This documents the changes between API version 2 (which was in operation since 2008) and version 3 (which started development in 2016 and was deployed in 2017-2018).
New features in WeatherAPI 3.0
The API framework and technology has been mostly rewritten, while preserving most of the 20K lines of code for the existing 48 products. In addition to better QA this has also enabled several new features:
Better security
The API now supports HTTPS everywhere, including internal links (e.g. available lists).
Better performance
Most products now use non-blocking IO for delivery of data, which means the web application does not have to wait idle while the backend is delivering data. This means the capability of handling many more simultaneous requests than before.
Swagger API metadata
All products now deliver a Swagger (a.k.a. OpenAPI) feed documenting the interface.
Better error reporting
All 4xx and 5xx errors now include an X-ErrorClass response header in addition to the HTTP status code. This makes it easier to identify what kind of situation is causing the error, instead of just trying to figure out from the status code (which is ambiguous).
Also, error messages are now delivered as plain text unless the client sends an "Accept: text/html" header (like all browsers).
Changes from 2.x
Unencrypted HTTP is no longer supported
HTTP requests will get a redirect to HTTPS.
Semicolon no longer parameter separator
All links now use ampersands to separate parameters in the query string. Requests with such were always handled correctly in 2.x, but all generated documentation and links (e.g. available) used semicolons whereas we now only use ampersands.
According to the new HTML5 specification, semicolon is no longer accepted as a valid parameter separator. The standard states that implementors should be "strictly splitting the string payload on U+0026 AMPERSAND characters (&)". The use of semicolon separators is hence deprecated in all new WeatherAPI products and version released from August 2016 onwards. For compatibility we will try to honor old requests as long as practically feasible.
Also, the undocumented uri_delimiter parameter (which could be used to force
the use of ampersands) is now ignored, unless you try to force back to
using semicolons (which are no longer supported).
Unexpectedmissingdata now 502 instead of 404
Sometimes data from the backend are not available. This used to be presented as a 404 Not Found, but as it really is an error on our side and not with the client this has been changed to 502 Bad Gateway.
Other status codes may also be changed if deemed necessary.
2017-06-22, Geir Aalberg