Node.js and Cassandra
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This document discusses using Node.js and Cassandra for highly concurrent systems. It explains that Node.js is well-suited for I/O-bound applications with low CPU usage that require high concurrency. This is because Node.js uses an event-driven, non-blocking model that handles connections efficiently in a single thread without much overhead. The document also introduces the Cassandra driver for Node.js, which features connection pooling, load balancing, retry functions, and row/field streaming for efficiently accessing Cassandra from Node.js applications. Examples are given showing how to perform queries, stream rows and fields to responses.
![The Driver for Cassandra
Sample: Json Web Api
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app.get('/user/:id', function (req, res, next){
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var query = 'SELECT * FROM users WHERE id = ?';
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cassandra.executeAsPrepared(query, [req.params.id], function (err, result) {
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if (err) return next(err);
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var row = result.rows[0];
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//Response: expose some properties of the user
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res.json({id: req.params.id, name: row.get('name')});
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});
});](https://image.slidesharecdn.com/nodejsandcassandra-131127112319-phpapp02/85/Node-js-and-Cassandra-12-320.jpg)
![The Driver for Cassandra
Sample: Field streaming
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app.get('/user/:id/image', function (req, res, next){
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var query = 'SELECT id, profile_image FROM users WHERE id = ?';
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cassandra.streamField(query, [req.params.id], function (err, row, image) {
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if (err) return next(err);
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//pipe the image stream to the response stream
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image.pipe(res);
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});
});](https://image.slidesharecdn.com/nodejsandcassandra-131127112319-phpapp02/85/Node-js-and-Cassandra-14-320.jpg)
![The Driver for Cassandra
Sample: Field streaming + image resizing
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app.get('/user/:id/image', function (req, res, next){
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var query = 'SELECT id, profile_image FROM users WHERE id = ?';
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cassandra.streamField(query, [req.params.id], function (err, row, image) {
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if (err) return next(err);
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//pipe the image stream to a resizer stream
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image.pipe(resizer).pipe(res);
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});
});](https://image.slidesharecdn.com/nodejsandcassandra-131127112319-phpapp02/85/Node-js-and-Cassandra-15-320.jpg)
Node.js and Cassandra
- 1. Node.js and Cassandra For highly concurrent systems
- 2. Software as a service Most common scenario • • • I/O Bound o db o other services o file system Low CPU usage Peaks and valleys
- 3. Why Node.js
- 4. Why Node.js Event-based • • • • Single threaded Minimum overhead per connection Predictable amount of memory under load Apache / IIS vs Nginx: Process-based vs event-loop Everything runs in parallel except your code
- 5. Why Node.js Event-based: Apache vs Nginx source webfaction.com
- 6. Why Node.js Async I/O • • Uses OS network interfaces + fixed thread pool Time spent: db connections / files
- 7. Why Node.js Javascript: Closures • • • • CPS: Continuation passing style The scope of the outer function -> inner function Javascript: Functional / Dynamic / Object oriented ... packet manager / os community / V8 / ubiquitous...
- 8. Why Node.js Stream everything • • • • Avoid buffering HTTP: Chunked requests and responses TCP: Chunks readable in a stream Stream Piping (UNIX like)
- 9. The Driver for Cassandra
- 10. The Driver for Cassandra Features • • • • • Connection pooling to multiple hosts Load balancing Automatic failover / retry Row and field streaming Queuing: Concurrent connecting / preparing
- 11. The Driver for Cassandra App Cassandra nodes A G E D C F H B
- 12. The Driver for Cassandra Sample: Json Web Api 1 app.get('/user/:id', function (req, res, next){ 2 var query = 'SELECT * FROM users WHERE id = ?'; 3 cassandra.executeAsPrepared(query, [req.params.id], function (err, result) { 4 if (err) return next(err); 5 var row = result.rows[0]; 6 //Response: expose some properties of the user 7 res.json({id: req.params.id, name: row.get('name')}); 8 9 }); });
- 13. The Driver for Cassandra How row streaming works Readable stream Transform stream Transform stream Socket Protocol Parser Chunks Heade r and body chunk s Client Row
- 14. The Driver for Cassandra Sample: Field streaming 1 app.get('/user/:id/image', function (req, res, next){ 2 var query = 'SELECT id, profile_image FROM users WHERE id = ?'; 3 cassandra.streamField(query, [req.params.id], function (err, row, image) { 4 if (err) return next(err); 5 //pipe the image stream to the response stream 6 image.pipe(res); 7 8 }); });
- 15. The Driver for Cassandra Sample: Field streaming + image resizing 1 app.get('/user/:id/image', function (req, res, next){ 2 var query = 'SELECT id, profile_image FROM users WHERE id = ?'; 3 cassandra.streamField(query, [req.params.id], function (err, row, image) { 4 if (err) return next(err); 5 //pipe the image stream to a resizer stream 6 image.pipe(resizer).pipe(res); 7 8 }); });
- 16. Moving forward Next features • • Multiple data centers support. Cassandra query tracing Contribute! :)
- 17. Thanks! Jorge Bay Gondra @jorgebg jorgebaygondra@gmail.com github.com/jorgebay/node-cassandra-cql npm install node-cassandra-cql
- 18. A Design Framework for Highly Concurrent Systems by Matt Welsh, Steven D. Gribble, Eric A. Brewer, and David Culler @ UC Berkeley Concurrency is not Parallelism (it's better) by Rob Pike @Google Go lang How the single threaded non blocking IO model works in Node.js References and further reading