newrelic: fix newrelic starting without license key.

Fix an issue where the New Relic agent always started in the production
environment, even when a license key wasn't configured.

Also make the New Relic agent log to stdout instead of log/newrelic_agent.log.

Gemfile

@@ -52,6 +52,7 @@ gem 'google-cloud-storage', require: "google/cloud/storage"
 gem 'ed25519'
 gem 'bcrypt_pbkdf' # https://github.com/net-ssh/net-ssh/issues/565
 gem 'terminal-table'
+gem 'newrelic_rpm', require: false
 
 group :production, :staging do
   gem 'unicorn', :platforms => :ruby
@@ -60,7 +61,6 @@ end
 
 group :production do
   gem 'unicorn-worker-killer'
-  gem 'newrelic_rpm'
   gem 'capistrano-deploytags', '~> 1.0.0', require: false
 end
 

config/danbooru_default_config.rb

@@ -581,6 +581,12 @@ module Danbooru
     def redis_url
       # "redis://localhost:6379"
     end
+
+    # Optional. The license key for your New Relic account.
+    # https://newrelic.com/
+    # https://docs.newrelic.com/docs/accounts/accounts-billing/account-setup/new-relic-license-key/
+    def new_relic_license_key
+    end
   end
 
   EnvironmentConfiguration = Struct.new(:config) do

config/initializers/00_newrelic.rb

@@ -0,0 +1,14 @@
+if Danbooru.config.new_relic_license_key.present?
+  require "new_relic/control"
+
+  # https://github.com/newrelic/newrelic-ruby-agent/blob/1ef4082fe97fd19aeccb3f392a44ef3becae66d3/lib/newrelic_rpm.rb#L40
+  # https://github.com/newrelic/newrelic-ruby-agent/blob/1ef4082fe97fd19aeccb3f392a44ef3becae66d3/lib/new_relic/agent.rb#L349
+  NewRelic::Control.instance.init_plugin(
+    app_name: Danbooru.config.canonical_app_name,
+    license_key: Danbooru.config.new_relic_license_key,
+    log_level: Danbooru.config.debug_mode ? "debug" : "error",
+    log: Rails.logger,
+    "rake.tasks": ["maintenance:.*"],
+    config: Rails.application.config,
+  )
+end

config/initializers/unicorn.rb

@@ -1,7 +0,0 @@
-# Ensure the agent is started using Unicorn.
-# This is needed when using Unicorn and preload_app is not set to true.
-# See https://newrelic.com/docs/ruby/no-data-with-unicorn
-if defined? ::NewRelic
-  ::NewRelic::Agent.manual_start
-  ::NewRelic::Agent.after_fork(:force_reconnect => true)
-end

lib/capistrano/tasks/symlink.rake

@@ -3,9 +3,6 @@ namespace :symlink do
   task :local_files do
     on roles(:app, :worker) do
       execute :ln, "-s", "#{deploy_to}/shared/config/danbooru_local_config.rb", "#{release_path}/config/danbooru_local_config.rb"
-      if test("[ -f #{deploy_to}/shared/config/newrelic.yml ]")
-        execute :ln, "-s", "#{deploy_to}/shared/config/newrelic.yml", "#{release_path}/config/newrelic.yml"
-      end
     end
   end
 

script/install/newrelic.yml

@@ -1,46 +0,0 @@
-# This file configures the New Relic Agent.  New Relic monitors Ruby, Java,
-# .NET, PHP, Python, Node, and Go applications with deep visibility and low
-# overhead.  For more information, visit www.newrelic.com.
-#
-# For full documentation of agent configuration options, please refer to
-# https://docs.newrelic.com/docs/agents/ruby-agent/installation-configuration/ruby-agent-configuration
-
-common: &default_settings
-  # Required license key associated with your New Relic account.
-  license_key: YOUR_LICENCE_KEY_HERE
-
-  # Your application name. Renaming here affects where data displays in New
-  # Relic.  For more details, see https://docs.newrelic.com/docs/apm/new-relic-apm/maintenance/renaming-applications
-  app_name: Danbooru
-
-  # To disable the agent regardless of other settings, uncomment the following:
-  # agent_enabled: false
-
-  # Logging level for log/newrelic_agent.log
-  log_level: info
-
-  # https://docs.newrelic.com/docs/agents/ruby-agent/background-jobs/rake-instrumentation
-  rake:
-    tasks: ["maintenance:.*"]
-
-# Environment-specific settings are in this section.
-# RAILS_ENV or RACK_ENV (as appropriate) is used to determine the environment.
-# If your application has other named environments, configure them here.
-development:
-  <<: *default_settings
-  app_name: Danbooru (Development)
-
-  # New Relic is disabled by default in the development environment. Uncomment to enable.
-  # monitor_mode: true
-
-test:
-  <<: *default_settings
-  # It doesn't make sense to report to New Relic from automated test runs.
-  monitor_mode: false
-
-staging:
-  <<: *default_settings
-  app_name: Danbooru (Staging)
-
-production:
-  <<: *default_settings