pull out dns and use a class level cache

.github/workflows/ci.yaml

@@ -5,8 +5,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        gemfile: [ activemodel6, activemodel7 ]
-        ruby: [3.1, 3.2, 3.3]
+        gemfile: [activemodel6, activemodel7, activemodel8]
+        ruby: [3.1, 3.2, 3.3, 3.4]
     runs-on: ubuntu-latest
     env:
       BUNDLE_GEMFILE: gemfiles/${{ matrix.gemfile }}.gemfile

gemfiles/activemodel8.gemfile

@@ -0,0 +1,5 @@
+source 'https://rubygems.org'
+
+gem 'activemodel', '~> 8.0'
+
+gemspec path: '../'

lib/valid_email2/address.rb

@@ -1,9 +1,8 @@
 # frozen_string_literal:true
 
 require "valid_email2"
-require "resolv"
 require "mail"
-require "valid_email2/dns_records_cache"
+require "valid_email2/dns"
 
 module ValidEmail2
   class Address
@@ -29,11 +28,10 @@ def self.permitted_multibyte_characters_regex=(val)
       @permitted_multibyte_characters_regex = val
     end
 
-    def initialize(address, dns_timeout = 5, dns_nameserver = nil)
+    def initialize(address, dns = Dns.new)
       @parse_error = false
       @raw_address = address
-      @dns_timeout = dns_timeout
-      @dns_nameserver = dns_nameserver
+      @dns = dns
 
       begin
         @address = Mail::Address.new(address)
@@ -103,14 +101,14 @@ def valid_mx?
       return false unless valid?
       return false if null_mx?
 
-      mx_or_a_servers.any?
+      @dns.mx_servers(address.domain).any? || @dns.a_servers(address.domain).any?
     end
 
     def valid_strict_mx?
       return false unless valid?
       return false if null_mx?
 
-      mx_servers.any?
+      @dns.mx_servers(address.domain).any?
     end
 
     private
@@ -126,7 +124,7 @@ def domain_is_in?(domain_list)
     end
 
     def mx_server_is_in?(domain_list)
-      mx_servers.any? { |mx_server|
+      @dns.mx_servers(address.domain).any? { |mx_server|
         return false unless mx_server.respond_to?(:exchange)
 
         mx_server = mx_server.exchange.to_s
@@ -145,41 +143,9 @@ def address_contain_multibyte_characters?
       @raw_address.each_char.any? { |char| char.bytesize > 1 && char !~ self.class.permitted_multibyte_characters_regex }
     end
 
-    def resolv_config
-      @resolv_config ||= begin
-        config = Resolv::DNS::Config.default_config_hash
-        config[:nameserver] = @dns_nameserver if @dns_nameserver
-        config
-      end
-
-      @resolv_config
-    end
-
-    def mx_servers
-      @mx_servers_cache ||= ValidEmail2::DnsRecordsCache.new
-
-      @mx_servers_cache.fetch(address.domain.downcase) do
-        Resolv::DNS.open(resolv_config) do |dns|
-          dns.timeouts = @dns_timeout
-          dns.getresources(address.domain, Resolv::DNS::Resource::IN::MX)
-        end
-      end
-    end
-
     def null_mx?
+      mx_servers = @dns.mx_servers(address.domain)
       mx_servers.length == 1 && mx_servers.first.preference == 0 && mx_servers.first.exchange.length == 0
     end
-
-    def mx_or_a_servers
-      @mx_or_a_servers_cache ||= ValidEmail2::DnsRecordsCache.new
-
-      @mx_or_a_servers_cache.fetch(address.domain.downcase) do
-        Resolv::DNS.open(resolv_config) do |dns|
-          dns.timeouts = @dns_timeout
-          (mx_servers.any? && mx_servers) ||
-            dns.getresources(address.domain, Resolv::DNS::Resource::IN::A)
-        end
-      end
-    end
   end
 end

lib/valid_email2/dns.rb

@@ -0,0 +1,71 @@
+require "resolv"
+
+module ValidEmail2
+  class Dns
+    MAX_CACHE_SIZE = 1_000
+    CACHE = {}
+
+    CacheEntry = Struct.new(:records, :cached_at, :ttl)
+
+    def self.prune_cache
+      entries_sorted_by_cached_at_asc = CACHE.sort_by { |key, data| data.cached_at }
+      entries_to_remove = entries_sorted_by_cached_at_asc.first(CACHE.size - MAX_CACHE_SIZE)
+      entries_to_remove.each { |key, _value| CACHE.delete(key) }
+    end
+
+    def self.clear_cache
+      CACHE.clear
+    end
+
+    def initialize(dns_timeout = 5, dns_nameserver = nil)
+      @dns_timeout = dns_timeout
+      @dns_nameserver = dns_nameserver
+    end
+
+    def mx_servers(domain)
+      fetch(domain, Resolv::DNS::Resource::IN::MX)
+    end
+
+    def a_servers(domain)
+      fetch(domain, Resolv::DNS::Resource::IN::A)
+    end
+
+    private
+
+    def prune_cache
+      self.class.prune_cache
+    end
+
+    def fetch(domain, type)
+      prune_cache if CACHE.size > MAX_CACHE_SIZE
+
+      domain = domain.downcase
+      cache_key = [domain, type]
+      cache_entry = CACHE[cache_key]
+
+      if cache_entry && Time.now - cache_entry.cached_at < cache_entry.ttl
+        return cache_entry.records
+      else
+        CACHE.delete(cache_key)
+      end
+
+      records = Resolv::DNS.open(resolv_config) do |dns|
+        dns.timeouts = @dns_timeout
+        dns.getresources(domain, type)
+      end
+
+      if records.any?
+        ttl = records.map(&:ttl).min
+        CACHE[cache_key] = CacheEntry.new(records: records, cached_at: Time.now, ttl: ttl)
+      end
+
+      records
+    end
+
+    def resolv_config
+      config = Resolv::DNS::Config.default_config_hash
+      config[:nameserver] = @dns_nameserver if @dns_nameserver
+      config
+    end
+  end
+end

lib/valid_email2/email_validator.rb

@@ -1,4 +1,5 @@
 require "valid_email2/address"
+require "logger" # Fix concurrent-ruby removing logger dependency which Rails itself does not have
 require "active_model"
 require "active_model/validations"
 
@@ -12,7 +13,8 @@ def validate_each(record, attribute, value)
       return unless value.present?
       options = default_options.merge(self.options)
 
-      addresses = sanitized_values(value).map { |v| ValidEmail2::Address.new(v, options[:dns_timeout], options[:dns_nameserver]) }
+      dns = ValidEmail2::Dns.new(options[:dns_timeout], options[:dns_nameserver])
+      addresses = sanitized_values(value).map { |v| ValidEmail2::Address.new(v, dns) }
 
       error(record, attribute) && return unless addresses.all?(&:valid?)