Inspired by HashiCorp's Consul Template, kube-template is a utility that queries a Kubernetes API server and uses its objects as input data for specified set of templates. Also it can run arbitrary commands for templates with updated output.
Please note this is work in progress.
- Install Go vendor tool:
go get -u github.com/kardianos/govendor - For Go 1.5 make sure you have set GO15VENDOREXPERIMENT=1 environment variable (set by default in Go 1.6)
git pull https://github.com/3cky/kube-template.gitcd kube-templatemake install
Docker
If you want to create a Docker image
- adjust Dockerfile in contrib/docker directory to fit your needs
- configure settings files in contrib/docker/conf directory
- issue
make docker
Note - the built image is already configured to automatically locate Kubernetes API along with everything is needed to connect (e.g. Certificate Authority file, security token and so on).
--alsologtostderr log to standard error as well as files
-c, --config string config file (default is ./kube-template.(yaml|json))
--dry-run don't write template output, dump result to stdout
--guess-kube-api-settings guess Kubernetes API settings from POD environment
--help-md get help in Markdown format
--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-flush-frequency duration Maximum number of seconds between log flushes (default 5s)
--logtostderr log to standard error instead of files (default true)
--master string Kubernetes API server address (default is http://127.0.0.1:8080/)
--once run template processing once and exit
-p, --poll-time duration Kubernetes API server poll time (0 disables server polling) (default 15s)
--stderrthreshold severity logs at or above this threshold go to stderr (default 2)
-t, --template stringSlice adds a new template to watch on disk in the format
'templatePath:outputPath[:command]'. This option is additive
and may be specified multiple times for multiple templates
-v, --v Level log level for V logs
--vmodule moduleSpec comma-separated list of pattern=N settings for file-filtered logging
Process single template using data from remote Kubernetes API server and exit:
$ kube-template \
--master="http://kube-api.server.com:8080" \
--template="/tmp/input.tmpl:/tmp/output.txt" \
--once Monitor local Kubernetes API server for updates every 30 seconds and update nginx and haproxy configuration files with reload:
$ kube-template \
--template="/tmp/nginx.tmpl:/etc/nginx/nginx.conf:service nginx reload" \
--template="/tmp/haproxy.tmpl:/etc/haproxy/haproxy.conf:service haproxy reload" \
--poll-time=30skube-template looks for kube-template.json or kube-template.yaml configuration file in current working directory or file name specified by --config command line option.
YAML configuration file example:
master: http://localhost:8080
poll-time: 10s
templates:
- path: in.txt.tmpl
output: out.txt
command: action.sh
- path: in.html.tmpl
output: out.htmlPlease note: templates specified on the command line take precedence over those defined in a config file.
- TERM, QUIT, INT: graceful shutdown
- HUP: reload configuration file
kube-template works with templates in the Go Template format. In addition to the standard template functions, kube-template provides the following functions:
{{pods "selector" "namespace"}}
Query Kubernetes API server for pods from given namespace (default if not specified) matching given selector (empty to get all pods).
Example:
{{range pods}}
{{.Name}}: {{.Status.Phase}}
{{end}}
{{services "selector" "namespace"}}
Query Kubernetes API server for services from given namespace (default if not specified) matching given selector (empty to get all services).
{{replicationcontrollers "selector" "namespace"}}
Query Kubernetes API server for replication controllers from given namespace (default if not specified) matching given selector (empty to get all replication controllers).
{{events "selector" "namespace"}}
Query Kubernetes API server for events from given namespace (default if not specified) matching given selector (empty to get all events).
{{endpoints "selector" "namespace"}}
Query Kubernetes API server for endpoints from given namespace (default if not specified) matching given selector (empty to get all endpoints).
{{nodes "selector"}}
Query Kubernetes API server for nodes matching given selector (empty to get all nodes).
{{namespaces "selector"}}
Query Kubernetes API server for namespaces matching given selector (empty to get all namespaces).
{{add a b}}
Returns the sum of two integers, a and b.
{{sub a b}}
Returns the subtract of integer b from integer a.
{{mul a b}}
Returns the multiplication of integer a by integer b.
Populate nginx upstream with pods labeled 'name=test-pod':
upstream test-pod-upstream {
{{with $pods := pods "name=test-pod"}}
ip_hash;
{{range $pods}}
server {{.Status.PodIP}}:8080;
{{end}}
{{else}}
# No pods with given label were found, use stub server
server 127.0.0.1:8081;
{{end}}
}
Create haproxy TCP balancer for pods listening on container port 9000:
{{with $pods := pods "name=test-pod"}}
{{$maxconn := 1000}}
listen test-pod-balancer
bind *:9000
mode tcp
maxconn {{mul $maxconn (len $pods)}}
balance roundrobin
{{range $pods}}
server {{.Name}} {{.Status.PodIP}}:9000 maxconn {{$maxconn}} check inter 5000 rise 3 fall 3
{{end}}
server stub 127.0.0.1:7690 backup
{{end}}
- Track Kubernetes changes using resource watch API
- More API and helper template functions
- Add options for API server authentication
- Add tests
- Fork it
- Create your feature branch (
git checkout -b my-new-feature) - Commit your changes (
git commit -am 'Add some feature') - Push to the branch (
git push origin my-new-feature) - Create new Pull Request
kube-template is released under the Apache 2.0 license. See LICENSE.txt