问题
I have a lambda function invoked as a custom resource via a CloudFormation template. It Creates/Deletes AWS Connect instances. The API calls work fine but I cannot seem to terminate the custom resource invocation, so the last CF block remains CREATE_IN_PROGRESS. No matter what I return from the async function it just won't terminate the CF execution with a success.
I'm able to use a non-async handler successfully as in https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/walkthrough-custom-resources-lambda-lookup-amiids.html but I need to make multiple API calls and await completions, hence the need for async handler.
Below is the code in it's simplest form, though I've tried just about everything, including using callback and context (ie exports.handler = async function(event, context, callback) {...}), both of which should be unnecessary with an async handler. I've tried using cfn-response to directly send a response which seems to be ignored with async handlers. I've tried returning directly the promises with and without the await before them, tried returning variables containing various responseStatus and responseData, nothing seems to work.
Transform: 'AWS::Serverless-2016-10-31'
Parameters:
IdentityManagementType:
Description: The type of identity management for your Amazon Connect users.
Type: String
AllowedValues: ["SAML", "CONNECT_MANAGED", "EXISTING_DIRECTORY"]
Default: "SAML"
InboundCallsEnabled:
Description: Whether your contact center handles incoming contacts.
Type: String
AllowedValues: [true, false]
Default: true
InstanceAlias:
Description: The name for your instance.
Type: String
MaxLength: 62
OutboundCallsEnabled:
Description: Whether your contact center allows outbound calls.
Type: String
AllowedValues: [true, false]
Default: true
DirectoryId:
Description: Optional. The identifier for the directory, if using this type of Identity Management.
Type: String
ClientToken:
Description: Optional. The idempotency token. Used for concurrent deployments
Type: String
MaxLength: 500
Region:
Description: Region to place the AWS Connect Instance
Type: String
Default: us-east-1
#Handler for optional values
Conditions:
HasClientToken: !Not
- !Equals
- ""
- !Ref ClientToken
HasDirectoryId: !Not
- !Equals
- ""
- !Ref DirectoryId
Resources:
CreateConnectInstance:
Type: AWS::Serverless::Function
Properties:
FunctionName: !Sub "${AWS::StackName}-AWSConnectInstance"
Handler: index.handler
Runtime: nodejs12.x
Description: Invoke a function to create an AWS Connect instance.
MemorySize: 128
Timeout: 30
Role: !GetAtt LambdaExecutionRole.Arn
Layers:
- !Sub "arn:aws:lambda:us-east-1:${AWS::AccountId}:layer:node_sdk:1"
Environment:
Variables:
IdentityManagementType:
Ref: IdentityManagementType
InboundCallsEnabled:
Ref: InboundCallsEnabled
InstanceAlias:
Ref: InstanceAlias
OutboundCallsEnabled:
Ref: OutboundCallsEnabled
Region:
Ref: Region
#Optional Values
ClientToken: !If
- HasClientToken
- !Ref ClientToken
- !Ref "AWS::NoValue"
DirectoryId: !If
- HasClientToken
- !Ref ClientToken
- !Ref "AWS::NoValue"
InlineCode: |
var aws = require("aws-sdk");
exports.handler = async function(event) {
console.log("REQUEST RECEIVED:\n" + JSON.stringify(event));
var connect = new aws.Connect({region: event.ResourceProperties.Region});
var isInboundCallsEnabled = (process.env.InboundCallsEnabled == 'true');
var isOutboundCallsEnabled = (process.env.OutboundCallsEnabled == 'true');
var createInstanceParams = {
InboundCallsEnabled: isInboundCallsEnabled,
OutboundCallsEnabled: isOutboundCallsEnabled,
IdentityManagementType: process.env.IdentityManagementType,
ClientToken: process.env.ClientToken,
DirectoryId: process.env.DirectoryId,
InstanceAlias: process.env.InstanceAlias
};
// Create AWS Connect instance using specified parameters
if (event.RequestType == "Create") {
return await connect.createInstance(createInstanceParams).promise();
// I can store this in a variable and read the contents fine, but...
// returning the promise does not terminate execution
}
};
InvokeCreateConnectInstance:
Type: Custom::CreateConnectInstance
Properties:
ServiceToken: !GetAtt CreateConnectInstance.Arn
Region: !Ref "AWS::Region"
The documentaiton at https://docs.aws.amazon.com/lambda/latest/dg/nodejs-handler.html explicitly states that you should be able to return await apiCall.promise() directly from any async function, exactly what I'm trying to do, such as
const s3 = new AWS.S3()
exports.handler = async function(event) {
return s3.listBuckets().promise()
}
Why can't I return from my async function? Again the API calls are working, the Connect instances are created and deleted (though I've omitted the delete code for brevity), but CF just hangs hours and hours until eventually saying "Custom Resource failed to stabilize in expected time"
Here's the inline code by itself for readability:
exports.handler = async function(event) {
console.log("REQUEST RECEIVED:\n" + JSON.stringify(event));
var connect = new aws.Connect({region: event.ResourceProperties.Region});
var isInboundCallsEnabled = (process.env.InboundCallsEnabled == 'true');
var isOutboundCallsEnabled = (process.env.OutboundCallsEnabled == 'true');
var createInstanceParams = {
InboundCallsEnabled: isInboundCallsEnabled,
OutboundCallsEnabled: isOutboundCallsEnabled,
IdentityManagementType: process.env.IdentityManagementType,
ClientToken: process.env.ClientToken,
DirectoryId: process.env.DirectoryId,
InstanceAlias: process.env.InstanceAlias
};
// Create AWS Connect instance using specified parameters
if (event.RequestType == "Create") {
return await connect.createInstance(createInstanceParams).promise();
// I can store this in a variable and read the contents fine, but...
