NOTE: This project is now managed by the OCS Organization. This repo is left as read-only.

You can access the new repo at https://github.com/observatorycontrolsystem/thumbnail-service/

Thumbnail service

This is a flask application that generates thumbnails from data stored on the LCOGT Science Archive.

Requirements

This script uses amazon S3 to temporarily store images. You'll need a bucket and the correct environmental variables set.

This script also relies on fits2image. Make sure it is installed in your virtualenv.

All other dependencies are listed in the pyproject.toml file and can be installed via poetry.

pip install --upgrade pip
pip install poetry
poetry install

poetry install will create a virtual environment for you, which will have all requirements installed.

Run the tests with poetry run pytest thumbservice/tests.py.

Configuration

This project can be configured using the following environment variables:

Environment Variable	Description	Default
ARCHIVE_API_URL	Archive API URL	http://localhost/
TMP_DIR	Temporary directory for image operations	'/tmp/'
AWS_BUCKET	AWS S3 Bucket to store thumbnails	'changeme'
AWS_ACCESS_KEY_ID	AWS Access Key ID for S3 Bucket	'changeme'
AWS_SECRET_ACCESS_KEY	AWS Secret Access Key for S3 Bucket	'changeme'
STORAGE_URL	URL for bucket storage if different than AWS. Defaults to None to connect to AWS S3	None
REQUIRED_FRAME_VALIDATION_KEYS	Keys from Archive API record required in order to create a thumbnail from the FITS image	'configuration_type,request_id,filename'
VALID_CONFIGURATION_TYPES	Only generate thumbnails from images of these configuration types	'ARC,BIAS,BPM,DARK,DOUBLE,EXPERIMENTAL,EXPOSE,GUIDE,LAMPFLAT,SKYFLAT,SPECTRUM,STANDARD,TARGET,TRAILED'
VALID_CONFIGURATION_TYPES_FOR_COLOR_THUMBS	Only generate color thumbnails from images of these configuration types	'EXPOSE,STANDARD'

Authorization

The API passes through the Authorization header to the archive API. You only need to provide this header if the data you are attempting to get a thumbnail for is proprietary. See the archive documentation for more details.

Endpoints

There are only 2 endpoints: /<frame_id>/ and /<basename>/ where frame_id is the ID of the frame in the archive, and basename is the base part of the filename (no file extension) you wish to make a thumbnail of. Using the frame_id is faster to return if you happen to know it ahead of time.

Both endpoints take the following query parameters:

• width
• height
• label
• image

Width and height are in pixels, label will appear as white text in the lower left had corner of the image.

They both return a url to the thumbnail file that will be good for 1 week unless the image parameter is supplied which will return an image directly.

Example

https://thumbnails.lcogt.net/3863274/?width=500&height=500&label=So%20many%20stars

Changelog

2.16

2020-02-15

• Fix hash used in s3 key to be stable given the same inputs
• Add hook to gunicorn configuration files to clear out the temp directory on startup

2.15

2020-01-03

• Clean up gunicorn config file as most configuration has been moved to the helm chart

2.14

2019-05-08

• Migrate to AWS V4 signatures
• Modernize docker image

2.13

2019-04-11

• Enable gunicorn error and access logs

2.12

2019-04-11

• Add /robots.txt and /favicon.ico endpoints
• Use gunicorn configuration file with child_exit server hook implemented for additional temp file cleanup actions on certain abrupt worker death #846

2.11

2019-04-05

• Update boto3, requests, and flask
• Temporary file cleanup improvements
• Validate frame before attempting thumbnail generation
• Update error handling

2.10

2019-02-16

• Update numpy version
• Add DejaVu True Type Fonts
• Add freetype dependency for text overlay support
• Use standard LCO Jenkins automated docker container build pipeline
• Migrate Docker container to Alpine Linux base

2.9

2018-11-13

• Upgrade requests
• Initialize a variable that could have been referenced before assignment

2.5

• 2017-05-15
• Upgrade Dockerfile to be more sensible, upgrade to python 3.6

2.4

2017-04-04

• Add better exception handling to clean up temporary files even if generation fails.

2.3

2017-03-17

• Add quality paramter and reduce default quality. Improves speed without a noticeable change in image quality.
• Improve filename key so that any differnt combination of parameters will reuslt in a new image.

2.2

2017-02-27

• Added median filtering support

2.1

2016-08-24

• Fixed bug where images of different reduction levels were used to compose color images

2.0

2016-08-17

• Added color image support! Use ?color=True for frames which belong to a request that have other exposures using red, visual and blue filters.

1.1

2016-08-11

• Added image url parameter to return image directly instead of json. Useful for using as the src attribute in img tags.