# Kubernetes Entrypoint [![Build Status](https://api.travis-ci.org/stackanetes/kubernetes-entrypoint.svg?branch=master "Build Status")](https://travis-ci.org/stackanetes/kubernetes-entrypoint) [![Container Repository on Quay](https://quay.io/repository/stackanetes/kubernetes-entrypoint/status "Container Repository on Quay")](https://quay.io/repository/stackanetes/kubernetes-entrypoint) [![Go Report Card](https://goreportcard.com/badge/stackanetes/kubernetes-entrypoint "Go Report Card")](https://goreportcard.com/report/stackanetes/kubernetes-entrypoint) ============ Kubernetes-entrypoint enables complex deployments on top of Kubernetes. ## Overview Kubernetes-entrypoint is meant to be used as a container entrypoint, which means it has to bundled in the container. Before launching the desired application, the entrypoint verifies and waits for all specified dependencies to be met. The Kubernetes-entrypoint queries directly the Kubernetes API and each container is self-aware of its dependencies and their states. Therefore, no centralized orchestration layer is required to manage deployments and scenarios such as failure recovery or pod migration become easy. ## Usage Kubernetes-entrypoint reads the dependencies out of environment variables passed into a container. There is only one required environment variable "COMMAND" which specifies a command (arguments delimited by whitespace) which has to be executed when all dependencies are resolved: `COMMAND="sleep inf"` Kubernetes-entrypoint introduces a wide variety of dependencies which can be used to better orchestrate once deployment. ## Supported types of dependencies All dependencies are passed as environement variables in format of `DEPENDENCY_` delimited by colon. For dependencies to be effective please use [readiness probes](http://kubernetes.io/docs/user-guide/production-pods/#liveness-and-readiness-probes-aka-health-checks) for all containers. ### Service Checks whether given kubernetes service has at least one endpoint. Example: `DEPENDENCY_SERVICE=mariadb,keystone-api` ### Container Within a pod composed of multiple containers, it waits for the containers specified by their names to start. This dependency requires a `POD_NAME` environement variable which can be easily passed through the [downward api](http://kubernetes.io/docs/user-guide/downward-api/). Example: `DEPENDENCY_CONTAINER=nova-libvirt,virtlogd` ### Daemonset Checks if a specified daemonset is already running on the same host, this dependency requires a `POD_NAME` env which can be easily passed through the [downward api](http://kubernetes.io/docs/user-guide/downward-api/). The `POD_NAME` variable is mandatory and is used to resolve dependencies. Example: `DEPENDENCY_DAEMONSET=openvswitch-agent` Simple example how to use downward API to get `POD_NAME` can be found [here](https://raw.githubusercontent.com/kubernetes/kubernetes.github.io/master/docs/user-guide/downward-api/dapi-pod.yaml). ### Job Checks if a given job succeded at least once. Example: `DEPENDENCY_JOBS=nova-init,neutron-init` ### Config This dependency performs a container level templating of configuration files. It can template an ip address `{{ .IP }}` and hostname `{{ .HOSTNAME }}`. Templated config has to be stored in an arbitrary directory `/configmaps//`. This dependency requires `INTERFACE_NAME` environment variable to know which interface to use for obtain ip address. Example: `DEPENDENCY_CONFIG=/etc/nova/nova.conf` The Kubernetes-entrypoint will look for the configuration file `/configmaps/nova.conf/nova.conf`, template `{{ .IP }} and {{ .HOSTNAME }}` tags and save the file as `/etc/nova/nova.conf`. ### Socket Checks whether a given file exists and container has rights to read it. Example: `DEPENDENCY_SOCKET=/var/run/openvswitch/ovs.socket` ## Image Build process for image is trigged after each commit. Can be found [here](https://quay.io/repository/stackanetes/kubernetes-entrypoint?tab=tags), and pulled by executing: `docker pull quay.io/stackanetes/kubernetes-entrypoint:v0.1.0` ## Examples [Stackanetes](http://github.com/stackanetes/stackanetes) uses kubernetes-entrypoint to manage dependencies when deploying OpenStack on Kubernetes.