Session tracking (#411)

* Added session tracking basics to notifier

* Added session config to config

* Added session tracking mechanisms

* Send bugsnag properties in headers

* Added backoff to delivery

* Minor updates and fixes

* Added tests for session-tracker

* Ensured success code is correctly checked before backoff

* Added hook to rails

* Ensured deliver doesn't send empty sessions

* Replaced rails sessions with rack to service both

* Complete re-do of backoff throttling

* Changed success criteria on sessions

* Added checks on asynchronous delivery

* Updated tests

* Added maximum amount of sessions to be sent at one time

* Added final attempt to send sessions at exit

* Style update

* Changed to sessionCounts

* Registered final at_exit block to send sessions

* Updated tests

* Fixed config ref

* Ensured thread sessions accessed through accessor

* Refactored some backoff functionality into functions

* Fixed issue with accessing get/set session

* Fixed issue with get_current_session calls

* Added session-tracking to rails-51 example

* Removed unnecessary info

* Added fallback to send sessions every 5 minutes

* Ensured deliver_fallback only terminated if exists

* Ensured headers are backwards compatible

* v6.3.0.beta.0

example/rails-51/config/initializers/bugsnag.rb

@@ -1,3 +1,4 @@
 Bugsnag.configure do |config|
-  config.api_key = "YOUR_API_KEY_HERE"
+  config.api_key = "YOUR_API_KEY"
+  config.track_sessions = true
 end

lib/bugsnag.rb

@@ -7,6 +7,7 @@
 require "bugsnag/report"
 require "bugsnag/cleaner"
 require "bugsnag/helpers"
+require "bugsnag/session_tracker"
 
 require "bugsnag/delivery"
 require "bugsnag/delivery/synchronous"
@@ -38,6 +39,8 @@ def configure
         configuration.warn("No valid API key has been set, notifications will not be sent")
         @key_warning = true
       end
+
+      session_tracker.config = configuration
     end
 
     # Explicitly notify of an exception
@@ -113,8 +116,8 @@ def notify(exception, auto_notify=false, &block)
 
         # Deliver
         configuration.info("Notifying #{configuration.endpoint} of #{report.exceptions.last[:errorClass]}")
-        payload_string = ::JSON.dump(Bugsnag::Helpers.trim_if_needed(report.as_json))
-        Bugsnag::Delivery[configuration.delivery_method].deliver(configuration.endpoint, payload_string, configuration)
+        options = {:headers => report.headers, :trim_payload => true}
+        Bugsnag::Delivery[configuration.delivery_method].deliver(configuration.endpoint, report.as_json, configuration, options)
       end
     end
 
@@ -124,6 +127,11 @@ def configuration
       @configuration || LOCK.synchronize { @configuration ||= Bugsnag::Configuration.new }
     end
 
+    def session_tracker
+      @session_tracker = nil unless defined?(@session_tracker)
+      @session_tracker || LOCK.synchronize { @session_tracker ||= Bugsnag::SessionTracker.new(configuration)}
+    end
+
     # Allow access to "before notify" callbacks
     def before_notify_callbacks
       Bugsnag.configuration.request_data[:before_callbacks] ||= []

lib/bugsnag/configuration.rb

@@ -7,6 +7,7 @@
 require "bugsnag/middleware/ignore_error_class"
 require "bugsnag/middleware/suggestion_data"
 require "bugsnag/middleware/classify_error"
+require "bugsnag/middleware/session_data"
 
 module Bugsnag
   class Configuration
@@ -22,7 +23,7 @@ class Configuration
     attr_accessor :app_type
     attr_accessor :meta_data_filters
     attr_accessor :endpoint
-    attr_accessor :logger
+    attr_accessor :logger 
     attr_accessor :middleware
     attr_accessor :internal_middleware
     attr_accessor :proxy_host
@@ -32,10 +33,13 @@ class Configuration
     attr_accessor :timeout
     attr_accessor :hostname
     attr_accessor :ignore_classes
+    attr_accessor :track_sessions
+    attr_accessor :session_endpoint
 
     API_KEY_REGEX = /[0-9a-f]{32}/i
     THREAD_LOCAL_NAME = "bugsnag_req_data"
     DEFAULT_ENDPOINT = "https://notify.bugsnag.com"
+    DEFAULT_SESSION_ENDPOINT = "https://sessions.bugsnag.com"
 
     DEFAULT_META_DATA_FILTERS = [
       /authorization/i,
@@ -57,6 +61,8 @@ def initialize
       self.hostname = default_hostname
       self.timeout = 15
       self.notify_release_stages = nil
+      self.track_sessions = false
+      self.session_endpoint = DEFAULT_SESSION_ENDPOINT
 
