ip tagging filter: support loading tags from file system

[ccaraman]

Description: IP tags can only be loaded via the v2 configurations. Extend the filter to support reading IP tags from the file system.

[htuch]

Should this be a DataSource?

[Radha13]

We (Slack) have a similar need and happy to work on the implementation.

We would want to add another argument ip_tag_path which should be oneof (either ip_list or ip_tag_path) in v4 and programmatically mutually exclusive in v3.

For our specific needs, we want to be able to update the file out-of-band, so it's important to watch for changes. Instead of a DataSource (which only supports static files), we want to use dispatcher.createFilesystemWatcher().

The content of the file will be type repeated IPTag ip_tags which will look like:

message IPTagFile {
  repeated IPTag ip_tags format
}

filter config looks like:

{
  "request_type": "...",
  "path": "/path/to/file",
  "ip_tags": [
    "ip_tag_name": "...",
    "ip_list": [],
  ]
}

File content looks like

[
  {
    "ip_tag_name": "...",
    "ip_list": []
  },
  {
    "ip_tag_name": "...",
    "ip_list": []
  },
  ...
]

With above, we can have country codes in ip_tag_name with associated IP list. If that looks acceptable to you, I'll go ahead and implement this. :bow:

[mattklein123]

@Radha13 yup this would be great!