Our objective is to invoke a Lambda Function from another Lambda Function.
Start with something simple: the "Hello World" of intra-lambda invocation:
Lambda_A invokes Lambda_B
with a payload containing a single parameter name:'Alex'.
Lambda_B responds with Payload: "Hello Alex".
First create Lambda_B which expects a name property
on the event parameter
and responds to request with "Hello "+event.name:
Lambda_B
exports.handler = function(event, context) {
console.log('Lambda B Received event:', JSON.stringify(event, null, 2));
context.succeed('Hello ' + event.name);
};Ensure that you give Lambda_B and Lambda_A the same role.
We created a new role lambdaexecute which has both AWSLambdaExecute and
AWSLambdaBasicExecutionRole (for some reason both were required):
Lambda_A
var AWS = require('aws-sdk');
AWS.config.region = 'eu-west-1';
var lambda = new AWS.Lambda();
exports.handler = function(event, context) {
var params = {
FunctionName: 'Lambda_B', // the lambda function we are going to invoke
InvocationType: 'RequestResponse',
LogType: 'Tail',
Payload: '{ "name" : "Alex" }'
};
lambda.invoke(params, function(err, data) {
if (err) {
context.fail(err);
} else {
context.succeed('Lambda_B said '+ data.Payload);
}
})
};Once you have saved both these Lambda functions, Test run Lambda_A:
The way we end up writing our functions is to first check that the lambda function being invoked actually exisits, and then invoke it based on its availability.
var AWS = require('aws-sdk');
AWS.config.region = 'eu-west-1';
var lambda = new AWS.Lambda();
exports.handler = function(event, context) {
var params = {
FunctionName: 'Lambda_B', // the lambda function we are going to invoke
InvocationType: 'RequestResponse',
LogType: 'Tail',
Payload: '{ "name" : "Alex" }'
};
function invokeFunction() {
lambda.invoke(params, function(err, data) {
if (err) {
context.fail(err);
} else {
context.succeed('Lambda_B said '+ data.Payload);
}
})
}
// check that the Lambda Function you want to invoke exists before invoking
lambda.getFunction({ FunctionName: params.FunctionName }, function(err, data) {
if (err) {
context.fail(params.FunctionName + 'FUNCTION NOT FOUND', err);
} else {
console.log(data);
console.log(' - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -');
invokeFunction();
}
});
};