@Bhavin, I think what Mike is saying is that the File Reader has a binary input which requires a binary formatter of some sort which does not pass through the document variables that would otherwise be available to the File Reader if it had a JSON input.
@mikeandrews, I’ve run into the same issue and the only way I’ve been able to get this to work in the past is with two pipelines. The first ending with a Pipeline Execute or For Each snap which would assign the filename variable value to a parameter provided by the second pipeline which contained the File Reader snap.
For the same or similar use case, a couple of years ago, I had suggested to a SnapLogic representatives the need to make pipeline parameters variable rather than static. I even suggested a new variable array could be added as a property to the pipe object. However, this was an in-person, casual conversation and may not have made it to the request queue.
[Added: I have made corrections to this post in my following response]
Binary documents have a “header” with properties that can be referenced using dollar variables. When looking at the preview data for a binary view in Designer, you should be able to see what properties are available, if any. Unfortunately, most Formatter snaps don’t have a way to fill in the header document with properties, which limits the possibilties. It’s a gap that needs to be addressed.
They are effectively variable when used through PipeExec, as you described, and that is the correct approach at this time. The reason parameters cannot be set is because all of the snaps are running in parallel. So, it’s impossible to say what the value of a parameter is at any point is if they can be changed. For example, if you had a Mapper setting a pipeline parameter followed by a JSON-Formatter and a File-Writer, the Mapper could have processed one to hundreds of documents before the Writer read the value of the pipeline parameter. Now, imagine if the value computed for the parameter changed for every document that it processed, you would never get consistent results.
