S3, Cassandra or Outer Space? Dumping Time Series Data using Spark

Demi Ben-Ari - VP R&D @

ROME 24-25 MARCH 2017

About Me

Demi Ben-Ari, Co-Founder & VP R&D @ Panorays● BS’c Computer Science – Academic College Tel-Aviv Yaffo● Co-Founder

○ “Big Things” Big Data Community○ Google Developer Group Cloud

In the Past:● Sr. Data Engineer - Windward● Team Leader & Sr. Java Software Engineer

Missile defense and Alert System - “Ofek” – IAFInterested in almost every kind of technology – A True Geek

Agenda

● Spark brief overview and Catch Up● Data flow and Environment● What’s our time series data like?● Where we started from - where we got to

○ Problems and our decisions○ Evolution of the solution

● Conclusions

Spark Brief Overview & Catchup

Scala & Spark (Architecture)

Scala REPL Scala Compiler

Spark Runtime

Scala Runtime

JVM

File System (eg. HDFS,

Cassandra, S3..)Cluster Manager (eg. Yarn, Mesos)

What kind of DSL is Apache Spark

● Centered around Collections● Immutable data sets equipped with functional transformations

● These are exactly the Scala collection operations

mapflatMap filter...

reducefold aggregate...

unionintersection ...

Spark is A Multi-Language Platform

● Why to use Scala instead of Python?○ Native to Spark, Can use

everything without translation

○ Types help

So Bottom Line…What’s Spark???

United Tools Platform

United Tools Platform - Single Framework

Batch

InteractiveStreaming

Single Framework

Data flow and Environment(Our Use Case)

Structure of the Data

● Maritime Analytics Platform

● Geo Locations + Metadata

● Arriving over time

● Different types of messages being reported by satellites

● Encoded

● Might arrive later than actually transmitted

Data Flow Diagram

External Data

Source

Analytics Layers

Data Pipeline

Parsed Raw

Entity Resolution Process

Building insightson top of the entities

Data Output Layer

Anomaly Detection

Trends

Environment Description

Cluster

Dev Testing Live Staging ProductionEnv

OB1K

RESTful Java Services

Basic Terms

● Missing Parts in Time Series Data◦ Data arriving from the satellites

● Might be causing delays because of bad transmission◦ Data vendors delaying the data stream ◦ Calculation in Layers may cause Holes in the Data

● Calculating the Data layers by time slices

Basic Terms

● Idempotence is the property of certain operations in mathematics and computer science, that can be applied multiple times without changing the result beyond the initial application.

● Function: Same input => Same output

Basic Terms

● Partitions == Parallelism

◦ Physical / Logical partitioning

● Resilient Distributed Datasets (RDDs) == Collections

◦ fault-tolerant collection of elements that can be operated on in parallel.

◦ Applying immutable transformations and actions over RDDs

What RDD’s really are?

So…..

The Problem - Receiving DATA

Beginning state, no data, and the timeline begins

T = 0

Level 3 Entity

Level 2 Entity

Level 1 Entity

The Problem - Receiving DATA

T = 10

Level 3 Entity

Level 2 Entity

Level 1 Entity

Computation sliding window size

Level 1 entities data arrives and gets stored

The Problem - Receiving DATA

T = 10

Level 3 Entity

Level 2 Entity

Level 1 Entity

Computation sliding window sizeLevel 3 entities are created on

top of Level 2’s Data(Decreased amount of data)

Level 2 entities are created on top of Level 1’s Data(Decreased amount of

data)

The Problem - Receiving DATA

T = 20

Level 3 Entity

Level 2 Entity

Level 1 Entity

Computation sliding window size

Because of the sliding window’s back size, level 2 and 3 entities

would not be created properly and there would be “Holes” in the Data

Level 1 entity's data arriving late

Solution to the Problem

● Creating Dependent Micro services forming a data pipeline◦ Mainly Apache Spark applications◦ Services are only dependent on the Data - not the previous

service’s run● Forming a structure and scheduling of “Back Sliding Window”

◦ Know your data and its relevance through time◦ Don’t try to foresee the future – it might Bias the results

Starting point & Infrastructure

How we started?

● Spark Standalone – via ec2 scripts◦ Around 5 nodes (r3.xlarge instances)◦ Didn’t want to keep a persistent HDFS – Costs a lot◦ 100 GB (per day) => ~150 TB for 4 years◦ Cost for server per year (r3.xlarge):

- On demand: ~2900$- Reserved: ~1750$

● Know your costs: http://www.ec2instances.info/

Know Your Costs

Decision

● Working with S3 as the persistence layer◦ Pay extra for

- Put (0.005 per 1000 requests)- Get (0.004 per 10,000 requests)

◦ 150TB => ~210$ for 4 years of Data● Same format as HDFS (CSV files)

◦ s3n://some-bucket/entity1/201412010000/part-00000◦ s3n://some-bucket/entity1/201412010000/part-00001◦ ……

What about the serving?

