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Rungkrit Titachotnimit
Rungkrit Titachotnimit

Reputation: 97

Redis Keyspace Notifications subscription for field&value

i'm currently working about Redis Expire Event

My goal : get the Value, Field to do something in next process after Data in Redis already expire

so i had found Redis Keyspace Notifications Feature That Allow client to Subscribe to Channel in Redis to Recieve Event affecting Data in reset like Expire

so i have some example code : https://github.com/toygame/nodejs-redis-keyspace-notifications

subscriber.subscribe("__keyevent@0__:expired")
subscriber.on('message', async(channel, message) => {
        // do somethings
        console.log(message);       
    })

Result : Key0

And this work find but the Result i got is only Key that i have set into redis and expired

I have already do some research https://medium.com/nerd-for-tech/redis-getting-notified-when-a-key-is-expired-or-changed-ca3e1f1c7f0a

but its found only Event that maybe i can get as result but not for Value, Field that i expect

is their anyway to get Those Value and Field ?

FYI. Document https://redis.io/topics/notifications

UPDATE according to this https://stackoverflow.com/a/42556450/11349357

Keyspace notifications do not report the value, only the key's name and/or command performed are included in the published message.The main underlaying reasoning for this is that Redis values can become quite large.

If you really really really need this kind of behavior, well that's pretty easy actually. Because keyspace notifications are using Pub/Sub messages, you can just call PUBLISH yourself after each relevant operation, and with the information that you're interested in.

look like i can't use this Redis Keyspace but i have to publish its on my own

Upvotes: 1

Views: 2143

Answers (1)

Guy Korland
Guy Korland

Reputation: 9568

You can use RedisGears to process keyspace notification and get both key and value.

You can write your processing code in python and register it in Redis. e.g. Capture each keyspace event and store to a Stream

GearsBuilder() \
.foreach(lambda x: execute('XADD', "notifications-stream", '*', *sum([[k,v] for k,v in x.items()],[]))) \
.register(prefix="person:*", eventTypes=['hset', 'hmset'], mode='sync')

You can read more about this example here: https://oss.redis.com/redisgears/examples.html#reliable-keyspace-notification

Upvotes: 1

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