CDE

• Cloud Database Engineering

• Responsible for providing data stores as

services @ Netflix

CDE Services

Agenda

• Cassandra @ Netflix

• Challenges

• Certification and benchmarking

• CDE Architecture

• 98% of streaming data is stored in Cassandra

• Data ranges from customer details to Viewing history / streaming bookmarks to billing and payment

Cassandra @ Netflix

Cassandra Footprint

• Hundreds of clusters

• Tens of Thousands of nodes

• PBs of data

• Millions of transactions / sec

Challenges

• Monitoring

• Maintenance

• Open source product

• Production readiness

Monitoring

• What do we monitor?– Latencies

• Co-ordinator Read 99th and 95th based on cluster configurations• Co-ordinator Write 99th and 95th based on cluster configurations

– Health• Health check (Powered by Mantis)• Gossip issues• Thrift/ Binary services status • Heap • Dmesg - Hardware and network issues

Monitoring

• Recent maintenances– Jenkins– User initiated maintenances

• Wide row metrics• Log file warning/ errors/exceptions

Common Approach

CRON System

JobRunnerJob

RunnerJobRunnerJob

Runner

Common Architecture

Problems inherent in polling

● Point-in-time snapshot, no state● Establishing a connection to a cluster when it’s

under heavy load is problematic● Not resilient to network hiccups, especially for

large clusters

A different approach

What if we had a continuous stream of fine-grained snapshots ?

Mantis Streaming System

Stream processing system built on Apache Mesos

– Provides a flexible programming model– Models computation as a distributed DAG– Designed for high throughput, low latency

Health Check using Mantis

SourceJob

LocalRingAgg

GlobalRingAgg

SourceJob

SourceJob

eu-west-1

us-east-1us-w

est-2

LocalRingAgg

LocalRingAgg

Score

S

Health EvaluatorConsumes ScoresFSM

Health Status

S

SS

SS

SS

Score

MM

MM

MM

That’s great, but...

Now the health of the fleet is encapsulated in a

single data stream, so how do we make sense of

that ?

Real Time Dash (Macro View)

Macro View of the fleet

Real Time Dash (Cluster View)

Real Time Dash (Perspective)

Benefits

● Faster detection of issues● Greater accuracy● Massive reduction in false positives● Separation of concerns (decouples detection

from remediation)

Known problems

• Distributed persistent stores (Not stateless)• Unresponsive nodes • Cloud• Configurations setup and tuning• Hot nodes / token distribution• Resiliency

• Bootstrapping and automated token assignment

• Backup and recovery/restore

• Centralized configuration management

• REST API for most nodetool commands

• C* JMX metrics collection

• Monitor C* health

Building C* in cloud with Priam

(1) Alternate availability zones (a, b, c) around the ring to ensure data is written tomultiple data centers.

(2) Survive the loss of a datacenter by ensuring that we only lose one node from each replication set.

A B

C

A

B

cA

B

C

A

B

C

Priam runs on each node and will:

* Assign tokens to each node, alternating (1) the AZs around the ring (2).

* Perform nightly snapshot backup to S3

* Perform incremental SSTable backups to S3

* Bootstrap replacement nodes to use vacated tokens

* Collect JMX metrics for our monitoring systems

* REST API calls to most nodetool functions

Cassandra

Priam

Tomcat

Putting it all together

Constructing a cluster in AWS

AMI contains os, base netflix packages and Cassandra and Priam

S3

28

Address DC Rack Status State Load Owns Token

…###.##.##.### eu---west 1a Up Normal 108.97 GB 16.67% …###.##.#.## us---east 1e Up Normal 103.72 GB 0.00% …##.###.###.### eu---west 1b Up Normal 104.82 GB 16.67% …##.##.##.### us---east 1c Up Normal 111.87 GB 0.00% …

###.##.##.### us---east 1e Up Normal 102.71 GB 0.00% …##.###.###.### eu---west 1b Up Normal 101.87 GB 16.67% …##.##.###.## us---east 1c Up Normal 102.83 GB 0.00% …###.##.###.## eu---west 1c Up Normal 96.66 GB 16.67% …##.##.##.### us---east 1d Up Normal 99.68 GB 0.00% …

Instance

Region

Availability Zone (AZ)

Autoscaling GroupsASGs do not map directly to nodetool ring output, but are used to define the cluster (# of instances, AZs, etc).

Amazon Machine Image Image loaded onto an AWS instance; all packages needed to run an application.

29

##.###.##.### eu---west 1c Up Normal 95.51 GB 16.67% …##.##.##.## us---east 1d Up Normal 105.85 GB 0.00% …##.###.##.### eu---west 1a Up Normal 91.25 GB 16.67% …

AWS Terminology

Constructing a cluster in AWS

Security Group

Defines access control between ASGs

Resiliency

• Instance

• AZ

• Multiple AZ

• Region

Resiliency - Instance

• RF=AZ=3

• Cassandra bootstrapping works really well

• Replace nodes immediately

• Repair on regular interval

Resiliency - One AZ

• RF=AZ=3• Alternating AZs ensures that each AZ has a full replica of

data• Provision cluster to run at 2/3 capacity• Ride out a zone outage; do not move to another zone• Bootstrap one node at a time• Repair after recovery

Resiliency - Multiple AZ

• Outage; can no longer satisfy quorum

• Restore from backup and repair

Resiliency - Region

• Connectivity loss between regions – operate as island

clusters until service restored

• Repair data between regions

NdBench - Netflix Data Benchmark

••••••

•

-

-

-

•

Stitching it together

C* as a Service - Architecture

JENKINS

WINSTON

EUNOMIA

Alert Atlas Mantis

C*

C*

C*PriamBolt

Cluster Metadata

Cluster Metadata/ Advisor

Maintenance

Remediation

C*

PAGE CDE

Alert if needed

Capacity Prediction

Outlier detection

C* Forklifter

NDBench

C* Explorer

Client Drivers

Log analysis

••