Starting January 2018, Amazon ECS will have a native Service Discovery experience for container-based applications. This feature enables developers to look up service dependencies using a friendly and predictable DNS name. In this session, we'll deep dive into ECS Service Discovery, how it will work, and why we built it.

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ECS Service Discovery
S h u b h a R a o , S r . P r o d u c t M a n a g e r , E l a s t i c C o n t a i n e r S e r v i c e
A l e x a n d r M o r o z , S r . P r o d u c t M a n a g e r , R o u t e 5 3

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Application communication is evolving
Functional calls
Find endpoints,
then connect
Across the room
Dynamic name,
number, and location
Across cities 1:1
Known endpoints, APIs

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Developers need to connect micro services
Build apps
invoking other
services by name
Ensure that service
name resolves to
correct IP/port
DEV OPS

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What is Service Discovery?
“Where is Service X?”
Friendly name -> IP + port
E.g., app: {10.0.4.5:8080, 10.0.4.6:8080 }

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Why is it non trivial?
Dynamic by design:
Number of containers & instances
Auto assigned IP addresses & ports
Placement, scheduling, scaling
Deployments and upgrades
Health and connectivity

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C u rre n t p at te r n s r e qu ir e in stall, se t u p an d m an ag e m e n t
Load Balancers Key-value store Service Mesh
Service
registry

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Decision criteria
Service registry
Discovery mechanism
Server side or client side
Registration mechanism
Third party or application framework

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E.g.,
Load Balancer
Benefits
Client is simpler
Drawbacks
Install, manage
Availability, capacity
More hops
Load Balancers – Server Side Discovery
Client
Server
Server
Server
Request Request
LB +
Service
Registry
Register
Register

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DNS based – Client Side Discovery
E.g.,
Route 53 Based
Benefits
Fewer hops
Drawbacks
Client must be registry aware
Client implements discovery logic
Client
Server
Server
Server
Service
Registry
Request
Register
Register
Register
Query

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Requires registrations by agents
E.g.,
Consul, Etcd and Zookeeper
Benefits
Registrar registers, unregisters
and performs health checks
Service less complex
Drawbacks
State may not reflect whether service can
handle requests, only active or unavailable
Install, configure and manage other
component, unless it is a part of infrastructure
Server
Server
Server
Service
Registry
Update Start, stop,
health change
Registrar/
service manager

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Requires registrations by agents
E.g.,
Consul, Etcd and Zookeeper
Benefits
Registrar registers, unregisters
and performs health checks
Service less complex
Drawbacks
State may not reflect whether service
can handle requests, only active or
unavailable
Install, configure and manage other
component, unless it is a part of
infrastructure
Client
Server
Server
Client
Key
Value
Service
Registry
Registrator
Server
Client
Key
Value
Key
Value
Master
Key
Value
Service
Registry
Key
Value
Key
Value
Master
Registrator

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Customers want it simpler!
Predictable
Names
for services
Auto updated
with latest,
healthy IP, port
Managed: No
overhead of
installation or
monitoring
High availability,
high scale
Extensible:
Flexible
boundaries for
auto discovery

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Introducing managed service discovery for ECS
You build apps where
services are invoked by
name & name resolves
to IP/port dynamically
You turn on service
discovery during
deployment —
service creation
DEV OPS

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ECS service discovery is powered by Route 53
ECS updates service registry based
on naming convention, task
registrations, de-registrations
and health
Route 53 provides Service Registry
Route 53ECS

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What’s new?

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Route 53 provides Service Registry
Route 53 provides APIs to create
• Namespace
• CNAME per service autoname
• A records per task IP
• SRV records per task IP + port
More details later in the presentation
Service
CNAME: A / SRV record
Namespace

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ECS schedules & places service endpoints
ECS Scheduler updates on:
• Service scaling
• Task registrations
• Task de-registrations
• Task health
• Scheduling / Placement changes
• ECS instance changes
ECS maintains latest state of the
dynamic environment in Service
Registry
Cluster: myapp
app
IP
web
IP
app
IP
web
IP
AZ 1 AZ 2

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ECS updates service endpoints in Route 53
Cluster: myapp
AZ 1 AZ 2
app
10.0.6.5:8080
web
10.0.8.6:8080
app
10.0.4.5:8080
web
10.0.3.6:8080
Namespace: myapp.local
Service
web.myapp.local CNAME
10.0.4.5:8080
10.0.3.6:8080
Service
app.myapp.local CNAME
10.0.6.5:8080
10.0.8.6:8080

