Service Discovery & Load-Balancing under Docker 1.12.0 @ Docker Meetup #22

Presenter Name : Ajeet Singh Raina

Presented Date: Aug 20, 2016

Presented at: Docker Bangalore Meetup #22

Service Discovery & Load-Balancing under Docker 1.12

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ABOUT ME

#Contribution:

- Frequent Blogger – http://www.collabnix.com

- Article Writing @ OSFY India

- Dell Community ( Containerizing Dell Legacy Application)

#Inside Dell:

- Project Lead Engineer(Global Solution Engineering)

- Worked in VMware, CGI , Dell R&D

- Solaris Lead Engineer ( Wiki Moderator)

• (t) – ajeetsraina (f) - Docker Public Group Moderator

#Reviewed Publications:

- Puppet for Containerization

- PowerCLI Cookbook

#Technology : Open Source Linux, Docker, Hadoop, Puppet

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Agenda

• What’s new in Docker 1.12 ? – Quick Recap

• What’s new in Docker Swarm Mode? – Quick Recap

• Service Discovery

- What is a Service?

- Basics of Service Discovery

- How it works?

- A Deep Dive

• Load-Balancing

- What’s new in 1.12 LB?

- Ingress Load-Balancing – A Deep Dive

- Routing Mesh

• Q&A

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What’s new in Docker 1.12? – A Recap

Swarm Mode Manager

TLS

Swarm Mode Worker

CertificateAuthority

Load Balancing

Service Discovery

Distributed store

Volumes

Networking

Plugins

ContainerRuntime

Orchestration Components

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What’s new in Swarm Mode? – A Recap

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Evolution of Service Discovery

Docker 1.9

/etc/hosts and /etc/resolv.conf

~ for the cluster service.

Cons:

- Corrupted /etc/hosts

- Lacking of Load-

Balancing Feature

- Complex way of Service

Discovery

Docker 1.10/1.11

- Embedded DNS

--network-alias=ALIAS

--link=CONTAINER_NAME:ALIAS

--dns=[IP_ADDRESS...]

--dns-search=DOMAIN

Cons:

- Service Discovery through External Discovery backend like Consul, zookeeper etc.

Docker 1.12

- No External Service Discovery

Backend Required

- Service Discovery plumbed directly into $docker service

- Service Discovery by Unqualified names.(Un-FQDN)

- Provided by Embedded DNS

- Highly Available

- Ability to discover both the services and tasks

-.

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What is Service?

• A Definition of tasks to be executed on the worker nodes

• A New API – $docker service is introduced in 1.12

• $docker service <= Evolution of $docker run

• Central structure of swarm system

• It manages replicated set of containers

• A task carries a Docker container + commands to run inside the container.

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Service Discoveryhelps service find and talk to each other

Serviceа Serviceb

Serviceb

Serviceb

Serviceb

Serviceb

Serviceb

Serviceb

Scaling

Scaling

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Service Discoveryhelps service find and talk to each other

Serviceа Serviceb

Serviceb

Serviceb

Serviceb

Scaling

Scaling

Understanding Service DiscoveryCluster

node1

node3

node2

node4

node5

node6

node7

DB

DB

DBAPI

API

API

Web

Web

Web

API

Understanding Service DiscoveryA Typical Swarm Cluster

node1

node3

node2

node4

node5

node6

node7

DB

DB

DBAPI

API

API

Web

Web

Web

API

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How Embedded DNS resolve unqualified names?

DNS Server Embedded into Docker Engine

DNS Request generated by container

Resolver tries to resolve 127.0.0.11

This loopback address is trapped

Send to random UDP/TCP port listening in Docker

daemon

Socket is created inside that namespace

Forward that request into the socket

DNS Server identifies the request via sockets

DNS Server is aware of the context of the container running that

particular service

Looks at /etc/resolv.confstating 127.0.0.11

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How Service Discovery works in Swarm Mode?

Create a new overlay network

Create a service and attach to this new

network

The swarm assign a VIP(Virtual IP Server)

and DNS entry to each service

The VIP(a private non-routable IP which uses

IPVS LB) maps to a DNS alias based upon

the service name.

Containers share DNS mappings for the

service via GOSSIP

Any container on the network can access

the service via its service name

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Swarm Cluster Setup

Master-1 Node-1 Node-3Node-2

ingress

docker_gwbridge

user_defined

Networks

- It is an overlay network on all exposed ports

exist.

- Follows a node port model(each service has

the same port on every node in the cluster).

- Numbered from 30000 through 32000.

- Used for Routing Mesh

- The default gateway network

- The only network with connectivity to

the outside world.

