Redis, PHP and SSE - why pub / sub if everything works?

Question

PHP

I asked myself a question about live notifications, I took a php lib to work with radishes, I took the client code from here https://www.w3schools.com/html/html5_serversenteve... I start it
- messages from the server come
in. Changed the value of the key in Redis - the new value
1 came. Question: often in this bundle it is advised to use Redis pub/sub. What for? After all, the updated data is arriving ... Explain on your fingers what is the advantage of using pub / sub in conjunction with SSE. Is it possible in php? Can you post a live code example? I tried several libraries from github, but I didn’t understand how to use pub / sub (
2. Another question: I didn’t quite understand what channel is in Redis. I open Redis DM - I see the key and value. I don’t see Channel.
3. And another follow-up question: in order to get data by key for a specific user, I will have to look at the user's session in the database (I plan to tie it to WP), how can I make sure that MySQL is not pulled once again?

Answer 1

Redis actually consists of two parts:
1. key-value store
2. channel
Channel cannot be seen through Redis DM.
The channel appears at the time of pub/sub and exists as long as there is someone pub/sub.
The channel is needed for instant mass mailing. All subs subscribed to the same channel instantly receive a message from pub. Messages are not stored anywhere, whoever has not received it will never receive it again, a kind of UDP message.
In this mode, redis supports as many clients as you can afford concurrent connections to the server. At the same time consuming relatively few resources.