Nat Monytor
Essentially a rewrite from the code here :
https://aws.amazon.com/articles/high-availability-for-amazon-vpc-nat-instances-an-example/
We needed big changes in order to avoid using :
- amazon-tuned centos AMIs (and the API helpers)
- chunks of messy shell scripts
- centralized and maintainable configuration
Usage
The script rely on requests and boto3. Python 3.6 was used for writing and testing
pip install -r requirements.txt
python3 monyt.py config_monyt.json
The configuration is done through the json file.
How
The script ping its peer, if it detects it down it will modify the route tables
For real ?
The program automagically search for instances which 'Name' tag matches '-nat-' (tag and pattern are configurable in the config_monyt.json file)
On your nat-instances, you will want to have the program launched upon startup.
Either:
- Write an init script relevant to the system you are running (initV, rc, systemd, ...)
- add a line such as :
screen -d -m python3 /path/to/monyt.py /path/to/config.jsonto/etc/rc.local(if you chose this option, the $PWD will be '/', the log will be found there by default (you can customize it in the json file))
Todo
Document the policies needed in order to avoid setting the aws-access-key being over-privileged