add the iproto.advertise section:

iproto:
  advertise:
    peer:
      login: replicator
    sharding:
      login: storage

In this section, the following options are configured:

iproto.advertise.peer specifies how to advertise the current instance to other cluster members. In particular, this option informs other replica set members that the replicator user should be used to connect to the current instance.
iproto.advertise.sharding specifies how to advertise the current instance to a router and rebalancer.

The cluster topology defined in the following section also specifies the iproto.advertise.client option for each instance. This option accepts a URI used to advertise the instance to clients. For example, Tarantool Cluster Manager uses these URIs to connect to cluster instances.

Step 3: Configuring bucket count

Specify the total number of buckets in a sharded cluster using the sharding.bucket_count option:

sharding:
  bucket_count: 1000

Step 4: Defining the cluster topology

Define the cluster topology inside the groups section. The cluster includes two groups:

storages includes two replica sets. Each replica set contains two instances.
routers includes one router instance.

Here is a schematic view of the cluster topology:

groups:
  storages:
    replicasets:
      storage-a:
        # ...
      storage-b:
        # ...
  routers:
    replicasets:
      router-a:
        # ...

To configure storages, add the following code inside the groups section:

storages:
  roles: [ roles.crud-storage ]
  app:
    module: storage
  sharding:
    roles: [ storage ]
  replication:
    failover: manual
  replicasets:
    storage-a:
      leader: storage-a-001
      instances:
        storage-a-001:
          iproto:
            listen:
            - uri: '127.0.0.1:3302'
            advertise:
              client: '127.0.0.1:3302'
        storage-a-002:
          iproto:
            listen:
            - uri: '127.0.0.1:3303'
            advertise:
              client: '127.0.0.1:3303'
    storage-b:
      leader: storage-b-001
      instances:
        storage-b-001:
          iproto:
            listen:
            - uri: '127.0.0.1:3304'
            advertise:
              client: '127.0.0.1:3304'
        storage-b-002:
          iproto:
            listen:
            - uri: '127.0.0.1:3305'
            advertise:
              client: '127.0.0.1:3305'

The main group-level options here are:

roles: This option enables the roles.crud-storage role provided by the CRUD module for all storage instances.
app: The app.module option specifies that code specific to storages should be loaded from the storage module. This is explained below in the Adding storage code section.
sharding: The sharding.roles option specifies that all instances inside this group act as storages. A rebalancer is selected automatically from two master instances.
replication: The replication.failover option specifies that a leader in each replica set should be specified manually.
replicasets: This section configures two replica sets that constitute cluster storages.

To configure a router, add the following code inside the groups section:
```
routers:
  roles: [ roles.crud-router ]
  app:
    module: router
  sharding:
    roles: [ router ]
  replicasets:
    router-a:
      instances:
        router-a-001:
          iproto:
            listen:
            - uri: '127.0.0.1:3301'
            advertise:
              client: '127.0.0.1:3301'
```
The main group-level options here are:
- roles: This option enables the roles.crud-router role provided by the CRUD module for a router instance.
- app: The app.module option specifies that code specific to a router should be loaded from the router module. This is explained below in the Adding router code section.
- sharding: The sharding.roles option specifies that an instance inside this group acts as a router.
- replicasets: This section configures a replica set with one router instance.

Resulting configuration

The resulting config.yaml file should look as follows:

credentials:
  users:
    replicator:
      password: 'topsecret'
      roles: [ replication ]
    storage:
      password: 'secret'
      roles: [ sharding ]

iproto:
  advertise:
    peer:
      login: replicator
    sharding:
      login: storage