// returning the promise does not terminate CF execution
}
};
UPDATE: I've implemented the sendResponse method exactly as shown in the AMI lookup example (the first link) and am sending exactly the correct structure for the response, it even includes the newly created connect instance ID in the data field:
{
"Status": "SUCCESS",
"Reason": "See the details in CloudWatch Log Stream: 2020/12/23/[$LATEST]6fef3553870b4fba90479a37b4360cee",
"PhysicalResourceId": "2020/12/23/[$LATEST]6fef3553870b4fba90479a37b4360cee",
"StackId": "arn:aws:cloudformation:us-east-1:642608065726:stack/cr12/1105a290-4534-11eb-a6de-0a8534d05dcd",
"RequestId": "2f7c3d9e-941f-402c-b739-d2d965288cfe",
"LogicalResourceId": "InvokeCreateConnectInstance",
"Data": {
"InstanceId": "2ca7aa49-9b20-4feb-8073-5f23d63e4cbc"
}
}
And STILL the custom resource will just not close in CloudFormation. I just don't understand why this is happening when I am returning the above to the event.responseURL. It's like specifying an async handler completely breaks the custom resource handler and prevents it from closing.
UPDATE: When I manually CURL the above response directly to the event.responseUrl the CF resource registers a success! WTF... I'm sending the exact same response as the lambda function is sending, and it accepts it from the CURL but not from my lambda function.
UPDATE: latest code including sendResponse, etc
var aws = require("aws-sdk");
exports.handler = async function(event, context, callback) {
console.log("REQUEST RECEIVED:\n" + JSON.stringify(event));
var connect = new aws.Connect({region: event.ResourceProperties.Region});
var isInboundCallsEnabled = (process.env.InboundCallsEnabled == 'true');
var isOutboundCallsEnabled = (process.env.OutboundCallsEnabled == 'true');
var createInstanceParams = {
InboundCallsEnabled: isInboundCallsEnabled,
OutboundCallsEnabled: isOutboundCallsEnabled,
IdentityManagementType: process.env.IdentityManagementType,
ClientToken: process.env.ClientToken,
DirectoryId: process.env.DirectoryId,
InstanceAlias: process.env.InstanceAlias
};
var responseStatus;
var responseData = {};
// Create Connect instance
if (event.RequestType == "Create") {
try {
var createInstanceRequest = await connect.createInstance(createInstanceParams).promise();
responseStatus = "SUCCESS";
responseData = {"InstanceId": createInstanceRequest.Id};
} catch (err) {
responseStatus = "FAILED";
responseData = {Error: "CreateInstance failed"};
console.log(responseData.Error + ":\n", err);
}
sendResponse(event, context, responseStatus, responseData);
return;
}
// Look up the ID and call deleteInstance.
