Download: Seqera containers Patch 2

[MatthiasZepper]

The uncoordinated adoption of Seqera Containers in modules before the associated YAML could be devised and supported by tools has broken 'nf-core download' (#3179). #3182 topped up the associated test to make pipeline developers aware, so they could patch the modules with Biocontainer URIs to restore offline support.

With #3244 (Patch 1), I added minimal support for Seqera Containers, but had to include a bypass in the prioritization function to support the Seqera Container's odd http:// paths, that directly deeplink into the last layer of the Docker OCI images.

This change, however, also bypassed the deduplication routine, such that a race condition could arise, if a pipeline used the same container image in multiple modules and the download was performed with multiple processes in parallel. This led to bug #3285 and an issue with the release PR of fastquorum, that is preventable by limiting the number of processes to 1.

This PR (Patch2) now fixes said bug. Additionally, it adds basic support for native Singularity images specified with oras:// paths, such that the Seqera Container http:// paths can be phased out again.

This is desirable, because for every Seqera Container http:// path module, the associated Docker image is downloaded/converted as well, but never used. For a medium sized pipeline, the tool therefore downloads a dozen or more useless Docker container images and since the conversion to Singularity is slow, this significantly bogs down nf-core download.

The new dedicated Seqera Container consolidation functionality is unfortunately flaky and may be too aggressive, in case multiple revisions of a pipeline are downloaded at the same time. While this is far from ideal, I prefer that issue over a pile of unused containers being downloaded each time. Only more verbose container URIs for Seqera Containers could prevent this from happening, but I think the changes to see that implemented are low.

Ultimately, we should either stick with Bioconda or implement the new container YAML format.

PR checklist

• This comment contains a description of changes (with reason)
• CHANGELOG.md is updated
• If you've fixed a bug or added code that should be tested, add tests!

[codecov]

Codecov Report

Attention: Patch coverage is 70.37037% with 8 lines in your changes missing coverage. Please review.

Project coverage is 75.65%. Comparing base (ba332b6) to head (2eca65c).

Files with missing lines	Patch %	Lines
nf_core/pipelines/download.py	70.37%	8 Missing ⚠️

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