Module: Mnemosyne::Support::Redis

Defined in:
lib/mnemosyne/support/redis.rb

Constant Summary collapse

KNOWN_ARGUMENTS =

A map of known commands to the arguments (identified by position) that should be included verbatim in the metadata. Arguments not listed here will be replaced by a “?” character.

The value can be a list of safe argument indices, or “*” (all).

{
  'BLPOP' => '*',
  'BRPOP' => '*',
  'EVALSHA' => [0, 1],
  'EXISTS' => '*',
  'EXPIRE' => '*',
  'GET' => '*',
  'HGET' => '*',
  'HGETALL' => '*',
  'HMGET' => '*',
  'HMSET' => [0, 1],
  'HSCAN' => '*',
  'INCRBY' => '*',
  'LLEN' => '*',
  'LPUSH' => [0],
  'LRANGE' => '*',
  'LREM' => [0, 1],
  'MGET' => '*',
  'MSET' => [0],
  'RPUSH' => [0],
  'RPOP' => '*',
  'SADD' => [0],
  'SCARD' => '*',
  'SCAN' => '*',
  'SCRIPT LOAD' => [],
  'SET' => [0],
  'SREM' => [0],
  'SSCAN' => '*',
  'UNLINK' => '*',
  'ZADD' => [0],
  'ZCARD' => '*',
  'ZINCRBY' => [0, 1],
  'ZRANGE' => '*',
  'ZRANGEBYSCORE' => '*',
  'ZREM' => [0],
  'ZREMRANGEBYSCORE' => '*',
  'ZREVRANGE' => '*',
  'ZSCAN' => '*'
}.freeze

Class Method Summary collapse

Class Method Details

.extract_command_names(commands) ⇒ Object 



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# File 'lib/mnemosyne/support/redis.rb', line 113

def extract_command_names(commands)
  commands.map do |c|
    # Depending on how the methods on the Redis gem are called,
    # there may be an additional level of nesting.
    c = c[0] if c[0].is_a?(Array)

    # For some commands, we also extract *some* of the arguments.
    name, args = parse_name_and_args(c)

    "#{name} #{args}".strip
  end.join("\n")
end

.extract_span_meta(commands, server_url) ⇒ Object 



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# File 'lib/mnemosyne/support/redis.rb', line 78

def extract_span_meta(commands, server_url)
  {
    server: server_url,

    # Each command is an array, consisting of the command name and any
    # arguments. We are only interested in the command name.
    commands: extract_command_names(commands),

    # If there are multiple commands, that must mean they were pipelined
    # (i.e. run in parallel).
    pipelined: commands.length > 1
  }
end

.instrument(commands, server_url) ⇒ Object 



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# File 'lib/mnemosyne/support/redis.rb', line 54

def instrument(commands, server_url)
  trace = ::Mnemosyne::Instrumenter.current_trace
  return yield unless trace

  span = ::Mnemosyne::Span.new 'db.query.redis',
    meta: extract_span_meta(commands, server_url)

  span.start!

  begin
    yield.tap do |retval|
      if defined?(::Redis::CommandError) && retval.is_a?(::Redis::CommandError)
        span.meta[:error] = retval.message
      end

      trace << span.finish!
    end
  rescue StandardError => e
    span.meta[:error] = e.message
    trace << span.finish!
    raise
  end
end

.parse_name_and_args(command) ⇒ Object 



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# File 'lib/mnemosyne/support/redis.rb', line 92

def parse_name_and_args(command)
  command = command.dup

  # Symbols and lower-case names are allowed
  name = command.delete_at(0).to_s.upcase

  allowed = KNOWN_ARGUMENTS[name] || []
  args = case allowed
           when '*' # All arguments considered safe
             command
           when Array # A list of allowed argument indices
             command.each_with_index.map do |arg, index|
               allowed.include?(index) ? arg : '?'
             end
           else # Unknown command - assume nothing is safe
             Array.new(command.length, '?')
         end.join(' ')

  [name, args]
end