Accept retrieving less fields than requested in MARS Web API? - download

Question

I'm trying to download a 25 day ahead forecast from the ECMWF MARS Web API for all of 2018. These forecasts (WAEF Control Forecast) are only published on mondays and thursdays, and here I'm running into problems fetching the data using the MARS Web API.
I tried requesting the intuitive 2018-01-01/to/2018-12-31, but since there are 5 days a week where there aren't any fields to retrieve, the request fails.
My MARS request file is as follows:
retrieve,
class=od,
date=2018-01-01/to/2018-12-31,
expver=1,
param=229.140/245.140,
step=600/624/648/672,
stream=waef,
time=00:00:00,
type=cf,
target="output.grib"
Which results in the following response:
...
mars - INFO - 20190215.100826 - Welcome to MARS
mars - INFO - 20190215.100826 - MARS Client build stamp: 20190130224336
mars - INFO - 20190215.100826 - MARS Client version: 6.23.3
mars - INFO - 20190215.100826 - MIR version: 1.1.2
mars - INFO - 20190215.100826 - Using ecCodes version 2.10.1
mars - INFO - 20190215.100826 - Using odb_api version: 0.15.9 (file format version: 0.5)
mars - INFO - 20190215.100826 - Maximum retrieval size is 30.00 G
retrieve,target="output.grib",stream=waef,param=229.140/245.140,padding=0,step=600/624/648/672,expver=1,time=00:00:00,date=2018-01-01/to/2018-12-31,type=cf,class=odmars - WARN - 20190215.100826 - For wave data, LEVTYPE forced to Surface
mars - INFO - 20190215.100826 - Automatic split by date is on
mars - INFO - 20190215.100826 - Request has been split into 12 monthly retrievals
mars - INFO - 20190215.100826 - Processing request 1
RETRIEVE,
CLASS = OD,
TYPE = CF,
STREAM = WAEF,
EXPVER = 0001,
REPRES = SH,
LEVTYPE = SFC,
PARAM = 229.140/245.140,
TIME = 0000,
STEP = 600/624/648/672,
DOMAIN = G,
TARGET = "output.grib",
PADDING = 0,
DATE = 20180101/20180102/20180103/20180104/20180105/20180106/20180107/20180108/20180109/20180110/20180111/20180112/20180113/20180114/20180115/20180116/20180117/20180118/20180119/20180120/20180121/20180122/20180123/20180124/20180125/20180126/20180127/20180128/20180129/20180130/20180131
mars - INFO - 20190215.100826 - Web API request id: xxx
mars - INFO - 20190215.100826 - Requesting 248 fields
mars - INFO - 20190215.100826 - Calling mars on 'marsod', callback on 36551
mars - INFO - 20190215.100827 - Server task is 228 [marsod]
mars - INFO - 20190215.100827 - Request cost: 72 fields, 17.2754 Mbytes on 1 tape, nodes: hpss [marsod]
2019-02-15 11:08:59 Request is active
mars - INFO - 20190215.102300 - Transfering 18114554 bytes
mars - WARN - 20190215.102301 - Visiting database marsod : expected 248, got 72
mars - ERROR - 20190215.102301 - Expected 248, got 72.
mars - ERROR - 20190215.102301 - Request failed
...
Is there any way to allow receiving less fields than requested or any other elegant solution to this problem other than only requesting the correct dates for mondays and thursdays?

Answer 1

I managed to find the answer in the MARS documentation after all. Using expect = any in the control section solved the issue. More information can be found here: https://confluence.ecmwf.int/pages/viewpage.action?pageId=43521134
retrieve,
class=od,
date=2018-01-01/to/2018-12-31,
expver=1,
param=229.140/245.140,
step=600/624/648/672,
stream=waef,
time=00:00:00,
type=cf,
expect=any,
target="output.grib"