sharding:
  bucket_count: 1000

groups:
  storages:
    roles: [ roles.crud-storage ]
    app:
      module: storage
    sharding:
      roles: [ storage ]
    replication:
      failover: manual
    replicasets:
      storage-a:
        leader: storage-a-001
        instances:
          storage-a-001:
            iproto:
              listen:
              - uri: '127.0.0.1:3302'
              advertise:
                client: '127.0.0.1:3302'
          storage-a-002:
            iproto:
              listen:
              - uri: '127.0.0.1:3303'
              advertise:
                client: '127.0.0.1:3303'
      storage-b:
        leader: storage-b-001
        instances:
          storage-b-001:
            iproto:
              listen:
              - uri: '127.0.0.1:3304'
              advertise:
                client: '127.0.0.1:3304'
          storage-b-002:
            iproto:
              listen:
              - uri: '127.0.0.1:3305'
              advertise:
                client: '127.0.0.1:3305'
  routers:
    roles: [ roles.crud-router ]
    app:
      module: router
    sharding:
      roles: [ router ]
    replicasets:
      router-a:
        instances:
          router-a-001:
            iproto:
              listen:
              - uri: '127.0.0.1:3301'
              advertise:
                client: '127.0.0.1:3301'

Adding storage code

Open the storage.lua file and define a space and indexes inside box.watch() as follows:

box.watch('box.status', function()
    if box.info.ro then
        return
    end

    box.schema.create_space('bands', {
        format = {
            { name = 'id', type = 'unsigned' },
            { name = 'bucket_id', type = 'unsigned' },
            { name = 'band_name', type = 'string' },
            { name = 'year', type = 'unsigned' }
        },
        if_not_exists = true
    })
    box.space.bands:create_index('id', { parts = { 'id' }, if_not_exists = true })
    box.space.bands:create_index('bucket_id', { parts = { 'bucket_id' }, unique = false, if_not_exists = true })
end)

The box.schema.create_space() function creates a space. Note that the created bands space includes the bucket_id field. This field represents a sharding key used to partition a dataset across different storage instances.
space_object:create_index() creates two indexes based on the id and bucket_id fields.

Adding router code

Open the router.lua file and load the vshard module as follows:

local vshard = require('vshard')

Configuring build settings

Open the sharded_cluster_crud-scm-1.rockspec file and add the following content:

package = 'sharded_cluster_crud'
version = 'scm-1'
source  = {
    url = '/dev/null',
}

dependencies = {
    'vshard == 0.1.27',
    'crud == 1.5.2'
}
build = {
    type = 'none';
}

The dependencies section includes the specified versions of the vshard and crud modules. To install dependencies, you need to build the application.

Building the application

In the terminal, open the tt environment directory. Then, execute the tt build command:

$ tt build sharded_cluster_crud
   • Running rocks make
No existing manifest. Attempting to rebuild...
   • Application was successfully built

This installs the vshard and crud modules defined in the *.rockspec file to the .rocks directory.

Working with the cluster

Starting instances

To start all instances in the cluster, execute the tt start command:

$ tt start sharded_cluster_crud
   • Starting an instance [sharded_cluster_crud:storage-a-001]...
   • Starting an instance [sharded_cluster_crud:storage-a-002]...
   • Starting an instance [sharded_cluster_crud:storage-b-001]...
   • Starting an instance [sharded_cluster_crud:storage-b-002]...
   • Starting an instance [sharded_cluster_crud:router-a-001]...

Bootstrapping a cluster

After starting instances, you need to bootstrap the cluster as follows:

Connect to the router instance using tt connect:

$ tt connect sharded_cluster_crud:router-a-001
   • Connecting to the instance...
   • Connected to sharded_cluster_crud:router-a-001

Call vshard.router.bootstrap() to perform the initial cluster bootstrap and distribute all buckets across the replica sets:
```
sharded_cluster_crud:router-a-001> vshard.router.bootstrap()
---
- true
...
```

Checking the cluster status

To check the cluster status, execute vshard.router.info() on the router:

sharded_cluster_crud::router-a-001> vshard.router.info()
---
- replicasets:
    storage-b:
      replica:
        network_timeout: 0.5
        status: available
        uri: storage@127.0.0.1:3305
        name: storage-b-002
      bucket:
        available_rw: 500
      master:
        network_timeout: 0.5
        status: available
        uri: storage@127.0.0.1:3304
        name: storage-b-001
      name: storage-b
    storage-a:
      replica:
        network_timeout: 0.5
        status: available
        uri: storage@127.0.0.1:3303
        name: storage-a-002
      bucket:
        available_rw: 500
      master:
        network_timeout: 0.5
        status: available
        uri: storage@127.0.0.1:3302
        name: storage-a-001
      name: storage-a
  bucket:
    unreachable: 0
    available_ro: 0
    unknown: 0
    available_rw: 1000
  status: 0
  alerts: []
...

