Friday, March 23, 2012

PyCon: Storm: the Hadoop of Realtime Stream Processing

See the website.

"Storm: Keeping it Real(time)."

Storm is from dotCloud which is a platform to scale web apps.

They're in the MEGA-DATA zone.

They were using RRD.

Storm is real-time, computation framework.

It can do distributed RPC and stream processing.

It focuses on continuous computation, such as counting all the things passing by on a stream.

Storm does for real-time what Hadoop does for batch processing.

It is a high-volume, distributed, horizontally scalable, continuous system.

Even if the control layer goes down, computation can keep going.

It's strategy for handling failures is to die and recover quickly.

It is fault tolerant, but not fault proof.

Data is processed at least once. With more work and massaging, they have support for "exactly once".

Storm does not handle persistence.

If failures happen, it resubmits stuff through the system.

It doesn't process batches reliability.

It complements Hadoop, but does not attempt to replace Hadoop.

It does not protect against human error.

He suggested that one day we'll use a mix of batching and streaming to get the benefits of both.

Storm has three core elements:
  1. Sprouts inject data into the system. This could be data from a queue. This could be data from the Twitter firehose.
  2. Streams are an unbounded sequence of storm tuples. These are like named tuples. All tuples of the same stream must have same "shape".
  3. Bolts take inputs and transform them to make output streams. 0 or more inputs produces 0 or more outputs. Most of the computation happens here.
Sprouts and bolts can both produce multiple output streams.

A topology is a set of sprouts and bolts connected by streams.

This is a higher-level abstraction than message passing.

All of this is done over 0mq. It uses ZooKeeper for discovery. Storm simplifies all of this.

They're handling 10k-100k requests per second at their company.

Storm is JVM based. It's a 50/50 mix of Java and Clojure. It has a multilingual API. Script bolts can be written using a thin shell that shells out to Python.

"Umbrella" protects you from the Storm. It lets you use Storm pretty much Java free.

He's using nested classes for declarative programming.

He deployed it on DOTCLOUD.

A storm topology can even have cycles.

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