webApp

VBDS Web App

This directory contains a VBDS web app that displays a menu of VBDS servers and image streams and lets you select an image stream to display.

For jpeg images, an HTML canvas is used. For FITS, the JS9 application is embedded in the page. It is assumed that the JS9 source is installed locally on the build host. A shell script is provided to copy the necessary files from the JS9 source to the web app's public directory.

After checking out JS9 and this project from Github, first edit and then run this script to "minify" and copy the JS9 dependencies:

cd webApp
./update-js9.sh         # Edit this script to set the location of the JS9 sources

This is required, since JS9 is not a React component and is not easily usable in a React app or via "npm install" (although it is available via npm). The JavaScript and CSS for JS9 are declared in public/index.html. Attempts to place it in a React component were so far not successful.

Prerequisites Required for Running App

The web app uses the CSW Location Service to locate the VBDS servers. To start the CSW services, run:

csw-services start

The latest versions of Node.js and npm must be installed.

Run the App in Local Environment

Run following commands in the terminal.

npm install
npm start

This should automatically open localhost:8080 in a browser.

Build the App for Production

Run following commands in the terminal.

npm install
npm run build

Testing the Display

One way to test the performance of the image viewer is to use vbds-client to publish all of the image files in a directory. For example, by running each of these commands in different terminal windows:

vbds-server --name server1
vbds-client --name server1 --create XXX --content-type "image/fits"
vbds-client --name server1 --repeat --publish XXX --delay "100 millis" --content-type 'image/fits' --data /my/image/directory

vbds-client --name server1 --create YYY --content-type "image/jpeg"
vbds-client --repeat --name server1 --publish YYY --content-type 'image/jpeg' --data /my/jpeg-image/directory

Where /my/image/directory is a directory containing a sequence of image files, in this case in FITS format. The --delay option gives the amount of time between images. You can specify a value like "1s" or "1 second" or "500 millis". If no --delay option is given, the images will be published as fast as the clients can handle them. The --repeat option causes the publisher to keep publishing the same files (all the ones in the directory, or matching the --suffix option). The --stats options causes the publisher to print statistics showing the throughput.

In the web app, refresh the page to update the list of servers and streams and select the stream XXX. While testing, it is best to display the web console in the browse to see any error messages.

For reference, here are the vbds-client command line options:

vbds-client 0.0.1
Usage: vbds-client [options]

  -n, --name <name>        The name of the vbds-server server(default: vbds)
  --create <stream name>   Creates a new VBDS stream with the given name
  --content-type <content-type>
                           Specifies the content type of the files in the stream
  --delete <stream name>   Deletes the VBDS stream with the given name
  -l, --list               List the available streams
  --stats                  Print timing statistics when publishing files
  --repeat                 Keep publishing the same files forever, until killed (for testing)
  --save-files             If true, save the files received by the subscription to the current directory with names like <streamName>-<count>
  --stats-interval <value>
                           If --stats option was given, controls how often statistics are printed (default: 1 = every time)
  --subscribe <stream name>
                           Subscribes to the given VBDS stream (see --action option)
  --dir <path>             Directory to hold received data files (default: current directory)
  -a, --action <shell-command>
                           A shell command to execute when a new file is received (args: file-name)
  --publish <stream-name>  Publish to the given stream (see --data option)
  --delay <duration>       Delay between publishing files in a directory (see --data)
  --data <file-name>       Specifies the file (or directory full of files) to publish
  --suffix <suffix>        Optional suffix for files to publish if the file given by --data is a directory
  --chunk-size <num-bytes>
                           Optional chunk size (to tune file transfer performance)
  --help
  --version

References

• ESW-TS Library - Link
• ESW-TS Library Documentation - Link