Why do documents routed to error output cause pipelines to fail when used through ULTRA tasks?

Question

I'm making a pipeline that fires a couple of REST POST calls in parallel and then updates a table in a database. It is going to be used via an ULTRA task. I'm using a script for certain transformations and mapping that I won't be able to do using traditional snaps as most of them are not ULTRA compatible (for example, tail and group by fields).

I'm aware that I need to maintain the lineage information for such pipelines to work through ULTRA tasks. Refer to the following documentation.

Script Snap Documentation

Whenever, I write the result to the output, I use something as follows.

this.output.write(doc, wrapper);

But there is no mention in the documentation about maintaining lineage information in case of errors. I have a similar wrapper in the catch block that I'm writing to error as follows.

this.error.write(wrapper); 

I'm getting the following error from this script.

Document created by 'Pre-DB Script[08755fd3-46b0-4f3a-b353-4a0685b649c4 -- 2b2bfab7-18f7-49ab-9a98-41bf0bc694eb]' does not contain lineage information and cannot be used as output from an Ultra pipeline

Resolution:
Use a Join snap to merge static documents into an Ultra input document or request that the snap be made Ultra-compatible

Reason:
The document was not created from an Ultra input document or was created by a Snap that is not Ultra-compatible

Following is the relevant bit of code.

var impl = {
    input: input,
    output: output,
    error: error,
    log: log,

    execute: function () {
        // Some variables
        var error = false;

        this.log.info("Executing Transform Script");
        while (this.input.hasNext()) {
            try {
                // Read the next document, wrap it in a map and write out the wrapper
                var doc = this.input.next();

                // Some operations

                if (!doc.successful) {
                    error = true;
                    throw { message: doc.errors.errorDetailMessage, original: doc };
                }

                var wrapper = new java.util.HashMap();
                // Add required fields to wrapper
                wrapper.put("original", doc);

                if (/* Should this wrapper be sent to output? */) {
                    if (!error) this.output.write(doc, wrapper);
                    error = false;
                }

                this.log.info("Transform Script finished");
            }
            catch (err) {
                var wrapper = new java.util.HashMap();
                wrapper.put("error", err.message);
                wrapper.put("original", err.original);
                this.log.error(err);
                this.error.write(wrapper);
            }
        }
    }
};

So, how can I resolve lineage information issues in cases where documents are routed to error path?

Answer 1

Turns out you can pass lineage information in error similar to output.

this.error.write(doc, wrapper);