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AWS Elastic Beanstalk master instance nodejs cron.
const logger = require('./logger'),
AWS = require('aws-sdk'),
CronJob = require('cron').CronJob;
AWS.config.update({region: 'us-east-1'}); // change to your region
var opts = {
credentials: new AWS.EC2MetadataCredentials()// default to use the credentials for the ec2 instance
};
var elasticbeanstalk = new AWS.ElasticBeanstalk(opts);
var ec2 = new AWS.EC2(opts);
var metadata = new AWS.MetadataService(opts);
function runTaskOnMaster(name, taskToRun) {
logger.info('Beginning task: ' + name);
return new Promise( (resolve, reject) => {
metadata.request('/latest/meta-data/instance-id', (err, InstanceId) => {
if (err) {return reject(err);}
return resolve(InstanceId)
});
})
.then((currentInstanceId) => {
console.log('InstanceId', currentInstanceId);
return new Promise( (resolve, reject) => {
var params = {
Filters: [
{
Name: 'resource-id',
Values: [currentInstanceId]
}
]
};
ec2.describeTags(params, (err, data) => {
if (err) {return reject('dt' + err);}
var envIdTag = data.Tags.find(t => t.Key === 'elasticbeanstalk:environment-id');
if (envIdTag === null) {
return reject('Failed to find the value of "elasticbeanstalk:environment-id" tag.');
}
elasticbeanstalk.describeEnvironmentResources({EnvironmentId: envIdTag.Value}, function (err, data) {
if (err) { return reject('de' + err); }
if (currentInstanceId !== data.EnvironmentResources.Instances[0].Id) { return resolve(false); }
return resolve(true);
});
});
});
})
.then( (isMaster) => {
if (!isMaster) {
logger.warn('Not running task as not master EB instance.');
} else {
logger.info('Identified as master EB instance. Running task.');
taskToRun();
}
})
.catch( (err) => logger.error(err));
}
logger.info('*** Starting Cron Jobs! ***');
new CronJob('0 */5 * * * *', function() { //every 5 min
runTaskOnMaster( 'Task 1', () => {
//do cron work here.
});
}, null, true);
@ayavilevich
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ayavilevich commented Feb 19, 2019

an async/await version based on this snippet
https://gist.github.com/ayavilevich/9cea31154a71d079cb5328006a72bd53

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