Module: DedupeRequests::Fingerprint

Defined in:
lib/dedupe_requests/fingerprint.rb

Overview

Computes a stable fingerprint for a request.

The fingerprint covers: caller_id + verb + path + query string + body. Time is NOT part of the fingerprint — the dedup window is the Redis TTL.

Constant Summary collapse

HASHERS =

Prefer OpenSSL (uses the CPU’s SHA instructions — several times faster on large bodies), falling back to the stdlib Digest when OpenSSL is unavailable or has the algorithm disabled (e.g. MD5 under FIPS). Output is identical.

{
  sha256: ["SHA256", Digest::SHA256],
  sha1: ["SHA1", Digest::SHA1],
  sha512: ["SHA512", Digest::SHA512],
  md5: ["MD5", Digest::MD5]
}.freeze
ALGORITHMS = 
HASHERS.transform_values do |(openssl_name, digest_class)|
  lambda do |data|
    OpenSSL::Digest.hexdigest(openssl_name, data)
  rescue StandardError
    digest_class.hexdigest(data)
  end
end.freeze

Class Method Summary collapse

Class Method Details

.body(request) ⇒ Object 



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# File 'lib/dedupe_requests/fingerprint.rb', line 68

def body(request)
  request.respond_to?(:raw_post) ? request.raw_post.to_s : read_and_rewind(request).to_s
end

.digest(parts, algorithm = :sha256) ⇒ Object

Length-prefixes each field so a value cannot “shift” across a field boundary and collide with a different set of fields.



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# File 'lib/dedupe_requests/fingerprint.rb', line 52

def digest(parts, algorithm = :sha256)
  data = Array(parts).map do |part|
    s = part.to_s
    "#{s.bytesize}:#{s}"
  end.join
  resolve(algorithm).call(data)
end

.for_request(request, config, caller_id: nil) ⇒ Object 



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# File 'lib/dedupe_requests/fingerprint.rb', line 37

def for_request(request, config, caller_id: nil)
  return config.fingerprint.call(request) if config.fingerprint

  parts = [
    caller_id.to_s,
    request.request_method.to_s,
    request.path.to_s,
    request.query_string.to_s,
    body(request)
  ]
  digest(parts, config.digest)
end

.read_and_rewind(request) ⇒ Object 



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# File 'lib/dedupe_requests/fingerprint.rb', line 72

def read_and_rewind(request)
  return "" unless request.respond_to?(:body) && request.body

  data = request.body.read
  request.body.rewind if request.body.respond_to?(:rewind)
  data
end

.resolve(algorithm) ⇒ Object 



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# File 'lib/dedupe_requests/fingerprint.rb', line 60

def resolve(algorithm)
  return algorithm if algorithm.respond_to?(:call)

  ALGORITHMS.fetch(algorithm.to_sym) do
    raise ArgumentError, "unknown digest #{algorithm.inspect} (known: #{ALGORITHMS.keys.join(', ')} or a callable)"
  end
end