Zookeeper Watcher Daemon Docs¶
About¶
zk_watcher is a simple service that registers
Ephemeral Nodes
in Apache Zookeeper based on the result of a healthcheck. The service is
available both as a Python script that you can run on your own, or as a Docker
image (nextdoor/zkwatcher)
that you can pull down.
The goal of zk_watcher is to monitor a particular service and register that
machine as a provider of that service at a given path on the Zookeeper
service.
A simple example is having zk_watcher monitor Apache httpd by running service
apache2 status at a regular interval and registers with ZooKeeper at a given
path (say /services/production/webservers). As long as the command returns
a safe exit code (0), zk_watcher will register with ZooKeeper that this
server is providing this particular service. If the hostname of the machine
is web1.mydomain.com, the registration path would look like this
/services/production/webservers/web1.mydomain.com:80
In the event that the service check fails, the host will be immediately de- registered from that path.