Module: StreamReader

Defined in:
lib/stream_reader.rb,
lib/stream_reader/version.rb

Constant Summary collapse

BATCH_SIZE =

Assume only one shard for now

10
VERSION = 
'0.1.0'

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.logger ⇒ Object 



5
6
7
 
# File 'lib/stream_reader.rb', line 5

def logger
  @logger ||= Logger.new(STDOUT)
end

Instance Method Details

#initialize(stream_name:, prefix: '') ⇒ Object 



13
14
15
16
17
18
 
# File 'lib/stream_reader.rb', line 13

def initialize(stream_name:, prefix: '')
  @stream_name = stream_name
  @prefix      = prefix
  @tracker     = SequenceNumberTracker.new(key_prefix: [ stream_name, prefix ].compact.join('-'))
  @logger      = StreamReader.logger
end

#run!(&block) ⇒ Object 



20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
 
# File 'lib/stream_reader.rb', line 20

def run!(&block)
  # Locate a shard id to iterate through - we only have one for now
  loop do
    begin
      iterator_opts = { stream_name: @stream_name, shard_id: shard_id }
      if seq = @tracker.last_sequence_number
        iterator_opts[:shard_iterator_type] = 'AFTER_SEQUENCE_NUMBER'
        iterator_opts[:starting_sequence_number] = seq
      else
        iterator_opts[:shard_iterator_type] = 'TRIM_HORIZON'
      end
      @logger.debug "Getting shard iterator for #{@stream_name} / #{seq}"
      resp = client.get_shard_iterator(iterator_opts)
      shard_iterator = resp.shard_iterator

      # Iterate!
      loop do
        sleep 1
        @logger.debug "Getting records for #{shard_iterator}"
        resp = client.get_records({
          shard_iterator: shard_iterator,
          limit: BATCH_SIZE,
        })

        resp.records.each do |record|
          ActiveSupport::Notifications.instrument('stream_reader.process_record',
                                                  stream_name: @stream_name,
                                                  prefix: @prefix,
                                                  shard_id: shard_id,
                                                  ms_behind: resp.millis_behind_latest) do
            AvroParser.new(record.data).each_with_schema_name(&block)
            @tracker.last_sequence_number = record.sequence_number
          end
        end

        shard_iterator = resp.next_shard_iterator
      end

    rescue Aws::Kinesis::Errors::ExpiredIteratorException
      @logger.debug "Iterator expired! Fetching a new one."
    end
  end
end