       # SystemExit and Interrupt are common Exception types seen with successful
       # exits and are not automatically reported to Bugsnag
@@ -81,6 +87,7 @@ def initialize
       self.internal_middleware.use Bugsnag::Middleware::IgnoreErrorClass
       self.internal_middleware.use Bugsnag::Middleware::SuggestionData
       self.internal_middleware.use Bugsnag::Middleware::ClassifyError
+      self.internal_middleware.use Bugsnag::Middleware::SessionData
 
       self.middleware = Bugsnag::MiddlewareStack.new
       self.middleware.use Bugsnag::Middleware::Callbacks

lib/bugsnag/delivery/synchronous.rb

@@ -4,13 +4,19 @@
 module Bugsnag
   module Delivery
     class Synchronous
-      HEADERS = {"Content-Type" => "application/json"}
+      BACKOFF_THREADS = {}
+      BACKOFF_REQUESTS = {}
+      BACKOFF_LOCK = Mutex.new
 
       class << self
-        def deliver(url, body, configuration)
+        def deliver(url, body, configuration, options={})
           begin
-            response = request(url, body, configuration)
+            response = request(url, body, configuration, options)
             configuration.debug("Request to #{url} completed, status: #{response.code}")
+            success = options[:success] || '200'
+            if options[:backoff] && !(response.code == success)
+              backoff(url, body, configuration, options)
+            end
           rescue StandardError => e
             # KLUDGE: Since we don't re-raise http exceptions, this breaks rspec
             raise if e.class.to_s == "RSpec::Expectations::ExpectationNotMetError"
@@ -22,9 +28,14 @@ def deliver(url, body, configuration)
 
         private
 
-        def request(url, body, configuration)
+        def request(url, body, configuration, options)
           uri = URI.parse(url)
 
+          if options[:trim_payload]
+            body = Bugsnag::Helpers.trim_if_needed(body)
+          end
+          payload = ::JSON.dump(body)
+
           if configuration.proxy_host
             http = Net::HTTP.new(uri.host, uri.port, configuration.proxy_host, configuration.proxy_port, configuration.proxy_user, configuration.proxy_password)
           else
@@ -39,14 +50,104 @@ def request(url, body, configuration)
             http.ca_file = configuration.ca_file if configuration.ca_file
           end
 
-          request = Net::HTTP::Post.new(path(uri), HEADERS)
-          request.body = body
+          headers = options.key?(:headers) ? options[:headers] : {}
+          headers.merge!(default_headers)
+
+          request = Net::HTTP::Post.new(path(uri), headers)
+          request.body = payload
+
           http.request(request)
         end
 
+        def backoff(url, body, configuration, options)
+          # Ensure we have the latest configuration for making these requests
+          @latest_configuration = configuration
+
+          BACKOFF_LOCK.lock
+          begin
+            # Define an exit function once to handle outstanding requests
+            @registered_at_exit = false unless defined?(@registered_at_exit)
+            if !@registered_at_exit
+              @registered_at_exit = true
+              at_exit do
+                backoff_exit
+              end
+            end
+            if BACKOFF_REQUESTS[url] && !BACKOFF_REQUESTS[url].empty?
+              last_request = BACKOFF_REQUESTS[url].last
+              new_body_length = ::JSON.dump(body).length
+              old_body_length = ::JSON.dump(last_request[:body]).length
+              if new_body_length + old_body_length >= Bugsnag::Helpers::MAX_PAYLOAD_LENGTH
+                BACKOFF_REQUESTS[url].push({:body => body, :options => options})
+              else
+                Bugsnag::Helpers::deep_merge!(last_request, {:body => body, :options => options})
+              end
+            else
+              BACKOFF_REQUESTS[url] = [{:body => body, :options => options}]
+            end
+            if !(BACKOFF_THREADS[url] && BACKOFF_THREADS[url].status)
+              spawn_backoff_thread(url)
+            end
+          ensure
+            BACKOFF_LOCK.unlock
+          end
+        end
+
+        def backoff_exit
+          # Kill existing threads
+          BACKOFF_THREADS.each do |url, thread|
+            thread.exit
+          end
+          # Retry outstanding requests once, then exit
+          BACKOFF_REQUESTS.each do |url, requests|
+            requests.map! do |req|
+              response = request(url, req[:body], @latest_configuration, req[:options])
+              success = req[:options][:success] || '200'
+              response.code == success
+            end
+            requests.reject! { |i| i }
+            @latest_configuration.warn("Requests to #{url} finished, #{requests.size} failed")
+          end
+        end
+
+        def spawn_backoff_thread(url)
+          new_thread = Thread.new(url) do |url|
+            interval = 2
+            while BACKOFF_REQUESTS[url].size > 0
+              sleep(interval)
+              interval = interval * 2
+              interval = 600 if interval > 600
+              BACKOFF_LOCK.lock
+              begin
+                BACKOFF_REQUESTS[url].map! do |req|
+                  response = request(url, req[:body], @latest_configuration, req[:options])
+                  success = req[:options][:success] || '200'
+                  if response.code == success
+                    @latest_configuration.debug("Request to #{url} completed, status: #{response.code}")
+                    false
+                  else
+                    req
+                  end
+                end
+                BACKOFF_REQUESTS[url].reject! { |i| !i }
+              ensure
+                BACKOFF_LOCK.unlock
+              end
+            end
+          end
+          BACKOFF_THREADS[url] = new_thread
+        end
+
         def path(uri)
           uri.path == "" ? "/" : uri.path
         end
+
+        def default_headers
+          {
+            "Content-Type" => "application/json",
+            "Bugsnag-Sent-At" =>  Time.now().utc().strftime('%Y-%m-%dT%H:%M:%S')
+          }
+        end
       end
     end
   end

