Class: Purplelight::Snapshot

Inherits:
Object
  • Object
show all
Defined in:
lib/purplelight/snapshot.rb

Overview

Snapshot orchestrates partition planning, parallel reads, and writing.

Constant Summary collapse

DEFAULTS = 
{
  format: :jsonl,
  compression: :zstd,
  batch_size: 2_000,
  partitions: (Etc.nprocessors * 2).clamp(4, 32),
  queue_size_bytes: 256 * 1024 * 1024,
  rotate_bytes: 256 * 1024 * 1024,
  read_concern: { level: :majority },
  read_preference: :primary,
  no_cursor_timeout: true
}.freeze

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(client:, collection:, output:, format: DEFAULTS[:format], compression: DEFAULTS[:compression], partitions: DEFAULTS[:partitions], batch_size: DEFAULTS[:batch_size], queue_size_bytes: DEFAULTS[:queue_size_bytes], rotate_bytes: DEFAULTS[:rotate_bytes], query: {}, projection: nil, hint: nil, mapper: nil, resume: { enabled: true, state_path: nil, overwrite_incompatible: false }, sharding: { mode: :by_size, part_bytes: DEFAULTS[:rotate_bytes], prefix: nil }, logger: nil, on_progress: nil, read_concern: DEFAULTS[:read_concern], read_preference: DEFAULTS[:read_preference], no_cursor_timeout: DEFAULTS[:no_cursor_timeout], telemetry: nil, compression_level: nil, writer_threads: 1, write_chunk_bytes: nil, parquet_row_group: nil, parquet_max_rows: nil) ⇒ Snapshot

Returns a new instance of Snapshot.



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# File 'lib/purplelight/snapshot.rb', line 34

def initialize(client:, collection:, output:, format: DEFAULTS[:format], compression: DEFAULTS[:compression],
               partitions: DEFAULTS[:partitions], batch_size: DEFAULTS[:batch_size],
               queue_size_bytes: DEFAULTS[:queue_size_bytes], rotate_bytes: DEFAULTS[:rotate_bytes],
               query: {}, projection: nil, hint: nil, mapper: nil,
               resume: { enabled: true, state_path: nil, overwrite_incompatible: false },
               sharding: { mode: :by_size, part_bytes: DEFAULTS[:rotate_bytes], prefix: nil },
               logger: nil, on_progress: nil, read_concern: DEFAULTS[:read_concern], read_preference: DEFAULTS[:read_preference],
               no_cursor_timeout: DEFAULTS[:no_cursor_timeout], telemetry: nil,
               compression_level: nil, writer_threads: 1, write_chunk_bytes: nil, parquet_row_group: nil,
               parquet_max_rows: nil)
  @client = client
  @collection = client[collection]
  @output = output
  @format = format.to_sym
  @compression = compression.to_sym
  @partitions = partitions
  @batch_size = batch_size
  @queue_size_bytes = queue_size_bytes
  @rotate_bytes = rotate_bytes
  @query = query || {}
  @projection = projection
  @hint = hint
  @mapper = mapper
  @resume = resume || { enabled: true }
  @sharding = sharding || { mode: :by_size }
  @logger = logger
  @on_progress = on_progress
  @read_concern = read_concern
  @read_preference = read_preference
  @no_cursor_timeout = no_cursor_timeout
  @compression_level = compression_level
  @writer_threads = writer_threads || 1
  @write_chunk_bytes = write_chunk_bytes
  @parquet_row_group = parquet_row_group
  @parquet_max_rows = parquet_max_rows

  @running = true
  if @on_progress
    @progress_mutex = Mutex.new
    @progress_cv = ConditionVariable.new
  end
  @telemetry_enabled = telemetry ? telemetry.enabled? : (ENV['PL_TELEMETRY'] == '1')
  @telemetry = telemetry || (
    @telemetry_enabled ? Telemetry.new(enabled: true) : Telemetry::NULL
  )
end

Class Method Details

.snapshot ⇒ Object 



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# File 'lib/purplelight/snapshot.rb', line 30

def self.snapshot(...)
  new(...).run
end

Instance Method Details

#run ⇒ Object

rubocop:disable Naming/PredicateMethod



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# File 'lib/purplelight/snapshot.rb', line 82

def run
  dir, prefix = resolve_output(@output, @format)
  manifest_path = File.join(dir, "#{prefix}.manifest.json")
  query_digest = Manifest.query_digest(@query, @projection)

  manifest = if @resume && @resume[:enabled] && File.exist?(manifest_path)
               m = Manifest.load(manifest_path)
               unless m.compatible_with?(collection: @collection.name, format: @format, compression: @compression,
                                         query_digest: query_digest)
                 if @resume[:overwrite_incompatible]
                   m = Manifest.new(path: manifest_path)
                 else
                   raise IncompatibleResumeError,
                         'existing manifest incompatible with request; pass overwrite_incompatible: true to reset'
                 end
               end
               m
             else
               Manifest.new(path: manifest_path)
             end

