Removed Flags struct, extended with comments and aws_ssm example in README

Author: kompotkot

README.md

@@ -20,10 +20,11 @@ except they explicitly `export` the environment variables. We source these envir
 run the development versions of our applications.
 
 It can sometimes be difficult to understand:
-1. Whether all the environment variables we *expect* to be defined in production actually have been.
+
+1. Whether all the environment variables we _expect_ to be defined in production actually have been.
 2. What the particular value of a production environment actually is.
 3. What the differences are between our expectations and the actual environment variables in a running
-application process.
+   application process.
 
 We are building and maintaining `checkenv` to make it easier for us to diagnose and fix issues with
 application configuration via environment variables. We stand in solidarity with anyone else who
@@ -40,3 +41,24 @@ binary which supports your needs.
 
 There is currently no need to support runtime plugins. Since doing so would make this program a lot
 more complicated, we have decided to forego runtime plugin functionality for now.
+
+## Usage
+
+```bash
+./checkenv plugins
+```
+
+Available plugins:
+
+-   env - Provides the environment variables defined in the checkenv process.
+-   file - Provides the environment variables defined in the env file with the given path.
+-   proc - Provides the environment variables set for the process with the given pid.
+-   aws_ssm - Provides environment variables defined in AWS Systems Manager Parameter Store.
+
+### aws_ssm plugin
+
+In order to fetch parameters with tags `Product` = `test` and `Node` = `true` with `export ` prefix execute following command
+
+```bash
+./checkenv show -export aws_ssm+Product:test,Node:true
+```

aws_ssm.go

@@ -1,4 +1,4 @@
-// checkenv plugin that provides the environment variables defined in the checkenv process.
+// checkenv plugin that provides environment variables defined in AWS System Manager Parameter Store.
 
 package main
 
@@ -11,19 +11,20 @@ import (
 func AWSSystemsManagerParameterStoreProvider(filter string) (map[string]string, error) {
 	environment := make(map[string]string)
 
-	AWSSystemsManagerFlags := aws_ssm.Flags{
-		Export:     false,
-		MaxResults: 10,
-		Outfile:    "",
-		Update:     false,
-	}
-	AWSSystemsManagerFlags.FilterTags = aws_ssm.ParseFilterTags(filter)
+	// Convert string of tags for filter to key:value structure
+	filterTags := aws_ssm.ParseFilterTags(filter)
 
 	ctx := context.Background()
+
 	api := aws_ssm.InitAWSClient(ctx)
-	keys := aws_ssm.FetchKeysOfParameters(ctx, api, AWSSystemsManagerFlags)
+
+	keys := aws_ssm.FetchKeysOfParameters(ctx, api, filterTags)
+
+	// Split slice of parameter keys to chunks by 10 (max len allowed by AWS)
+	// and fetch values for required parameters
 	keyChunks := aws_ssm.GenerateChunks(keys, 10)
-	parameters := aws_ssm.FetchParameters(ctx, api, keyChunks, AWSSystemsManagerFlags)
+	parameters := aws_ssm.FetchParameters(ctx, api, keyChunks)
+
 	for _, parameter := range parameters {
 		environment[parameter.Name] = parameter.Value
 	}

aws_ssm/aws_ssm.go

@@ -11,7 +11,10 @@ import (
 	"github.com/aws/aws-sdk-go-v2/service/ssm"
 )
 
-type AWSSystemsManagerParameterStore interface {
+// AWSSystemsManagerParameterStoreAPI defines the interface
+// for the GetParameters and DescribeParameters function.
+// We use this interface to test the function using a mocked service
+type AWSSystemsManagerParameterStoreAPI interface {
 	GetParameters(
 		ctx context.Context,
 		params *ssm.GetParametersInput,
@@ -33,11 +36,11 @@ type AWSSystemsManagerParameterStore interface {
 // Output:
 // 		If success, a GetParametersOutput object containing the result of the service call and nil
 // 		Otherwise, nil and an error from the call to GetParameters
-func ExecGetParameters(c context.Context, api AWSSystemsManagerParameterStore, input *ssm.GetParametersInput) (*ssm.GetParametersOutput, error) {
+func ExecGetParameters(c context.Context, api AWSSystemsManagerParameterStoreAPI, input *ssm.GetParametersInput) (*ssm.GetParametersOutput, error) {
 	return api.GetParameters(c, input)
 }
 
