Log warning when REST server has its url-rewriter overwritten

[rjrudin]

This is to provide some warning to a user who specifies a URL rewriter that is not recognized by ML as a valid rewriter path, and thus the GET call to /v1/rest-apis will not return the server, which usually leads to an error.

[rjrudin]

@jkerr5 How about this warning when a REST server is updated with a url-rewriter that does not have the string 'rest-api' in it? (and that seems to be the requirement - I tested a url-rewriter of just 'rest-api', and that worked):

11:01:37.911 [main] WARN c.m.a.c.a.UpdateRestApiServersCommand - The REST server is being updated with a url-rewriter that does not contain the string 'rest-api' in its URI. This may result in a 'Port is in use' exception if the command for creating a REST server is run. This is because the command to create a REST server first sends a GET to /v1/rest-apis, and that endpoint only returns servers that have the string 'rest-api' in the URI of the url-rewriter. It is recommended to include the string 'rest-api' in the URI of a url-rewriter for a REST server to avoid this problem.

Then, if the error does occur, ml-app-deployer will also include this warning before the exception is logged:

11:04:53.478 [main] WARN c.m.m.r.restapis.RestApiManager - Caught exception due to a port being in use; this may because the REST server already exists but is using a rewriter that the /v1/rest-apis endpoint does not recognize as a REST rewriter, and thus the /v1/rest-apis endpoint does not think that the REST server has been created yet. The error is then because an attempt is made to create the REST server but it fails because the port is already in use. To fix this, try modifying the URI of the rewriter module so it contains the string 'rest-api'.