Class: Dalli::Protocol::Meta::ResponseProcessor

Inherits:
Object
  • Object
show all
Defined in:
lib/dalli/protocol/response_processor.rb

Overview

Class that encapsulates logic for processing meta protocol responses from memcached. Includes logic for pulling data from an IO source and parsing into local values. Handles errors on unexpected values.

Constant Summary collapse

EN = 
'EN'
END_TOKEN = 
'END'
EX = 
'EX'
HD = 
'HD'
MN = 
'MN'
NF = 
'NF'
NS = 
'NS'
OK = 
'OK'
RESET = 
'RESET'
STAT = 
'STAT'
VA = 
'VA'
VERSION = 
'VERSION'
SERVER_ERROR = 
'SERVER_ERROR'
T_OK = 
[OK].freeze
T_RESET = 
[RESET].freeze
T_EN_HD = 
[EN, HD].freeze
T_VERSION = 
[VERSION].freeze
T_VA_EN_HD = 
[VA, EN, HD].freeze
T_HD_NF_EX = 
[HD, NF, EX].freeze
T_HD_NS_NF_EX = 
[HD, NS, NF, EX].freeze
T_VA_NF_NS_EX = 
[VA, NF, NS, EX].freeze
T_END_TOKEN_STAT = 
[END_TOKEN, STAT].freeze

Instance Method Summary collapse

Constructor Details

#initialize(io_source, value_marshaller) ⇒ ResponseProcessor

Returns a new instance of ResponseProcessor.



36
37
38
39
 
# File 'lib/dalli/protocol/response_processor.rb', line 36

def initialize(io_source, value_marshaller)
  @io_source = io_source
  @value_marshaller = value_marshaller
end

Instance Method Details

#bitflags_from_tokens(tokens) ⇒ Object 



231
232
233
 
# File 'lib/dalli/protocol/response_processor.rb', line 231

def bitflags_from_tokens(tokens)
  value_from_tokens(tokens, 'f').to_i
end

#body_len_from_tokens(tokens) ⇒ Object 



263
264
265
 
# File 'lib/dalli/protocol/response_processor.rb', line 263

def body_len_from_tokens(tokens)
  value_from_tokens(tokens, 's').to_i
end

#build_metadata_result(tokens) ⇒ Object 



84
85
86
87
88
89
90
 
# File 'lib/dalli/protocol/response_processor.rb', line 84

def build_metadata_result(tokens)
  {
    value: nil, cas: cas_from_tokens(tokens),
    won_recache: tokens.include?('W'), stale: tokens.include?('X'),
    lost_recache: tokens.include?('Z')
  }
end

#cas_from_tokens(tokens) ⇒ Object 



235
236
237
 
# File 'lib/dalli/protocol/response_processor.rb', line 235

def cas_from_tokens(tokens)
  value_from_tokens(tokens, 'c').to_i
end

#consume_all_responses_until_mn ⇒ Object 



153
154
155
156
157
158
 
# File 'lib/dalli/protocol/response_processor.rb', line 153

def consume_all_responses_until_mn
  tokens = next_line_to_tokens

  tokens = next_line_to_tokens while tokens.first != MN
  true
end

#decr_incr ⇒ Object 



118
119
120
121
122
123
124
 
# File 'lib/dalli/protocol/response_processor.rb', line 118

def decr_incr
  tokens = error_on_unexpected!(T_VA_NF_NS_EX)
  return false if [NS, EX].include?(tokens.first)
  return nil if tokens.first == NF

  read_line.to_i
end

#error_on_unexpected!(expected_codes) ⇒ Object

Raises:



221
222
223
224
225
226
227
228
229
 
# File 'lib/dalli/protocol/response_processor.rb', line 221

def error_on_unexpected!(expected_codes)
  tokens = next_line_to_tokens

  return tokens if expected_codes.include?(tokens.first)

  raise Dalli::ServerError, tokens.join(' ').to_s if tokens.first == SERVER_ERROR

  raise Dalli::DalliError, "Response error: #{tokens.first}"
end

#flush ⇒ Object 



136
137
138
139
140
 
# File 'lib/dalli/protocol/response_processor.rb', line 136

def flush
  error_on_unexpected!(T_OK)

  true
end

#full_response_from_buffer(tokens, body, resp_size) ⇒ Object 



177
178
179
180
 
# File 'lib/dalli/protocol/response_processor.rb', line 177

def full_response_from_buffer(tokens, body, resp_size)
  value = @value_marshaller.retrieve(body, bitflags_from_tokens(tokens))
  [tokens.first == VA, cas_from_tokens(tokens), key_from_tokens(tokens), value, resp_size]
end

#getk_response_from_buffer(buf, offset = 0) ⇒ Object

This method returns an array of values used in a pipelined getk process. The first value is the number of bytes by which to advance the pointer in the buffer. If the complete response is found in the buffer, this will be the response size. Otherwise it is zero.