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Services connect to latest endpoints via DNS
Service
web.myapp.local CNAME
10.0.4.5:8080
10.0.3.6:8080
app
>dig web.myapp.local
> 10.0.4.5:8080
>
app web
web
Cluster: myapp DNS Server:
AZ 1 AZ 2

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Benefits of this approach
Cluster: myapp
AZ 1 AZ 2
Service
Namespace
Managed
Just turn on
Highly available
Tied to Route 53
availability, scale
Extensible
Public APIs that can be
used across AWS
Works across clusters,
accounts, AZs
Works across AWS services

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DEMO

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Enables these use cases
1
Blue green deployments
• myapp.staging.local
• myapp.prod.local
• Private IP
• abstract cluster
details
2
Internal micro services
• web.myapp.local
• Expose Private IP
3
External micro services
• web.myapp.mycompa
ny.com
• Expose public IP or
ELB EIP
• network + container
health check

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Enables these use cases
4
Across ECS & EKS
• Service1.myapp.ecs
• Service2.myapp.eks
5
Across ECS &
AWS & onPrem
• Service1.myapp.ecs
• Service2.myapp.ec2
• Service3.myapp.onprem
6
Expose to service mesh
• Service1.myapp.local
• Service2.myapp.local

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Under the hood

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ECS
Cluster
VPC
Services can discover other services using DNS
Service Green -> Service Blue
(option 1)
• Green does a DNS query
• Query hits internal vpc
DNS server
• Green get a list of IP / IP+Port
• Green communicates with
that IP/ IP + Port
(option 2)
• Green calls Service endpoint
via an API
• Gets list of all IP/ IP+port for
a service
Public DNS:
Public DNS:Private DNS:
blue.colors.local: IP1, IP4, IP5
green.colors.local: IP2, IP3
ECS Control Plane
Cluster: Colors
Service: Blue
Task Defn: Blue
# of tasks: 3
Service: Green
Task Defn: Green
# of tasks: 3
Namespace: colors.local
Service
Blue
Service
Green
Hosted Zone: colors.local Route 53
Control Plane
Service Scheduluer
Docker
ECS
Agent
Task Green
Container
Docker ECS Agent
Task Blue
Container
Task Blue
Container
AZ 1 AZ 2
Docker ECS Agent
Task Blue
Container
Task Blue
Container

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ECS
Cluster
VPC
Services can discover other services using DNS
Public DNS:
Public DNS:Private DNS:
blue.colors.local: IP1
green.colors.local: IP2, IP3, IP4
Cluster: Colors
Service: Blue
Task Defn: Blue
# of tasks: 1
Service: Green
Task Defn: Green
# of tasks: 3
Namespace: colors.local
Service
Blue
Service
Green
Hosted Zone: colors.local Route 53
Control Plane
IP 3
Docker
ECS
Agent
Task Green
Container
Docker ECS Agent
Task Blue
Container
IP 1
Task Blue
Container
IP 2
AZ 1 AZ 2
Docker ECS Agent
Task Blue
Container
IP 4
ECS Control Plane
Service Scheduler
Route 53 Internal
1. Distribute ECS Task endpoints to
DNS servers
ECS -> Route 53
1. Register it with R53 Service
ECS Internal
1. Start Task
2. Get Task ENI (awsvpc mode)
ECS -> Route 53
1. Create Namespace (one per cluster)
2. Create R53 Service (one per
ECS Service)

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ECS
Cluster
VPC
Services can discover other services using DNS
ECS –> R53 ongoing
1. Register/ Deregister Tasks
into Route 53 Service based
on task state and health
2. Updates Tasks in Route 53
Service on cluster auto
scaling or service scaling
Route 53 Ongoing
1. For Service query, return
IP/Port
2. For Task Health Check
details, update DNS servers
3. For ECS Task state changes,
update DNS servers
Public DNS:
Public DNS:Private DNS:
blue.colors.local: IP1, IP5
green.colors.local: IP2, IP3, IP4
Cluster: Colors
Service: Blue
Task Defn: Blue
# of tasks: 2
Service: Green
Task Defn: Green
# of tasks: 3
Namespace: colors.local
Service
Blue
Service
Green
Hosted Zone: colors.local Route 53
Control Plane
IP 3
Docker
ECS
Agent
Task Green
Container
Docker ECS Agent
Task Blue
Container
IP 1
Task Blue
Container
IP 2
AZ 1 AZ 2
Docker ECS Agent
Task Blue
Container
IP 5
Task Blue
Container
IP 4
ECS Control Plane
Service Scheduluer