MongoDB for Serving

Worker 1

Worker 2

….

….

…

…

Worker N

MongoDBReplica Set

Spark Cluster

Master

Write

Read

Spark Slave - Server Specs

● Instance Type: r3.xlarge● CPU’s: 4● RAM: 30.5GB● Storage: ephemeral● Amount: 10+

MongoDB - Server Specs

● MongoDB version: 2.6.1● Instance Type: m3.xlarge (AWS)● CPU’s: 4● RAM: 15GB● Storage: EBS ● DB Size: ~500GB● Collection Indexes: 5 (4 compound)

The Problem

● Batch jobs ◦ Should run for 5-10 minutes in total◦ Actual - runs for ~40 minutes

● Why?◦ ~20 minutes to write with the Java mongo driver – Async

(Unacknowledged) ◦ ~20 minutes to sync the journal◦ Total: ~ 40 Minutes of the DB being unavailable ◦ No batch process response and no UI serving

Alternative Solutions

● Sharded MongoDB (With replica sets)◦ Pros:

- Increases Throughput by the amount of shards- Increases the availability of the DB

◦ Cons:- Very hard to manage DevOps wise (for a small team of

developers)- High cost of servers – because each shared need 3 replicas

Workflow with MongoDB

Worker 1

Worker 2

….

….

…

…

Worker N

Spark Cluster

Master

Write

Read

Master

Our DevOps – After that solution

We had no DevOps guy at that time at all

☹

Alternative Solutions

● Apache Cassandra◦ Pros:

- Very large developer community- Linearly scalable Database- No single master architecture- Proven working with distributed engines like Apache Spark

◦ Cons:- We had no experience at all with the Database- No Geo Spatial Index – Needed to implement by ourselves

The Solution

● Migration to Apache Cassandra ● Create easily a Cassandra cluster using DataStax Community

AMI on AWS ◦ First easy step – Using the spark-cassandra-connector

(Easy bootstrap move to Spark ⬄ Cassandra)◦ Creating a monitoring dashboard to Cassandra

Workflow with Cassandra

Worker 1

Worker 2

….

….

…

…

Worker N

Cassandra Cluster

Spark Cluster

Write

Read

Result

● Performance improvement ◦ Batch write parts of the job run in 3 minutes instead of ~ 40

minutes in MongoDB● Took 2 weeks to go from “Zero to Hero”, and to ramp up a

running solution that work without glitches

So (Again)?

Transferring the Heaviest Process

● Micro service that runs every 10 minutes● Writes to Cassandra 30GB per iteration

◦ (Replication factor 3 => 90GB)● At first took us 18 minutes to do all of the writes

◦ Not Acceptable in a 10 minute process

Cluster On OpsCenter - Before

Transferring the Heaviest Process

● Solutions◦ We chose the i2.xlarge◦ Optimization of the Cluster◦ Changing the JDK to Java-8

- Changing the GC algorithm to G1◦ Tuning the Operation system

- Ulimit, removing the swap◦ Write time went down to ~5 minutes (For 30GB RF=3)

Sounds good right? I don’t think so

Cloud Watch After Tuning

Cloud Watch After Tuning

The Solution

● Taking the same Data Model that we held in Cassandra (All of the Raw data per 10 minutes) and put it on S3◦ Write time went down from ~5 minutes to 1.5 minutes

● Added another process, not dependent on the main one, happens every 15 minutes◦ Reads from S3, downscales the amount and Writes them to

Cassandra for serving

Parsed Raw

Static / Aggregated

Data

Spark Analytics Layers

UI Serving

Downscaled Data

Heavy Fusion

Process

How it looks after all?

Conclusion

● Always give an estimate to your data◦ Frequency◦ Volume◦ Arrangement of the previous phase

● There is no “Best” persistence layer◦ There is the right one for the job◦ Don’t overload an existing solution

Conclusion

● Spark is a great framework for distributed collections◦ Fully functional API◦ Can perform imperative actions

● “With great power, comes lots of partitioning”◦ Control your work and

data distribution via partitions

● https://www.pinterest.com/pin/155514993354583499/ (Thanks)

Questions?

● LinkedIn● Twitter: @demibenari● Blog:

http://progexc.blogspot.com/● demi.benari@gmail.com

● “Big Things” Community

�Meetup, YouTube, Facebook, Twitter

● GDG Cloud