This document discusses service discovery in Docker using NGINX and NGINX Plus with Consul. It begins with an introduction to service discovery and why it is important for microservices applications. It then covers how open source NGINX integrates with Consul using Consul Template, noting limitations around increased memory usage. The document also discusses two methods for NGINX Plus integration - using the dynamic reconfiguration API with Consul watches, and DNS resolution using SRV records from Consul. It provides comparisons between the two methods and links to demo repositories.

1. Service Discovery in
Docker Using NGINX
and NGINX Plus with
Consul
- Kunal Pariani (Pre-Sales Engineer @ NGINX)

2. #nginx #nginxconf2
Agenda
• What is service discovery & why it matters
• How open source NGINX integrates with Consul & Consul Template
• How NGINX Plus makes the integration easier
1. Using HTTP-based Dynamic Reconfiguration API **
2. DNS Resolution using SRV records **
3. Comparison between the two methods
• Q & A
** Live demo to show that stuff works !!

3. Service Discovery

4. #nginx #nginxconf4
What It Is & Why It Matters
• Microservices-based applications are dynamic in nature
• Good way to stay on top of the current state of all the
services is to use service discovery
• Its the process of discovering the service locations
• Integration with NGINX enables automatic addition or
removal of the service instances from the load-
balancing pool
• No direct modification to NGINX configuration,
achieving automation

5. Open Source NGINX with
Consul & Consul Template

6. #nginx #nginxconf
Open Source NGINX with Consul
& Consul Template

7. #nginx #nginxconf
• https://github.com/nginxinc/NGINX-
Demos/tree/master/consul-template-demo
Want to try it ?

8. #nginx #nginxconf
• NGINX reloads every time there is a change in Consul
• Can lead to increased memory usage & eventually
overload the system
Limitations

9. #nginx #nginxconf9
NGINX Plus Improves the
Integration
• Method #1
Using HTTP-based dynamic reconfiguration API with Consul
watches
• Method #2
DNS Resolution using SRV records from Consul

10. Dynamic Reconfiguration
API Method

11. #nginx #nginxconf11
Dynamic Reconfiguration API in NGINX Plus
• Configuration
upstream backend {
zone backend 64k;
server app-server;
}
server {
listen 8080; # Listen on a local port
location /upstream_conf {
allow 10.0.0.0/8; # Allow access only from LAN
deny all; # Deny everyone else
upstream_conf;
}
}

12. #nginx #nginxconf
Dynamic Reconfiguration API &
Consul with Watches

13. #nginx #nginxconf
• https://github.com/nginxinc/NGINX-
Demos/tree/master/consul-api-demo
Its Demo Time
:)

14. DNS Resolution
Using SRV Records

15. #nginx #nginxconf
DNS for Service Discovery
• DNS resolver in NGINX can point to the DNS interface of any
service discovery tool
• Open source NGINX can query for DNS A records to get all
the IP addresses associated with a domain name
• NGINX supports DNS queries over both UDP & TCP
• Honors the TTL in the DNS response, or you can override it
using the valid parameter to the resolver directive

16. #nginx #nginxconf
• No support for DNS SRV records, A records only
- NGINX Plus only
• Port numbers have to be statically defined
• Not suitable for microservices environments
Limitations with Open
Source NGINX

17. #nginx #nginxconf17
DNS SRV Records with
NGINX Plus
• SRV record includes extra information like port number, weight, and priority
• service parameter: enables resolving of SRV records and sets the service
name & protocol
• resolve parameter: Monitors changes in SRV records and automatically
modifies upstream configuration without the need for reload
http {
resolver <consul-dns-ip> valid=2s;
upstream backends {
zone backends 64k;
server service.consul service=http resolve;
}
}

18. #nginx #nginxconf
DNS SRV Records with
NGINX Plus

19. #nginx #nginxconf
• https://github.com/nginxinc/NGINX-
Demos/tree/master/consul-dns-srv-demo
Demo Time Again..

20. #nginx #nginxconf20
Comparison of the HTTP API & DNS
Methods
HTTP-based API method DNS-based method
Push v/s pull method Push method
No polling
Consul watches triggers NGINX
Plus to reconfigure
Pull method
Keep polling DNS periodically
Additional DNS traffic
Reaction time Immediate since it’s a push method Depends on how often DNS gets
queried—NGINX Plus can query DNS
as often as every 1 second
Integration work Yes
Create and manage an external
script which gets triggered every time
there is a change in Consul
No
No separate script or integration
needed
Caveats API requests should be made
against a healthy NGINX Plus server
DNS server needs to be highly
available
Specify multiple name servers using
the resolver directive

21. #nginx #nginxconf21
How to Try Out NGINX Plus?
• Sign up for the 30-day free trial
https://www.nginx.com/#free-trial
• Developer License
https://www.nginx.com/developer-license/
Password: nginxconf16dev

22. #nginx #nginxconf22
Additional Resources
• Service Discovery in a Microservices Architecture
• Using DNS for Service Discovery with NGINX and NGINX Plus
• Service Discovery for NGINX Plus Using Consul APIs
• Service Discovery for NGINX Plus Using DNS SRV Records from Consul
• Service Discovery for NGINX Plus with etcd
• Service Discovery for NGINX Plus with ZooKeeper

23. Q&A

24. #nginx #nginxconf
Thank You
24
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