Migrating from EC2 to Atlas 

! Jesse Dearing Lead Site Reliability Engineer 

InVisionApp 

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MongoDB @ InVision • Chef to manage EC2 instances and MongoDB • 28 MongoDB replica sets across 4 environments • 1500-2000 documents per second retrieved, 300-600 documents per second created or modified 

MongoDB @ InVision • Powers various features of our application • We find it useful for when a document model makes the most sense • Example of this is Inspect 

Starting out with Mongo on AWS • Provision EC2 instances • Chef, Puppet, Ansible, or manually install and configure MongoDB • Set it up as a replica set • Maybe even sharded 

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You still have to take care of • Backups • Monitoring • Alerting • Security • Updates 

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Why? This is what I do • Your job is to maintain MongoDB infrastructure • What are the hiring projections for your team? • At InVision we believe in multiplying the efforts of our teams while growing them at a linear growth (a la SRE) 

Classic Build vs Buy Proposition DevOps edition • You and your team are smart and capable, of course you can build it! 

Classic Build vs Buy Proposition DevOps edition • Do you have the time to maintain the new infrastructure? • Do you want to answer the pager for when your EC2 instances have issues? 

Why we switched to Atlas • Easier management of the aforementioned reasons • Easy to use REST API • Graphical dashboards 

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How do we get on Atlas? 

Preparation • Atlas requires SSL • Set up AWS VPC peering • VPN and Security setup • Make sure we were using Amazon DNS 

Preparation • Pick a network CIDR that won’t collide with your networks • We have multiple VPCs for different environments so we picked something like 10.200.0.0/16 • Assess current instances I/O, CPU, and Memory and figure out how they can map to the Atlas instance types • Make sure you don’t have any locale requirements for your Mongo data 

Preparation • Need to be on MongoDB 3.x using WiredTiger • Test on replicas and use testing/staging environments 

Migration • Simple • Just write a simple daemon in C++ that tails and parses the oplog and replay it in your Atlas MongoDB cluster 

Just Kidding 

Atlas Live Migration • MongoDB announced live migration to Atlas in March • Built into the web UI • Or you can use mongomirror 

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Create Atlas cluster 

Create Instance to run mongomirror 

Perform initial sync 

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Stream oplog to sync 

Cut over application 

Post Migration • Set up alerts • Start with a low watermark until you have a good baseline after a week or so • Update runbooks and test backup restores 

Where we’ve gone • With a good API we’ve found that we can automate provisioning • Self service integration into provisioning • Deploying a new service? Want some MongoDB with that? 

Automation • The REST API is pretty easy to use • We’ve incorporated it into our Ansible scripts • Source at github.com/jessedearing/ansible- mongodb-atlas 

Using Ansible to easily add new Mongo Replicasets 1 --- 2 - hosts: mongodb_atlas 3 connection: local 4 roles: 5 - role: mongodb_atlas 6 clusters: 7 - name: staging-mongo-loginapi 8 size: M30 9 state: present 10 - name: prod-mongo-loginapi 11 size: M30 12 state: present 

Using Ansible to easily add new Mongo Replicasets 1 --- 2 - hosts: mongodb_atlas 3 connection: local 4 roles: 5 - role: mongodb_atlas 6 clusters: 7 - name: staging-mongo-loginapi 8 size: M30 9 state: present 10 - name: prod-mongo-loginapi 11 size: M30 12 state: present 1 --- 2 - hosts: mongodb_atlas 3 connection: local 4 roles: 5 - role: mongodb_atlas 6 clusters: 7 - name: staging-mongo-loginapi 8 size: M30 9 state: present 10 - name: prod-mongo-loginapi 11 size: M30 12 state: present 13 - name: test-mongo-loginapi 14 size: M10 15 state: present 

Go give Atlas a shot • Requires MongoDB SSL • Pick your region and a network CIDR that doesn’t collide with your existing CIDR • mongomirror or live migrate • Leave running MongoDB to the experts 

Thanks! 

Questions?