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![5
Evolution of Service Discovery
Docker 1.9
/etc/hosts and /etc/resolv.conf
~ for the cluster service.
Disadvantage:
- 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
- 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 ~ A First Class Citizen
- Network is scope of discoverability.
- Service Discovery by Unqualified
names.(Un-FQDN)
- Provided by Embedded DNS
- Highly Available
- Ability to discover both the services
and tasks
-.](https://image.slidesharecdn.com/ajeetdocker1-160831210902/85/Best-ways-to-use-Docker-1-12-Service-Discovery-by-Docker-Captain-Ajeet-Raina-5-320.jpg?cb=1472677826)
![Creating a new
overlay network
12
Demonstrating Service Discovery under Swarm Mode
$docker network create
-d overlay collabnet
--subnet 10.0.3.0
--opt encrypted
Creating a service
DNSRR VIP
$docker service create
–endpoint-mode dnsrr
-–name wordpressapp
--replicas 5
--network collabnet
$docker service create
-–name wordpressapp
--replicas 5
--publish 80:80/tcp
--network collabnet
Virtual IP (VIP)
Assignment to each
Service
$ docker service inspect
--format=='{{json
.Endpoint.VirtualIPs}}'
wordpressapp
{"NetworkID":"9eyjm4uv4ynmz
0aubfqxise29","Addr":"10.0.0.4/2
4"}]
VIP maps to DNS alias
The VIP(a private non-
routable IP which uses IPVS
LB) maps to a DNS alias
based upon the service
name.
DNS shared via
GOSSIP
Containers share DNS
mappings for the service
via GOSSIP
Service Discovery via
service Name
Any container on the
network can access the
service via its service
name](https://image.slidesharecdn.com/ajeetdocker1-160831210902/85/Best-ways-to-use-Docker-1-12-Service-Discovery-by-Docker-Captain-Ajeet-Raina-12-320.jpg?cb=1472677826)
Uploaded byDocker, Inc.
Best ways to use Docker 1.12 Service Discovery by Docker Captain Ajeet Raina
For the Docker Online Meetup #42, Ajeet will shared his key takeaways and the best ways to use Docker 1.12 Service Discovery. Ajeet Singh Raina is currently working as Technical Lead Engineer in the Enterprise Solution Group at Dell India R&D and has solid understanding of a diverse range of IT infrastructure, system management, system integration engineering and quality assurance. Ajeet has a great passion for upcoming trends and technologies. He loves contributing towards Open source space through writing and blogging @ http://www.collabnix.com.
![Vibe Coding vs. Spec-Driven Development [Free Meetup]](https://cdn.slidesharecdn.com/ss_thumbnails/vibecodingvsspecdrivendevelopment-251209105622-43f455e7-thumbnail.jpg?width=640&height=640&fit=bounds)
Best ways to use Docker 1.12 Service Discovery by Docker Captain Ajeet Raina
- 1. Service Discovery underDocker 1.12 Presenter Name : Ajeet Singh Raina Presented Date: Aug 31, 2016 Presented at: Docker Online Meetup
- 2. 2 ABOUT ME #Contribution: - FrequentBlogger – http://www.collabnix.com - @Docker Captain - 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
- 3. 3 Agenda • What’s newin Docker 1.12 Swarm Mode? – A Quick Recap • Evolution of Service Discovery • Definition of Service – An Approach to Service Discovery • How Service Discovery works? • A Quick Demo of Service Discovery • Key Takeaways
- 4. 4 What’s new inDocker 1.12?
- 5. 5 Evolution of ServiceDiscovery Docker 1.9 /etc/hosts and /etc/resolv.conf ~ for the cluster service. Disadvantage: - 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 - 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 ~ A First Class Citizen - Network is scope of discoverability. - Service Discovery by Unqualified names.(Un-FQDN) - Provided by Embedded DNS - Highly Available - Ability to discover both the services and tasks -.
- 6. 6 What is Service? -A central structure and the primary root of user interaction with the Swarm System - The definition of the tasks to execute on the worker nodes - Tasks => workloads (container workloads as of now), Unikernel & VMs(in future) Types Global Services ( $docker service create –mode=global) Replicated Services ( $docker service create –replicas 5)
- 7.
- 8. Understanding Service Discovery ATypical Swarm Cluster node1 node3 node2 node4 node5 node6 node7 DB DB DBAPI API API Web Web Web API
- 9. 9 Service Discovery helps servicesfind and talk to each other Serviceа Serviceb address
- 10. 10 Service Discovery helps servicefind and talk to each other Serviceа Serviceb Serviceb Serviceb Serviceb Serviceb Serviceb Serviceb Scaling Scaling
- 11. DNS Request generated by container 11 HowEmbedded DNS resolve unqualified names? $nslookup wordpressapp $ping wordpressapp $dig wordpressdb Socket is created inside the container namespace Send to random UDP/TCP port listening in Docker daemon Loopback address is trapped 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.conf inside the container $cat /etc/resolv.conf nameserver 127.0.0.11 options ndots:0
- 12. Creating a new overlaynetwork 12 Demonstrating Service Discovery under Swarm Mode $docker network create -d overlay collabnet --subnet 10.0.3.0 --opt encrypted Creating a service DNSRR VIP $docker service create –endpoint-mode dnsrr -–name wordpressapp --replicas 5 --network collabnet $docker service create -–name wordpressapp --replicas 5 --publish 80:80/tcp --network collabnet Virtual IP (VIP) Assignment to each Service $ docker service inspect --format=='{{json .Endpoint.VirtualIPs}}' wordpressapp {"NetworkID":"9eyjm4uv4ynmz 0aubfqxise29","Addr":"10.0.0.4/2 4"}] VIP maps to DNS alias The VIP(a private non- routable IP which uses IPVS LB) maps to a DNS alias based upon the service name. DNS shared via GOSSIP Containers share DNS mappings for the service via GOSSIP Service Discovery via service Name Any container on the network can access the service via its service name
- 13.
- 14.
- 15. 15 Network - thescope of Service Discoverability Master-1 Node-1 Node-3Node-2 collabnet wordpress db.1 VIP(10.0.0.2) wordpress app.1 wordpress app.5 wordpress app.4 wordpress app.2 wordpress app.3 VIP(10.0.0.4)Wordpressapp Wordpressdb collabnet1 Wordpressdb 1.1 Wordpressdb1 VIP(10.0.1.2) Services
- 16.
- 17. 17 Key Takeaways Service Discovery: •Service is now a first class citizen and plumbed directly into $docker service . • Services can be published using two modes: VIP and DNSRR • You can resolve a particular service by using its Unqualified names. • You don't need to expose service-specific ports to make the service available to other services on the same overlay network. • Virtual IP is not going to change even if you scale out the services or bring down the containers running that service. • Trying to do: $ping VIP doesn’t work and is as designed. Technically, IPVS is a TCP/UDP load-balancer, while ping uses ICMP and hence IPVS is not going to load-balance the ping request. • For VIP based services the reason ping works on the local node is because the VIP is added a 2nd IP address on the overlay network interface. • When you use DNS-RR mode, services don't have a VIP allocated. Instead service names resolves to one of the backend container IPs randomly. • Service Discovery is scoped within a network.