How to choose different Lambda function while Start Streaming to Amazon Elasticsearch Service - amazon-web-services

Question

Following this Streaming CloudWatch Logs Data to Amazon Elasticsearch Service, it's working fine to stream cloud watch log to ELK having one log group and one Lambda function.
But now I want to change target lambda function for my other logs group, but I am not able to do that as there is no option in AWS console.
Any Help will be appreciated.
Thanks

Answer 1

I was streaming to ELK using the AWS console option which is Start Streaming to Amazon Elasticsearch Service, But I failed to change or choose different lambda function as there is only lambda function can be selected for any log group using this option.
So, I create new lambda function and set stream target to AWS lambda function,
Here is the code that all you need, Node version for lambda function is 4.* as it was some issue with the new version but the pulse point is it does not require any extra NPM packages.
// v1.1.2
var https = require('https');
var zlib = require('zlib');
var crypto = require('crypto');
var endpoint = 'search-my-test.us-west-2.es.amazonaws.com';
exports.handler = function(input, context) {
// decode input from base64
var zippedInput = new Buffer(input.awslogs.data, 'base64');
// decompress the input
zlib.gunzip(zippedInput, function(error, buffer) {
if (error) { context.fail(error); return; }
// parse the input from JSON
var awslogsData = JSON.parse(buffer.toString('utf8'));
// transform the input to Elasticsearch documents
var elasticsearchBulkData = transform(awslogsData);
// skip control messages
if (!elasticsearchBulkData) {
console.log('Received a control message');
context.succeed('Control message handled successfully');
return;
}
// post documents to the Amazon Elasticsearch Service
post(elasticsearchBulkData, function(error, success, statusCode, failedItems) {
console.log('Response: ' + JSON.stringify({
"statusCode": statusCode
}));
if (error) {
console.log('Error: ' + JSON.stringify(error, null, 2));
if (failedItems && failedItems.length > 0) {
console.log("Failed Items: " +
JSON.stringify(failedItems, null, 2));
}
context.fail(JSON.stringify(error));
} else {
console.log('Success: ' + JSON.stringify(success));
context.succeed('Success');
}
});
});
};
function transform(payload) {
if (payload.messageType === 'CONTROL_MESSAGE') {
return null;
}
var bulkRequestBody = '';
payload.logEvents.forEach(function(logEvent) {
var timestamp = new Date(1 * logEvent.timestamp);
// index name format: cwl-YYYY.MM.DD
var indexName = [
'prod-background-wo-' + timestamp.getUTCFullYear(), // year
('0' + (timestamp.getUTCMonth() + 1)).slice(-2), // month
('0' + timestamp.getUTCDate()).slice(-2) // day
].join('.');
var source = buildSource(logEvent.message, logEvent.extractedFields);
source['response_time'] = source["end"] - source["start"];
source['#id'] = logEvent.id;
source['#timestamp'] = new Date(1 * logEvent.timestamp).toISOString();
source['#message'] = logEvent.message;
source['#owner'] = payload.owner;
source['#log_group'] = payload.logGroup;
source['#log_stream'] = payload.logStream;
var action = { "index": {} };
action.index._index = indexName;
action.index._type = payload.logGroup;
action.index._id = logEvent.id;
bulkRequestBody += [
JSON.stringify(action),
JSON.stringify(source),
].join('\n') + '\n';
});
return bulkRequestBody;
}
function buildSource(message, extractedFields) {
if (extractedFields) {
var source = {};
for (var key in extractedFields) {
if (extractedFields.hasOwnProperty(key) && extractedFields[key]) {
var value = extractedFields[key];
if (isNumeric(value)) {
source[key] = 1 * value;
continue;
}
jsonSubString = extractJson(value);
if (jsonSubString !== null) {
source['$' + key] = JSON.parse(jsonSubString);
}
source[key] = value;
}
}
return source;
}
jsonSubString = extractJson(message);
if (jsonSubString !== null) {
return JSON.parse(jsonSubString);
}
return {};
}
function extractJson(message) {
var jsonStart = message.indexOf('{');
if (jsonStart < 0) return null;
var jsonSubString = message.substring(jsonStart);
return isValidJson(jsonSubString) ? jsonSubString : null;
}
function isValidJson(message) {
try {
JSON.parse(message);
} catch (e) { return false; }
return true;
}
function isNumeric(n) {
return !isNaN(parseFloat(n)) && isFinite(n);
}
function post(body, callback) {
var requestParams = buildRequest(endpoint, body);
var request = https.request(requestParams, function(response) {
var responseBody = '';
response.on('data', function(chunk) {
responseBody += chunk;
});
response.on('end', function() {
var info = JSON.parse(responseBody);
var failedItems;
var success;
if (response.statusCode >= 200 && response.statusCode < 299) {
failedItems = info.items.filter(function(x) {
return x.index.status >= 300;
});
success = {
"attemptedItems": info.items.length,
"successfulItems": info.items.length - failedItems.length,
"failedItems": failedItems.length
};
}
var error = response.statusCode !== 200 || info.errors === true ? {
"statusCode": response.statusCode,
"responseBody": responseBody
} : null;
callback(error, success, response.statusCode, failedItems);
});
}).on('error', function(e) {
callback(e);
});
request.end(requestParams.body);
}
function buildRequest(endpoint, body) {
var endpointParts = endpoint.match(/^([^\.]+)\.?([^\.]*)\.?([^\.]*)\.amazonaws\.com$/);
var region = endpointParts[2];
var service = endpointParts[3];
var datetime = (new Date()).toISOString().replace(/[:\-]|\.\d{3}/g, '');
var date = datetime.substr(0, 8);
var kDate = hmac('AWS4' + process.env.AWS_SECRET_ACCESS_KEY, date);
var kRegion = hmac(kDate, region);
var kService = hmac(kRegion, service);
var kSigning = hmac(kService, 'aws4_request');
var request = {
host: endpoint,
method: 'POST',
path: '/_bulk',
body: body,
headers: {
'Content-Type': 'application/json',
'Host': endpoint,
'Content-Length': Buffer.byteLength(body),
'X-Amz-Security-Token': process.env.AWS_SESSION_TOKEN,
'X-Amz-Date': datetime
}
};
var canonicalHeaders = Object.keys(request.headers)
.sort(function(a, b) { return a.toLowerCase() < b.toLowerCase() ? -1 : 1; })
.map(function(k) { return k.toLowerCase() + ':' + request.headers[k]; })
.join('\n');
var signedHeaders = Object.keys(request.headers)
.map(function(k) { return k.toLowerCase(); })
.sort()
.join(';');
var canonicalString = [
request.method,
request.path, '',
canonicalHeaders, '',
signedHeaders,
hash(request.body, 'hex'),
].join('\n');
var credentialString = [ date, region, service, 'aws4_request' ].join('/');
var stringToSign = [
'AWS4-HMAC-SHA256',
datetime,
credentialString,
hash(canonicalString, 'hex')
] .join('\n');
request.headers.Authorization = [
'AWS4-HMAC-SHA256 Credential=' + process.env.AWS_ACCESS_KEY_ID + '/' + credentialString,
'SignedHeaders=' + signedHeaders,
'Signature=' + hmac(kSigning, stringToSign, 'hex')
].join(', ');
return request;
}
function hmac(key, str, encoding) {
return crypto.createHmac('sha256', key).update(str, 'utf8').digest(encoding);
}
function hash(str, encoding) {
return crypto.createHash('sha256').update(str, 'utf8').digest(encoding);
}