This blog has explained a few Serverless concepts with code samples:

This particular blog entry will show how to use AWS Lambda to store tweets of a tweeter in Couchbase. Here are the high level components:

lambda-twitter-couchbase

The key concepts are:

Complete sample code for this blog is available at github.com/arun-gupta/twitter-n1ql.

Serverless Application Model

Serverless Application Model, or SAM, defines simplified syntax for expressing serverless resources. SAM extends AWS CloudFormation to
add support for API Gateway, AWS Lambda and Amazon DynamoDB. Read more details in Microservice using AWS Serverless Application Model and Couchbase.
For our application, SAM template is available at github.com/arun-gupta/twitter-n1ql/blob/master/template-example.yml and shown below:

What do we see here?

  • Function is packaged and available in a S3 bucket
  • Handler class is org.sample.twittter.TwitterRequestHandler and is at github.com/arun-gupta/twitter-n1ql/blob/master/twitter-feed/src/main/java/org/sample/twitter/TwitterRequestHandler.java.
    It looks like:

    By default, this class reads the twitter handle of Donald Trump. More fun on that coming in a subsequent blog.
  • COUCHBASE_HOST and COUCHBASE_BUCKET_PASSWORD are environment variables that provide EC2 host where Couchbase database is running and the password of the bucket.
  • Function can be triggered by different events. In our case, this is triggered every three hours. More details about the expression used here are at Schedule Expressions Using Rate or Cron.

Fetching Tweets using Twitter4J

Tweets are read using Twitter4J API. It is an unofficial Twitter API that provides a Java abstraction over Twitter REST API. Here is a simple example:

Twitter4J Docs and Javadocs are pretty comprehensive. Twitter API allows to read only last 200 tweets. Lambda function is invoked every 3 hours.
The tweet frequency of @realDonaldTrump is not 200 every 3 hours, at least yet. If it does reach that dangerous level then we can adjust the rate to trigger Lambda function more frequently.
JSON representation of each tweet is stored in Couchbase server using Couchbase Java SDK. AWS Lambda supports Node, Python and C#. And so
you can use Couchbase Node SDK, Couchbase Python SDK or
Couchbase .NET SDK to write these functions as well. Twitter4J API allows to fetch tweets since the id of a particular tweet. This allows to
ensure that duplicate tweets are not fetched. This requires us to sort all tweets in a particular order and then pick the id of the most recent tweet. This was solved using the simple N1QL query:

The syntax is very SQL-like. More on this in a subsequent blog.

Store Tweets in Couchbase

The final item is to store the retrieved tweets in Couchbase. Value of COUCHABSE_HOST environment variable is used to connect to the Couchbase instance. The value of COUCHBASE_BUCKET_PASSWORD environment variable
is to connect to the secure bucket where all JSON documents are stored. Its very critical that the bucket be password protected and not directly specified in the source code. More on this in a subsequent blog. The JSON document
is upserted (insert or update) in Couchbase using the Couchbase Java API:

This Lambda Function has been running for a few days now and has captured 258 tweets from @realDonaldTrump.

An interesting analysis of his tweets is coming shortly!

Talk to us:

Complete sample code for this blog is available at github.com/arun-gupta/twitter-n1ql.

Posted by Arun Gupta, VP, Developer Advocacy, Couchbase

Arun Gupta is the vice president of developer advocacy at Couchbase. He has built and led developer communities for 10+ years at Sun, Oracle, and Red Hat. He has deep expertise in leading cross-functional teams to develop and execute strategy, planning and execution of content, marketing campaigns, and programs. Prior to that he led engineering teams at Sun and is a founding member of the Java EE team. Gupta has authored more than 2,000 blog posts on technology. He has extensive speaking experience in more than 40 countries on myriad topics and is a JavaOne Rock Star for three years in a row. Gupta also founded the Devoxx4Kids chapter in the US and continues to promote technology education among children. An author of several books on technology, an avid runner, a globe trotter, a Java Champion, a JUG leader, NetBeans Dream Team member, and a Docker Captain, he is easily accessible at @arungupta.

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