The output includes the following sections:

replicasets: contains information about storages and their availability.
bucket: displays the total number of read-write and read-only buckets that are currently available for this router.
status: the number from 0 to 3 that indicates whether there are any issues with the cluster. 0 means that there are no issues.
alerts: might describe the exact issues related to bootstrapping a cluster, for example, connection issues, failover events, or unidentified buckets.

Writing and selecting data

To insert sample data, call crud.insert_many() on the router:

crud.insert_many('bands', {
    { 1, box.NULL, 'Roxette', 1986 },
    { 2, box.NULL, 'Scorpions', 1965 },
    { 3, box.NULL, 'Ace of Base', 1987 },
    { 4, box.NULL, 'The Beatles', 1960 },
    { 5, box.NULL, 'Pink Floyd', 1965 },
    { 6, box.NULL, 'The Rolling Stones', 1962 },
    { 7, box.NULL, 'The Doors', 1965 },
    { 8, box.NULL, 'Nirvana', 1987 },
    { 9, box.NULL, 'Led Zeppelin', 1968 },
    { 10, box.NULL, 'Queen', 1970 }
})

Calling this function distributes data evenly across the cluster nodes.

To get a tuple by the specified ID, call the crud.get() function:

sharded_cluster_crud:router-a-001> crud.get('bands', 4)
---
- rows:
  - [4, 161, 'The Beatles', 1960]
  metadata: [{'name': 'id', 'type': 'unsigned'}, {'name': 'bucket_id', 'type': 'unsigned'},
    {'name': 'band_name', 'type': 'string'}, {'name': 'year', 'type': 'unsigned'}]
- null
...

To insert a new tuple, call crud.insert():

sharded_cluster_crud:router-a-001> crud.insert('bands', {11, box.NULL, 'The Who', 1962})
---
- rows:
  - [11, 652, 'The Who', 1962]
  metadata: [{'name': 'id', 'type': 'unsigned'}, {'name': 'bucket_id', 'type': 'unsigned'},
    {'name': 'band_name', 'type': 'string'}, {'name': 'year', 'type': 'unsigned'}]
- null
...

Checking data distribution

To check how data is distributed across the replica sets, follow the steps below:

Connect to any storage in the storage-a replica set:

$ tt connect sharded_cluster_crud:storage-a-001
   • Connecting to the instance...
   • Connected to sharded_cluster_crud:storage-a-001

Then, select all tuples in the bands space:

sharded_cluster_crud:storage-a-001> box.space.bands:select()
---
- - [1, 477, 'Roxette', 1986]
  - [2, 401, 'Scorpions', 1965]
  - [4, 161, 'The Beatles', 1960]
  - [5, 172, 'Pink Floyd', 1965]
  - [6, 64, 'The Rolling Stones', 1962]
  - [8, 185, 'Nirvana', 1987]
...

Connect to any storage in the storage-b replica set:

$ tt connect sharded_cluster_crud:storage-b-001
   • Connecting to the instance...
   • Connected to sharded_cluster_crud:storage-b-001

Select all tuples in the bands space to make sure it contains another subset of data:

sharded_cluster_crud:storage-b-001> box.space.bands:select()
---
- - [3, 804, 'Ace of Base', 1987]
  - [7, 693, 'The Doors', 1965]
  - [9, 644, 'Led Zeppelin', 1968]
  - [10, 569, 'Queen', 1970]
  - [11, 652, 'The Who', 1962]
...

Версия:

Creating a sharded cluster

Prerequisites

Creating a cluster application

Developing the application

Configuring instances to run

Configuring the cluster

Step 1: Configuring credentials

Step 2: Specifying advertise URIs

Step 3: Configuring bucket count

Step 4: Defining the cluster topology

Resulting configuration

Adding storage code

Adding router code

Configuring build settings

Building the application

Working with the cluster

Starting instances

Bootstrapping a cluster

Checking the cluster status

Writing and selecting data

Checking data distribution