ProductSet-Reader never passes a valid source product downstream — reproducible on SNAP 12 and 13

Microwave Toolbox Problem Reports
1

Hi all,

I’ve been having issues with ProductSet-Reader and was lead down a rabbit-hole by claude. I’ve seen mention of similar issues from almost 10 years ago here but nothing seems to help.

The issue: ProductSet-Reader reports success (logs done., no warnings or errors at the node itself) but doesn’t actually hand off a usable source product to whatever comes next in the graph. Every downstream operator I’ve tried fails with the same error:

org.esa.snap.core.gpf.OperatorException: Operator '<OpName>': Mandatory source product (field 'sourceProduct') not set.

I’ve confirmed this is not specific to any one downstream operator — I tested Write, Subset, and TOPSAR-Split directly after ProductSet-Reader in turn, and all three fail identically. So it seems to be something in how ProductSet-Reader itself hands off its output within the graph, rather than anything about the operator that follows it.

Minimal repro:

xml

<graph id="Graph">
    <version>1.0</version>
    <node id="ProductSet-Reader">
        <operator>ProductSet-Reader</operator>
        <parameters class="com.bc.ceres.binding.dom.XppDomElement">
            <fileList>/path/to/your_file.zip</fileList>
        </parameters>
    </node>
    <node id="Subset">
        <operator>Subset</operator>
        <sources>
            <sourceProduct refid="ProductSet-Reader"/>
        </sources>
        <parameters class="com.bc.ceres.binding.dom.XppDomElement">
        </parameters>
    </node>
    <node id="Write">
        <operator>Write</operator>
        <sources>
            <sourceProduct refid="Subset"/>
        </sources>
        <parameters class="com.bc.ceres.binding.dom.XppDomElement">
            <file>/tmp/test_output</file>
            <formatName>BEAM-DIMAP</formatName>
        </parameters>
    </node>
</graph>

Run with gpt graph.xml -e, and it fails at the Subset node with the “Mandatory source product not set” error, even though ProductSet-Reader logged as complete just before it.

What I’ve ruled out:

  • File path issues (tested with symlinks and direct paths)

  • fileList formatting (tested plain string and comma-separated, per the schema from gpt ProductSet-Reader -h)

  • <sources/> presence/absence on the reader node

  • SNAP version — reproduces identically on SNAP 12.0.0 and SNAP 13.0.0

  • GUI vs CLI — reproduces in both the Graph Builder and via gpt

  • Operator-specific quirks — same failure with Write, Subset, and TOPSAR-Split

Also worth noting: while cross-checking with a different product type (Sentinel-2), ProductSet-Reader in the GUI Graph Builder froze entirely rather than erroring — possibly a related instability in the same operator, though a different symptom.

Why I’m posting this here: I found two older threads describing what looks like the exact same problem:

Using Read instead of ProductSet-Reader for a single-file works fine but it’s not really a solution I’m happy with.

Maybe I’ve missed something when going through the forum so apologies if that’s the case.

Thanks!

2

The reason you encounter the “Mandatory source product” error is that the operator (e.g. subset) expects a single source product rather than a set of products. If you want to process multiple products with a single graph, I recommend using the Batch Processing functionality in SNAP. For more details, please refer to this tutorial https://step.esa.int/docs/tutorials/S1TBX%20Time-series%20analysis%20with%20Sentinel-1.pdf.