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AWS stream logs from "cloudwatch -> lambda -> es" node.js lambda-code
// v1.1.2
var https = require('https');
var zlib = require('zlib');
var crypto = require('crypto');
var endpoint = '<aws es endpoint>';
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 = [
'cwl-' + 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['@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);
}
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