Serfnode

Add serf powers to your containers.

Quickstart

Dependencies: docker and fig.

Clone this repo and build the base image for the serfnodes:
```
$ git clone https://github.com/waltermoreira/serfnode.git
$ cd serfnode/serfnode
$ make
```
This will generate an image with name serfnode.
Go to the example directory to see an example of use. See Structure to read about its components.

Build it and test it with:
```
$ cd ../example
$ make
# Launch a node with role "exampleA"
$ ROLE=exampleA fig -p exampleA up
```
(the -p parameter is only to overwrite the default project name and to avoid collision when starting another node from the same directory.)

We can test another nodes joining by starting the same container with a different role.

First we get the contact information for the node we just started:

$ docker exec exampleA_example_1 cat /node_info
{"node": "13024227bdce4a3682c482ab0cbfd89e", "bind_port": 7946,
"advertise": "172.17.0.111", "rpc_port": 7373}

We start a new node with:

$ ROLE=exampleB CONTACT=172.17.0.111:7946 fig -p exampleB up

We now can check that the nodes are joined:

$ docker exec -it exampleA_example_1 bash
root@b87605caaadd:/# serf members
0b2c3818c9f94fb692a839c1b92de154  172.17.0.112:7946  alive  bind=7946,rpc=7373,role=exampleB,adv=172.17.0.112
13024227bdce4a3682c482ab0cbfd89e  172.17.0.111:7946  alive  role=exampleA,adv=172.17.0.111,bind=7946,rpc=7373

The supervisor events received by serf can be seen in /var/log/supervisor/serfnode-*.

The events can also be triggered with:

root@b87605caaadd:/# serf query where '{"role":"exampleB"}'
Query 'where' dispatched
Ack from '13024227bdce4a3682c482ab0cbfd89e'
Ack from '0b2c3818c9f94fb692a839c1b92de154'
Response from '0b2c3818c9f94fb692a839c1b92de154': {"ip": "172.17.0.112", "advertise": "172.17.0.112", "rpc": "7373", "bind": "7946"}

SUCCESS
Total Acks: 2
Total Responses: 1
root@b87605caaadd:/#

The where event was answered only by the matching role node. By default, all the nodes respond the events, for example:

root@b87605caaadd:/# serf query hello '{"who":"Walter"}'
Query 'hello' dispatched
Ack from '13024227bdce4a3682c482ab0cbfd89e'
Ack from '0b2c3818c9f94fb692a839c1b92de154'
Response from '0b2c3818c9f94fb692a839c1b92de154': Hello there, Walter!

SUCCESS
Response from '13024227bdce4a3682c482ab0cbfd89e': Hello there, Walter!

SUCCESS
Total Acks: 2
Total Responses: 2
root@b87605caaadd:/#

Structure

A serfnode powered container inherits from the serfnode image and adds extra handlers and actors.

To write your own handlers, create the file handler/my_handler.py with a class inheriting from BaseHandler (see the example in the example/handler directory).

There are three kind of events:

supervisor events: any change of state of processes in supervisor get broadcasted to the cluster via the supervisor event. The payload includes information on the process, node, and change of state.
custom events: arbitrary events defined by the user with arbitrary payload. They are triggered by serf event or serf query.
members joining/leaving/failing: see serf for documentation.

Any serfnode also respond to two events: where and where_actor, with information about the node ip and the actors currently running in that node.

Actors

Actors can be defined in the file handler/actors.py (see example in the example/handler directory), inheriting from ProcessActor or ThreadedActor.

Schedule actors to start at startup time by adding them to supervisor. The ExampleActor in example/handler/actors.py gets scheduled with the following file added to /etc/supervisor/conf.d/:

# file: example.conf
[program:example]
command=/handler/start_actor.py ExampleActor
autostart=true
autorestart=true

joestubbs/serfnode

Serfnode

Quickstart

Structure

Actors