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https://github.com/goliatone/dmon

Docker health check over TCP. Simple OK/KO
https://github.com/goliatone/dmon

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Docker health check over TCP. Simple OK/KO

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README 

        
# dmon



Simple TCP server to remotely check container health status. 



Your service should connect over TCP and send a challenge with `docker:` to which `dmon` will answer with the string "OK\r" if the container is running or "KO\r" if the container is not running.



Under the hood `dmon` uses `docker inspect` to figure out if a container is running or not.



---



## Development

Install dependencies.



TCP server:

```

"github.com/firstrow/tcp_server"

```



Binary data builder:

```

$ go get -u github.com/jteeuwen/go-bindata/...

```



```

go-bindata -o bin.go bin/check

```



Change the package of the generated asset to `data`, and move to a data directory. If we change the contents of bin dir, we should recompile.



Build:

```

$ go build -o dmon && chmod 775

```



Run:



```

$ ./dmon

```



Open a `netcat` connection and send a container id:



```

$ nc localhost 9386

menagerie

OK

```

It will return **KO** if the container **menagerie** was not found, and **OK** it container was found.



We can pass a container id or a container name.



```

$ nc localhost 9386

ed8bc298f850

OK

```



```

$ docker ps

CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS                    NAMES

ed8bc298f850        b8e8e082f4e5        "node app.js"       About an hour ago   Up About an hour    0.0.0.0:1337->1337/tcp   menagerie

```



## Deployment

To run `docker` without `sudo` command.



Create the `docker` group and add your user:

```

sudo usermod -a -G docker ubuntu

```

Run `newgrp docker` to recognize the new group or log out and log in to have the change applied to groups.



Add upstart `dmon.conf` file. Read more on the [upstart cookbook][uc]



Check if conf file is ok:



Add logrotate conf file, `/etc/logrotate.d/dmon`:



```

/var/log/dmon.log {

    weekly

    size 20M

    missingok

    rotate 52

    notifempty

    nocreate

}

```



Ensure your port is reachable from outside of the box, if you are on an EC2 instance add a rule to the security group of the machine.

`dmon` listends on port **9386** by default:



* port: 9386

* protocol: tcp

* Source: 0.0.0.0/0



Copy the `dmon` binary in `/opt/`, copy the upstart config file into `/etc/init/dmon.conf`.

Check the syntax of the conf, and start the service:



```

$ init-checkconf /etc/init/dmon.conf

File /etc/init/dmon.conf: syntax ok

$ sudo initctl start dmon

```



>initctl: Rejected send message, 1 matched rules; type="method_call", sender=":1.9" (uid=1000 pid=2379 comm="initctl reload-configuration ") interface="com.ubuntu.Upstart0_6" member="ReloadConfiguration" error name="(unset)" requested_reply="0" destination="com.ubuntu.Upstart" (uid=0 pid=1 comm="/sbin/init")



This error is usually fixed by running the `initctl` command with `sudo`.



If you run `initctl status dmon` you should see something along the lines of:



```

dmon start/running, process 31128`

```



Once you have the service running, then you can test it from the CLI:



```

$ nc 192.168.0.4 9386

```

Then just type your command `docker:`.



## Development

If you need to build the binary on Ubuntu:



```

# apt-get install golang

```



Set `GOPATH`:

```

$ export GOPATH=/opt/GO

```



You might need to `apt-get install git` and some other dependencies.



```

$ git clone https://github.com/goliatone/dmon.git

```



[uc]: http://upstart.ubuntu.com/cookbook/#pre-start-example-debian-and-ubuntu-specific



->



mkdir /opt/dmon/



sudo install



```shell

#!/bin/sh



cd /opt



wget https://s3.amazonaws.com/com.goliatone.dmon/ubuntu/dmon

wget https://s3.amazonaws.com/com.goliatone.dmon/ubuntu/dmon.conf

wget https://s3.amazonaws.com/com.goliatone.dmon/ubuntu/dmon.log



chmod +x /opt/dmon



cp /opt/dmon.conf /etc/init/dmon.conf

cp /opt/dmon.log /etc/logrotate.d/dmon



initctl start dmon



```



## Publish



```

s3cmd put conf/dmon s3://com.goliatone.dmon/ubuntu/dmon --acl-public

s3cmd put conf/dmon.log s3://com.goliatone.dmon/ubuntu/dmon.log --acl-public

s3cmd put conf/dmon.conf s3://com.goliatone.dmon/ubuntu/dmon.conf --acl-public

s3cmd put conf/install s3://com.goliatone.dmon/ubuntu/install --acl-public

```



## Roadmap



Handle multiple containers per command:



```

docker:container1|container2|container3|container4

```