Node.js / AWS Lambda 在发送 SNS 推送之前结束

Question

也许擅长 Node.js 的人可以解决这个问题。

在 Amazon Web Service 上编写和测试我的代码时，我注意到 Lambda 有时会在 SNS 发布之前结束函数。我认为问题可能正在发生，因为“context.done”被提前调用。但从逻辑上讲，这种情况不应该发生。重要信息：代码正常工作！ （除了我之前提到的事情）。

代码的基本思想是：一旦 DynamoDB 中的条目发生变化，Lambda 就会做出反应并通过 SNS 推送通知“所有者”。

感谢您的帮助！

---

此代码在 Lambda 实例上运行。

console.log('Loading function');
var aws = require('aws-sdk');
var doc = require('dynamodb-doc');
var dynamo = new doc.DynamoDB();
exports.handler = function(event, context){

    var target = null;
    var status = null;

    event.Records.forEach(function(record){

            console.log("Function Invoked");
            console.log("Function Event: "+record.eventName);

            if(record.eventName === "MODIFY")
            {
                db_record_exists(record, function(r) {
                    if (r) {

                        if(r.handle == "true"){
                            creator = r.creator;
                            participant = r.participant;

                            creator = JSON.stringify(creator);
                            status = JSON.stringify(record.dynamodb.NewImage.status.S);
                            creator = creator.replace(/"/g, "");
                            status = status.replace(/"/g, "");

                            participant = JSON.stringify(record.dynamodb.NewImage.participant.S);
                            participant = participant.replace(/"/g, "");

                            console.log("creator: "+ creator);
                            console.log("status: "+ status);
                            console.log("participant is: "+ participant);

                            getCredentialsMovement(creator,participant,function(response){
                                console.log("RESPONSE: "+ response);

                                sendSNSmovement(response, status, context);

                            });

                        }else{
                            context.done();
                        }
                    }
                });
            }else if(record.eventName == "INSERT"){
                db_record_exists(record, function(r) {
                    if (r) {

                        if(r.handle == "true"){
                            creator = r.creator;
                            participant = r.participant;

                            creator = JSON.stringify(creator);
                            status = JSON.stringify(record.dynamodb.NewImage.status.S);
                            creator = creator.replace(/"/g, "");
                            status = status.replace(/"/g, "");

                            participant = JSON.stringify(record.dynamodb.NewImage.participant.S);
                            participant = participant.replace(/"/g, "");

                            console.log("creator: "+ creator);
                            console.log("status: "+ status);
                            console.log("participant is: "+ participant);

                            getCredentialsInvitation(creator,participant,function(response){
                                console.log("RESPONSE: "+ response);

                                sendSNSinvitation(response, context);

                            });

                        }else{
                            context.done();
                        }
                    } else context.done();
                });
            }else{
                context.done();
            }
        }
    );
};



function db_record_exists(record, callback){

    var users = {};
    users.creator = record.dynamodb.NewImage.creator.S;
    users.participant = record.dynamodb.NewImage.participant.S;

    if(users.creator != users.participant){
        users.handle = "true";
    }else{
        users.handle = "false";
    }

    callback(users);
}

function shutdown(context){
    context.done();
}


function sendSNSmovement(creator_information, status, context){

    var sns = new aws.SNS();
    var payload_negative = creator_information.name + " has declined your event!";
    var payload_positive = creator_information.name + " has accepted your event!";
    //var payload_positive = "Positive";

    var payload_accepted = {
        "GCM": "{ \"data\": { \"message\": \"Your event has been accepted!!\"} }"
    };

    var payload_declined = { "GCM": "{ \"data\":  { \"message\": \"Your event has been declined!\" } }" };

    //   console.log("Standart Message as JSON: "+ payload_declined.GCM);

    payload_declined.GCM = "{ \"data\": { \"message\": \""+payload_negative+"\" } }";
    payload_accepted.GCM = "{ \"data\": { \"message\": \""+payload_positive+"\" } }";


