sheldonh/etcd-observer repository overview

⁠etcd-observer

etcd-observer is a long-lived process that watches an etcd key and sends it to an HTTP end point on change.

⁠Usage

Configuration is performed through environment variables.

• ETCD_KEY - The etcd key to watch (mandatory, no default).
• ETCD_PEERS - A whitespace-delimited list of one or more etcd peer URLs (default: http://127.0.0.1:4001).
• ETCD_PORT_4001_TCP_ADDR - The address of an etcd peer if ETCD_PEERS is not given (default: 127.0.0.1).
• ETCD_PORT_4001_TCP_PORT - The port of an etcd peer if ETCD_PEERS is not given (default: 4001).
• NOTIFY_URL - The HTTP end point to notify on change (default: http://127.0.0.1:8080/).
• NOTIFY_PORT_8080_TCP_ADDR - The address of the HTTP end point if NOTIFY_URL is not given (default: 127.0.0.1).
• NOTIFY_PORT_8080_TCP_PORT - The port of the HTTP end point if NOTIFY_URL is not given (default: 8080).
• NOTIFY_PATH - The path of the HTTP end point if NOTIFY_URL is not given (default: /).

The value of the etcd key is submitted as the body of an HTTP PUT to the NOTIFY_URL on startup, and on change thereafter.

⁠Examples

The following docker process is used to apply redis master/slave topology changes to a linked redis dictator:

docker run -d \
	--link etcd:etcd \
	--link redis-1-dictator:notify \
	-e NOTIFY_PATH=/master
	-e ETCD_KEY=/config/redis-1/topology \
	sheldonh/etcd-observer

In a less dynamic environment, the same might be accomplished as follows:

docker run -d \
	-e ETCD_PEERS="http://10.0.0.2:4001 http://10.0.0.3:4001 http://10.0.0.3:4001" \
	-e ETCD_KEY="/config/redis-1/topology" \
	-e NOTIFY_URL="http://10.0.0.10:8080/master" \
	sheldonh/etcd-observer