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function.go
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function.go
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package function
import (
"bytes"
"encoding/json"
"errors"
"fmt"
"io/ioutil"
"math/rand"
"net/http"
"net/url"
"path"
"time"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/awserr"
"github.com/aws/aws-sdk-go/aws/credentials"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/aws/aws-sdk-go/service/lambda"
)
// Function represents a function deployed on one of the supported providers.
type Function struct {
Space string `json:"space" validate:"required,min=3,space"`
ID ID `json:"functionId" validate:"required,functionid"`
Provider *Provider `json:"provider" validate:"required"`
}
// Functions is an array of functions.
type Functions []*Function
// ID uniquely identifies a function.
type ID string
// Provider provides provider specific info about a function.
type Provider struct {
Type ProviderType `json:"type" validate:"required,eq=awslambda|eq=http|eq=weighted|eq=emulator"`
// AWS Lambda function
ARN string `json:"arn,omitempty"`
Region string `json:"region,omitempty"`
AWSAccessKeyID string `json:"awsAccessKeyId,omitempty"`
AWSSecretAccessKey string `json:"awsSecretAccessKey,omitempty"`
AWSSessionToken string `json:"awsSessionToken,omitempty"`
// Group weighted function
Weighted WeightedFunctions `json:"weighted,omitempty"`
// HTTP function
URL string `json:"url,omitempty" validate:"omitempty,url"`
// Emulator function
EmulatorURL string `json:"emulatorUrl,omitempty"`
APIVersion string `json:"apiVersion,omitempty"`
}
// ProviderType represents what kind of function provider this is.
type ProviderType string
const (
// AWSLambda represents AWS Lambda function.
AWSLambda ProviderType = "awslambda"
// Weighted contains a set of other functions and their load balancing weights.
Weighted ProviderType = "weighted"
// HTTPEndpoint represents function defined as HTTP endpoint.
HTTPEndpoint ProviderType = "http"
// Emulator represents a function registered with the local emulator.
Emulator ProviderType = "emulator"
)
// Call tries to send a payload to a target function
func (f *Function) Call(payload []byte) ([]byte, error) {
switch f.Provider.Type {
case AWSLambda:
return f.callAWSLambda(payload)
case Emulator:
return f.callEmulator(payload)
case HTTPEndpoint:
return f.callHTTP(payload)
}
return []byte{}, errors.New("calling this kind of function is not implemented")
}
// WeightedFunction is a function along with its load-balacing proportional weight.
type WeightedFunction struct {
FunctionID ID `json:"functionId" validate:"required"`
Weight uint `json:"weight" validate:"required"`
}
// WeightedFunctions is a slice of WeightedFunction's that you can choose from based on weight
type WeightedFunctions []WeightedFunction
// Choose uses the function weights to pick a single one.
func (w WeightedFunctions) Choose() (ID, error) {
var chosenFunction ID
if len(w) == 1 {
chosenFunction = w[0].FunctionID
} else {
weightTotal := uint(0)
for _, wf := range w {
weightTotal += wf.Weight
}
if weightTotal < 1 {
err := errors.New("target function weights sum to 0, there is not one function to target")
return ID(""), err
}
chosenWeight := uint(1 + rand.Intn(int(weightTotal)))
weightsSoFar := uint(0)
for _, wf := range w {
chosenFunction = wf.FunctionID
weightsSoFar += wf.Weight
if weightsSoFar >= chosenWeight {
break
}
}
}
return chosenFunction, nil
}
// nolint: gocyclo
func (f *Function) callAWSLambda(payload []byte) ([]byte, error) {
config := aws.NewConfig().WithRegion(f.Provider.Region)
if f.Provider.AWSAccessKeyID != "" && f.Provider.AWSSecretAccessKey != "" {
config = config.WithCredentials(credentials.NewStaticCredentials(f.Provider.AWSAccessKeyID, f.Provider.AWSSecretAccessKey, f.Provider.AWSSessionToken))
}
awsSession, err := session.NewSession(config)
if err != nil {
return nil, &ErrFunctionProviderError{err}
}
awslambda := lambda.New(awsSession)
invokeOutput, err := awslambda.Invoke(&lambda.InvokeInput{
FunctionName: &f.Provider.ARN,
Payload: payload,
})
if err != nil {
if awserr, ok := err.(awserr.Error); ok {
switch awserr.Code() {
case "AccessDeniedException":
case "InvalidSignatureException":
case "UnrecognizedClientException":
return nil, &ErrFunctionAccessDenied{awserr}
case lambda.ErrCodeServiceException:
return nil, &ErrFunctionProviderError{awserr}
default:
return nil, &ErrFunctionCallFailed{awserr}
}
}
}
if invokeOutput.FunctionError != nil {
return nil, &ErrFunctionError{errors.New(*invokeOutput.FunctionError)}
}
return invokeOutput.Payload, err
}
func (f *Function) callHTTP(payload []byte) ([]byte, error) {
client := http.Client{
Timeout: time.Second * 5,
}
resp, err := client.Post(f.Provider.URL, "application/json", bytes.NewReader(payload))
if err != nil {
return nil, &ErrFunctionCallFailed{err}
}
if resp.StatusCode == http.StatusInternalServerError {
return nil, &ErrFunctionError{fmt.Errorf("HTTP status code: %d", http.StatusInternalServerError)}
}
defer resp.Body.Close()
return ioutil.ReadAll(resp.Body)
}
func (f *Function) callEmulator(payload []byte) ([]byte, error) {
type emulatorInvokeSchema struct {
FunctionID string `json:"functionId"`
Payload interface{} `json:"payload"`
}
client := http.Client{
Timeout: time.Second * 5,
}
var invokePayload interface{}
err := json.Unmarshal(payload, &invokePayload)
if err != nil {
return nil, err
}
emulatorURL, err := url.Parse(f.Provider.EmulatorURL)
if err != nil {
return nil, fmt.Errorf("Invalid Emulator URL %q for Function %q", f.Provider.EmulatorURL, f.ID)
}
switch f.Provider.APIVersion {
case "v0":
emulatorURL.Path = path.Join(f.Provider.APIVersion, "emulator/api/functions/invoke")
default:
return nil, fmt.Errorf("Invalid Emulator API version %q for Function %q", f.Provider.APIVersion, f.ID)
}
emulatorPayload, err := json.Marshal(emulatorInvokeSchema{FunctionID: string(f.ID), Payload: invokePayload})
if err != nil {
return nil, err
}
resp, err := client.Post(emulatorURL.String(), "application/json", bytes.NewReader(emulatorPayload))
if err != nil {
return nil, &ErrFunctionCallFailed{err}
}
if resp.StatusCode == http.StatusInternalServerError {
return nil, &ErrFunctionError{fmt.Errorf("HTTP status code: %d", http.StatusInternalServerError)}
}
defer resp.Body.Close()
return ioutil.ReadAll(resp.Body)
}