Improve client-side error response messages

[kellyi]

Overview

This PR adds some infrastructure to send more descriptive error messages back to the client and to catch other exceptions. I set it up by adding an ErrorHandler trait which conforms to akka-http's custom exception handling along with some case classes to match on some known exceptions we throw in the app -- for missing required fields & invalid raster ops. These are sent back as 400s; for other unforeseen exceptions we send back a 500 along with the exception message.

I also set this up to print the exception messages to the service console. I think we should configure these to log, too, but it seems like it may require some work to get LazyLogging to work with/supplant log4j, the latter of which is there via Spark.

We have #63 for configuring the logger.

Connects #69

Testing Instructions

• get this branch, then ./scripts/server
• send a variety of malformed requests to the server and verify that you get appropriate messages back and that you see the exceptions printed to the console

[rajadain]

Testing independently seems to be working very well:

http --print HhBb :8090/run < SquareKmPpt.json.txt

POST /run HTTP/1.1
Accept: application/json, */*
Accept-Encoding: gzip, deflate
Connection: keep-alive
Content-Length: 447
Content-Type: application/json
Host: localhost:8090
User-Agent: HTTPie/0.9.9

{
    "input": {
        "operationType": "RasterGroupedAverage",
        "pixelIsArea": true,
        "polygon": [
            "{\"type\":\"MultiPolygon\",\"coordinates\":[[[[-75.17123123758348,39.94946918388007],[-75.1595030153462,39.94946918388007],[-75.1595030153462,39.95845957765271],[-75.17123123758348,39.95845957765271],[-75.17123123758348,39.94946918388007]]]]}"
        ],
        "polygonCRS": "LatLng",
        "rasterCRS": "ConusAlbers",
        "rasters": [],
        "zoom": 0
    }
}

HTTP/1.1 400 Bad Request
Content-Length: 29
Content-Type: text/plain; charset=UTF-8
Date: Mon, 18 Sep 2017 21:30:45 GMT
Server: akka-http/10.0.9

Missing required targetRaster

http --print HhBb :8090/run < SquareKmPpt.json.txt

POST /run HTTP/1.1
Accept: application/json, */*
Accept-Encoding: gzip, deflate
Connection: keep-alive
Content-Length: 498
Content-Type: application/json
Host: localhost:8090
User-Agent: HTTPie/0.9.9

{
    "input": {
        "operationType": "RasterGroupedAverage",
        "pixelIsArea": true,
        "polygon": [
            "{\"type\":\"MultiPolygon\",\"coordinates\":[[[[-75.17123123758348,39.94946918388007],[-75.1595030153462,39.94946918388007],[-75.1595030153462,39.95845957765271],[-75.17123123758348,39.95845957765271],[-75.17123123758348,39.94946918388007]]]]}"
        ],
        "polygonCRS": "LatLng",
        "rasterCRS": "ConusAlbers",
        "rasters": [],
        "targetRaster": "climatology-ppt-14-epsg5070",
        "zoom": 0
    }
}

HTTP/1.1 500 Internal Server Error
Content-Length: 132
Content-Type: text/plain; charset=UTF-8
Date: Mon, 18 Sep 2017 21:30:22 GMT
Server: akka-http/10.0.9

geotrellis.spark.io.package$LayerNotFoundError: Layer Layer(name = "climatology-ppt-14-epsg5070", zoom = 0) not found in the catalog

Going to test out in MMW now.

[rajadain]

I agree that printing is fine for now, and we'll do logging properly with #63. Nice job using the Error Handler pattern of AKKA for this, and subclassing all errors from a custom GeoprocessingError. 👍

[kellyi]

Thanks! It occurred to me that we don't need the values from some of pattern matches here:

https://github.com/WikiWatershed/mmw-geoprocessing/pull/75/files#diff-21f7ae43c2d12dffcf68e5c22e585faaR25

... so I'm going to squash a fixup to remove them if they're not used.