Configuration

Configuration files overview

The following files contain configuration settings:

• conf/base.config: Where cpu, memory and time parameters can be set for the different workflow processes. You will likely need to adjust parameters within this file for your computing environment.

• conf/modules.config: contains error strategy, output director structure and execution instruction parameters. It is unadvised to alter this file unless involved in pipeline development, or tuning to a system.

• nextflow.config: contains default tool settings that tie to CLI options. These options can be directly set within the params section of this file in cases when a user has optimized their pipeline usage and has identified the flags they will use every time the pipeline is run.

Base configuration (conf/base.config)

Within this file computing resources can be configured for each process. Mikrokondo uses labels to define resource requirements for each process, here are their definitions:

• process_single: processes requiring only a single core and low memory (e.g., listing of directories).
• process_low: processes that would typically run easily on a small laptop (e.g., staging of data in a Python script).
• process_medium: processes that would typically run on a desktop computer equipped for playing newer video games (Memory or computationally intensive applications that can be parallelized, e.g., rendering, processing large files in memory or running BLAST).
• process_high: processes that would typically run on a high performance desktop computer (Memory or computationally intensive application, e.g., performing de novo assembly or performing BLAST searches on large databases).
• process_long: modifies/overwrites the amount of time allowed for any of the above processes to allow for certain jobs to take longer (e.g., performing de novo assembly with less computational resources or performing global alignments on divergent sequences).
• process_high_memory: modifies/overwrites the amount of memory given to any process and grant significantly more memory to any process (Aids in metagenomic assembly or clustering of large datasets).

For actual resource amounts allotted to each process definition, see the conf/base.config file Process-specific resource requirements section.

Hardcoded tool configuration (nextflow.config)

All Command line arguments and defaults can be set and/or altered in the nextflow.config file, params section. For a full list of parameters to be altered please refer to the nextflow.config file in the repo. Some common arguments have been listed in the Common command line arguments section of the docs and further description of tool parameters can also be found in tool specific parameters.

Example: if your laboratory typically sequences using Nanopore chemistry "r1041_e82_400bps_hac_v4.2.0", the following code would be substituted in the params section of the nextflow.config file:

nanopore_chemistry = "r1041_e82_400bps_hac_v4.2.0" // Note the quotes around the value

With this change, you would no longer need to explicitly state the nanopore chemistry as an extra CLI argument when running mikrokondo.

Quality control report configuration

WARNING: Tread carefully here, as this will require modification of the nextflow.config file. Make sure you have saved a back up of your nextflow.config file before playing with these option

QCReport field desciption

The section of interest is the QCReport fields in the params section of the nextflow.config. There are multiple sections with values that can be modified or you can add data for a different organism. The default values in the pipeline are set up for Illumina data so you may need to adjust settingS for Nanopore or Pacbio data.

An example of the QCReport structure is shown below. With annotation describing the values.

NOTE: The values below do not affect the running of the pipeline, these values only affect the final quality messages output by the pipeline.

QCReport {
    escherichia // Generic top level name fo the field, it is name is technically arbitrary but it nice field name keeps things organized
    {
        search = "Escherichia coli" // The phrase that is searched for in the species_top_hit field mentioned above. The search is for containment so if you wanted to look for E.coli and E.albertii you could just set the value too "Escherichia"
        raw_average_quality = 30 // Minimum raw average quality of all bases in the sequencing data. This value is generated before the decontamination procedure.
        min_n50 = 95000 // The minimum n50 value allowed from quast
        max_n50 = 6000000 // The maximum n50 value allowed from quast
        min_nr_contigs = 1 // the minimum number of contigs a sample is allowed to have, a value of 1 works as a sanity check
        max_nr_contigs = 500 // The maximum number of contigs the organism in the search field is allowed to have. to many contigs could indicate a bad assembly or contamination
        min_length = 4500000 // The minimum genome length allowed for the organism specified in the search field
        max_length = 6000000 // The maxmimum genome length the organism in the search field is allowed to have
        max_checkm_contamination = 3.0 // The maximum level of allowed contamination allowed by CheckM
        min_average_coverage = 30 // The minimum average coverage allowed
    }
    // DO NOT REMOVE THE FALLTRHOUGH FIELD AS IT IS NEEDED TO CAPTURE OTHER ORGANISMS
    fallthrough // The fallthrough field exist as a default value to capture organisms where no quality control data has been specified
    {
        search = "No organism specific QC data available."
        raw_average_quality = 30
        min_n50 = null
        max_n50 = null
        min_nr_contigs = null
        max_nr_contigs = null
        min_length = null
        max_length = null
        max_checkm_contamination = 3.0
        min_average_coverage = 30
    }
}