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ECS
Cluster
VPC
Services can discover other services using DNS
Service Green -> Service Blue
(option 1)
• Green does a DNS query
• Query hits internal vpc
DNS server
• Green get a list of IP / IP+Port
• Green communicates with
that IP/ IP + Port
(option 2)
• Green calls Service endpoint
via an API
• Gets list of all IP/ IP+port for
a service
Public DNS:
Public DNS:Private DNS:
blue.colors.local: IP1, IP5
green.colors.local: IP2, IP3, IP4
Cluster: Colors
Service: Blue
Task Defn: Blue
# of tasks: 3
Service: Green
Task Defn: Green
# of tasks: 2
Namespace: colors.local
Service
Blue
Service
Green
Hosted Zone: colors.local Route 53
Control Plane
IP 3
Docker
ECS
Agent
Task Green
Container
Docker ECS Agent
Task Blue
Container
IP 1
Task Blue
Container
IP 2
AZ 1 AZ 2
Docker ECS Agent
Task Blue
Container
IP 5
Task Blue
Container
IP 4
Health Check Health Check
Health Check
ECS Control Plane
Service Scheduluer

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Requirements
• Requires Task Networking—network
mode “awsvpc”
• Requires specifying container health
check endpoint for essential containers
in task
• Console workflow has assumes 1:1:1
mapping of vpc-cluster-app
• Dependent on Route 53 propagation
delay for registering new IPs (scaling)
or stopping traffic to unhealthy tasks
• Client side logic needed for query,
resolution and retries, 8 DNS records
fetched in each query
• Private VPC: container health check
only, no way to add on network health
Launching in Q1 2018

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Amazon Route 53 Auto Naming

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What is Route 53 Auto Naming?
API that powers ECS
Service Discovery
Service name registration and
management tool
DNS-based service discovery
mechanism

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Namespace Service Service Instance
Introducing new abstractions
Instance
172.10.0.1
frontend
ServiceNamespace
test.internal

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Logical group of services
Private or public visibility
Service-linked hosted zone in
Amazon Route 53
Namespace management APIs:
createPublicDnsNamespace
createPrivateDnsNamespace
deleteNamespace
listNamespaces
getNamespace
Service
Namespace
staging.internal
frontend
Namespace
backend

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ECS: application component run on
one or many tasks
Auto Naming: service naming and
health checking template
Service management APIs:
createService
deleteService
updateService
listServices
getService
Service
staging.internal
frontend
Name = frontend
Record type = A
TTL = 60 sec
Check health = Yes
HC type = path-based
HC path = /ping
Service
Namespace

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Service Instance
staging.internal
frontend
Name = frontend
Record type = A
TTL = 60 sec
Check health = Yes
HC type = path-based
HC path = /ping
Instance
172.10.0.1
Service
Instance
172.10.0.2
Instance
172.10.0.3
Represents an actual endpoint
Addressable by ip or ip:port
Service Instance
management APIs:
registerInstance
deregisterInstance
listInstances
getInstance
getInstanceHealthStatus
Namespace

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Route 53 Auto Naming Route 53 Route 53 Health Check EndpointECS
Route 53 Auto Naming Route 53 Route 53 Health Check EndpointECS
loop
createPrivateDNSNamespace
operationID
createService(DNS,HealthCheck)
store DNS and health check temaplate
service details
loop
loop
[Multiple Instance Registration]
registerInstance(service, IP)
add operation to batch
operationID
create health check
HealthCheckID
Create DNS records
[Health Checking]
create health status
[Auto Naming Batch Processing]
Route 53 Auto Naming workflow

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Discovery over DNS
* If health-checking is enabled for the corresponding Route 53 Auto Naming Service
Auto Naming uses Route 53
Multivalue Answer Routing
Each DNS query returns up to 8
healthy* endpoints
Client-side load balancing

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Amazon Route 53 Auto Naming benefits
Managed API designed for
micro-service architectures
Regional control plane for
better availability
Discovery via Route 53 DNS
with 100% availability SLA

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