  manifest.configure!(collection: @collection.name, format: @format, compression: @compression, query_digest: query_digest, options: {
                        partitions: @partitions,
                        batch_size: @batch_size,
                        queue_size_bytes: @queue_size_bytes,
                        rotate_bytes: @rotate_bytes,
                        hint: @hint,
                        read_concern: (@read_concern.is_a?(Hash) ? @read_concern : { level: @read_concern }),
                        no_cursor_timeout: @no_cursor_timeout,
                        writer_threads: @writer_threads,
                        compression_level: @compression_level || ENV['PL_ZSTD_LEVEL']&.to_i,
                        write_chunk_bytes: @write_chunk_bytes || ENV['PL_WRITE_CHUNK_BYTES']&.to_i,
                        parquet_row_group: @parquet_row_group || ENV['PL_PARQUET_ROW_GROUP']&.to_i,
                        parquet_max_rows: @parquet_max_rows,
                        sharding: @sharding,
                        resume_overwrite_incompatible: @resume && @resume[:overwrite_incompatible] ? true : false,
                        telemetry: @telemetry_enabled
                      }, partition_count: @partitions)

  # Reuse the original ranges on resume. Replanning against a growing collection
  # can move partition boundaries and replay rows under the old checkpoints.
  t_plan = @telemetry.start(:partition_plan_time)
  partition_filters = manifest.partition_filters
  unless partition_filters
    partition_filters = Partitioner.object_id_partitions(collection: @collection, query: @query,
                                                         partitions: @partitions, telemetry: @telemetry)
    manifest.configure_partition_filters!(partition_filters)
  end
  @telemetry.finish(:partition_plan_time, t_plan)

  # Reader queue
  queue = ByteQueue.new(max_bytes: @queue_size_bytes)

  # Writer
  writer_count = @format == :jsonl ? [@writer_threads.to_i, 1].max : 1
  part_sequence = WriterJSONL::PartSequence.new(manifest.parts.length) if @format == :jsonl
  writers = case @format
            when :jsonl
              Array.new(writer_count) do
                WriterJSONL.new(directory: dir, prefix: prefix, compression: @compression,
                                rotate_bytes: @rotate_bytes, logger: @logger, manifest: manifest,
                                compression_level: @compression_level, write_chunk_bytes: @write_chunk_bytes,
                                part_sequence:)
              end
            when :csv
              single_file = @sharding && @sharding[:mode].to_s == 'single_file'
              [WriterCSV.new(directory: dir, prefix: prefix, compression: @compression,
                             rotate_bytes: @rotate_bytes, logger: @logger, manifest: manifest,
                             single_file:, compression_level: @compression_level)]
            when :parquet
              single_file = @sharding && @sharding[:mode].to_s == 'single_file'
              row_group = @parquet_row_group || ENV['PL_PARQUET_ROW_GROUP']&.to_i ||
                          WriterParquet::DEFAULT_ROW_GROUP_SIZE
              [WriterParquet.new(directory: dir, prefix: prefix, compression: @compression, logger: @logger,
                                 manifest:, single_file:, row_group_size: row_group,
                                 rotate_rows: @parquet_max_rows)]
            else
              raise ArgumentError, "format not implemented: #{@format}"
            end

  # Start reader threads
  readers = partition_filters.each_with_index.map do |pf, idx|
    Thread.new do
      local_telemetry = @telemetry_enabled ? Telemetry.new(enabled: true) : Telemetry::NULL
      read_partition(idx: idx, filter_spec: pf, queue: queue, batch_size: @batch_size, manifest: manifest, telemetry: local_telemetry)
      # Merge per-thread telemetry
      @telemetry.merge!(local_telemetry) if @telemetry_enabled
    end
  end

  # Writer loops
  writer_telemetries = []
  writer_threads = writers.map do |writer|
    writer_telemetry = @telemetry_enabled ? Telemetry.new(enabled: true) : Telemetry::NULL
    writer_telemetries << writer_telemetry
    Thread.new(writer, writer_telemetry) do |worker_writer, worker_telemetry|
      Thread.current[:pl_telemetry] = worker_telemetry if @telemetry_enabled
      loop do
        batch = queue.pop
        break if batch.nil?

        worker_writer.write_many(batch)
      end
    ensure
      worker_writer.close
    end
  end

  progress_thread = if @on_progress
                      Thread.new do
                        loop do
                          @progress_mutex.synchronize { @progress_cv.wait(@progress_mutex, 2) }
                          break unless @running

                          @on_progress.call({ queue_bytes: queue.size_bytes })
                        end
                      end
                    end

  # Join readers
  readers.each(&:join)
  queue.close
  writer_threads.each(&:join)
  writer_telemetries.each { |writer_telemetry| @telemetry.merge!(writer_telemetry) } if @telemetry_enabled
  if progress_thread
    @progress_mutex.synchronize do
      @running = false
      @progress_cv.broadcast
    end
    progress_thread.join
  else
    @running = false
  end
  if @telemetry_enabled
    total = @telemetry.timers.values.sum
    breakdown = @telemetry.timers
                          .sort_by { |_k, v| -v }
                          .map { |k, v| [k, v, total.zero? ? 0 : ((v / total) * 100.0)] }
    if @logger
      @logger.info('Telemetry (seconds and % of timed work):')
      breakdown.each { |k, v, pct| @logger.info("  #{k}: #{v.round(3)}s (#{pct.round(1)}%)") }
    else
      puts 'Telemetry (seconds and % of timed work):'
      breakdown.each { |k, v, pct| puts "  #{k}: #{v.round(3)}s (#{pct.round(1)}%)" }
    end
  end
  true
end