Example adding quality control data for Salmonella

If you wanted to add quality control data for Salmonella you can start off by using the template below:

VAR_NAME { // Replace VAR name with the genus name of your sample, only use ASCII (a-zA-Z) alphabet characters in the name and replace spaces, punctuation and other special characters with underscores (_)
    search = "Search phrase" // Search phrase for your species top_hit, Note the quotes
    raw_average_quality = // 30 is a default value please change it as needed
    min_n50 = // Set your minimum n50 value
    max_n50 = // Set a maximum n50 value
    min_nr_contigs = // Set a minimum number of contigs
    max_nr_contigs = // The maximum number of contings
    min_length = // Set a minimum genome length
    max_length = // set a maximum genome length
    max_checkm_contamination = // Set a maximum level of contamination to use
    min_average_coverage = // Set the minimum coverage value
}

For Salmonella I would fill in the values like so.

salmonella {
    search = "Salmonella"
    raw_average_quality = 30
    min_n50 = 95000
    max_n50 = 6000000
    min_nr_contigs = 1
    max_nr_contigs = 200
    min_length = 4400000
    max_length = 6000000
    max_checkm_contamination = 3.0
    min_average_coverage = 30
}

After having my values filled out, I can simply add them to the QCReport section in the nextflow.config file.

    QCReport {
        escherichia {
            search = "Escherichia coli"
            raw_average_quality = 30
            min_n50 = 95000
            max_n50 = 6000000
            min_nr_contigs = 1
            max_nr_contigs = 500
            min_length = 4500000
            max_length = 6000000
            max_checkm_contamination = 3.0
            min_average_coverage = 30
        } salmonella { // NOTE watch the opening and closing brackets
            search = "Salmonella"
            raw_average_quality = 30
            min_n50 = 95000
            max_n50 = 6000000
            min_nr_contigs = 1
            max_nr_contigs = 200
            min_length = 4400000
            max_length = 6000000
            max_checkm_contamination = 3.0
            min_average_coverage = 30
        }
        fallthrough {
            search = "No organism specific QC data available."
            raw_average_quality = 30
            min_n50 = null
            max_n50 = null
            min_nr_contigs = null
            max_nr_contigs = null
            min_length = null
            max_length = null
            max_checkm_contamination = 3.0
            min_average_coverage = 30
        }
    }

Quality Control Fields

This section affects the behaviours of the final summary quality control messages and is noted in the QCReportFields within the nextflow.config. I would advise against manipulating this section unless you really know what you are doing.

TODO test what happens if no quality msg is available for the bool fields types.

Each value in the QC report fields contains the following fields.

• Field name
  • path: path to the information in the summary report JSON
  • coerce_type: Type to be coreced too, can be a Float, Integer, or Bool
  • compare_fields: A list of fields corresponding to fields in the QCReport section of the nextflow.config. If two values are specified it will be assumed you wish to check that a value is in between a range of values.
  • comp_type: The comparison type specified, 'ge' for greater or equal, 'le' for less than or equal, 'bool' for true or false or 'range' for checking if a value is between two values.
  • on: A boolean value for disabling a comparison
  • low_msg: A message for if a value is less than its compared value (optional)
  • high_msg: A message for if value is above a certain value (optional)

An example of what these fields look like is:

QCReportFields {
    raw_average_quality {
        path = [params.raw_reads.report_tag, "combined", "qual_mean"]
        coerce_type = 'Float'
        compare_fields = ['raw_average_quality']
        comp_type = "ge"
        on = true
        low_msg = "Base quality is poor, resequencing is recommended."
    }
}