Class: Karafka::Pro::Processing::Coordinators::VirtualOffsetManager

Inherits:
Object
  • Object
show all
Defined in:
lib/karafka/pro/processing/coordinators/virtual_offset_manager.rb

Overview

Note:

We still use the regular coordinator “real” offset management as we want to have them as separated as possible because the real seek offset management is also used for pausing, filtering and others and should not be impacted by the virtual one

Note:

This manager is not thread-safe by itself. It should operate from coordinator locked locations.

Manager that keeps track of our offsets with the virtualization layer that are local to given partition assignment. It allows for easier offset management for virtual virtual partition cases as it provides us ability to mark as consumed and move the real offset behind as expected.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(topic, partition, offset_metadata_strategy) ⇒ VirtualOffsetManager

Note:

We need topic and partition because we use a seek message (virtual) for real offset management. We could keep real message reference but this can be memory consuming and not worth it.

Returns a new instance of VirtualOffsetManager.

Parameters:

  • topic (String)
  • partition (Integer)
  • offset_metadata_strategy (Symbol) —

    what metadata should we select. That is, should we use the most recent or one picked from the offset that is going to be committed



50
51
52
53
54
55
56
57
58
59
 
# File 'lib/karafka/pro/processing/coordinators/virtual_offset_manager.rb', line 50

def initialize(topic, partition, offset_metadata_strategy)
  @topic = topic
  @partition = partition
  @groups = []
  @marked = {}
  @offsets_metadata = {}
  @real_offset = -1
  @offset_metadata_strategy = offset_metadata_strategy
  @current_offset_metadata = nil
end

Instance Attribute Details

#groups ⇒ Object (readonly)

Returns the value of attribute groups.



39
40
41
 
# File 'lib/karafka/pro/processing/coordinators/virtual_offset_manager.rb', line 39

def groups
  @groups
end

Instance Method Details

#clear ⇒ Object

Clears the manager for a next collective operation



62
63
64
65
66
67
68
 
# File 'lib/karafka/pro/processing/coordinators/virtual_offset_manager.rb', line 62

def clear
  @groups.clear
  @offsets_metadata.clear
  @current_offset_metadata = nil
  @marked.clear
  @real_offset = -1
end

#mark(message, offset_metadata) ⇒ Object

Marks given message as marked (virtually consumed). We mark given message offset and other earlier offsets from the same group as done and we can refresh our real offset representation based on that as it might have changed to a newer real offset.

Parameters:

  • message (Karafka::Messages::Message) —

    message coming from VP we want to mark

  • offset_metadata (String, nil) —

    offset metadata. nil if none



87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
 
# File 'lib/karafka/pro/processing/coordinators/virtual_offset_manager.rb', line 87

def mark(message, offset_metadata)
  offset = message.offset

  # Store metadata when we materialize the most stable offset
  @offsets_metadata[offset] = offset_metadata
  @current_offset_metadata = offset_metadata

  group = nil
  position = nil

  @groups.each do |reg_group|
    pos = reg_group.index(offset)

    if pos
      group = reg_group
      position = pos
      break
    end
  end

  # This case can happen when someone uses MoM and wants to mark message from a previous
  # batch as consumed. We can add it, since the real offset refresh will point to it
  unless group
    group = [offset]
    position = 0
    @groups << group
  end

  # Mark all previous messages from the same group also as virtually consumed
  group[0..position].each do |markable_offset|
    # Set previous messages metadata offset as the offset of higher one for overwrites
    # unless a different metadata were set explicitely
    @offsets_metadata[markable_offset] ||= offset_metadata
    @marked[markable_offset] = true
  end

  # Recompute the real offset representation
  materialize_real_offset
end

#mark_until(message, offset_metadata) ⇒ Object

Mark all from all groups including the message. Useful when operating in a collapsed state for marking

Parameters:



131
132
133
134
135
136
137
138
139
140
141
142
143
144
 
# File 'lib/karafka/pro/processing/coordinators/virtual_offset_manager.rb', line 131

def mark_until(message, offset_metadata)
  mark(message, offset_metadata)

  @groups.each do |group|
    group.each do |offset|
      next if offset > message.offset

      @offsets_metadata[offset] = offset_metadata
      @marked[offset] = true
    end
  end

  materialize_real_offset
end

#markable ⇒ Array<Messages::Seek, String>

Returns markable message for real offset marking and its associated metadata.

Returns:

  • (Array<Messages::Seek, String>) —

    markable message for real offset marking and its associated metadata

Raises:



159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
 
# File 'lib/karafka/pro/processing/coordinators/virtual_offset_manager.rb', line 159

def markable
  raise Errors::InvalidRealOffsetUsageError unless markable?

  offset_metadata = case @offset_metadata_strategy
  when :exact
    @offsets_metadata.fetch(@real_offset)
  when :current
    @current_offset_metadata
  else
    raise Errors::UnsupportedCaseError, @offset_metadata_strategy
  end

  [
    Messages::Seek.new(
      @topic,
      @partition,
      @real_offset
    ),
    offset_metadata
  ]
end

#markable? ⇒ Boolean

Is there a real offset we can mark as consumed

Returns:

  • (Boolean) 


153
154
155
 
# File 'lib/karafka/pro/processing/coordinators/virtual_offset_manager.rb', line 153

def markable?
  !@real_offset.negative?
end

#marked ⇒ Array<Integer>

Returns Offsets of messages already marked as consumed virtually.

Returns:

  • (Array<Integer>) —

    Offsets of messages already marked as consumed virtually



147
148
149
 
# File 'lib/karafka/pro/processing/coordinators/virtual_offset_manager.rb', line 147

def marked
  @marked.select { |_, status| status }.map { |offset, _| offset }.sort
end

#register(offsets_group) ⇒ Object

Registers an offset group coming from one virtual consumer. In order to move the real underlying offset accordingly, we need to make sure to track the virtual consumers offsets groups independently and only materialize the end result.

Parameters:

  • offsets_group (Array<Integer>) —

    offsets from one virtual consumer



75
76
77
78
79
 
# File 'lib/karafka/pro/processing/coordinators/virtual_offset_manager.rb', line 75

def register(offsets_group)
  @groups << offsets_group

  offsets_group.each { |offset| @marked[offset] = false }
end