forked from krakend/krakend-lambda
/
backend.go
186 lines (157 loc) · 4.46 KB
/
backend.go
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package lambda
import (
"bytes"
"context"
"encoding/base64"
"encoding/json"
"errors"
"io/ioutil"
"strings"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/request"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/aws/aws-sdk-go/service/lambda"
"github.com/devopsfaith/krakend/config"
"github.com/devopsfaith/krakend/logging"
"github.com/devopsfaith/krakend/proxy"
)
const (
Namespace = "github.com/devopsfaith/krakend-lambda"
)
var (
errBadStatusCode = errors.New("aws lambda: bad status code")
errNoConfig = errors.New("aws lambda: no extra config defined")
errBadConfig = errors.New("aws lambda: unable to parse the defined extra config")
)
type Invoker interface {
InvokeWithContext(aws.Context, *lambda.InvokeInput, ...request.Option) (*lambda.InvokeOutput, error)
}
type AwsLambdaResponse struct {
StatusCode int `json:"statusCode"`
Body string `json:"body"`
Headers struct {
ContentType string `json:"Content-Type"`
} `json:"headers"`
}
func BackendFactory(l logging.Logger, bf proxy.BackendFactory) proxy.BackendFactory {
return BackendFactoryWithInvoker(l, bf, invokerFactory)
}
func invokerFactory(o *Options) Invoker {
if o.Config == nil {
return lambda.New(session.New())
}
return lambda.New(session.Must(session.NewSession(o.Config)))
}
func BackendFactoryWithInvoker(l logging.Logger, bf proxy.BackendFactory, invokerFactory func(*Options) Invoker) proxy.BackendFactory {
return func(remote *config.Backend) proxy.Proxy {
ecfg, err := getOptions(remote)
if err != nil {
return bf(remote)
}
i := invokerFactory(ecfg)
return func(ctx context.Context, r *proxy.Request) (*proxy.Response, error) {
l.Info("Attempt to invoke lambda function")
payload, err := ecfg.PayloadExtractor(r)
if err != nil {
return nil, err
}
input := &lambda.InvokeInput{
ClientContext: aws.String(base64.StdEncoding.EncodeToString([]byte("{ \"client\": {\"app_title\": \"KrakenD\"} }"))),
FunctionName: aws.String(ecfg.FunctionExtractor(r)),
InvocationType: aws.String("RequestResponse"),
LogType: aws.String("Tail"),
Payload: payload,
// Qualifier: aws.String("1"),
}
result, err := i.InvokeWithContext(ctx, input)
if err != nil {
return nil, err
}
if result.StatusCode == nil || *result.StatusCode != 200 {
return nil, errBadStatusCode
}
var data AwsLambdaResponse
if err := json.Unmarshal(result.Payload, &data); err != nil {
return nil, err
}
response := &proxy.Response{
Metadata: proxy.Metadata{
StatusCode: int(*data.StatusCode),
Headers: data.Headers,
},
Data: data.Body,
IsComplete: true,
}
if result.ExecutedVersion != nil {
response.Metadata.Headers["X-Amz-Executed-Version"] = []string{*result.ExecutedVersion}
}
return response, nil
}
}
}
func getOptions(remote *config.Backend) (*Options, error) {
v, ok := remote.ExtraConfig[Namespace]
if !ok {
return nil, errNoConfig
}
ecfg, ok := v.(map[string]interface{})
if !ok {
return nil, errBadConfig
}
var funcExtractor functionExtractor
funcName, ok := ecfg["function_name"].(string)
if ok {
funcExtractor = func(_ *proxy.Request) string {
return funcName
}
} else {
funcParamName, ok := ecfg["function_param_name"].(string)
if !ok {
funcParamName = "function"
}
funcExtractor = func(r *proxy.Request) string {
return r.Params[funcParamName]
}
}
cfg := &Options{
FunctionExtractor: funcExtractor,
}
if remote.Method == "GET" {
cfg.PayloadExtractor = fromParams
} else {
cfg.PayloadExtractor = fromBody
}
region, ok := ecfg["region"].(string)
if !ok {
return cfg, nil
}
cfg.Config = &aws.Config{
Region: aws.String(region),
}
if endpoint, ok := ecfg["endpoint"].(string); ok {
cfg.Config.WithEndpoint(endpoint)
}
if retries, ok := ecfg["max_retries"].(int); ok {
cfg.Config.WithMaxRetries(retries)
}
return cfg, nil
}
type Options struct {
PayloadExtractor payloadExtractor
FunctionExtractor functionExtractor
Config *aws.Config
}
type functionExtractor func(*proxy.Request) string
type payloadExtractor func(*proxy.Request) ([]byte, error)
func fromParams(r *proxy.Request) ([]byte, error) {
buf := new(bytes.Buffer)
params := map[string]string{}
for k, v := range r.Params {
params[strings.ToLower(k)] = v
}
err := json.NewEncoder(buf).Encode(params)
return buf.Bytes(), err
}
func fromBody(r *proxy.Request) ([]byte, error) {
return ioutil.ReadAll(r.Body)
}