Varnish Otel 2.4.0 Release

varnish-otel is now compatible with Varnish Cache >= 9.0.1. Note that tracing will still require vmod-otel, which is a Varnish Enterprise feature, but metrics and logging will work without extra configuration on the Varnish side.

Two new resource attributes are now automatically populated:

• varnish.version: detected using varnishd -V at startup.
• service.instance.id: seethe new OTEL_VARNISH_INSTANCE_ID variable below.

New environment variables:

• OTEL_VARNISH_INSTANCE_ID controls how service.instance.id is set:
  • none: doesn’t set the attribute.
  • uuid: generate a UUIDv4.
  • hostname: reads the hostname.
  • auto (default): use the hostname if not empty, otherwise, generate a UUIDv4.
• OTEL_VARNISH_LOG_RECORD_FILTER allows to pass -x/-X/-i/-I arguments to varnishlog-json. This notably permits filtering sensitive headers that shouldn’t be logged.

Other changes:

• Only metrics with a counter (c) or gauge (g) flag are exported; bitfield metrics are now ignored.
• Errors from the logging subprocesses are now logged at Warn level instead of Debug.
• Metrics are now parsed as uint64, preventing overflows on large counters.