prometheus: Azure SD with Public IP Address: panic: runtime error: invalid memory address or nil pointer dereference

Version

Docker image prom/prometheus, tags latest and main, both have the same problem.

Problem

We’re receiving a panic from Azure SD plugin whenever it tries to enumerate our VMs. The problem is caused by an incorrect nil check as seen below:

https://github.com/prometheus/prometheus/blob/579331446a04503b2b1515767e7ceaceab2c6342/discovery/azure/azure.go#L374-L376

Fix

The current code is checking ip.PublicIPAddress.PublicIPAddressPropertiesFormat but is dereferencing ip.PublicIPAddress.IPAddress. We should nil check ip.PublicIPAddress.IPAddress instead.

Stacktrace

Feb 08 17:14:17 prometheus docker[8302]: panic: runtime error: invalid memory address or nil pointer dereference
Feb 08 17:14:17 prometheus docker[8302]: [signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0xeb0ac1]
Feb 08 17:14:17 prometheus docker[8302]: goroutine 776 [running]:
Feb 08 17:14:17 prometheus docker[8302]: github.com/prometheus/prometheus/discovery/azure.(*Discovery).refresh.func1(0xd9bebd0f7c815613, {{0xc00194db80, 0x92}, {0xc001950228, 0x11}, {0xc001950240, 0x11}, {0xc0019726f0, 0x21}, {0xc001a62590, ...}, ...})
Feb 08 17:14:17 prometheus docker[8302]:         /app/discovery/azure/azure.go:375 +0x7a1
Feb 08 17:14:17 prometheus docker[8302]: created by github.com/prometheus/prometheus/discovery/azure.(*Discovery).refresh
Feb 08 17:14:17 prometheus docker[8302]:         /app/discovery/azure/azure.go:321 +0xd52