Refactor ResolveRemoteAccountService (#4258)

* Refactor ResolveRemoteAccountService

* Remove trailing whitespace

* Use redis locks around critical ResolveRemoteAccountService code

* Add test for race condition of lock

4 files changed, 138 insertions, 55 deletions

diff --git a/Gemfile b/Gemfile
index a6c2b2d65..f4d889165 100644
--- a/Gemfile
+++ b/Gemfile
@@ -52,6 +52,7 @@ gem 'rack-timeout', '~> 0.4'
 gem 'rails-i18n', '~> 5.0'
 gem 'rails-settings-cached', '~> 0.6'
 gem 'redis', '~> 3.3', require: ['redis', 'redis/connection/hiredis']
+gem 'mario-redis-lock', '~> 1.2', require: 'redis_lock'
 gem 'rqrcode', '~> 0.10'
 gem 'ruby-oembed', '~> 0.12', require: 'oembed'
 gem 'sanitize', '~> 4.4'
diff --git a/Gemfile.lock b/Gemfile.lock
index f637c9bbe..6f0621f5f 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -242,6 +242,8 @@ GEM
       nokogiri (>= 1.5.9)
     mail (2.6.6)
       mime-types (>= 1.16, < 4)
+    mario-redis-lock (1.2.0)
+      redis (~> 3, >= 3.0.5)
     method_source (0.8.2)
     microformats (4.0.7)
       json
@@ -535,6 +537,7 @@ DEPENDENCIES
   letter_opener_web (~> 1.3)
   link_header (~> 0.0)
   lograge (~> 0.5)
+  mario-redis-lock (~> 1.2)
   microformats (~> 4.0)
   mime-types (~> 3.1)
   nokogiri (~> 1.7)
diff --git a/app/services/resolve_remote_account_service.rb b/app/services/resolve_remote_account_service.rb
index d2dfda824..c948243ec 100644
--- a/app/services/resolve_remote_account_service.rb
+++ b/app/services/resolve_remote_account_service.rb
@@ -11,97 +11,153 @@ class ResolveRemoteAccountService < BaseService
   # @param [String] uri User URI in the form of username@domain
   # @return [Account]
   def call(uri, update_profile = true, redirected = nil)
-    username, domain = uri.split('@')
+    @username, @domain = uri.split('@')
 
-    return Account.find_local(username) if TagManager.instance.local_domain?(domain)
+    return Account.find_local(@username) if TagManager.instance.local_domain?(@domain)
 
-    account = Account.find_remote(username, domain)
-    return account unless account_needs_webfinger_update?(account)
+    @account = Account.find_remote(@username, @domain)
+
+    return @account unless webfinger_update_due?
 
     Rails.logger.debug "Looking up webfinger for #{uri}"
 
-    data = Goldfinger.finger("acct:#{uri}")
+    @webfinger = Goldfinger.finger("acct:#{uri}")
 
-    raise Goldfinger::Error, 'Missing resource links' if data.link('http://schemas.google.com/g/2010#updates-from').nil? || data.link('salmon').nil? || data.link('http://webfinger.net/rel/profile-page').nil? || data.link('magic-public-key').nil?
+    raise Goldfinger::Error, 'Missing resource links' if links_missing?
 
-    # Disallow account hijacking
-    confirmed_username, confirmed_domain = data.subject.gsub(/\Aacct:/, '').split('@')
+    confirmed_username, confirmed_domain = @webfinger.subject.gsub(/\Aacct:/, '').split('@')
 
-    unless confirmed_username.casecmp(username).zero? && confirmed_domain.casecmp(domain).zero?
+    if confirmed_username.casecmp(@username).zero? && confirmed_domain.casecmp(@domain).zero?
+      @username = confirmed_username
+      @domain   = confirmed_domain
+    else
       return call("#{confirmed_username}@#{confirmed_domain}", update_profile, true) if redirected.nil?
-      raise Goldfinger::Error, 'Requested and returned acct URI do not match'
+      raise Goldfinger::Error, 'Requested and returned acct URIs do not match'
     end
 
