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DiceDB

GET.WATCH

The GET.WATCH command is a novel feature designed to provide real-time updates to clients based on changes in underlying data. It allows clients to subscribe to a key and receive notifications whenever the key is updated.

This command is what makes DiceDB different from Redis and uniquely positions it as the easiest and most intuitive way to build real-time reactive applications like leaderboards, documents etc.

Protocol Support

ProtocolSupported
TCP-RESP✅
HTTP✅
WebSocket✅

Syntax

Terminal window
GET.WATCH <key>

Parameters

ParameterDescriptionTypeRequired
keykey which the client would like to get updates onStringYes

Return Value

ConditionReturn Value
Command is successfulreturns a message similar to subscribe

Behavior

  • The client establishes a subscription to the specified key.
  • The initial result set based on the current data is sent to the client.
  • DiceDB continuously monitors the key specified in the command.
  • Whenever data changes that might affect the query result, the query is reevaluated.

Errors

  1. Missing Key
    • Error Message: (error) ERROR wrong number of arguments for 'get.watch' command
    • Occurs if no Key is provided.

Example Usage

Basic Usage

Let’s explore a practical example of using the GET.WATCH command to create a real-time journal which takes backup periodically.

Terminal window
127.0.0.1:7379> GET.WATCH journal:user:0
GET.WATCH
Command: GET
Fingerprint: 4016579015
Data: Hello World

This query does the following:

  • Monitors key matching the name journal:user:0

When the key is updated using following set of commands from another client:

Terminal window
127.0.0.1:7379> set journal:user:0 "Hello World, I am user 0 of dice db"
OK
127.0.0.1:7379> set journal:user:0 "Hello World, I am user 0 of dice db, and i am going to demonstrate the use of watch commands"
OK
127.0.0.1:7379> set journal:user:0 "Hello World, I am user 0 of dice db, and i am going to demonstrate the use of watch and unwatch commands."
OK

The client will receive a message similar to the following:

Terminal window
Command: GET
Fingerprint: 4016579015
Data: Hello World, I am user 0 of dice db
Command: GET
Fingerprint: 4016579015
Data: Hello World, I am user 0 of dice db, and i am going to demonstrate the use of watch commands
Command: GET
Fingerprint: 4016579015
Data: Hello World, I am user 0 of dice db, and i am going to demonstrate the use of watch and unwatch commands.

Notes

Use the GET.UNWATCH command to unsubscribe from a key. This will stop the client from receiving updates on the key. Please refer to the GET.UNWATCH command documentation for more information.

following are the related commands to GET.WATCH: