Remove Logstash integration

We’ve implemented log shipping at the platform level and this custom
code to send our logs to Logstash is no longer required.

Gemfile

@@ -59,8 +59,6 @@ gem "clockwork"
 
 # Generate JSON Web Tokens
 gem "jwt"
-gem "logstash-logger"
-gem "rails_semantic_logger"
 
 gem 'activerecord-session_store'
 
@@ -95,3 +93,7 @@ end
 group :development, :test, :review do
   gem "factory_bot_rails"
 end
+
+group :development, :production do
+  gem "rails_semantic_logger"
+end

Gemfile.lock

@@ -251,9 +251,6 @@ GEM
     language_server-protocol (3.17.0.3)
     launchy (2.5.2)
       addressable (~> 2.8)
-    logstash-event (1.2.02)
-    logstash-logger (0.26.1)
-      logstash-event (~> 1.2)
     loofah (2.22.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
@@ -602,7 +599,6 @@ DEPENDENCIES
   jsbundling-rails
   jwt
   launchy
-  logstash-logger
   okcomputer
   omniauth-oauth2 (~> 1.8)
   omniauth-rails_csrf_protection

config/environments/development.rb

@@ -59,4 +59,8 @@
 
   # Uncomment if you wish to allow Action Cable access from any origin.
   # config.action_cable.disable_request_forgery_protection = true
+  #
+  config.log_level = :debug                       # Or :info
+  config.log_format = :color                      # Console colorised non-json output
+  config.semantic_logger.backtrace_level = :debug # Show file and line number (expensive: not for production)
 end

config/environments/production.rb

@@ -80,4 +80,9 @@
 
   # Do not dump schema after migrations.
   config.active_record.dump_schema_after_migration = false
+
+  config.log_level = :info                                # Or :warn, or :error
+  config.log_format = :json                               # For parsing in Logit
+  config.rails_semantic_logger.add_file_appender = false  # Don't log to file
+  config.active_record.logger = nil                       # Don't log SQL
 end

config/initializers/semantic_logger.rb

@@ -1,50 +1,10 @@
-class LogStashFormatter < SemanticLogger::Formatters::Raw
-  def call(log, logger)
-    super(log, logger)
+return unless defined?(SemanticLogger)
 
-    format_exception
-    format_stacktrace
-
-    hash.to_json
-  end
-
-  def format_exception
-    exception_message = hash.dig(:exception, :message)
-    return if exception_message.blank?
-
-    hash[:message] = "Exception occured: #{exception_message}"
-  end
-
-  def format_stacktrace
-    stack_trace = hash.dig(:exception, :stack_trace)
-    return if stack_trace.blank?
-
-    hash[:stacktrace] = stack_trace.first(3)
-    hash[:exception].delete(:stack_trace)
-  end
+Rails.application.configure do
+  config.semantic_logger.application = "" # This is added by logstash from its tags
+  config.log_tags = [:request_id]         # Prepend all log lines with the following tags
 end
 
-if ENV["LOGSTASH_HOST"] && ENV["LOGSTASH_PORT"]
-  warn("logstash configured, sending logs there")
-
-  # For some reason logstash / elasticsearch drops events where the payload
-  # is a hash. These are more conveniently accessed at the top level of the
-  # event, anyway, so we move it there.
-  customize_event = ->(event) do
-    if event["payload"].present?
-      event.append(event["payload"])
-      event["payload"] = nil
-    end
-  end
-
-  logger =
-    LogStashLogger.new(
-      {
-        host: ENV["LOGSTASH_HOST"],
-        port: ENV["LOGSTASH_PORT"],
-        ssl_enable: true,
-        type: :tcp
-      }.merge(customize_event:)
-    )
-  SemanticLogger.add_appender(logger:, level: :info, formatter: LogStashFormatter.new)
-end
+SemanticLogger.add_appender(io: $stdout, level: Rails.application.config.log_level,
+formatter: Rails.application.config.log_format)
+Rails.application.config.logger.info('Application logging to STDOUT')