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I'm trying to run the WDL tasks from the GTEx RNA-Seq pipeline with Cromwell using AWS Batch as a backend.

I store the STAR alignment index on an Elastic Block Store since my Cromwell server instance lacks sufficient disk space. The EBS Block is mounted to my Cromwell server at /data. The STAR index is located at /data/genomic-references/rnaseq/star_index_oh50.

Try as I might, I cannot get Cromwell to run the STAR task correctly.

My JSON inputs file:

 {
   "rnaseq_pipeline_fastq_workflow.prefix": "s3://mybucket/test/CL100148068",
   "rnaseq_pipeline_fastq_workflow.star.fastq1": "s3://anotherbucket/genotypedata/sample1.fq.gz",
   "rnaseq_pipeline_fastq_workflow.star.star_index": "/data/genomic-references/rnaseq/star_index_oh50/",
   "rnaseq_pipeline_fastq_workflow.star.memory": "32",
   "rnaseq_pipeline_fastq_workflow.star.num_threads": "4",
   "rnaseq_pipeline_fastq_workflow.star.disk_space": "200",
   "rnaseq_pipeline_fastq_workflow.star.num_preempt": "0" 
 }

Error message:

tar: /data/genomic-references/rnaseq/star_index_oh50/: Cannot open: No such file or directory

Note that /data/genomic-references/rnaseq/star_index_oh50/ does exist and is readable.

The relevant command in the GTEx container is here:

tar -xvvf ${star_index} -C star_index --strip-components=1

If the files are stored locally, then why does tar fail to wrap the directory?

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Somebody helped me with this one through other channels, but I wanted to make it publicly available:

Make a tarball of the STAR index. The option --strip-components=1 strips the first level of the path from the untarred items; thus, the expected tarball was made with something like

tar -cvf ${star_index} the_star_index_directory/

Then point Cromwell/WDL to the tarball, e.g. on S3. The GTEx container will unwrap the tarball on the fly during execution.

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