Add HTTP url quantizer

lib/ddtrace.rb

@@ -4,6 +4,7 @@
 require 'ddtrace/pin'
 require 'ddtrace/tracer'
 require 'ddtrace/error'
+require 'ddtrace/quantization/http'
 require 'ddtrace/pipeline'
 require 'ddtrace/configuration'
 require 'ddtrace/patcher'

lib/ddtrace/quantization/http.rb

@@ -0,0 +1,86 @@
+require 'uri'
+require 'set'
+
+module Datadog
+  module Quantization
+    # Quantization for HTTP resources
+    module HTTP
+      PLACEHOLDER = '?'.freeze
+
+      module_function
+
+      def url(url, options = {})
+        url!(url, options)
+      rescue StandardError
+        options[:placeholder] || PLACEHOLDER
+      end
+
+      def url!(url, options = {})
+        options ||= {}
+
+        URI.parse(url).tap do |uri|
+          # Format the query string
+          if uri.query
+            query = query(uri.query, options[:query])
+            uri.query = (!query.nil? && query.empty? ? nil : query)
+          end
+
+          # Remove any URI framents
+          uri.fragment = nil unless options[:fragment] == :show
+        end.to_s
+      end
+
+      def query(query, options = {})
+        query!(query, options)
+      rescue StandardError
+        options[:placeholder] || PLACEHOLDER
+      end
+
+      def query!(query, options = {})
+        options ||= {}
+        options[:show] = options[:show] || []
+        options[:exclude] = options[:exclude] || []
+
+        # Short circuit if query string is meant to exclude everything
+        # or if the query string is meant to include everything
+        return '' if options[:exclude] == :all
+        return query if options[:show] == :all
+
+        collect_query(query, uniq: true) do |key, value|
+          if options[:exclude].include?(key)
+            [nil, nil]
+          else
+            value = options[:show].include?(key) ? value : nil
+            [key, value]
+          end
+        end
+      end
+
+      # Iterate over each key value pair, yielding to the block given.
+      # Accepts :uniq option, which keeps uniq copies of keys without values.
+      # e.g. Reduces "foo&bar=bar&bar=bar&foo" to "foo&bar=bar&bar=bar"
+      def collect_query(query, options = {})
+        return query unless block_given?
+        uniq = options[:uniq].nil? ? false : options[:uniq]
+        keys = Set.new
+
+        delims = query.scan(/(^|&|;)/).flatten
+        query.split(/[&;]/).collect.with_index do |pairs, i|
+          key, value = pairs.split('=', 2)
+          key, value = yield(key, value, delims[i])
+          if uniq && keys.include?(key)
+            ''
+          elsif key && value
+            "#{delims[i]}#{key}=#{value}"
+          elsif key
+            "#{delims[i]}#{key}".tap { keys << key }
+          else
+            ''
+          end
+        end.join.sub(/^[&;]/, '')
+      end
+
+      private_class_method :collect_query
+    end
+  end
+end

