sefran3 : fdsnws-dataselect stream with no data badly handled

[jmsaurel]

When using fdsnws-dataselect archive source, the handling of a stream returning no data should be improved. Here is the current situation

• if the fdsnws returns 204 for no data, wget hang up indefinitely
• if the fdsnws returns 404 for no data (option nodata=404), sefran3 throw an error because there is an empty mseed file.

Possible solution :

• use curl instead of wget (curl doesn't hang up when http return code is 204)
• if mseed file is empty, just spit an error message and continue

[beaudu]

ok, it seems that these problems have been solved in the fdsnws-dataselect for PROCS (readfmtdata_miniseed.m). We have to adapt the solution to sefran3, which does not use generic proc's data functions reading since sefran3 is not formally a proc. Possibly but harder work, modify sefran3 data reading part to use data reading like other procs do... but this leads to a broad question that is to make sefran3 a real proc associated to a list of nodes...

[jmsaurel]

we could simplify the code by using POST method instead of GET. The loop on sfr writes the post file and a single wget command is used to retrieve all the channels. I will try that.

Using readfmtdata would of course be nicer, but requires more work.

[jmsaurel]

Commit d1e3b uses POST method and should solve the issue and improve the efficiency

Now, only one request is made for each SefraN minute and it's much less likely that there is no data at all.