ssmconfig

import "github.com/ianlopshire/go-ssm-config"

SSMConfig is a utility for loading configuration parameters from AWS SSM (Parameter Store) directly into a struct. This package is largely inspired by kelseyhightower/envconfig.

Motivation

This package was created to reduce the boilerplate code required when using Parameter Store to provide configuration to AWS Lambda functions. It should be suitable for additional applications.

Usage

Set some parameters in AWS Parameter Store:

Name	Value	Type	Key ID
/exmaple_service/prod/debug	false	String	-
/exmaple_service/prod/port	8080	String	-
/exmaple_service/prod/user	Ian	String	-
/exmaple_service/prod/rate	0.5	String	-
/exmaple_service/prod/secret	zOcZkAGB6aEjN7SAoVBT	SecureString	alias/aws/ssm

Write some code:

package main

import (
    "fmt"
    "log"
    "time"

    ssmconfig "github.com/ianlopshire/go-ssm-config"
)

type Config struct {
    Debug  bool    `ssm:"debug" default:"true"`
    Port   int     `ssm:"port"`
    User   string  `ssm:"user"`
    Rate   float32 `ssm:"rate"`
    Secret string  `ssm:"secret" required:"true"`
}

func main() {
    var c Config
    err := ssmconfig.Process("/example_service/prod/", &c)
    if err != nil {
        log.Fatal(err.Error())
    }
    
    format := "Debug: %v\nPort: %d\nUser: %s\nRate: %f\nSecret: %s\n"
    _, err = fmt.Printf(format, c.Debug, c.Port, c.User, c.Rate, c.Secret)
    if err != nil {
        log.Fatal(err.Error())
    }
}

Result:

Debug: false
Port: 8080
User: Ian
Rate: 0.500000
Secret: zOcZkAGB6aEjN7SAoVBT

Additional examples can be found in godoc.

Struct Tag Support

ssmconfig supports the use of struct tags to specify parameter name, default value, and required parameters.

type Config struct {
    Param         string `ssm:"param"`
    RequiredParam string `ssm:"required_param" required:"true"`
    DefaultParam  string `ssm:"default_param" default:"foobar"`
}

The ssm tag is used to lookup the parameter in Parameter Store. It is joined to the base path passed into Process(). If the ssm tag is missing ssmconfig will ignore the struct field.

The default tag is used to set the default value of a parameter. The default value will only be set if Parameter Store returns the parameter as invalid.

The required tag is used to mark a parameter as required. If Parameter Store returns a required parameter as invalid, ssmconfig will return an error.

The behavior of using the default and required tags on the same struct field is currently undefined.

Supported Struct Field Types

ssmconfig supports these struct field types:

string
int, int8, int16, int32, int64
bool
float32, float64

More supported types may be added in the future.

Licence

MIT