Redis database support

[Jibin-Tomy-Narvar]

Add support for databases in a Redis cluster.

[kmuthukk]

Hi @Jibin-Tomy-Narvar

So the ask is for namespacing (via the "select <db_index>" like operation that Redis supports), too allow for different namespaces to co-exist, and be created/dropped independent of each other, correct?

regards,
Kannan

[Jibin-Tomy-Narvar]

Hi @kmuthukk ,

My expectation was to be able to create a database with a name and connect to it. After that all the subsequent operations should be performed with respect to that database.

Thanks
Jibin

[kmuthukk]

Makes sense. Thanks.

@amitanandaiyer : Assigning this one to you.

[rkarthik007]

Redis Database Support

Motivation

This feature allows apps to interact with only their data by creating “databases” in order to achieve this. With YugaByte DB (which offers a persistent and elastic Redis database across multiple nodes) this feature has a lot of value.

Usage

By default, all queries are applied to the database 0.

NOTE: YEDIS will support <db-id> being any free form string or number.

New commands have been added for this feature. These commands may be issued from the redis-cli or any other client that supports issuing free form commands (unlike java/jedis).

• CreateDB
  Databases other than the default (“0”) database are expected to be pre-created before being used.

• ListDB
  This API will list all databases.

• DeleteDB
  This command will delete a database.

• Select
  To select another database, the client issues the following command:
  select <db-id>
  All operations following the above from that client will be carried out against the chosen <db-id> until the next select command is issued.

To process a select statement, the query layer will confirm that the target database already exists. It then updates the RedisConnectionContext to start using the selected database.

Design

In YugaByte DB, each Redis database is modeled as a separate DocDB table.

Database X would map to the redis table redis_X (with the exception of database 0 which maps to redis for backward compatibility).

For example:

• Database “0” would map to redis
• Database “1” would map to redis_1
• Database “foo” would map to redis_foo

The Redis connection context will maintain the information about the database currently in use by each client connection.

The Redis service will translate the database-id from the Redis connection context into an appropriate redis-table-name. and use it for communicating with the tablets using the ybclient.

New Commands