lib/bugsnag/delivery/thread_queue.rb

@@ -8,7 +8,7 @@ class ThreadQueue < Synchronous
       MUTEX = Mutex.new
 
       class << self
-        def deliver(url, body, configuration)
+        def deliver(url, body, configuration, options={})
           @configuration = configuration
 
           start_once!
@@ -19,7 +19,7 @@ def deliver(url, body, configuration)
           end
 
           # Add delivery to the worker thread
-          @queue.push proc { super(url, body, configuration) }
+          @queue.push proc { super(url, body, configuration, options) }
         end
 
         private

lib/bugsnag/helpers.rb

@@ -23,6 +23,30 @@ def self.trim_if_needed(value)
       remove_metadata_from_events(reduced_value)
     end
 
+    def self.deep_merge(l_hash, r_hash)
+      l_hash.merge(r_hash) do |key, l_val, r_val|
+        if l_val.is_a?(Hash) && r_val.is_a?(Hash)
+          deep_merge(l_val, r_val)
+        elsif l_val.is_a?(Array) && r_val.is_a?(Array)
+          l_val.concat(r_val)
+        else
+          r_val
+        end
+      end
+    end
+
+    def self.deep_merge!(l_hash, r_hash)
+      l_hash.merge!(r_hash) do |key, l_val, r_val|
+        if l_val.is_a?(Hash) && r_val.is_a?(Hash)
+          deep_merge(l_val, r_val)
+        elsif l_val.is_a?(Array) && r_val.is_a?(Array)
+          l_val.concat(r_val)
+        else
+          r_val
+        end
+      end
+    end
+
     private
 
     TRUNCATION_INFO = '[TRUNCATED]'

lib/bugsnag/integrations/rack.rb

@@ -34,6 +34,7 @@ def initialize(app)
     def call(env)
       # Set the request data for bugsnag middleware to use
       Bugsnag.configuration.set_request_data(:rack_env, env)
+      Bugsnag.session_tracker.create_session
 
       begin
         response = @app.call(env)

lib/bugsnag/integrations/rails/controller_methods.rb

@@ -5,6 +5,7 @@ def self.included(base)
     end
 
     module ClassMethods
+
       private
       def before_bugsnag_notify(*methods, &block)
         _add_bugsnag_notify_callback(:before_callbacks, *methods, &block)

lib/bugsnag/middleware/session_data.rb

@@ -0,0 +1,21 @@
+module Bugsnag::Middleware
+  class SessionData
+    def initialize(bugsnag)
+      @bugsnag = bugsnag
+    end
+
+    def call(report)
+      session = Bugsnag::SessionTracker.get_current_session
+      unless session.nil?
+        if report.unhandled
+          session[:events][:unhandled] += 1
+        else
+          session[:events][:handled] += 1
+        end
+        report.session = session
+      end
+
+      @bugsnag.call(report)
+    end
+  end
+end

lib/bugsnag/report.rb

@@ -17,8 +17,9 @@ class Report
 
     MAX_EXCEPTIONS_TO_UNWRAP = 5
 
-    CURRENT_PAYLOAD_VERSION = "2"
+    CURRENT_PAYLOAD_VERSION = "4.0"
 
+    attr_reader   :unhandled
     attr_accessor :api_key
     attr_accessor :app_type
     attr_accessor :app_version
@@ -31,6 +32,7 @@ class Report
     attr_accessor :meta_data
     attr_accessor :raw_exceptions
     attr_accessor :release_stage
+    attr_accessor :session
     attr_accessor :severity
     attr_accessor :severity_reason
     attr_accessor :user
@@ -92,7 +94,7 @@ def as_json
         },
         exceptions: exceptions,
         groupingHash: grouping_hash,
-        payloadVersion: CURRENT_PAYLOAD_VERSION,
+        session: session,
         severity: severity,
         severityReason: severity_reason,
         unhandled: @unhandled,
@@ -108,7 +110,6 @@ def as_json
 
       # return the payload hash
       {
-        :apiKey => api_key,
         :notifier => {
           :name => NOTIFIER_NAME,
           :version => NOTIFIER_VERSION,
@@ -118,6 +119,14 @@ def as_json
       }
     end
 
+    def headers
+      {
+        "Bugsnag-Api-Key" => api_key,
+        "Bugsnag-Payload-Version" => CURRENT_PAYLOAD_VERSION,
+        "Bugsnag-Sent-At" => Time.now().utc().strftime('%Y-%m-%dT%H:%M:%S')
+      }
+    end
+
     def ignore?
       @should_ignore
     end