1.
Nathan Marz
Twitter
Distributed and fault-tolerant realtime computation
Storm

2.
Basic info
• Open sourced September 19th
• Implementation is 12,000 lines of code
• Used by over 25 companies
• >2280 watchers on Github (most watched
JVM project)
• Very active mailing list
• >1700 messages
• >520 members

3.
Before Storm
Queues Workers

4.
Example
(simplified)

5.
Example
Workers schemify tweets
and append to Hadoop

6.
Example
Workers update statistics on URLs by
incrementing counters in Cassandra

7.
Problems
• Scaling is painful
• Poor fault-tolerance
• Coding is tedious

8.
What we want
• Guaranteed data processing
• Horizontal scalability
• Fault-tolerance
• No intermediate message brokers!
• Higher level abstraction than message passing
• “Just works”

9.
Storm
Guaranteed data processing
Horizontal scalability
Fault-tolerance
No intermediate message brokers!
Higher level abstraction than message passing
“Just works”

10.
Stream
processing
Continuous
computation
Distributed
RPC
Use cases

11.
Storm Cluster

12.
Storm Cluster
Master node (similar to Hadoop JobTracker)

13.
Storm Cluster
Used for cluster coordination

14.
Storm Cluster
Run worker processes

15.
Starting a topology

16.
Killing a topology

17.
Concepts
• Streams
• Spouts
• Bolts
• Topologies

18.
Streams
Unbounded sequence of tuples
Tuple Tuple Tuple Tuple Tuple Tuple Tuple

19.
Spouts
Source of streams

20.
Spout examples
• Read from Kestrel queue
• Read from Twitter streaming API

21.
Bolts
Processes input streams and produces new streams

22.
Bolts
• Functions
• Filters
• Aggregation
• Joins
• Talk to databases

23.
Topology
Network of spouts and bolts

24.
Tasks
Spouts and bolts execute as
many tasks across the cluster

25.
Stream grouping
When a tuple is emitted, which task does it go to?

26.
Stream grouping
• Shuffle grouping: pick a random task
• Fields grouping: mod hashing on a
subset of tuple fields
• All grouping: send to all tasks
• Global grouping: pick task with lowest id

27.
Topology
shuffle
[“url”]
shuffle
shuffle
[“id1”,“id2”]
all

28.
Streaming word count
TopologyBuilder is used to construct topologies in Java

29.
Streaming word count
Define a spout in the topology with parallelism of 5 tasks

30.
Streaming word count
Split sentences into words with parallelism of 8 tasks

31.
Consumer decides what data it receives and how it gets grouped
Streaming word count
Split sentences into words with parallelism of 8 tasks

32.
Streaming word count
Create a word count stream

33.
Streaming word count
splitsentence.py

34.
Streaming word count

35.
Streaming word count
Submitting topology to a cluster

36.
Streaming word count
Running topology in local mode

37.
Demo

38.
Distributed RPC
Data flow for Distributed RPC

39.
DRPC Example
Computing “reach” of a URL on the fly

40.
Reach
Reach is the number of unique people
exposed to a URL on Twitter

41.
Computing reach
URL
Tweeter
Tweeter
Tweeter
Follower
Follower
Follower
Follower
Follower
Follower
Distinct
follower
Distinct
follower
Distinct
follower
Count Reach

42.
Reach topology

43.
Reach topology

44.
Reach topology

45.
Reach topology
Keep set of followers for
each request id in memory

46.
Reach topology
Update followers set when
receive a new follower

47.
Reach topology
Emit partial count after
receiving all followers for a
request id

48.
Demo

49.
Guaranteeing message
processing
“Tuple tree”

50.
Guaranteeing message
processing
• A spout tuple is not fully processed until all
tuples in the tree have been completed

51.
Guaranteeing message
processing
• If the tuple tree is not completed within a
specified timeout, the spout tuple is replayed

52.
Guaranteeing message
processing
Reliability API

53.
Guaranteeing message
processing
“Anchoring” creates a new edge in the tuple tree

54.
Guaranteeing message
processing
Marks a single node in the tree as complete

55.
Guaranteeing message
processing
• Storm tracks tuple trees for you in an
extremely efficient way

56.
Transactional topologies
How do you do idempotent counting with an
at least once delivery guarantee?

57.
Won’t you overcount?
Transactional topologies

58.
Transactional topologies solve this problem
Transactional topologies

59.
Built completely on top of Storm’s primitives
of streams, spouts, and bolts
Transactional topologies

60.
Batch 1 Batch 2 Batch 3
Transactional topologies
Process small batches of tuples

61.
Batch 1 Batch 2 Batch 3
Transactional topologies
If a batch fails, replay the whole batch

62.
Batch 1 Batch 2 Batch 3
Transactional topologies
Once a batch is completed, commit the batch

63.
Batch 1 Batch 2 Batch 3
Transactional topologies
Bolts can optionally implement “commit” method

64.
Commit 1
Transactional topologies
Commits are ordered. If there’s a failure during
commit, the whole batch + commit is retried
Commit 1 Commit 2 Commit 3 Commit 4 Commit 4

65.
Example

66.
Example
New instance of this object
for every transaction attempt

67.
Example
Aggregate the count for
this batch

68.
Example
Only update database if
transaction ids differ

69.
Example
This enables idempotency since
commits are ordered

70.
Example
(Credit goes to Kafka guys
for figuring out this trick)

71.
Transactional topologies
Multiple batches can be processed in parallel,
but commits are guaranteed to be ordered

72.
• Will be available in next version of Storm
(0.7.0)
• Requires a source queue that can replay
identical batches of messages
• Aiming for first TransactionalSpout
implementation to use Kafka
Transactional topologies

73.
Storm UI

74.
Storm on EC2
https://github.com/nathanmarz/storm-deploy
One-click deploy tool

75.
Starter code
https://github.com/nathanmarz/storm-starter
Example topologies

76.
Documentation

77.
Ecosystem
• Scala, JRuby, and Clojure DSL’s
• Kestrel,AMQP, JMS, and other spout adapters
• Serializers
• Multilang adapters
• Cassandra, MongoDB integration

78.
Questions?
http://github.com/nathanmarz/storm

79.
Future work
• State spout
• Storm on Mesos
• “Swapping”
• Auto-scaling
• Higher level abstractions