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Creating a new overlay network

$ docker network create \

--driver overlay \

collabnet

Master-1

ingress

docker_gwbridge

Node-1 Node-3Node-2

collabnet

Networks

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Creating a service “wordpressdb”

$ docker service create \

--replicas 1 \

--name wordpressdb \

- -network collabnet \

-- env MYSQL_ROOT_PASSWORD=collab123 \

--env MYSQL_DATABASE=wordpress \

--name wordpressdb \

mysql:latest


collabnet

wordpress

db.1

VIP(10.0.0.2)

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Creating a service “wordpressapp”

$ docker service create \

--env WORDPRESS_DB_HOST=wordpressdb \

--env WORDPRESS_DB_PASSWD=collab123 \

--replicas 5 --network collabnet -- name wordpressapp \

--publish 80:80/tcp \

wordpress:latest


collabnet

wordpress

db.1VIP(10.0.0.2)

wordpress

app.1

wordpress

app.5

wordpress

app.4wordpress

app.2

wordpress

app.3VIP(10.0.0.4)

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Inspecting the services

$ docker service inspect \

--format=='{{json .Endpoint.VirtualIPs}}' \

wordpressapp

[{"NetworkID":"c4caizphmdpuhm1gjdle8eaal","Addr":"10.255.0.7/16"},

{"NetworkID":"9eyjm4uv4ynmz0aubfqxise29","Addr":"10.0.0.4/24"}]

$ docker service inspect \

--format=='{{json .Endpoint.VirtualIPs}}' \

wordpressdb

[{"NetworkID":"9eyjm4uv4ynmz0aubfqxise29","Addr":"10.0.0.2/24"}]

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Verifying Service Discovery


collabnet

wordpress

db.1VIP(10.0.0.2)

wordpress

app.1

wordpress

app.5

wordpress

app.4wordpress

app.2

wordpress

app.3VIP(10.0.0.4)Wordpressapp

Wordpressdb

Services

$ping <service>

returns <VIP>

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collabnet

wordpress

db.1VIP(10.0.0.2)

wordpress

app.1

wordpress

app.5

wordpress

app.4wordpress

app.2

wordpress


Wordpressdb

Services

$dig <service>

returns <VIP>

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collabnet

wordpress

db.1VIP(10.0.0.2)

wordpress

app.1

wordpress

app.5

wordpress

app.4wordpress

app.2

wordpress


Wordpressdb

Services

$nslookup <service>

returns <VIP>

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collabnet

wordpress

db.1VIP(10.0.0.2)

wordpress

app.1

wordpress

app.5

wordpress

app.4wordpress

app.2

wordpress


Wordpressdb

Services

$wget –O- wordpressapp

returns <VIP>

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Network - the scope of Service Discoverability


collabnet

wordpress

db.1VIP(10.0.0.2)

wordpress

app.1

wordpress

app.5

wordpress

app.4wordpress

app.2

wordpress


Wordpressdb

collabnet1

Wordpressdb

1.1Wordpressdb1 VIP(10.0.1.2)

Services

Load-Balancing under Docker 1.12

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Basics of Load-Balancing

A Load-Balancer distributes request

among the healthy nodes

- Provides high availability by detecting server or

component failure & re-configuring the system appropriately

- Assigns workload to a set of networked computer nodes

LB

Node-1 Node-3Node-2

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What’s new in 1.12 Load-Balancing?

• Decentralized, Highly Available – LB instance plumbed into every container instance

• Internal Load Balancer – Provided by Embedded DNS

• Can be used to discover both service & tasks

• VIP based services uses IPVS(IP Virtual Server) – Layer-4 LB

• Kernel module ( ip_vs) for LB

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How LB works?

External LB/HA-Proxy/NginX

Host-port:{10.128.0.4:80} Host-port:{10.128.0.3:80}

Service1 sandbox

IPVS

Service1 sandbox

IPVS

10.0.0.5 10.0.0.6 10.0.0.7 10.0.0.8

Ingress Network

Host:10.128.0.4 Host:10.128.0.3

Public

1 Client access using :80

Plumb the request to

sandbox running on

10.128.0.3

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3 Packets enters the mangle

table, Pre-routing firewall

mark of 0x101 => 257

Inside the sandbox, the re-

routing chain gets created

under NAT table.

Then ipvsdm uses 257

firewall mark to round robin

across the multiple nodes

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6

5

SRC NAT under NAT table

ensure that packet has to

be come back to Ingress

network so as to return in

the original format

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Accessing the network sandbox• How to find the sandboxID?

• Where’s sandbox located?

Network namespace managed by overlay network

driver(creating a bridge, terminating VXLAN tunnel etc.

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Inspecting the sandbox

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Routing Mesh

• Routing Mesh is NOT Load-Balancer

• Routing Mesh makes use of LB aspects

• It provides global publish port for a given service

• Built-in routing mesh for edge routing

• Worker nodes themselves participate in ingress routing mesh

• Port management at global Swarm Cluster level.

THANK YOU

Service Discovery & Load-Balancing under Docker 1.12.0 @ Docker Meetup #22

Engineering

Transcript of Service Discovery & Load-Balancing under Docker 1.12.0 @ Docker Meetup #22