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Distributed, fault-tolerant, transactional

Real-Time Integration: MongoDB and SQL Databases

Eugene DvorkinArchitect, WebMD

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WebMD: A lot of data; a lot of traffic

~900 millions page view a month~100 million unique visitors a month

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How We Use MongoDB

User Activity

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Why Move Data to RDBMS?

Preserve existing investment in BI and data warehouse

To use analytical database such as VerticaTo use SQL

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Why Move Data In Real-time?

Batch process is slow

No ad-hoc queries

No real-time reports

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Challenge in moving data

Transform Document to Relational Structure Insert into RDBMS at high rate

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Challenge in moving data

Scale easily as data volume and velocity increase

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Our Solution to move data in Real-time: Storm

tem. Storm – open source distributed real-time computation system.

Developed by Nathan Marz - acquired by Twitter

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Hadoop Storm

Our Solution to move data in Real-time: Storm

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Why STORM?

JVM-based framework

Guaranteed data processing

Supports development in multiple

languages

Scalable and transactional

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Overview of Storm cluster

Master Node

Cluster Coordination

run worker processes

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Storm Abstractions

Tuples, Streams, Spouts, Bolts and Topologies

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Tuples

(“ns:events”,”email:edvorkin@gmail.com”)

Ordered list of elements

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Stream

Unbounded sequence of tuples

Example: Stream of messages from message queue

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Spout

Read from stream of data – Queues, web logs, API calls, mongoDB oplogEmit documents as tuples

Source of Streams

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BoltsProcess tuples and create new streams

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Bolts

Apply functions /transformsCalculate and aggregate data (word count!)Access DB, API , etc.Filter dataMap/Reduce

Process tuples and create new streams

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Topology

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Topology

Storm is transforming and moving data

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MongoDB

How To Read All Incoming Data from MongoDB?

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MongoDB

How To Read All Incoming Data from MongoDB?

Use MongoDB OpLog

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What is OpLog?

Replication mechanism in MongoDBIt is a Capped Collection

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Spout: reading from OpLog

Located at local database, oplog.rs collection

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Spout: reading from OpLog

Operations: Insert, Update, Delete

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Spout: reading from OpLog

Name space: Table – Collection name

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Spout: reading from OpLog

Data object:

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Sharded cluster

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Automatic discovery of sharded cluster

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Example: Shard vs Replica set discovery

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Example: Shard discovery

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Spout: Reading data from OpLog

How to Read data continuously from OpLog?

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Spout: Reading data from OpLog

How to Read data continuously from OpLog?

Use Tailable Cursor

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Example: Tailable cursor - like tail –f

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Manage timestamps

Use ts (timestamp in oplog entry) field to track processed records

If system restart, start from recorded ts

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Spout: reading from OpLog

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SPOUT – Code Example

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TOPOLOGY

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Working With Embedded Arrays

Array represents One-to-Many relationship in RDBMS

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Example: Working with embedded arrays

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Example: Working with embedded arrays

{_id: 1, ns: “person_awards”, o: { award: 'National Medal of Science', year: 1975, by: 'National Science Foundation' }}

{ _id: 1, ns: “person_awards”,o: {award: 'Turing Award', year: 1977, by: 'ACM' }}

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Example: Working with embedded arrays

public void execute(Tuple tuple) {

.........

if (field instanceof BasicDBList) {

BasicDBObject arrayElement=processArray(field)

......

outputCollector.emit("documents", tuple, arrayElement);

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Parse documents with Bolt

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{"ns": "people", "op":"i", o : { _id: 1, name: { first: 'John', last: 'Backus' }, birth: 'Dec 03, 1924’}

["ns": "people", "op":"i", [“id”:1, "name_first": "John", "name_last":"Backus", "birth": "DEc 03, 1924" ]]

Parse documents with Bolt

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@Override

public void execute(Tuple tuple) {

......

final BasicDBObject oplogObject =

(BasicDBObject)tuple.getValueByField("document");

final BasicDBObject document =

(BasicDBObject)oplogObject.get("o");

......

outputValues.add(flattenDocument(document));

outputCollector.emit(tuple,outputValues);

Parse documents with Bolt

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Write to SQL with SQLWriter Bolt

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Write to SQL with SQLWriter Bolt

["ns": "people", "op":"i", [“id”:1, "name_first": "John", "name_last":"Backus", "birth": "Dec 03, 1924" ]

]insert into people (_id,name_first,name_last,birth) values

(1,'John','Backus','Dec 03,1924') ,

insert into people_awards

(_id,awards_award,awards_award,awards_by) values (1,'Turing

Award',1977,'ACM'),

insert into people_awards

(_id,awards_award,awards_award,awards_by) values (1,'National

Medal of Science',1975,'National Science Foundation')

