I'm trying to create a Lambda function that will restart Apache on an arbitrary number of EC2s. There should be a 15 second delay in between each restart operation. This Lambda will be triggered via an ELB and an HTTP request. To avoid the request timing out, I'd like the code to return a response as soon as I get the instance IDs that I want to restart Apache on, but so far, it's only doing one. Is this possible?
My code is below
'use strict'
const AWS = require('aws-sdk')
const ssm = new AWS.SSM()
const ec2 = new AWS.EC2()
const documentName = 'reloadApache'
// Amount of time to wait in between restarting Apache instances
const waitTime = process.env.WAIT_TIME
// Bind prefix to log levels
console.debug = console.log.bind(null, '[DEBUG]')
console.log = console.log.bind(null, '[LOG]')
console.info = console.info.bind(null, '[INFO]')
console.warn = console.warn.bind(null, '[WARN]')
console.error = console.error.bind(null, '[ERROR]')
/*
* This is intended to communicate with an Amazon ELB. Request / response from
* https://docs.aws.amazon.com/elasticloadbalancing/latest/application/lambda-functions.html
*
* It expects the "event" object to have a member, "path", containing the URL path the function
* was called from. This path is expected to match either "/apachereload/all" or
* "/apachereload/<IP>", where <IP> is an IPv4 address in dotted quad (e.g. 10.154.1.1) notation
*/
module.exports.apachereload = async event => {
const [service, ip] = event.path.split('/').slice(1)
const ok = {
isBase64Encoded: false,
statusCode: 200,
statusDescription: '200 OK',
headers: {
'Set-cookie': 'cookies',
'Content-Type': 'application/json'
},
body: ''
}
const badRequest = {
isBase64Encoded: false,
statusCode: 400,
statusDescription: '400 Bad Request',
headers: {
'Set-cookie': 'cookies',
'Content-Type': 'text/html; charset=utf-8'
},
body: '<html><head><title>Bad Request</title></head>' +
'<body><p>Your browser sent a request this server could not understand.</p></body></html>'
}
const internalServerError = {
isBase64Encoded: false,
statusCode: 500,
statusDescription: '500 Internal Server Error',
headers: {
'Set-cookie': 'cookies',
'Content-Type': 'text/html; charset=utf-8'
},
body: '<html><head><title>It\'s not you, it\'s us</title></head>' +
'<body><p>Well, this is embarrassing. Looks like there\'s a problem on ' +
'our end. We\'ll get it sorted ASAP.</p></body></html>'
}
const notFound = {
isBase64Encoded: false,
statusCode: 404,
statusDescription: '404 Not Found',
headers: {
'Set-cookie': 'cookies',
'Content-Type': 'text/html; charset=utf-8'
},
body: '<html><head><title>Not Found</title></head>' +
'<body><p>No resources were found matching your query</p></body></html>'
}
let response
console.info('Request ' + event.path)
// Send 400 back on an unexpected service
if (service !== 'apachereload') {
console.info('Rejecting request; invalid service "' + service + '"')
response = badRequest
} else if (ip !== 'all' && !ip.match(/^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}/)) {
console.info('Rejecting request; expected IP address or "all", got "' + ip + '"')
response = badRequest
}
console.log('Event: ' + JSON.stringify(event, null, 2) + '\n')
console.log('IP: ' + ip + '\n')
const instanceIds = await getMatchingInstances(ip)
if (instanceIds.length === 0) {
response = notFound
return response
}
response = ok
response.body = JSON.stringify({ instanceIds: instanceIds })
return Promise.resolve(response).then(reloadInstances(instanceIds))
}
/*
* Reload Apache on the EC2 instance with the given IP.
*
* params:
* * ip - IP address of the EC2 to reload Apache on. Pass "all" to restart
* all EC2s marked as Apache boxen (i.e. with tag "apache" having value "true")
*
* returns Promise chaining the AWS EC2 "describe-instances" request and the SSM
* "send-command" request
*/
const getMatchingInstances = (ip) => {
const params = { Filters: [] }
if (ip === 'all') {
params.Filters.push({ Name: 'tag:okToRestart', Values: ['true'] })
} else {
params.Filters.push({ Name: 'private-ip-address', Values: [ip] })
}
console.log('describeInstances params: ' + JSON.stringify(params, null, 2) + '\n')
/*
* Retrieve a list of EC2 instance IDs matching the parameters above
*/
return ec2.describeInstances(params).promise()
// build a list of instance IDs
.then((awsResponse) => {
console.log('describeInstances response: ' + JSON.stringify(awsResponse, null, 2) + '\n')
const instanceIds = []
awsResponse.Reservations.forEach((reservation) => {
reservation.Instances.forEach((instance) => {
const instanceId = instance.InstanceId
console.log('Found instance ID ' + instanceId + '\n')
instanceIds.push(instanceId)
})
})
return instanceIds
})
}
/*
* Build a promise chain for each EC2 instance Apache is to be restarted on.
* For each instance in the list, we will wait process.env.WAIT_TIME ms before going
* on to the next instance.
*/
const reloadInstances = async instanceIds => {
return instanceIds.reduce(async (promiseChain, nextInstanceId, i) => {
await promiseChain
const waitTime = i < (instanceIds.length - 1) ? process.env.WAIT_TIME : 0
return restartApacheOnInstance(nextInstanceId)
.delay(waitTime)
}, Promise.resolve('INIITAL'))
}
/*
* restart Apache on one or more EC2 instances. Helper method for apacheReload()
*
* params:
* * instanceIds - array of EC2 instance IDs to send the "restart Apache" command to
*
* returns Promise containing AWS SSM "send-command" request for the given instance IDs
*
*/
const restartApacheOnInstance = async instanceId => {
console.info('Restart Apache on instance(s) ' + instanceId + '\n')
const params = {
DocumentName: documentName,
InstanceIds: [instanceId],
TimeoutSeconds: process.env.SSM_SEND_COMMAND_TIMEOUT
}
return ssm.sendCommand(params).promise().then(result => {
console.debug('SSM sendCommand result: ' + JSON.stringify(result, null, 2) + '\n')
return result
})
}
/*
* Returns a promise that waits a given amount of time before resolving
*
* Args:
* * time: Amount of time, in ms, to wait
* * value: Optional value that the returned promise will resolve with
*/
// https://stackoverflow.com/questions/39538473/using-settimeout-on-promise-chain
function delay (time, value) {
console.debug('delay args: ' + JSON.stringify({ time: time, value: value }))
return new Promise(resolve => {
console.debug('Wait ' + time + ' ms')
setTimeout(resolve.bind(null, value), time)
})
}
/*
* Attach delay() to all Promises
*/
Promise.prototype.delay = function (time) {
return this.then(function (value) {
return delay(time, value)
})
}
