support caching of all telemetry data

[frzifus]

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Is your feature request related to a problem? Please describe. I would like to cache telemetry data on disk in something like a ringbuffer. The objective is to keep as much data as possible available when a device is not connected to the Internet. Even in case a device gets restarted the meantime.

Describe the solution you'd like A way to backup and retrieve data independently from the exporter.

1. Something like a storage extension which can be used in exporters. Not sure if thats what this is about?
2. A processor implementation? As far as I understand the interface, it should be possible to implement the desired behavior.

Describe alternatives you've considered A kind of "buffer exporter", which embeds further exporters. (I am not a fan of this idea).

e.g.:

exporters:
  buffer:
    size: 2GB
    retry: 1m
    forward:
      otlp:
        endpoint: remote:4317