The remaining three values in the array are the ResponseHeader, key, and value.



192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
 
# File 'lib/dalli/protocol/response_processor.rb', line 192

def getk_response_from_buffer(buf, offset = 0)
  # Find the header terminator starting from offset
  term_idx = buf.byteindex(TERMINATOR, offset)
  return [0] unless term_idx

  header = buf.byteslice(offset, term_idx - offset)
  tokens = header.split
  header_len = header.bytesize + TERMINATOR.length

  # The body len is removed from the tokens array
  body_len = body_len_from_tokens(tokens)

  # We have a complete response that has no body.
  # This is either the response to the terminating
  # noop or, if the status is not MN, an intermediate
  # error response that needs to be discarded.
  return [true, header_len] if body_len.zero?

  resp_size = header_len + body_len + TERMINATOR.length
  # The header is in the buffer, but the body is not.  As we don't have
  # a complete response, don't advance the buffer
  return [0] unless buf.bytesize >= offset + resp_size

  # The full response is in our buffer, so parse it and return
  # the values
  body = buf.byteslice(offset + header_len, body_len)
  full_response_from_buffer(tokens, body, resp_size)
end

#hit_status_from_tokens(tokens) ⇒ Object

Returns true if item was previously hit, false if first access, nil if not requested The h flag returns h0 (first access) or h1 (previously accessed)



250
251
252
253
254
255
 
# File 'lib/dalli/protocol/response_processor.rb', line 250

def hit_status_from_tokens(tokens)
  hit_token = tokens.find { |t| t.start_with?('h') && t.length == 2 }
  return nil unless hit_token

  hit_token[1] == '1'
end

#key_from_tokens(tokens) ⇒ Object 



239
240
241
242
243
244
245
246
 
# File 'lib/dalli/protocol/response_processor.rb', line 239

def key_from_tokens(tokens)
  encoded_key = value_from_tokens(tokens, 'k')
  if tokens.delete('b')
    KeyRegularizer.decode(encoded_key)
  else
    encoded_key
  end
end

#last_access_from_tokens(tokens) ⇒ Object

Returns seconds since last access, or nil if not requested The l flag returns l



259
260
261
 
# File 'lib/dalli/protocol/response_processor.rb', line 259

def last_access_from_tokens(tokens)
  value_from_tokens(tokens, 'l').to_i
end

#meta_delete ⇒ Object 



113
114
115
116
 
# File 'lib/dalli/protocol/response_processor.rb', line 113

def meta_delete
  tokens = error_on_unexpected!(T_HD_NF_EX)
  tokens.first == HD
end

#meta_get_with_metadata(cache_nils: false, return_hit_status: false, return_last_access: false) ⇒ Object

Returns a hash with all requested metadata:

  • :value - the cached value (or nil if miss)
  • :cas - the CAS value (if return_cas was requested)
  • :won_recache - true if client won the right to recache (W flag)
  • :stale - true if the item is stale (X flag)
  • :lost_recache - true if another client is already recaching (Z flag)
  • :hit_before - true/false if item was previously accessed (h flag, if requested)
  • :last_access - seconds since last access (l flag, if requested)

Used by meta_get for comprehensive metadata retrieval. Supports thundering herd protection (N/R flags) and metadata flags (h/l/u).



75
76
77
78
79
80
81
82
 
# File 'lib/dalli/protocol/response_processor.rb', line 75

def meta_get_with_metadata(cache_nils: false, return_hit_status: false, return_last_access: false)
  tokens = error_on_unexpected!(T_VA_EN_HD)
  result = build_metadata_result(tokens)
  result[:hit_before] = hit_status_from_tokens(tokens) if return_hit_status
  result[:last_access] = last_access_from_tokens(tokens) if return_last_access
  result[:value] = parse_value_from_tokens(tokens, cache_nils)
  result
end

#meta_get_with_value(cache_nils: false) ⇒ Object 



41
42
43
44
45
46
47
 
# File 'lib/dalli/protocol/response_processor.rb', line 41

def meta_get_with_value(cache_nils: false)
  tokens = error_on_unexpected!(T_VA_EN_HD)
  return cache_nils ? ::Dalli::NOT_FOUND : nil if tokens.first == EN
  return true unless tokens.first == VA

  @value_marshaller.retrieve(read_data(tokens[1].to_i), bitflags_from_tokens(tokens))
end

