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https://github.com/nacmartin/eredis_smart_sub
Layer on top of eredis (erlang redis client) to multiplex sub connections among several subscriptor processes in pubsub
https://github.com/nacmartin/eredis_smart_sub
Last synced: 6 days ago
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Layer on top of eredis (erlang redis client) to multiplex sub connections among several subscriptor processes in pubsub
- Host: GitHub
- URL: https://github.com/nacmartin/eredis_smart_sub
- Owner: nacmartin
- License: mit
- Created: 2015-01-18T18:23:02.000Z (almost 10 years ago)
- Default Branch: master
- Last Pushed: 2015-02-20T18:41:23.000Z (almost 10 years ago)
- Last Synced: 2024-10-30T02:43:41.399Z (about 2 months ago)
- Language: Erlang
- Homepage:
- Size: 207 KB
- Stars: 5
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# eredis_smart_sub
**eredis_smart_sub** is a layer on top of [eredis](https://github.com/wooga/eredis) to multiplex sub connections among several subscriptor processes in pubsub context
eredis, a more low-level approach to redis pubsub, requires a process to be the controller of every subscription done in a connection. However, if you have multiple processes that want to subscribe to different channels, you are faced with a decision:
- Open a Redis connection for each process that wants to subscribe to channels. However, this can cause you to have to open several connections to Eedis. There are some issues here:
* While cheap, redis connections are not free.
* A linux machine is capped to 65535 ports.
* This kind of problem is not the type one likes to face in the middle of the night.
* Opening a connection for every Erlang process does not feel very clean, does it?
- Write a layer on top of eredis with a process that will receive all the messages and send them back to the processes that are listening to the corresponding channels.
eredis_smart_sub implements this second approach, providing that layer.
## Installation
With [rebar](https://github.com/basho/rebar):
Add this line to your deps in `rebar.config`:
```
{eredis, ".*", {git, "git://github.com/wooga/eredis.git", {tag, "v0.2"}}}
```
## Usage
### Startup
Start eredis_sub
```erlang
{ok, EredisSubClient} = eredis_sub:start_link(),
% Start eredis_smart_sub with the eredis_sub client
% eredis_smart_sub will be assigned as the controller process of the eredis_sub client
{ok, SubClient} = eredis_smart_sub:start_link(EredisSubClient),
```
### Subscription
Now we can subscribe to channels from any process, and messages received in their channels will be sent to these processes
```erlang
gen_server:cast(SubClient, {subscribe, [<<"channel1">>], self()}),
```
Now the process can receive messages.
Publish something to `channel1` and run
```erlang
Message = receive
{message, M} -> M
end.
```
### Unsubscription
When the process is done with a channel can unsubscribe from it (or from a list of channels).
```erlang
gen_server:cast(SubClient, {unsubscribe, [<<"channel1">>], self()}),
```
### Handling of death of subscriptor processes
If the subscriber process dies `eredis_smart_sub` will send UNSUSCRIBE messages to redis for the channels where the process was the only subscriber. It is a bit more expensive, though, than simply unsubscribing explicitely from the channels we were subscribed to before termination. Of course, one never knows when a process is going to die in a pool of blood, so `eredis_smart_sub` has this covered.
## To build
- Get [rebar](https://github.com/basho/rebar).
```
rebar get-deps
rebar compile
```
## To run tests
```
rebar compile eunit skip_deps=true
```