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Join-Fork operator


The Join-Fork operator combines the functionality of the Join and Fork operators.
Like the Join operator, it receives multiple inputs and merges them, then, like the Fork operator, it propagates its output to all the blocks downstream.
The Join-Fork operator is used to simultaneously end a parallel portion of the workflow and start another.

The same result can be achieved by putting a Join block and a Fork block one after the other, but Join-Fork helps keep the diagram more compact.

A Join-Fork block must have at least two incoming connections with upstream blocks and two or three outgoing connections with downstream blocks to be valid.

Old version

There are two versions of the component available: the latest and 1.0.0. This version is present for backward compatibility with old workflows created with previous versions of NL Flow. For new workflows always use the latest version.

The blocks of version 1.0.0 are identical to those of version 1.9 of NL Flow, however something has changed in the block properties: the name of the block, instead of editing the Block name field, can be modified by selecting Edit component name .
Also, a version 1.0.0 block doesn't have the Maximum number of flow branches that can fail without propagating the error property described below.


The output of Join-Fork is the same as that of a Join block: a JSON object that represents the composition of the outputs of the branches converging in it.

Block properties

Block properties can be set by editing the block.
A Join-Fork operator block has these properties:

  • Block name
  • Component version (read only)
  • Block ID (read only)
  • Maximum number of flow branches that can fail without propagating the error: as for the Join operator, value 0 indicates that any error of any upstream branch makes the Join-Fork block produce an error which can lead to a general workflow error. A different value, integer and positive, indicates the maximum number of branches whose errors are ignored, so to have Join-Fork aggregate the output of the other, non failing, branches and not raise an error.
    Even if errors are ignored they are still visible in the verbose output of the workflow.