ejt

Small tool to convert jsonnet to yaml/json

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Background

I want to use envoy to replace nginx in some small environments. These environments are not suitable for installing complex envoy control panels because these environments are simple or lightweight, but also need to be flexible enough to dynamically change settings at any time. envoy provides dynamic-resources-from-filesystem which is very suitable, but there are many problems with writing configuration directly using yaml. For example, it is impossible to disperse complex configurations into a single small file and import using techniques such as import/include. Most similar listeners/clusters repeat the same attribute values every time, and envoy will only reload dynamic when moving dynamic-resources specified content.

jsonnet can solve these yaml deficiencies very well, so I wrote this small tool to convert jsonnet to yaml and automatically copy yaml to the target path monitored by envoy dynamic-resources.

In addition, because the structure of jsonnet/json/yaml is consistent, the conversion from jsonnet to json is also supported by the way.

How To Use

Create the ejt.jsonnet definition file, you can execute the following command to create the definition file in the current working directory:

ejt init

ejt.jsonnet defines where to get jsonnet from, where to output the transpiled code, and where to move or copy the output archives for an envoy-like monitoring system to trigger updates. which ends up looking like this:

{
  version: 'v0.0.1',
  endpoints: [
    {
      output: './dst',  // redirect output structure to the directory.
      target: './envoy',  // target root directory.
      source: './src',  // source root directory.
      resources: [
        'envoy.jsonnet',
      ],
    },
  ],
}

After writing your jsonnet, execute the following command to generate yaml and move to the target path:

ejt yaml -m

std.extVar

Several default extension variables are provided since v0.0.5, which can be obtained using std.extVar

std.extVar('dev')

var	type	value
dev	string	0
ejt.version	string	ejt build version
ejt.os	string	ejt build os
ejt.arcg	string	ejt build arch
ejt.go_version	string	ejt build by go version
ejt.jsonnet	string	ejt used jsonnet version
ejt.dir	string	ejt.jsonnet project dir

std.native

Several extended native functions are provided starting from v0.0.5, which can be called using std.native

std.native('os.readText')('a.txt')

function os.readText(filename: string): string

function filepath.join(dir: string, name:string): string
function filepath.clean(filename: string): string
function filepath.abs(filename: string): string
function filepath.isAbs(filename: string): boolean
function filepath.base(filename: string): string
function filepath.dir(filename: string): string
function filepath.ext(filename: string): string