if (event.RequestType == "Delete") {
var instanceId;
var listInstanceRequest = await connect.listInstances({}).promise();
listInstanceRequest.InstanceSummaryList.forEach(instance => {
if (instance.InstanceAlias == createInstanceParams.InstanceAlias) {
instanceId = instance.Id;
}
});
if (instanceId !== undefined) {
try {
var deleteInstanceRequest = await connect.deleteInstance({"InstanceId": instanceId}).promise();
responseStatus = "SUCCESS";
responseData = {"InstanceId": instanceId};
} catch (err) {
responseStatus = "FAILED";
responseData = {Error: "DeleteInstance call failed"};
console.log(responseData.Error + ":\n", err);
}
} else {
responseStatus = "FAILED";
responseData = {Error: "DeleteInstance failed; no match found"};
console.log(responseData.Error);
}
sendResponse(event, context, responseStatus, responseData);
return;
}
};
// Send response to the pre-signed S3 URL
function sendResponse(event, context, responseStatus, responseData) {
var responseBody = JSON.stringify({
Status: responseStatus,
Reason: "CloudWatch Log Stream: " + context.logStreamName,
PhysicalResourceId: context.logStreamName,
StackId: event.StackId,
RequestId: event.RequestId,
LogicalResourceId: event.LogicalResourceId,
Data: responseData
});
console.log("RESPONSE BODY:\n", responseBody);
var https = require("https");
var url = require("url");
var parsedUrl = url.parse(event.ResponseURL);
var options = {
hostname: parsedUrl.hostname,
port: 443,
path: parsedUrl.path,
method: "PUT",
headers: {
"content-type": "",
"content-length": responseBody.length
}
};
console.log("SENDING RESPONSE...\n");
var request = https.request(options, function(response) {
console.log("STATUS: " + response.statusCode);
console.log("HEADERS: " + JSON.stringify(response.headers));
// Tell AWS Lambda that the function execution is done
context.done();
});
request.on("error", function(error) {
console.log("sendResponse Error:" + error);
// Tell AWS Lambda that the function execution is done
context.done();
});
// write data to request body
request.write(responseBody);
request.end();
}
Been at this for two days now :(
PS in the logs the "RESPONSE BODY" is shown as expected like I copied above, and log shows the "SENDING RESPONSE" but does not get to the the "STATUS: " and "HEADERS: " portion of the request.https() call, which makes me think something with async interferes with this call... IDK
回答1:
This one was really tricky but finally have everything figured out. I had to make the sendResponse function asynchronous by adding a promise to it, awaiting that promise and returning it. This allowed me to ultimately call "return await sendResponse(event, context, responseStatus, responseData);" and finally everything is working, both create and delete operations are successful and the CloudFormation custom resource completes as expected. Phew. Posting code here in hopes that others will benefit from it.
var aws = require("aws-sdk");
exports.handler = async function(event, context, callback) {
console.log("REQUEST RECEIVED:\n" + JSON.stringify(event));
var connect = new aws.Connect({region: event.ResourceProperties.Region});
var isInboundCallsEnabled = (process.env.InboundCallsEnabled == 'true');
var isOutboundCallsEnabled = (process.env.OutboundCallsEnabled == 'true');
var createInstanceParams = {
InboundCallsEnabled: isInboundCallsEnabled,
OutboundCallsEnabled: isOutboundCallsEnabled,
IdentityManagementType: process.env.IdentityManagementType,
ClientToken: process.env.ClientToken,
DirectoryId: process.env.DirectoryId,
InstanceAlias: process.env.InstanceAlias
};
var responseStatus;
var responseData = {};
if (event.RequestType == "Create") {
try {
var createInstanceRequest = await connect.createInstance(createInstanceParams).promise();
responseStatus = "SUCCESS";
responseData = {"InstanceId": createInstanceRequest.Id};
} catch (err) {
responseStatus = "FAILED";
responseData = {Error: "CreateInstance failed"};
console.log(responseData.Error + ":\n", err);
}
return await sendResponse(event, context, responseStatus, responseData);
}
if (event.RequestType == "Delete") {
var instanceId;
var listInstanceRequest = await connect.listInstances({}).promise();
listInstanceRequest.InstanceSummaryList.forEach(instance => {
if (instance.InstanceAlias == createInstanceParams.InstanceAlias) {
instanceId = instance.Id;
}
});
if (instanceId !== undefined) {
try {
var deleteInstanceRequest = await connect.deleteInstance({"InstanceId": instanceId}).promise();
responseStatus = "SUCCESS";
responseData = {"InstanceId": instanceId};
} catch (err) {
responseStatus = "FAILED";
responseData = {Error: "DeleteInstance call failed"};
console.log(responseData.Error + ":\n", err);
}
} else {
responseStatus = "FAILED";
responseData = {Error: "DeleteInstance failed; no match found"};
console.log(responseData.Error);
}
return await sendResponse(event, context, responseStatus, responseData);
}
};
async function sendResponse(event, context, responseStatus, responseData) {
let responsePromise = new Promise((resolve, reject) => {
var responseBody = JSON.stringify({
Status: responseStatus,
Reason: "CloudWatch Log Stream: " + context.logStreamName,
PhysicalResourceId: context.logStreamName,
StackId: event.StackId,
RequestId: event.RequestId,
LogicalResourceId: event.LogicalResourceId,
Data: responseData
});
console.log("RESPONSE BODY:\n", responseBody);
var https = require("https");
var url = require("url");
var parsedUrl = url.parse(event.ResponseURL);
var options = {
hostname: parsedUrl.hostname,
port: 443,
path: parsedUrl.path,
method: "PUT",
headers: {
"content-type": "",
"content-length": responseBody.length
}
};
console.log("SENDING RESPONSE...\n");
var request = https.request(options, function(response) {
console.log("STATUS: " + response.statusCode);
console.log("HEADERS: " + JSON.stringify(response.headers));
resolve(JSON.parse(responseBody));
context.done();
});
request.on("error", function(error) {
console.log("sendResponse Error:" + error);
reject(error);
context.done();
});
request.write(responseBody);
request.end();
});
return await responsePromise;
}
来源：https://stackoverflow.com/questions/65417223/async-lambda-function-returning-promise-or-sending-responseurl-does-not-termina