Allow to define operation parameters dynamically

[danielmitterdorfer]

After #58 and #64 are implemented, we can have parameters for operations. However, these parameters are only static but for certain use cases we want to change parameter values for each invocation. Examples are:

• Retrieving random documents (see Running a get request with randomly generated ids #106)
• Dynamically changing the terms that should be queried in order to provoke query cache misses
• Dynamically creating synthetic data for indexing instead of defining a data file

[AndyDev2017]

@danielmitterdorfer
Hi, I would like to know if the requirement "Dynamically changing the terms that should be queried in order to provoke query cache misses" was implemented as I would like the means to supply a list of query terms to be randomly used. Thanks, Andrew

[danielmitterdorfer]

@AndyDev2017 yes this has been implemented. You need to write something called a "custom parameter source" to make this work. An example is provided in the docs. With #365
we will implement better support in Rally.

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