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@Override public void prepare(.....) {.... Class.forName("com.vertica.jdbc.Driver"); con = DriverManager.getConnection(dBUrl, username,password);

@Override public void execute(Tuple tuple) { String insertStatement=createInsertStatement(tuple); try { Statement stmt = con.createStatement(); stmt.execute(insertStatement); stmt.close();

Write to SQL with SQLWriter Bolt

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Topology Definition

TopologyBuilder builder = new TopologyBuilder();// define our spoutbuilder.setSpout(spoutId, new MongoOpLogSpout("mongodb://", opslog_progress)builder.setBolt(arrayExtractorId ,new ArrayFieldExtractorBolt(),5).shuffleGrouping(spoutId)builder.setBolt(mongoDocParserId, new MongoDocumentParserBolt()).shuffleGrouping(arrayExtractorId,documentsStreamId)builder.setBolt(sqlWriterId, new SQLWriterBolt(rdbmsUrl,rdbmsUserName,rdbmsPassword)).shuffleGrouping(mongoDocParserId)

LocalCluster cluster = new LocalCluster();cluster.submitTopology("test", conf, builder.createTopology());

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Topology Definition

TopologyBuilder builder = new TopologyBuilder();// define our spoutbuilder.setSpout(spoutId, new MongoOpLogSpout("mongodb://", opslog_progress)builder.setBolt(arrayExtractorId ,new ArrayFieldExtractorBolt(),5).shuffleGrouping(spoutId)builder.setBolt(mongoDocParserId, new MongoDocumentParserBolt()).shuffleGrouping(arrayExtractorId,documentsStreamId)builder.setBolt(sqlWriterId, new SQLWriterBolt(rdbmsUrl,rdbmsUserName,rdbmsPassword)).shuffleGrouping(mongoDocParserId)

LocalCluster cluster = new LocalCluster();cluster.submitTopology("test", conf, builder.createTopology());

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Topology Definition

TopologyBuilder builder = new TopologyBuilder();// define our spoutbuilder.setSpout(spoutId, new MongoOpLogSpout("mongodb://", opslog_progress)builder.setBolt(arrayExtractorId ,new ArrayFieldExtractorBolt(),5).shuffleGrouping(spoutId)builder.setBolt(mongoDocParserId, new MongoDocumentParserBolt()).shuffleGrouping(arrayExtractorId,documentsStreamId)builder.setBolt(sqlWriterId, new SQLWriterBolt(rdbmsUrl,rdbmsUserName,rdbmsPassword)).shuffleGrouping(mongoDocParserId)

LocalCluster cluster = new LocalCluster();cluster.submitTopology("test", conf, builder.createTopology());

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Topology Definition

TopologyBuilder builder = new TopologyBuilder();// define our spoutbuilder.setSpout(spoutId, new MongoOpLogSpout("mongodb://", opslog_progress)builder.setBolt(arrayExtractorId ,new ArrayFieldExtractorBolt(),5).shuffleGrouping(spoutId)builder.setBolt(mongoDocParserId, new MongoDocumentParserBolt()).shuffleGrouping(arrayExtractorId,documentsStreamId)builder.setBolt(sqlWriterId, new SQLWriterBolt(rdbmsUrl,rdbmsUserName,rdbmsPassword)).shuffleGrouping(mongoDocParserId)

StormSubmitter.submitTopology("OfflineEventProcess", conf,builder.createTopology())

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Lesson learned

By leveraging MongoDB Oplog or

other capped collection, tailable cursor

and Storm framework, you can build

fast, scalable, real-time data

processing pipeline.

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Resources

Book: Getting started with StormStorm Project wikiStorm starter projectStorm contributions projectRunning a Multi-Node Storm cluster tutorialImplementing real-time trending topicA Hadoop Alternative: Building a real-time data pipeline with StormStorm Use cases

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Resources (cont’d)

Understanding the Parallelism of a Storm TopologyTrident – high level Storm abstraction A practical Storm’s Trident API Storm online forumMongo connector from 10gen Labs MoSQL streaming Translator in RubyProject source codeNew York City Storm Meetup

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Questions

Eugene Dvorkin, Architect, WebMD edvorkin@webmd.net Twitter: @edvorkin LinkedIn: eugenedvorkin

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Next Sessions at 2:505th Floor:

West Side Ballroom 3&4: Data Modeling Examples from the Real World

West Side Ballroom 1&2: Growing Up MongoDB

Juilliard Complex: Business Track: MetLife Leapfrogs Insurance Industry with MongoDB-Powered Big Data Application

Lyceum Complex: Ask the Experts: MongoDB Monitoring and Backup Service Session

7th Floor:

Empire Complex: How We Fixed Our MongoDB Problems

SoHo Complex: High Performance, High Scale MongoDB on AWS: A Hands On Guide