Telemetry Forwarding Investigation

forwardingservice.md

Telemetry forwarding

We need a service behind a static public IP to communicate telemetry events to Application Insights

Telemetry collection endpoint: https://github.com/microsoft/ApplicationInsights-Home/blob/master/EndpointSpecs/ENDPOINT-PROTOCOL.md

https://dc.services.visualstudio.com/v2/track

Squid Proxy

https://phoenixnap.com/kb/setup-install-squid-proxy-server-ubuntu

https://cloudinfrastructureservices.co.uk/how-to-setup-squid-proxy-cache-in-azure/

Should we use a proxy?

• Using a proxy changes client SDK implementation
  • To open a tunnel, a proxy expects a HTTP CONNECT request:

    CONNECT dc.services.visualstudio.com:443 HTTP/1.1
    Host: dc.services.visualstudio.com:443
    User-Agent: curl/7.64.0
    Proxy-Connection: Keep-Alive
    

• IP whitelisting is a policy constraint. Should we engineer around a policy constraint?

Proxy pros

• Easy to set up
• Minimal maintenance overhead

Proxy cons

• Client SDK must support proxy (HTTP CONNECT)
• Security policy concern
• Requires whitelisting an additional IP
• Pay for VM

Node.js forwarding service

Forward requests using a minimal express server

Pros

• Can run on the same machine as signalling
• Allowed under existing security policy
• No need to whitelist another IP

Cons

• Development & maintenance overhead
• Sharing a machine with signalling doesn't scale
• Running on its own machine requires whitelisting an additional IP
• Pay to run on its own machine