Large Scale NoSQL DB Migration

- Under Fire -

Ido Barkan

- Proprietary & Confidential -

Agenda

● What is Appsflyer?● Motivation and limitations● War plan● What have we learned?

What is Appsflyer?~25B events per day

Installs DB- Zoom in

app installs writer

2K write IOPS

app events enrichments 180k read

IOPS

We need to replace CouchBase

● Scale out is out of control(45 r3.4xl instances)

● XDCR can’t keep up● Daily backups take more than a day● Paid support is not good enough

chosen solution: Aerospike

Rules of the game- starting point

● # of records: ~ 2,000,000,000 (repl. factor 3)

● Read intensive: 180K read + 2K write IOPS

● # of machines: 45 r3.4xlarge● Cost: ~ 30,000 $ per month● Time frame: a few months.

Mission critical

Why is data migration harderthan in a relational DB?

Relational DB NoSql DB

Data types conventional blob, JSON, specialized bins

Vendors a few 100+

Query Language

SQL N1QL, SQL, JavaScript, HTTP/REST-- creating views/ MapReduce style

Schema Yes Maybe

Migration tools

Yes DIY

Rules of the game

No DowntimeNo data loss

War plan- easy part

● Write new installs/updates to BOTH● Continue reading from the OLD DBApplication

Breathing (testing) time

test test test● Sizing RAM/Disk● Expected load● Metrics● Alerting● Logs● Backups

Easy part (Cont.)

● Write new installs/updates to NEW DB● Read from BOTH DBs

● A fraction of records (not VIP)

● Do NOT delete yet!● Have metrics on

misses

Breathing timeTest Test Test● Sizing (again)● Expected load (with reads)● Metrics (again)

Is that it?

If your data is short lived- you are mostly done.

Otherwise...

`Manual` partMigrating the long tail

Dumperview (query)dump keys/records

Kafka as a buffer

Loader-> write(do not overwrite)

values

Detour: DB views

function (doc, meta) {emit(meta.expiration, doc.id);}

key (sorting) value

Map function (JS)

● Record itself is NOT a part of the view

`Manual` partMigrating the long tail

Dumperview (query)dump keys/records

Kafka as a buffer

Loader-> write(do not overwrite)

values

New Cluster

● # of records: ~ 2,000,000,000 ● 2AZ- repl. factor 2 in each one● IOPS, same and growing● # of machines: 2 x 5 i3.4xlarge● Cost: ~ 10,000 $ per month (⅓)

What have we learned?

1. Plan, Plan, Plan.2. Go easy: test a sample before you start

(1 app / API / Customer).3. Breath (read: test) between stages.4. Do NOT delete until you have to.5. slower -> safer (-> $$$).

Thank you!

ido@appsflyer.com