"Learning Objectives: - Learn the basics of DNS service discovery - Learn common implementation patterns for service discovery - Learn how to start using Amazon ECS service discovery"

1. © 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved.
Nathan Peck
April 23, 2018
Introducing ECS Service
Discovery
Communication service for building
containerized microservices on AWS

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

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Developers need to connect microservices
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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Decision criteria
Discovery mechanism
How does an application send traffic to a
service from the registry?
Registration mechanism
How is a service added to the registry?
Service Registry
Where is info about services stored?

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Current patterns require install, setup and management
Load Balancers Key-value store Service Mesh
Service
registry

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Load Balancers – Server Side Discovery
E.g.,
Load Balancer
Benefits
Client is simpler
Drawbacks
Install, manage
Availability, capacity
More hops
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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This should be easier!
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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Demo
https://servicediscovery.ranman.com/

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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 & Kubernetes
• Service1.myapp.ecs
• Service2.myapp.eks
5
Across ECS &
AWS &On-Prem
• Service1.myapp.ecs
• Service2.myapp.ec2
• Service3.myapp.onprem
6
Expose to service mesh
• Service1.myapp.local
• Service2.myapp.local

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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 + portService
CNAME: A / SRV record
Namespac
e

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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
• Setup once, use forever
Highly available
• Same availability and
scalability as Route 53
Extensible
• Public APIs that can be used
across AWS
• Works across clusters,
accounts, AZs
• Works across AWS services

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

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Namespace
Logical group of services
Private or public visibility
Service-linked hosted zone in
Amazon Route 53
Service
staging.internal
frontend
Namespace
backend

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Namespace
Namespace management APIs:
createPublicDnsNamespace
createPrivateDnsNamespace
deleteNamespace
listNamespaces
getNamespace
Service
staging.internal
frontend
Namespace
backend

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

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

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Service Instance
staging.internal
frontend
Service
Instance
172.10.0.3
Namespace
Instance
172.10.0.1
Instance
172.10.0.2
Name = frontend
Record type = A
TTL = 60 sec
Check health = Yes
HC type = path-based
HC path = /ping
Service Instance
management APIs:
registerInstance
deregisterInstance
listInstances
getInstance
getInstanceHealthStatus

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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
[MultipleInstance Registration]
registerInstance(service,IP)
add operationto batch
operationID
create healthcheck
HealthCheckID
Create DNS records
[Health Checking]
create healthstatus
[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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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
Private DNS:
blue.colors.local: green.colors.local:
ECS Control Plane
Cluster: Colors
Service: Blue
Task Defn: Blue
# of tasks: 3
Service: Green
Task Defn: Green
# of tasks: 1
Namespace: colors.local
Service
Blue
Service Green
Hosted Zone: colors.local Route 53
Control Plane
Service Scheduler
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

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ECS
Cluster
VPC
Services can discover other services using DNS
Private DNS:
blue.colors.local: IP1, IP2, IP4
green.colors.local: IP3
Cluster: Colors
Service: Blue
Task Defn: Blue
# of tasks: 3
Service: Green
Task Defn: Green
# of tasks: 1
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/ DeregisterTasks into
Route 53 Service based on task
state and health
2. UpdatesTasks in Route 53
Service on cluster auto scaling or
service scaling
Route 53 Ongoing
1. For Service query, return IP/Port
2. ForTask HealthCheck details,
update DNS servers
3. For ECSTask state changes,
update DNS servers
Private DNS:
blue.colors.local: IP1,IP2,IP5,IP4
green.colors.local: IP3
Cluster: Colors
Service: Blue
Task Defn: Blue
# of tasks: 4
Service: Green
Task Defn: Green
# of tasks: 1
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 Scheduler

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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
Private DNS:
blue.colors.local: IP1,IP2,IP5,IP4
green.colors.local: IP 3
Cluster: Colors
Service: Blue
Task Defn: Blue
# of tasks: 4
Service: Green
Task Defn: Green
# of tasks: 1
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
ECS Control Plane
Service Scheduler

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Requirements & Limits
• Tasks must use “awsvpc” network mode
• Must specify container health check
endpoint for essential containers in task
• Console workflow assumes 1:1:1
mapping between 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

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How do I use it?
• Native integration with Amazon ECS
Works with Fargate and EC2 launch types
• Also available for Kubernetes!
https://github.com/kubernetes-incubator/external-dns
• Available in all AWS regions where Amazon ECS and Route 53 Auto
Naming are available
https://aws.amazon.com/about-aws/global-infrastructure/regional-product-services

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Thank You!
peckn@amazon.com
nathankpeck
nathanpeck
Learn more at https://aws.amazon.com/ecs/resources