Nextflow DSL2多样本并行处理适配及S3输入读取方案问询

一、输入解析：兼容新旧格式 + 支持S3输入文件 #

1. 实现--input_list读取S3 YAML文件 #

在主脚本或nextflow.config中处理参数，用Groovy原生工具读取S3路径的配置文件：

params.input_list = null
params.samples = []

// 读取S3上的样本列表文件
if (params.input_list) {
    def yamlFile = file(params.input_list) // Nextflow自动处理S3路径访问
    def yamlContent = new groovy.yaml.YamlSlurper().parse(yamlFile.text)
    params.samples = yamlContent.samples ?: []
}

// 兼容旧版无`samples`字段的单样本输入
if (params.samples.isEmpty()) {
    def singleSample = [
        id: params.sample_id ?: "default_sample",
        fastq_r1: params.fastq_r1,
        fastq_r2: params.fastq_r2,
        // 补充其他原单样本必填参数
    ]
    params.samples = [singleSample]
}

2. 输入合法性校验 #

避免无效样本导致流程失败：

params.samples.each { sample ->
    assert sample.id : "样本ID不能为空"
    assert sample.fastq_r1 : "样本${sample.id}的R1序列路径缺失"
}

二、样本并行化：绑定流程与样本上下文 #

将样本列表转为Nextflow通道，每个样本作为独立任务单元，确保全流程步骤关联同一样本参数：

// 创建样本通道：每个元素为包含完整参数的Map
Channel.fromList(params.samples)
    .set { sampleChannel }

// 示例流程步骤：FastQC
process FastQC {
    executor = 'awsbatch'
    queue = 'your-batch-queue'
    container = 'quay.io/biocontainers/fastqc:0.11.9--hdfd78af_1'

    input:
    tuple val(sample)

    output:
    tuple val(sample.id), path("${sample.id}_fastqc.*")

    script:
    """
    fastqc ${sample.fastq_r1} ${sample.fastq_r2 ?: ''} -o .
    """
}

// 示例流程步骤：序列比对（依赖FastQC结果）
process Alignment {
    executor = 'awsbatch'
    queue = 'your-batch-queue'
    container = 'docker.io/bwa-mem2/bwa-mem2:2.2.1'

    input:
    tuple val(sample), path(fastqc_files)
    path ref_genome from refGenomeChannel

    output:
    tuple val(sample.id), path("${sample.id}.bam"), path("${sample.id}.bam.bai")

    script:
    """
    bwa-mem2 mem ${ref_genome} ${sample.fastq_r1} ${sample.fastq_r2 ?: ''} | samtools sort -o ${sample.id}.bam -
    samtools index ${sample.id}.bam
    """
}

// 流程串联
workflow {
    refGenomeChannel = Channel.fromPath(params.ref_genome)
    fastqcOut = FastQC(sampleChannel)
    alignOut = Alignment(fastqcOut, refGenomeChannel)
    // 后续步骤按此模式串联
}

三、AWS Batch适配配置 #

在nextflow.config中配置调度参数，适配批量任务运行：

process {
    executor = 'awsbatch'
    queue = 'default-batch-queue'
    memory = 16.GB
    cpus = 4
    maxParallelism = 100 // 根据队列容量调整并发数
}

aws {
    region = 'us-east-1'
    batch {
        cliPath = '/usr/local/bin/aws' // 容器内AWS CLI路径
    }
}

workDir = 's3://your-bucket/nextflow-workdir' // 工作目录指定到S3，避免本地存储瓶颈

四、指定输出结构 #

通过publishDir将每个样本结果输出到独立S3路径：

process FastQC {
    // ... 其他配置 ...
    publishDir = [
        path: "s3://output-bucket/${sample.id}/fastqc",
        mode: 'copy',
        overwrite: false
    ]
}

process Alignment {
    // ... 其他配置 ...
    publishDir = [
        path: "s3://output-bucket/${sample.id}/alignment",
        mode: 'copy',
        overwrite: false
    ]
}

五、测试验证 #

1. 单样本兼容测试：

nextflow run main.nf --sample_id test_sample --fastq_r1 s3://input-bucket/test_r1.fq.gz --fastq_r2 s3://input-bucket/test_r2.fq.gz

2. 多样本批量测试：
   创建s3://input-bucket/samples.yaml：

samples:
  - id: sample_001
    fastq_r1: s3://input-bucket/sample_001_r1.fq.gz
    fastq_r2: s3://input-bucket/sample_001_r2.fq.gz
  - id: sample_002
    fastq_r1: s3://input-bucket/sample_002_r1.fq.gz
    fastq_r2: s3://input-bucket/sample_002_r2.fq.gz

运行命令：

nextflow run main.nf --input_list s3://input-bucket/samples.yaml

内容的提问来源于stack exchange，提问作者user3214212