Prototypcial implementation of a REST server supporting the proposed, extended Memento-Protocol. Please note, this is not an implementation intended for production use, but rather a working demonstration of the proposed protocol extensions.
This implementation features the following Memento protocol extensions
memento-datetime and accept-datetime headersmemento-datetime as a response header for PUT and POST requestsPUT requests with a memento-datetime header at an archiving endpoint, to allow the storage of Mementos created at another URI-R memento-datetime-range requests to TimeMaps and returns only the requested range of Mementos.as well as the known features of a Memento protocol implementation that combines TimeGates, Original Resources and Memento storage on the same server.
URI-R via HTTP GET as well as headers pointing to the TimeMap and TimeGate for that URI-RURI-Ms associated with a URI-R, either completely or paged.URI-R, if the accept-datetime header is set in a GET request.URI-M.The server implementation is written in Typescript for Node v14 and uses Express v4.17 as the web framework to handle RESTful requests.
Redis v6 is used as an in-memory backend to store Mementos. The Node server interfaces with the Redis backend using NodeRedis.
The node server accepts HTTP requests and handles them using Express. Mementos are directly stored in the Redis backend using Redis Streams. Corresponding information on the used data structures, as well as time and space complexity, can be found in the respective Redis documentations. The different operations are implemented as follows:
PUT requests may create new resources at any path on the server.
The server stores Mementos to a specific resource as a Redis Stream.
Additionally a List of timestamps is used for each resource to be able to quickly assemble a TimeMap, if requested.
Redis returns a Timestamp if an element is added to a Stream. This Timestamp is formatted in RFC3339 and returned as a memento-datetime header with the response to the request.
HTTP DELETE requests to an existing resource add a Tombstone element to the Redis Stream and do not change the List managing the TimeMap.
For simple GET requests to resources, the last element of the Redis Stream is retrieved and returned.
If an accept-datetime header is present, the associated Memento is retrieved from the Stream via the provided Timestamp.
If a simple GET request is directed to a deleted resource, the tombstone stored in Redis is interpreted, and the status code 410 Gone is returned. However, Mementos may still be retrieved via accept-datetime requests to that resource.
If a TimeMap is requested, it is assembled from the information in the Redis List, which only contains the Timestamps for a resource. The correct range of the List is requested from Redis using lrange if a paged TimeMap, or a TimeMap range is requested.
The TypeDoc Documentation documents the functions and classes of the FactServer.
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