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paramcache.go
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paramcache.go
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package paramcache
import (
"log"
"os"
"strconv"
"time"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/awserr"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/aws/aws-sdk-go/service/ssm"
)
//SSMParameterStoreCache setup
type SSMParameterStoreCache struct {
Value *ssm.GetParameterOutput
CacheExpires int64
}
const (
cacheDefaultTimeout int64 = 300
)
var (
//override via environment var SSM_CACHE_ENABLED
cacheEnabled string = "TRUE"
//override via environment var SSM_CACHE_TIMEOUT
cacheTimeout int64 = cacheDefaultTimeout
//override via environment var SSM_VERBOSE
verbose string = "FALSE"
awsRegion string = ""
//the cache store
parameterStore = make(map[string]SSMParameterStoreCache)
//shared session
sess *session.Session = nil
)
//AWSSession create AWS Session for reuse
func AWSSession(s *session.Session) *session.Session {
if s == nil {
sessionNew := session.Must(session.NewSessionWithOptions(session.Options{
Config: aws.Config{
Region: aws.String(awsRegion),
},
}))
return sessionNew
}
return s
}
//Setup configures paramcache via environment variables
//Configurable variables are as follows
//SSM_CACHE_ENABLED (default: TRUE)
//SSM_VERBOSE (default: FALSE)
//SSM_CACHE_TIMEOUT (default: TRUE)
//AWS_REGION is set by lambda and not configurable
func setup() {
//get environment vars
if val, ok := os.LookupEnv("SSM_CACHE_ENABLED"); ok {
cacheEnabled = val
}
if val, ok := os.LookupEnv("SSM_VERBOSE"); ok {
verbose = val
}
if val, ok := os.LookupEnv("SSM_CACHE_TIMEOUT"); ok {
if timeout, err := strconv.ParseInt(val, 10, 64); err == nil {
if timeout >= 0 {
cacheTimeout = timeout
}
}
}
if val, ok := os.LookupEnv("AWS_REGION"); ok {
awsRegion = val
}
//create aws session
if sess == nil {
sess = AWSSession(nil)
}
}
//GetParameterStoreValue returns a string, stringlist or securestring from SSM and caches the value if configured to do so.
func GetParameterStoreValue(param string) (*ssm.GetParameterOutput, error) {
setup()
//return value if already cached
if cacheEnabled == "true" || cacheEnabled == "TRUE" {
if parameter, ok := parameterStore[param]; ok {
if time.Now().Unix() < parameter.CacheExpires {
if verbose == "true" || verbose == "TRUE" {
log.Printf("SSM ParamCache: %s - from cache", param)
}
return parameter.Value, nil
}
}
}
ssmService := ssm.New(sess)
paramOutput, err := ssmService.GetParameter(&ssm.GetParameterInput{
Name: aws.String(param),
WithDecryption: aws.Bool(true),
})
if err != nil {
if aerr, ok := err.(awserr.Error); ok {
log.Printf("Error: SSM ParamCache: %v", aerr.Error())
} else {
log.Printf("Error: SSM ParamCache: %v", err)
}
return nil, err
}
//store value in cache
if cacheEnabled == "true" || cacheEnabled == "TRUE" {
if verbose == "true" || verbose == "TRUE" {
log.Printf("SSM ParamCache: %s - not from cache, caching for %v seconds", param, cacheTimeout)
}
t := time.Now()
cacheExpires := t.Unix() + cacheTimeout
p := &SSMParameterStoreCache{
Value: paramOutput,
CacheExpires: cacheExpires,
}
parameterStore[param] = *p
}
return paramOutput, nil
}