Disappearing ESA ODP data sources

[forman]

Actual behavior

Updating the data source list with results retrieved from ODP ESGF / CSW service can take some time if the the data store selector is "ESA CCI Open Data Portal".

If the data store selector in the DATA SOURCES panel is switched to "local" while ODP data sources are being updated (see TASKS panel) and then switched back to "ESA CCI Open Data Portal" a second task is invoked. Every time the selector is switched back to "ESA CCI Open Data Portal" a new task will be invoked. Only the first task will return the list of ODP data sources, the subsequent, redundant calls all return an empty lists resulting in no ODP data sources being available.

Note, that this will likely happen to first time users when waiting for the ODP data sources to appear then meanwhile exploring what other data stores exist in Cate.

Expected behavior

Switching back the data store selector to "ESA CCI Open Data Portal" should not invoke a new update task at all, besides the bug that any additional invocation returns empty lists.

Step to reproduce

1. delete directory $home/.cate/data_stores/esa_cci_odp
2. start Cate Desktop
3. while data sources are loaded from ODP (while Status Bar and TASKS panel indicate so) switch between "Local Data Sources" and "ESA CCI Open Data Portal" data store

Specifications

Cate 0.9.0.dev7