Truncate 'metadata' app.crash event payload

fixes cloudfoundry/capi-release#152
fixes cloudfoundry/capi-release#162

[#168010974 #170222110]

Authored-by: Aakash Shah <ashah@pivotal.io>

Author: Aakash Shah

app/repositories/app_event_repository.rb

@@ -4,6 +4,8 @@ module VCAP::CloudController
   module Repositories
     class AppEventRepository
       include AppManifestEventMixins
+      TRUNCATED_SUFFIX = ' (truncated)'.freeze
+      TRUNCATE_THRESHOLD = 10000
 
       CENSORED_FIELDS   = [:encrypted_environment_json,
                            :command,
@@ -17,6 +19,8 @@ def create_app_exit_event(app, droplet_exited_payload)
 
         actor    = { name: app.name, guid: app.guid, type: 'app' }
         metadata = droplet_exited_payload.slice('instance', 'index', 'cell_id', 'exit_status', 'exit_description', 'reason')
+        metadata['exit_description'] = metadata['exit_description'].truncate(TRUNCATE_THRESHOLD, omission: TRUNCATED_SUFFIX)
+
         create_app_audit_event('app.crash', app, app.space, actor, metadata)
       end
 

spec/unit/repositories/app_event_repository_spec.rb

@@ -187,13 +187,14 @@ module Repositories
 
       describe '#create_app_exit_event' do
         let(:exiting_process) { ProcessModelFactory.make }
+        let(:exit_description) { 'X' * AppEventRepository::TRUNCATE_THRESHOLD * 2 }
         let(:droplet_exited_payload) {
           {
             'instance' => 'abc',
             'index' => '2',
             'cell_id' => 'some-cell',
             'exit_status' => '1',
-            'exit_description' => 'shut down',
+            'exit_description' => exit_description,
             'reason' => 'evacuation',
             'unknown_key' => 'something'
           }
@@ -213,7 +214,8 @@ module Repositories
           expect(event.metadata['cell_id']).to eq('some-cell')
           expect(event.metadata['index']).to eq('2')
           expect(event.metadata['exit_status']).to eq('1')
-          expect(event.metadata['exit_description']).to eq('shut down')
+          expect(event.metadata['exit_description'].length).to eq(AppEventRepository::TRUNCATE_THRESHOLD)
+          expect(event.metadata['exit_description']).to eq(exit_description.truncate(AppEventRepository::TRUNCATE_THRESHOLD, omission: ' (truncated)'))
           expect(event.metadata['reason']).to eq('evacuation')
         end