BLAST-CPU

BLAST-CPU

This recipe shows how to run a parallelized BLAST pipeline by chunking an input fasta file and running multiple tasks in parallel using Azure Batch.

Configuration

Please see refer to this set of sample configuration files for this recipe.

Pool Configuration

Pool properties such as publisher, offer, sku, vm_size and vm_count should be set to your desired values.

The example pool configuration file utilizes 5 low priority VMs which can be adjusted to your scenario requirements.

Global Configuration

The global configuration should set the following properties:

batch_shipyard:
  storage_account_settings: mystorageaccount
global_resources:
  docker_images:
    - python:3-alpine
    - quay.io/biocontainers/blast:2.7.1--h4422958_6

The docker_images array contains references to the tools required for the BLAST pipeline.

Job/Task Execution Model and Configuration

The pipeline will take advantage of task dependencies to ensure tasks are processed one after the next after successful completion of each. The first stage, represented in jobs-split.yaml will take an input fasta file and chunk them into individual query files. These chunks are then uploaded to the specified storage account to be retrieved by the parallelized BLAST stage. In the parallelized BLAST stage, represented by the jobs-blast.yaml file, each individual query file is run across its own individual task. If multiple compute nodes (or nodes with a larger max_tasks_per_node setting that are able to accommodate the tasks) are available, then the requisite blast commands are run in parallel. Batch Shipyard automatically generates the correct number of parallel tasks via a task_factory that iterates over the chunked query fasta files generated in the earlier stage. Finally, a merge_task is run which collates all of the top-10 hits for each individual chunk into a results text file.

Please see the jobs configuration for the full example.

Execution

The following outlines a sample execution based on this recipe's configuration:

# create the pool
shipyard pool add

# add the fasta splitter task to create chunked queries for parallelization
shipyard jobs add --jobs jobs-split.yaml --tail stdout.txt

# add the parallelized blast executions with result merge
shipyard jobs add --jobs jobs-blast.yaml

# poll the merge task until it completes
shipyard jobs tasks list --jobid blast --taskid merge-task-00000 --poll-until-tasks-complete

# optionally egress the results.txt file from the compute node to local machine
shipyard data files task --filespec blast,merge-task-00000,wd/results.txt

# clean up
shipyard jobs del -y --jobs jobs-blast.yaml
shipyard pool del -y