Have bulk parameter source provide the bulk size

[danielmitterdorfer]

At the moment, Rally's bulk index runner determines the actual bulk size (which is normally equal to the bulk size that the user has defined except maybe for the last bulk that might contain less documents than the bulk size). However, the bulk parameter source usually has this information already. Hence, we should determine this information already in the bulk parameter source and provide it as parameter bulk-sizeto the runner.

This change is completely internal to Rally and will not affect users. However, it will affect anybody that has written a custom bulk parameter source. This change is forward-compatible, i.e. these users can already adjust their parameter sources to provide an additional parameter bulk-size and newer versions of Rally will just work.

[danielmitterdorfer]

Pinging @cdahlqvist: This will affect custom bulk parameter sources in your tracks.

Here is a specific example of what you need to change based on elasticlogs_bulk_source.py:

old:

response = { "body": bulk_array, "action_metadata_present": True }

new:

response = { "body": bulk_array, "action_metadata_present": True, "bulk-size": self._bulk_size }

You can make the change at any point in time you want. Older versions of Rally will ignore this parameter, newer versions will use the new parameter.