dependency-watchdog

When etcd becomes unavailable, the control-plane components go into CrashloopBackoff. The control-plane components can remain unavailable for some time even after etcd becomes ready and available. dependency-watchdog helps to alleviate the delay where control plane components remain unavailable by finding the respective pods in CrashloopBackoff and restarting them once etcd becomes ready and available.

Table of Contents

• Prerequisites
• Build
• Dependency management
  • Updating dependencies
• Usage

Prerequisites

Although the following installation instructions are for Mac OS X, similar alternate commands could be found for any Linux distribution

Installing Golang environment

Install the latest version of Golang (at least v1.9.4 is required). For Mac OS, you could use Homebrew:

brew install golang

For other OS, please check Go installation documentation.

Make sure to set your $GOPATH environment variable properly (conventionally, it points to $HOME/go).

For your convenience, you can add the bin directory of the $GOPATH to your $PATH: PATH=$PATH:$GOPATH/bin, but it is not necessarily required.

We use Dep for managing golang package dependencies. Please install it on Mac OS via

brew install dep

On other operating systems, please check the Dep installation documentation and the Dep releases page. After downloading the appropriate release in your $GOPATH/bin folder, you need to make it executable via chmod +x <dep-release> and rename it to dep via mv dep-<release> dep.

Golint

In order to perform linting on the Go source code, please install Golint:

go get -u github.com/golang/lint/golint

Installing git

We use git as VCS which you would need to install.

On Mac OS run

brew install git

Installing Docker (Optional)

In case you want to build Docker images, you have to install Docker itself. We recommend using Docker for Mac OS X which can be downloaded from here.

Build

First, you need to create a target folder structure before cloning and building dependency-watchdog.

mkdir -p ~/go/src/github.com/gardener
cd ~/go/src/github.com/gardener
git clone https://github.com/gardener/dependency-watchdog.git
cd dependency-watchdog

To build the binary in your local machine environment, use make target build-local.

make build-local

This will build the binary dependency-watchdog under the bin directory.

Next you can make it available to use as shell command by moving the executable to /usr/local/bin.

Dependency management

We use Dep to manage golang dependencies.. In order to add a new package dependency to the project, you can perform dep ensure -add <PACKAGE> or edit the Gopkg.toml file and append the package along with the version you want to use as a new [[constraint]].

Updating dependencies

The Makefile contains a rule called revendor which performs a dep ensure -update and a dep prune command. This updates all the dependencies to its latest versions (respecting the constraints specified in the Gopkg.toml file). The command also installs the packages which do not already exist in the vendor folder but are specified in the Gopkg.toml (in case you have added new ones).

make revendor

The dependencies are installed into the vendor folder which should be added to the VCS.

⚠️ Make sure you test the code after you have updated the dependencies!

Usage

Use the help option of the dependency-watchdog command to show usage details.

dependency-watchdog --help
Usage of ./bin/dependency-watchdog:
      --alsologtostderr                  log to standard error as well as files
      --config-file string               path to the config file that has the service depenancies (default "config.yaml")
      --kubeconfig string                path to the kube config file (default "kubeconfig.yaml")
      --log_backtrace_at traceLocation   when logging hits line file:N, emit a stack trace (default :0)
      --log_dir string                   If non-empty, write log files in this directory
      --log_file string                  If non-empty, use this log file
      --log_file_max_size uint           Defines the maximum size a log file can grow to. Unit is megabytes. If the value is 0, the maximum file size is unlimited. (default 1800)
      --logtostderr                      log to standard error instead of files (default true)
      --master string                    The address of the Kubernetes API server. Overrides any value in kubeconfig. Only required if out-of-cluster.
      --skip_headers                     If true, avoid header prefixes in the log messages
      --skip_log_headers                 If true, avoid headers when openning log files
      --stderrthreshold severity         logs at or above this threshold go to stderr (default 2)
  -v, --v Level                          number for the log level verbosity
      --vmodule moduleSpec               comma-separated list of pattern=N settings for file-filtered logging
      --watch-duration string            The duration to watch dependencies after the service is ready. (default "2m")