-    return Account.find_local(confirmed_username) if TagManager.instance.local_domain?(confirmed_domain)
+    return Account.find_local(@username) if TagManager.instance.local_domain?(@domain)
 
-    confirmed_account = Account.find_remote(confirmed_username, confirmed_domain)
-    if confirmed_account.nil?
-      Rails.logger.debug "Creating new remote account for #{uri}"
+    RedisLock.acquire(lock_options) do |lock|
+      if lock.acquired?
+        @account = Account.find_remote(@username, @domain)
 
-      domain_block = DomainBlock.find_by(domain: domain)
-      account = Account.new(username: confirmed_username, domain: confirmed_domain)
-      account.suspended   = true if domain_block && domain_block.suspend?
-      account.silenced    = true if domain_block && domain_block.silence?
-      account.private_key = nil
-    else
-      account = confirmed_account
+        create_account if @account.nil?
+        update_account
+
+        update_account_profile if update_profile
+      end
     end
 
-    account.last_webfingered_at = Time.now.utc
+    @account
+  end
 
-    account.remote_url  = data.link('http://schemas.google.com/g/2010#updates-from').href
-    account.salmon_url  = data.link('salmon').href
-    account.url         = data.link('http://webfinger.net/rel/profile-page').href
-    account.public_key  = magic_key_to_pem(data.link('magic-public-key').href)
+  private
 
-    body, xml = get_feed(account.remote_url)
-    hubs      = get_hubs(xml)
+  def links_missing?
+    @webfinger.link('http://schemas.google.com/g/2010#updates-from').nil? ||
+      @webfinger.link('salmon').nil? ||
+      @webfinger.link('http://webfinger.net/rel/profile-page').nil? ||
+      @webfinger.link('magic-public-key').nil?
+  end
 
-    account.uri     = get_account_uri(xml)
-    account.hub_url = hubs.first.attribute('href').value
+  def webfinger_update_due?
+    @account.nil? || @account.last_webfingered_at.nil? || @account.last_webfingered_at <= 1.day.ago
+  end
 
-    begin
-      account.save!
-      get_profile(body, account) if update_profile
-    rescue ActiveRecord::RecordNotUnique
-      # The account has been added by another worker!
-      return Account.find_remote(confirmed_username, confirmed_domain)
-    end
+  def create_account
+    Rails.logger.debug "Creating new remote account for #{@username}@#{@domain}"
 
-    account
+    @account = Account.new(username: @username, domain: @domain)
+    @account.suspended   = true if auto_suspend?
+    @account.silenced    = true if auto_silence?
+    @account.private_key = nil
   end
 
-  private
+  def update_account
+    @account.last_webfingered_at = Time.now.utc
+    @account.remote_url          = atom_url
+    @account.salmon_url          = salmon_url
+    @account.url                 = url
+    @account.public_key          = public_key
+    @account.uri                 = canonical_uri
+    @account.hub_url             = hub_url
+    @account.save!
+  end
 
-  def account_needs_webfinger_update?(account)
-    account&.last_webfingered_at.nil? || account.last_webfingered_at <= 1.day.ago
+  def auto_suspend?
+    domain_block && domain_block.suspend?
   end
 
-  def get_feed(url)
-    response = Request.new(:get, url).perform
-    raise Goldfinger::Error, "Feed attempt failed for #{url}: HTTP #{response.code}" unless response.code == 200
-    [response.to_s, Nokogiri::XML(response)]
+  def auto_silence?
+    domain_block && domain_block.silence?
   end
 
-  def get_hubs(xml)
-    hubs = xml.xpath('//xmlns:link[@rel="hub"]')
-    raise Goldfinger::Error, 'No PubSubHubbub hubs found' if hubs.empty? || hubs.first.attribute('href').nil?
-    hubs
+  def domain_block
+    return @domain_block if defined?(@domain_block)
+    @domain_block = DomainBlock.find_by(domain: @domain)
   end
 
