For BD-1007: Polyglot refactoring for dockerizing SSes, mainly in the POL-SS communication part.
In the existing architecure, Polyglot is a server, while a SS is also a server. Refer to the development notes at the "Polyglot / SoftwareServer Documentation" page, POL goes to RabbitMQ, gets the consumer IPs as the SSes, connects to the URL "<ip>:8182/applications". If the URL is accessible and contains valid content, Polyglot adds the IP to its server list.
SS supports many REST endpoints. POL uses the following two endpoints:
- /alive
This returns a timestamp (a long integer) to indicate the start time of the SS. (long int, plain text)
Used for adding a SS in discoveryAMQ() if POL gets a valid long int, and removing a SS in heartbeat() if POL does not get a valid long int from the ep. - /applications
This returns a JSON array, such as "[{"alias":"daffodil","conversions":[{"inputs":["csv"],"outputs":["xml"]},{"inputs":["pgm"],"outputs":["xml"]}]},{"alias":"flac","conversions":[{"inputs":["aif","aiff","fla","flac","wav"],"outputs":["aif","aiff","fla","flac","wav"]}]".
Used for adding a SS and updating the IO graph in discoveryAMQ().
Proposed design:
- SS registration with polyglot.
- Add 1 exchange/queue for SS registration with polyglot.
Set its TTL to say 5 secs, so msgs are discarded in such time. - SS publishes msgs to this queue, regarding aliveness, and conversion capabilities.
- Add 1 exchange/queue for SS registration with polyglot.
In "checkin", SS posts the content of a converted file and Polyglot saves it, instead of creating a "<file>.url" file.