Squashed commit of the following:

commit 10456b1e9240886432f565dd17689080bbb133b9
Merge: 312c1a9bdf8 a5f4627857b
Author: Shinya Maeda <shinya@gitlab.com>
Date:   Thu Nov 29 14:33:21 2018 +0900

    Merge branch 'master-ce' into add-counter-for-trace-chunks

commit 312c1a9bdf8efc45c3fed5ff50f05cc589bbb4ed
Author: Shinya Maeda <shinya@gitlab.com>
Date:   Wed Nov 28 20:06:18 2018 +0900

    Fix coding offence

commit e397cc2ccc1b2cf7f8b3558b8fa81fe2aa0ab366
Author: Shinya Maeda <shinya@gitlab.com>
Date:   Wed Nov 28 14:40:24 2018 +0900

    Fix tracking archive failure

1 files changed, 18 insertions, 4 deletions

diff --git a/spec/workers/ci/archive_traces_cron_worker_spec.rb b/spec/workers/ci/archive_traces_cron_worker_spec.rb
index 23f5dda298a..8cd1c7e3906 100644
--- a/spec/workers/ci/archive_traces_cron_worker_spec.rb
+++ b/spec/workers/ci/archive_traces_cron_worker_spec.rb
@@ -46,13 +46,27 @@ describe Ci::ArchiveTracesCronWorker do
       let!(:build) { create(:ci_build, :success, :trace_live) }
 
       before do
-        allow_any_instance_of(Gitlab::Ci::Trace).to receive(:archive!).and_raise('Unexpected error')
+        allow_any_instance_of(Gitlab::Ci::Trace).to receive(:archive_stream!).and_raise('Unexpected error')
       end
 
-      it 'puts a log' do
-        expect(Rails.logger).to receive(:error).with("Failed to archive stale live trace. id: #{build.id} message: Unexpected error")
+      it 'increments Prometheus counter, sends crash report to Sentry and ignore an error for continuing to archive' do
+        expect(Gitlab::Sentry)
+          .to receive(:track_exception)
+          .with(RuntimeError,
+                issue_url: 'https://gitlab.com/gitlab-org/gitlab-ce/issues/51502',
+                extra: { job_id: build.id } ).once
 
-        subject
+        expect(Rails.logger)
+          .to receive(:error)
+          .with("Failed to archive trace. id: #{build.id} message: Unexpected error")
+          .and_call_original
+
+        expect(Gitlab::Metrics)
+          .to receive(:counter)
+          .with(:job_trace_archive_failed_total, "Counter of failed attempts of trace archiving")
+          .and_call_original
+
+        expect { subject }.not_to raise_error
       end
     end
   end