はじめに

CSVファイルのデータをAWSのS3に保存するロジックを実装したので、よかったら参考にしてみてください。
Rails: 5.2.6
Ruby: 2.7.2

実装したコード

S３のバケットに例: 2021_10/2021_10_01.csv といったファイル名で出力されます。
こちらは毎日バッチで実行することを想定して作成おります。

export_csv.rb

# frozen_string_literal: true

require 'csv'
require 'aws-sdk-s3'

class ExportCsv
  def self.execute(params)
    output = CSV.generate do |csv|
      csv << params['headers']
      params['values'].each do |value|
        csv << value
      end
    end

    export_csv_to_s3(output, params)
  end

  def self.export_csv_to_s3(data, params)
    s3_client = Aws::S3::Client.new(stub_responses: Rails.env.test?,
                                    access_key_id: params['access_key_id'],
                                    secret_access_key: params['secret_access_key'],
                                    region: params['region'])
    bucket_name = params['bucket_name']
    folder_name = Time.current.yesterday.strftime('%Y_%m').to_s
    file_name = "#{Time.current.yesterday.strftime('%Y_%m_%d')}.csv"

    file_full_path = "#{folder_name}/#{file_name}"

    # バケットの存在確認とアクセス権の確認
    if bucket_exists_and_accessible?(s3_client, bucket_name)
      Rails.logger.info "Bucket '#{bucket_name}' exists and is accessible to you."
    else
      Rails.logger.info "Bucket '#{bucket_name}' does not exist " \
        'or is not accessible to you.'
    end
    
    # ファイルアップロードが完了したか確認
    if file_uploaded?(s3_client, bucket_name, file_full_path, data)
      Rails.logger.info "Object '#{file_full_path}' uploaded to bucket '#{bucket_name}'."
    else
      Rails.logger.info "Object '#{file_full_path}' not uploaded to bucket '#{bucket_name}'."
    end
  end

  def self.bucket_exists_and_accessible?(s3_client, bucket_name)
    s3_client.head_bucket(bucket: bucket_name)
    return true
  rescue StandardError
    return false
  end

  def self.file_uploaded?(s3_client, bucket_name, path, data)
    response = s3_client.put_object(
      bucket: bucket_name,
      key: path,
      body: data,
      content_type: 'text/csv'
    )
    return true if response.etag
  rescue StandardError => e
    Rails.logger.info "Error uploading object: #{e.message}"
    return false
  end

  private_class_method :export_csv_to_s3,
                       :bucket_exists_and_accessible?,
                       :file_uploaded?
end