Limit number of active Channels

[will-moore]

When using the omero-ms-image-region microservice, the number of active channels is limited by default to 10 (configurable at https://github.com/glencoesoftware/omero-ms-image-region/blob/a3c6e61ecb02c608f4c1f8c296c259d7de9f5cc3/src/dist/conf/config.yaml#L12)

The limit can be queried at
https://github.com/glencoesoftware/omero-ms-image-region/blob/master/src/main/java/com/glencoesoftware/omero/ms/image/region/ImageRegionMicroserviceVerticle.java#L486

Although I don't see how that method maps to a URL that can be accessed by iviewer?

Even when microservices are not deployed, users may wish to configure a limit on active channels. This could (should) be a new server-side configuration (allow it to be accessed via the rendering engine itself as well as other clients.

[will-moore]

We can query microservice like this:

await fetch("https://idr.openmicroscopy.org/omero_ms_image_region/", {method: "OPTIONS"}).then(r => r.json())

or

$ curl -s -X OPTIONS https://idr.openmicroscopy.org/omero_ms_image_region/
{
  "provider" : "ImageRegionMicroservice",
  "version" : "0.10.0",
  "features" : [ "flip", "mask-color", "png-tiles", "quantization", "support-missing-channels" ],
  "options" : {
    "maxTileLength" : 2048,
    "maxPlaneWidth" : 3192,
    "maxPlaneHeight" : 3192,
    "maxActiveChannels" : 10,
    "cacheControl" : "private, max-age=3600"
  }
}