-func ExecDescribeParameters(c context.Context, api AWSSystemsManagerParameterStore, input *ssm.DescribeParametersInput) (*ssm.DescribeParametersOutput, error) {
+func ExecDescribeParameters(c context.Context, api AWSSystemsManagerParameterStoreAPI, input *ssm.DescribeParametersInput) (*ssm.DescribeParametersOutput, error) {
 	return api.DescribeParameters(c, input)
 }
 

aws_ssm/aws_ssm_test.go

@@ -2,22 +2,12 @@ package aws_ssm
 
 // Parameter structure for storing final result from AWS SSM
 type Parameter struct {
-	Name   string
-	Value  string
-	Export string
+	Name  string
+	Value string
 }
 
 // Tags for filter defined by user
 type FilterTag struct {
 	Name  string
 	Value string
 }
-
-// Contains command-line flags defined by user
-type Flags struct {
-	Export     bool
-	MaxResults int
-	Outfile    string
-	FilterTags []FilterTag
-	Update     bool
-}

aws_ssm/data.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"fmt"
 	"log"
-	"os"
 	"strings"
 
 	"github.com/aws/aws-sdk-go-v2/service/ssm"
@@ -14,7 +13,7 @@ import (
 // Fetch values for parameters
 // Inputs:
 //		chunks: list of lists with parameter key values
-func FetchParameters(ctx context.Context, api AWSSystemsManagerParameterStore, chunks [][]string, flags Flags) []Parameter {
+func FetchParameters(ctx context.Context, api AWSSystemsManagerParameterStoreAPI, chunks [][]string) []Parameter {
 	var parameters []Parameter
 
 	for _, chunk := range chunks {
@@ -30,9 +29,6 @@ func FetchParameters(ctx context.Context, api AWSSystemsManagerParameterStore, c
 			parameter := Parameter{
 				Name: *p.Name, Value: *p.Value,
 			}
-			if flags.Export {
-				parameter.Export = "export "
-			}
 			parameters = append(parameters, parameter)
 		}
 	}
@@ -44,22 +40,22 @@ func FetchParameters(ctx context.Context, api AWSSystemsManagerParameterStore, c
 // Fetch list of parameter keys from AWS with defined filters
 func FetchKeysOfParameters(
 	ctx context.Context,
-	api AWSSystemsManagerParameterStore,
-	flags Flags,
+	api AWSSystemsManagerParameterStoreAPI,
+	filterTags []FilterTag,
 ) []string {
 	var parameters []string
 
 	// Set parameter filters
 	parameterFilters := []types.ParameterStringFilter{}
-	for _, ft := range flags.FilterTags {
+	for _, ft := range filterTags {
 		filterKey := fmt.Sprintf("tag:%s", ft.Name)
 		parameterFilters = append(parameterFilters, types.ParameterStringFilter{
 			Key:    &filterKey,
 			Values: []string{ft.Value},
 		})
 	}
 	describeInput := &ssm.DescribeParametersInput{
-		MaxResults:       int32(flags.MaxResults),
+		MaxResults:       10,
 		ParameterFilters: parameterFilters,
 	}
 	n := 0
@@ -126,30 +122,3 @@ func ParseFilterTags(filterTagsStr string) []FilterTag {
 
 	return filterTags
 }
-
-// WriteToFile generate or update existing file and
-// flash to it environment variables
-func WriteToFile(parameters []Parameter, outfile string, update bool, export bool) {
-	flag := os.O_TRUNC | os.O_CREATE | os.O_WRONLY
-	if update {
-		flag = os.O_APPEND | os.O_CREATE | os.O_WRONLY
-	}
-
-	f, err := os.OpenFile(
-		outfile,
-		flag,
-		0644,
-	)
-	if err != nil {
-		log.Fatalf("Unable to open file %s, error: %s", outfile, err)
-	}
-	defer f.Close()
-
-	parametersStr := ""
-	for _, p := range parameters {
-		parametersStr += fmt.Sprintf("%s%s=%s\n", p.Export, p.Name, p.Value)
-	}
-	if _, err := f.WriteString(parametersStr); err != nil {
-		log.Fatalf("Unable to write to file %s, error: %s", outfile, err)
-	}
-}

aws_ssm/data.json aws_ssm/data_test.jsonaws_ssm/data.json renamed to aws_ssm/data_test.json

@@ -108,13 +108,13 @@ func main() {
 		}
 
 		for providerSpec := range spec.providersFull {
-			fmt.Printf("# %s - all variables:\n", providerSpec)
+			fmt.Printf("# Generated with %s - all variables:\n", providerSpec)
 			for k, v := range providedVars[providerSpec] {
 				fmt.Printf("%s%s=%s\n", exportPrefix, k, v)
 			}
 		}
 		for providerSpec, queriedVars := range spec.providerVars {
-			fmt.Printf("# %s - specific variables:\n", providerSpec)
+			fmt.Printf("# Generated with %s - specific variables:\n", providerSpec)
 			definedVars := providedVars[providerSpec]
 			for k := range queriedVars {
 				v, ok := definedVars[k]