#meta_get_with_value_and_cas ⇒ Object 



49
50
51
52
53
54
55
56
57
 
# File 'lib/dalli/protocol/response_processor.rb', line 49

def meta_get_with_value_and_cas
  tokens = error_on_unexpected!(T_VA_EN_HD)
  return [nil, 0] if tokens.first == EN

  cas = cas_from_tokens(tokens)
  return [nil, cas] unless tokens.first == VA

  [@value_marshaller.retrieve(read_data(tokens[1].to_i), bitflags_from_tokens(tokens)), cas]
end

#meta_get_without_value ⇒ Object 



59
60
61
62
 
# File 'lib/dalli/protocol/response_processor.rb', line 59

def meta_get_without_value
  tokens = error_on_unexpected!(T_EN_HD)
  tokens.first == EN ? nil : true
end

#meta_set_append_prepend ⇒ Object 



106
107
108
109
110
111
 
# File 'lib/dalli/protocol/response_processor.rb', line 106

def meta_set_append_prepend
  tokens = error_on_unexpected!(T_HD_NS_NF_EX)
  return false unless tokens.first == HD

  true
end

#meta_set_with_cas ⇒ Object 



99
100
101
102
103
104
 
# File 'lib/dalli/protocol/response_processor.rb', line 99

def meta_set_with_cas
  tokens = error_on_unexpected!(T_HD_NS_NF_EX)
  return false unless tokens.first == HD

  cas_from_tokens(tokens)
end

#next_line_to_tokens ⇒ Object 



282
283
284
285
 
# File 'lib/dalli/protocol/response_processor.rb', line 282

def next_line_to_tokens
  line = read_line
  line&.split || []
end

#parse_value_from_tokens(tokens, cache_nils) ⇒ Object 



92
93
94
95
96
97
 
# File 'lib/dalli/protocol/response_processor.rb', line 92

def parse_value_from_tokens(tokens, cache_nils)
  return cache_nils ? ::Dalli::NOT_FOUND : nil if tokens.first == EN
  return unless tokens.first == VA

  @value_marshaller.retrieve(read_data(tokens[1].to_i), bitflags_from_tokens(tokens))
end

#pipelined_delete_non_deletions ⇒ Object

Consumes the responses to a batch of quiet (pipelined) delete requests, which are terminated by a noop (MN). In quiet mode memcached suppresses the success response for each deleted key, so every line received before the terminator corresponds to a key that was NOT deleted -- a miss (NF) or an error. Returns that count so callers can derive the number of successful deletes as (keys_sent - non_deletions).



167
168
169
170
171
172
173
174
175
 
# File 'lib/dalli/protocol/response_processor.rb', line 167

def pipelined_delete_non_deletions
  non_deletions = 0
  tokens = next_line_to_tokens
  until tokens.first == MN
    non_deletions += 1
    tokens = next_line_to_tokens
  end
  non_deletions
end

#read_data(data_size) ⇒ Object 



287
288
289
 
# File 'lib/dalli/protocol/response_processor.rb', line 287

def read_data(data_size)
  @io_source.read(data_size + TERMINATOR.bytesize)&.chomp!(TERMINATOR)
end

#read_line ⇒ Object 



278
279
280
 
# File 'lib/dalli/protocol/response_processor.rb', line 278

def read_line
  @io_source.read_line&.chomp!(TERMINATOR)
end

#reset ⇒ Object 



142
143
144
145
146
 
# File 'lib/dalli/protocol/response_processor.rb', line 142

def reset
  error_on_unexpected!(T_RESET)

  true
end

#stats ⇒ Object 



126
127
128
129
130
131
132
133
134
 
# File 'lib/dalli/protocol/response_processor.rb', line 126

def stats
  tokens = error_on_unexpected!(T_END_TOKEN_STAT)
  values = {}
  while tokens.first != END_TOKEN
    values[tokens[1]] = tokens[2]
    tokens = next_line_to_tokens
  end
  values
end

#value_from_tokens(tokens, flag) ⇒ Object 



267
268
269
270
271
272
273
274
275
276
 
# File 'lib/dalli/protocol/response_processor.rb', line 267

def value_from_tokens(tokens, flag)
  # NB: as an optimization, we're mutating the matching token in place
  # so there is a baked assumption that we're only accessing each token at most once.
  index = tokens.find_index { |t| t.start_with?(flag) }
  if index
    tokens.delete_at(index).delete_prefix!(flag)
  else
    0
  end
end

#version ⇒ Object 



148
149
150
151
 
# File 'lib/dalli/protocol/response_processor.rb', line 148

def version
  tokens = error_on_unexpected!(T_VERSION)
  tokens.last
end