render

README

render

Universal data-driven templates for generating textual output. Can be used as a single static binary (no dependencies) or as a golang library.

Just some of the things to render:

• configuration files
• Infrastructure as Code files (e.g. CloudFormation templates)
• Kubernetes manifests

The renderer extends go-template and Sprig functions.

If you are interested in one of the use cases, take a look at this blog post about Kubernetes resources rendering. Also see Helm compatibility.

• Installation
  • Binaries
  • Via Go
• Usage
  • Command line
  • Notable standard and sprig functions
  • Custom functions
  • Helm compatibility
  • Limitations and future work
• Contribution
• Development
• The Name

Installation

Binaries

For binaries please visit the Releases Page.

The binaries are statically compiled and does not require any dependencies.

Via Go

$ go get github.com/VirtusLab/render

Usage

$ render --help
NAME:
   render - Universal file renderer

USAGE:
   render [global options] command [command options] [arguments...]

VERSION:
   v0.1.1-55cc832

AUTHOR:
   VirtusLab

COMMANDS:
     help, h  Shows a list of commands or help for one command

GLOBAL OPTIONS:
   --debug, -d               run in debug mode
   --indir value             the input directory, can't be used with --out
   --outdir value            the output directory, the same as --outdir if empty, can't be used with --in
   --in value                the input template file, stdin if empty, can't be used with --outdir
   --out value               the output file, stdout if empty, can't be used with --indir
   --config value            optional configuration YAML file, can be used multiple times
   --set value, --var value  additional parameters in key=value format, can be used multiple times
   --help, -h                show help
   --version, -v             print the version

Notes:

• --in, --out take only files (not directories), --in will consume any file as long as it can be parsed
• stdin and stdout can be used instead of --in and --out
• --config accepts any YAML file, can be used multiple times, the values of the configs will be merged
• --set, --var are the same (one is used in Helm, the other in Terraform), we provide both for convenience, any values set here will override values form configuration files

Command line

Example usage of render with stdin, stdout and --var:

$ echo "something {{ .value }}" | render --var "value=new"
something new

Example usage of render with --in, --out and --config:

$ echo "something {{ .value }}" > test.txt.tmpl
$ echo "value: new" > test.config.yaml
$ ./render --in test.txt.tmpl --out test.txt --config test.config.yaml
$ cat test.txt
something new

Also see a more advanced template example.

As a library

package example

import (
    "github.com/VirtusLab/render/renderer"
    "github.com/VirtusLab/render/renderer/parameters"
)

func CustomRender(template string, opts []string, params parameters.Parameters) (string, error) {
    return renderer.New(
    	renderer.WithOptions(opts...),
        renderer.WithParameters(params),
        renderer.WithSprigFunctions(),
        renderer.WithExtraFunctions(),
        renderer.WithCryptFunctions(),
    ).Render(template)
}

See also other functions.

Also see tests for more usage examples.

Notable standard and sprig functions

• indent
• default
• ternary
• toJson
• b64enc, b64dec

All syntax and functions:

• Go template functions
• Sprig functions

Custom functions

• render - calls the render from inside of the template, making the renderer recursive (also accepts an optional template parameters override)
• readFile - reads a file from a path, relative paths are translated to absolute paths, based on root function
• root - the root path, used for relative to absolute path translation in any file based operations; by default PWD is used
• toYaml - provides a configuration data structure fragment as a YAML format
• gzip, ungzip - use gzip compression and extraction inside the templates, for best results use with b64enc and b64dec

See also example template and a more detailed documentation.

Cloud KMS (AWS, Amazon, Google) based cryptography functions form crypt:

• encryptAWS - encrypts data using AWS KMS, for best results use with gzip and b64enc
• decryptAWS - decrypts data using AWS KMS, for best results use with ungzip and b64dec
• encryptGCP - encrypts data using GCP KMS, for best results use with gzip and b64enc
• decryptGCP - decrypts data using GCP KMS, for best results use with ungzip and b64dec
• encryptAzure - encrypts data using Azure Key Vault, for best results use with gzip and b64enc
• decryptAzure - decrypts data using Azure Key Vault, for best results use with ungzip and b64dec

Helm compatibility

As of now, there is a limited Helm 2 Chart compatibility, simple Charts will render just fine.

There is no plan to implement full compatibility with Helm, because of unnecessary complexity that would bring.

Limitations and future work

Planned new features

• .renderignore files

Operating system support

We provide cross-compiled binaries for most platforms, but is currently used mainly with linux/amd64.

Contribution

Feel free to file issues or pull requests.

Development

export GOPATH=$HOME/go
export PATH=$PATH:$GOPATH/bin

mkdir -p $GOPATH/src/github.com/VirtusLab
cd $GOPATH/src/github.com/VirtusLab/render
git clone git@github.com:VirtusLab/render.git
cd render

go get -u github.com/golang/dep/cmd/dep
make all

The name

We believe in obvious names. It renders. It's a verb. It's render.