-  def get_account_uri(xml)
-    author_uri = xml.at_xpath('/xmlns:feed/xmlns:author/xmlns:uri')
+  def atom_url
+    @atom_url ||= @webfinger.link('http://schemas.google.com/g/2010#updates-from').href
+  end
+
+  def salmon_url
+    @salmon_url ||= @webfinger.link('salmon').href
+  end
+
+  def url
+    @url ||= @webfinger.link('http://webfinger.net/rel/profile-page').href
+  end
+
+  def public_key
+    @public_key ||= magic_key_to_pem(@webfinger.link('magic-public-key').href)
+  end
+
+  def canonical_uri
+    return @canonical_uri if defined?(@canonical_uri)
+
+    author_uri = atom.at_xpath('/xmlns:feed/xmlns:author/xmlns:uri')
 
     if author_uri.nil?
-      owner = xml.at_xpath('/xmlns:feed').at_xpath('./dfrn:owner', dfrn: DFRN_NS)
+      owner      = atom.at_xpath('/xmlns:feed').at_xpath('./dfrn:owner', dfrn: DFRN_NS)
       author_uri = owner.at_xpath('./xmlns:uri') unless owner.nil?
     end
 
     raise Goldfinger::Error, 'Author URI could not be found' if author_uri.nil?
-    author_uri.content
+
+    @canonical_uri = author_uri.content
+  end
+
+  def hub_url
+    return @hub_url if defined?(@hub_url)
+
+    hubs = atom.xpath('//xmlns:link[@rel="hub"]')
+
+    raise Goldfinger::Error, 'No PubSubHubbub hubs found' if hubs.empty? || hubs.first['href'].nil?
+
+    @hub_url = hubs.first['href']
+  end
+
+  def atom_body
+    return @atom_body if defined?(@atom_body)
+
+    response = Request.new(:get, atom_url).perform
+
+    raise Goldfinger::Error, "Feed attempt failed for #{atom_url}: HTTP #{response.code}" unless response.code == 200
+
+    @atom_body = response.to_s
+  end
+
+  def atom
+    return @atom if defined?(@atom)
+    @atom = Nokogiri::XML(atom_body)
+  end
+
+  def update_account_profile
+    RemoteProfileUpdateWorker.perform_async(@account.id, atom_body.force_encoding('UTF-8'), false)
   end
 
-  def get_profile(body, account)
-    RemoteProfileUpdateWorker.perform_async(account.id, body.force_encoding('UTF-8'), false)
+  def lock_options
+    { redis: Redis.current, key: "resolve:#{@username}@#{@domain}" }
   end
 end
diff --git a/spec/services/resolve_remote_account_service_spec.rb b/spec/services/resolve_remote_account_service_spec.rb
index ad4d436ba..c51588210 100644
--- a/spec/services/resolve_remote_account_service_spec.rb
+++ b/spec/services/resolve_remote_account_service_spec.rb
@@ -68,4 +68,27 @@ RSpec.describe ResolveRemoteAccountService do
     expect(account.domain).to eq 'localdomain.com'
     expect(account.remote_url).to eq 'https://webdomain.com/users/foo.atom'
   end
+
+  it 'processes one remote account at a time using locks' do
+    wait_for_start = true
+    fail_occurred  = false
+    return_values  = []
+
+    threads = Array.new(5) do
+      Thread.new do
+        true while wait_for_start
+        begin
+          return_values << subject.call('foo@localdomain.com')
+        rescue ActiveRecord::RecordNotUnique
+          fail_occurred = true
+        end
+      end
+    end
+
+    wait_for_start = false
+    threads.each(&:join)
+
+    expect(fail_occurred).to be false
+    expect(return_values).to_not include(nil)
+  end
 end