    //   console.log("Standart Message as JSON: "+ payload_declined.GCM);
    //  console.log("Standart Message as String: "+ JSON.stringify(payload_declined));


    payload_accepted = JSON.stringify(payload_accepted);
    payload_declined = JSON.stringify(payload_declined);

    var payload;

    if(status == "true"){
        payload = payload_accepted;
    }else{
        payload = payload_declined;
    }


    var params = {
        TargetArn: creator_information.arn,
        MessageStructure: 'json',
        Message: payload
    };

    sns.publish(
        params, function(err, data) {
            if (err) {
                console.log(err.stack);
// Notify Lambda that we are finished, but with errors

                context.done(err, 'Brians Function Finished with Errors!');

            }else{
                console.log('push sent');
                console.log(data);
// Notify Lambda that we are finished

                context.done();
            }

        });
}

function sendSNSinvitation(creator_information,context){

    var sns = new aws.SNS();
    var payload_message = creator_information.name + " has invited you to an event!";

    var payload = {
        "GCM": "{ \"data\": { \"message\": \"Your event has been accepted!!\"} }"
    };


    payload.GCM = "{ \"data\": { \"message\": \""+payload_message+"\" } }";



    payload = JSON.stringify(payload);


    var params = {
        TargetArn: creator_information.arn,
        MessageStructure: 'json',
        Message: payload
    };

    sns.publish(
        params, function(err, data) {
            if (err) {
                console.log(err.stack);

// Notify Lambda that we are finished, but with errors

                context.done(err, 'Brians Function Finished with Errors!');

            }else{
                console.log('push sent');
                console.log(data);
// Notify Lambda that we are finished

                context.done();
            }
        });
}

function getCredentialsMovement(creator,participant,callback) {

    var params_name = {

        TableName : "users",
        Key : {
            "id" : participant
        },

        ProjectionExpression: 'person_name'

    };
    var params_arn = {

        TableName : "users",
        Key : {
            "id" : creator
        },

        ProjectionExpression: 'arn'

    };

    dynamo.getItem(params_name, function(err, data) {

        var response = {};

        if (err) {
            console.log(err);
            return err;
        }
        else {
            console.log("creators name is: "+data.Item.person_name);
            response.name = data.Item.person_name;
            dynamo.getItem(params_arn, function(err, data) {


                if (err) {
                    console.log(err);
                    return err;
                }
                else {
                    console.log(data.Item.arn);

                    response.arn = data.Item.arn;

                    return callback(response);
                }
            });


        }
    });

}
function getCredentialsInvitation(creator,participant,callback) {

    var params_name = {

        TableName : "users",
        Key : {
            "id" : creator
        },

        ProjectionExpression: 'person_name'

    };
    var params_arn = {

        TableName : "users",
        Key : {
            "id" : participant
        },

        ProjectionExpression: 'arn'

    };

    dynamo.getItem(params_name, function(err, data) {

        var response = {};

        if (err) {
            console.log(err);
            return err;
        }
        else {
            console.log("creators name is: "+data.Item.person_name);
            response.name = data.Item.person_name;
            dynamo.getItem(params_arn, function(err, data) {


                if (err) {
                    console.log(err);
                    return err;
                }
                else {
                    console.log(data.Item.arn);

                    response.arn = data.Item.arn;

                    return callback(response);
                }
            });


        }
    });

}

Answer 1

我不知道你的代码到底哪里出错了，但我有一些调试它的建议：

1. 为您的 Lambda 函数启用 CloudWatch Logs。
2. 确保通过代码的每条唯一路径都有独特的日志消息，这样您就可以区分哪些场景有效，哪些无效。
3. 我统计了对context.done() 的9 次调用，分布在多个函数中。您应该将其减少到一个或两个（成功/错误）。不要让每个函数都调用context.done()，而是让它们使用回调将状态返回给您的顶级处理程序。
4. 您可以考虑使用 Promises 或 async 之类的库来使回调链更易于理解。

Answer 2

似乎 contex.done() 调用在逻辑上不是独立的。您有一个 for 循环，其中包含异步调用。如果事件中有多条记录，它们有可能同时被处理，其中一条可能会调用 context.done() 而另一条仍未完成。

假设您有两个 MODIFY 事件进入此代码，第一个 db_record_exist 函数返回 r.handle = "true"，第二个返回 false。第一个将继续异步调用 getCredentials(dynamo.getItem)。同时将处理第二条记录并调用 context.done() 从而结束 lambda 函数而不等待来自 dynamo 的响应