spec/ddtrace/quantization/http_spec.rb

@@ -0,0 +1,228 @@
+# encoding: utf-8
+require 'spec_helper'
+
+require 'ddtrace/quantization/http'
+
+RSpec.describe Datadog::Quantization::HTTP do
+  describe '#url' do
+    subject(:result) { described_class.url(url, options) }
+    let(:options) { {} }
+
+    context 'given a URL' do
+      let(:url) { 'http://example.com/path?category_id=1&sort_by=asc#featured' }
+
+      context 'default behavior' do
+        it { is_expected.to eq('http://example.com/path?category_id&sort_by') }
+      end
+
+      context 'default behavior for an array' do
+        let(:url) { 'http://example.com/path?categories[]=1&categories[]=2' }
+        it { is_expected.to eq('http://example.com/path?categories[]') }
+      end
+
+      context 'with query: show: value' do
+        let(:options) { { query: { show: ['category_id'] } } }
+        it { is_expected.to eq('http://example.com/path?category_id=1&sort_by') }
+      end
+
+      context 'with query: show: :all' do
+        let(:options) { { query: { show: :all } } }
+        it { is_expected.to eq('http://example.com/path?category_id=1&sort_by=asc') }
+      end
+
+      context 'with query: exclude: value' do
+        let(:options) { { query: { exclude: ['sort_by'] } } }
+        it { is_expected.to eq('http://example.com/path?category_id') }
+      end
+
+      context 'with query: exclude: :all' do
+        let(:options) { { query: { exclude: :all } } }
+        it { is_expected.to eq('http://example.com/path') }
+      end
+
+      context 'with show: :all' do
+        let(:options) { { fragment: :show } }
+        it { is_expected.to eq('http://example.com/path?category_id&sort_by#featured') }
+      end
+
+      context 'with Unicode characters' do
+        # URLs do not permit unencoded non-ASCII characters in the URL.
+        let(:url) { "http://example.com/path?繋がってて" }
+        it { is_expected.to eq(described_class::PLACEHOLDER) }
+      end
+    end
+  end
+
+  describe '#query' do
+    subject(:result) { described_class.query(query, options) }
+
+    context 'given a query' do
+      context 'and no options' do
+        let(:options) { {} }
+
+        context 'with a single parameter' do
+          let(:query) { 'foo=foo' }
+          it { is_expected.to eq('foo') }
+
+          context 'with an invalid byte sequence' do
+            # \255 is off-limits https://en.wikipedia.org/wiki/UTF-8#Codepage_layout
+            # There isn't a graceful way to handle this without stripping interesting
+            # characters out either; so just raise an error and default to the placeholder.
+            let(:query) { "foo\255=foo" }
+            it { is_expected.to eq('?') }
+          end
+        end
+
+        context 'with multiple parameters' do
+          let(:query) { 'foo=foo&bar=bar' }
+          it { is_expected.to eq('foo&bar') }
+        end
+
+        context 'with array-style parameters' do
+          let(:query) { 'foo[]=bar&foo[]=baz' }
+          it { is_expected.to eq('foo[]') }
+        end
+
+        context 'with semi-colon style parameters' do
+          let(:query) { 'foo;bar' }
+          # Notice semicolons aren't preseved... no great way of handling this.
+          # Semicolons are illegal as of 2014... so this is an edge case.
+          # See https://www.w3.org/TR/2014/REC-html5-20141028/forms.html#url-encoded-form-data
+          it { is_expected.to eq('foo;bar') }
+        end
+
+        context 'with object-style parameters' do
+          let(:query) { 'user[id]=1&user[name]=Nathan' }
+          it { is_expected.to eq('user[id]&user[name]') }
+
+          context 'that are complex' do
+            let(:query) { 'users[][id]=1&users[][name]=Nathan&users[][id]=2&users[][name]=Emma' }
+            it { is_expected.to eq('users[][id]&users[][name]') }
+          end
+        end
+      end
+
+      context 'and a show: :all option' do
+        let(:query) { 'foo=foo&bar=bar' }
+        let(:options) { { show: :all } }
+        it { is_expected.to eq(query) }
+      end
+
+      context 'and a show option' do
+        context 'with a single parameter' do
+          let(:query) { 'foo=foo' }
+          let(:key) { 'foo' }
+          let(:options) { { show: [key] } }
+          it { is_expected.to eq('foo=foo') }
+
+          context 'that has a Unicode key' do
+            let(:query) { '繋=foo' }
+            let(:key) { '繋' }
+            it { is_expected.to eq('繋=foo') }
+
+            context 'that is encoded' do
+              let(:query) { '%E7%B9%8B=foo' }
+              let(:key) { '%E7%B9%8B' }
+              it { is_expected.to eq('%E7%B9%8B=foo') }
+            end
+          end
+
+          context 'that has a Unicode value' do
+            let(:query) { 'foo=繋' }
+            let(:key) { 'foo' }
+            it { is_expected.to eq('foo=繋') }
+
+            context 'that is encoded' do
+              let(:query) { 'foo=%E7%B9%8B' }
+              it { is_expected.to eq('foo=%E7%B9%8B') }
+            end
+          end
+
+          context 'that has a Unicode key and value' do
+            let(:query) { '繋=繋' }
+            let(:key) { '繋' }
+            it { is_expected.to eq('繋=繋') }
+
+            context 'that is encoded' do
+              let(:query) { '%E7%B9%8B=%E7%B9%8B' }
+              let(:key) { '%E7%B9%8B' }
+              it { is_expected.to eq('%E7%B9%8B=%E7%B9%8B') }
+            end
+          end
+        end
+
+        context 'with multiple parameters' do
+          let(:query) { 'foo=foo&bar=bar' }
+          let(:options) { { show: ['foo'] } }
+          it { is_expected.to eq('foo=foo&bar') }
+        end
+
+        context 'with array-style parameters' do
+          let(:query) { 'foo[]=bar&foo[]=baz' }
+          let(:options) { { show: ['foo[]'] } }
+          it { is_expected.to eq('foo[]=bar&foo[]=baz') }
+
+          context 'that contains encoded braces' do
+            let(:query) { 'foo[]=%5Bbar%5D&foo[]=%5Bbaz%5D' }
+            it { is_expected.to eq('foo[]=%5Bbar%5D&foo[]=%5Bbaz%5D') }
+
+            context 'that exactly matches the key' do
+              let(:query) { 'foo[]=foo%5B%5D&foo[]=foo%5B%5D' }
+              it { is_expected.to eq('foo[]=foo%5B%5D&foo[]=foo%5B%5D') }
+            end
+          end
+        end
+
+        context 'with object-style parameters' do
+          let(:query) { 'user[id]=1&user[name]=Nathan' }
+          let(:options) { { show: ['user[id]'] } }
+          it { is_expected.to eq('user[id]=1&user[name]') }
+
+          context 'that are complex' do
+            let(:query) { 'users[][id]=1&users[][name]=Nathan&users[][id]=2&users[][name]=Emma' }
+            let(:options) { { show: ['users[][id]'] } }
+            it { is_expected.to eq('users[][id]=1&users[][name]&users[][id]=2') }
+          end
+        end
+      end
+
+      context 'and an exclude: :all option' do
+        let(:query) { 'foo=foo&bar=bar' }
+        let(:options) { { exclude: :all } }
+        it { is_expected.to eq('') }
+      end
+
+      context 'and an exclude option' do
+        context 'with a single parameter' do
+          let(:query) { 'foo=foo' }
+          let(:options) { { exclude: ['foo'] } }
+          it { is_expected.to eq('') }
+        end
+
+        context 'with multiple parameters' do
+          let(:query) { 'foo=foo&bar=bar' }
+          let(:options) { { exclude: ['foo'] } }
+          it { is_expected.to eq('bar') }
+        end
+
+        context 'with array-style parameters' do
+          let(:query) { 'foo[]=bar&foo[]=baz' }
+          let(:options) { { exclude: ['foo[]'] } }
+          it { is_expected.to eq('') }
+        end
+
+        context 'with object-style parameters' do
+          let(:query) { 'user[id]=1&user[name]=Nathan' }
+          let(:options) { { exclude: ['user[name]'] } }
+          it { is_expected.to eq('user[id]') }
+
+          context 'that are complex' do
+            let(:query) { 'users[][id]=1&users[][name]=Nathan&users[][id]=2&users[][name]=Emma' }
+            let(:options) { { exclude: ['users[][name]'] } }
+            it { is_expected.to eq('users[][id]') }
+          end
+        end
+      end
+    end
+  end
+end