How do I write a pre/post traffic hook function in go? - go

Question

I started using AWS SAM and for now I only have some unit tests, but I want to try to run integration tests in a pre traffic hook function.
Unfortunately there seems to be no code example for Golang, all I could find was for Javascript.
From this example I pieced together that I have to use the code deploy SDK and call PutLifecycleEventHookExecutionStatus, but the specifics remain unclear. The aws code example repo for go has no examples for code deploy either.
More Information about the topic that I am looking for is available here https://github.com/awslabs/serverless-application-model/blob/master/docs/safe_lambda_deployments.rst#pretraffic-posttraffic-hooks.
I want to start out by testing a lambda function that simply queries DynamoDB.

Answer 1

Something like this works:
package main
import (
"context"
"encoding/json"
"github.com/aws/aws-lambda-go/lambda"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/aws/aws-sdk-go/service/codedeploy"
)
type CodeDeployEvent struct {
DeploymentId string `json:"deploymentId"`
LifecycleEventHookExecutionId string `json:"lifecycleEventHookExecutionId"`
}
func HandleRequest(ctx context.Context, event CodeDeployEvent) (string, error) {
// add some tests here and change status flag as needed . . .
client := codedeploy.New(session.New())
params := &codedeploy.PutLifecycleEventHookExecutionStatusInput{
DeploymentId: &event.DeploymentId,
LifecycleEventHookExecutionId: &event.LifecycleEventHookExecutionId,
Status: "Succeeded",
}
req, _ := client.PutLifecycleEventHookExecutionStatusRequest(params)
_ = req.Send()
}

Answer 2

I got around to implement this and want to share my complete solution.
After figuring out how to use it, I decided against using it, because there are a couple of drawbacks.
there is no way to expose a new version of the canary to a dedicated portion of the user base, that means sometimes they'll hit the new or the old version
invoking functions that publish to sns will trigger all downstream actions, which might get the new or the old version of the downstream services, which would cause a lot of problems in case of breaking APIs
IAM changes affect both version immediately, possibly breaking the old version.
Instead, I deploy everything to a pre prod account, run my integration and e2e tests and if they succeed I'll deploy to prod
the cdk code to create a canary deployment:
const versionAlias = new lambda.Alias(this, 'Alias', {
aliasName: "alias",
version: this.lambda.currentVersion,
})
const preHook = new lambda.Function(this, 'LambdaPreHook', {
description: "pre hook",
code: lambda.Code.fromAsset('dist/upload/convert-pre-hook'),
handler: 'main',
runtime: lambda.Runtime.GO_1_X,
memorySize: 128,
timeout: cdk.Duration.minutes(1),
environment: {
FUNCTION_NAME: this.lambda.currentVersion.functionName,
},
reservedConcurrentExecutions: 5,
logRetention: RetentionDays.ONE_WEEK,
})
// this.lambda.grantInvoke(preHook) // this doesn't work, I need to grant invoke to all functions :s
preHook.addToRolePolicy(new iam.PolicyStatement({
actions: [
"lambda:InvokeFunction",
],
resources: ["*"],
effect: iam.Effect.ALLOW,
}))
const application = new codedeploy.LambdaApplication(this, 'CodeDeployApplication')
new codedeploy.LambdaDeploymentGroup(this, 'CanaryDeployment', {
application: application,
alias: versionAlias,
deploymentConfig: codedeploy.LambdaDeploymentConfig.ALL_AT_ONCE,
preHook: preHook,
autoRollback: {
failedDeployment: true,
stoppedDeployment: true,
deploymentInAlarm: false,
},
ignorePollAlarmsFailure: false,
// alarms:
// autoRollback: codedeploy.A
// postHook:
})
My go code of the pre hook function. PutLifecycleEventHookExecutionStatus tells code deploy if the pre hook succeeded or not. Unfortunately in case you fail the deployment message, the message you get in the cdk deploy output is utterly useless, so you need to check the pre/post hook logs.
In order to actually run the integration test I simply invoke the lambda and check if an error occurred.
package main
import (
"encoding/base64"
"fmt"
"log"
"os"
"github.com/aws/aws-lambda-go/lambda"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/aws/aws-sdk-go/service/codedeploy"
lambdaService "github.com/aws/aws-sdk-go/service/lambda"
)
var svc *codedeploy.CodeDeploy
var lambdaSvc *lambdaService.Lambda
type codeDeployEvent struct {
DeploymentId string `json:"deploymentId"`
LifecycleEventHookExecutionId string `json:"lifecycleEventHookExecutionId"`
}
func handler(e codeDeployEvent) error {
params := &codedeploy.PutLifecycleEventHookExecutionStatusInput{
DeploymentId: &e.DeploymentId,
LifecycleEventHookExecutionId: &e.LifecycleEventHookExecutionId,
}
err := handle()
if err != nil {
log.Println(err)
params.Status = aws.String(codedeploy.LifecycleEventStatusFailed)
} else {
params.Status = aws.String(codedeploy.LifecycleEventStatusSucceeded)
}
_, err = svc.PutLifecycleEventHookExecutionStatus(params)
if err != nil {
return fmt.Errorf("failed putting the lifecycle event hook execution status. the status was %s", *params.Status)
}
return nil
}
func handle() error {
functionName := os.Getenv("FUNCTION_NAME")
if functionName == "" {
return fmt.Errorf("FUNCTION_NAME not set")
}
log.Printf("function name: %s", functionName)
// invoke lambda via sdk
input := &lambdaService.InvokeInput{
FunctionName: &functionName,
Payload: nil,
LogType: aws.String(lambdaService.LogTypeTail), // returns the log in the response
InvocationType: aws.String(lambdaService.InvocationTypeRequestResponse), // synchronous - default
}
err := input.Validate()
if err != nil {
return fmt.Errorf("validating the input failed: %v", err)
}
resp, err := lambdaSvc.Invoke(input)
if err != nil {
return fmt.Errorf("failed to invoke lambda: %v", err)
}
decodeString, err := base64.StdEncoding.DecodeString(*resp.LogResult)
if err != nil {
return fmt.Errorf("failed to decode the log: %v", err)
}
log.Printf("log result: %s", decodeString)
if resp.FunctionError != nil {
return fmt.Errorf("lambda was invoked but returned error: %s", *resp.FunctionError)
}
return nil
}
func main() {
sess, err := session.NewSession()
if err != nil {
return
}
svc = codedeploy.New(sess)
lambdaSvc = lambdaService.New(sess)
lambda.Start(handler)
}