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20170830_srecon17_2.4

20170830_srecon17_2.4

Anycast is not loadbalancing

1 - Start the story

How do you scale ?
* Start with 1 Server
* More servers
* Tell clients about new servers ?

2 - What is AnyCast ?

What
- Network magic
- Configure the same IP on multiple devices
- Let the “netwrk” decide wich server receive the request

Pros:
- Simple client config
- Simple horizontal scaling
- Low dependency

Good for:
- Staless app
- “Simple” HA

3 - Catch ?

NOT lbs
- no control where is the request going
- no way to “stop accepting new request” BUT “keep serving existing”
- no traffic shapping

Monitoring ?
- Probe are basics
- Not easy to know from wich server the issue comes from
- May fall in a case were no backend is the closest for the Anycast probe …

Failure modes
- By default, no check of pool member ships
- No nothion on Pool

4 - Don’t believe in Magic

Anycast is usefull

But
- it is load DISTRIBUTION