Stringify sidekiq job args in logs

If these logs are sent to Elasticsearch, it will not be able to process
nested object fields, as this causes a type mismatch with scalar
elements in the same array across log lines.

lib/gitlab/sidekiq_logging/structured_logger.rb

@@ -85,7 +85,11 @@ module Gitlab
         job['pid'] = ::Process.pid
 
         job.delete('args') unless ENV['SIDEKIQ_LOG_ARGUMENTS']
-        job['args'] = Gitlab::Utils::LogLimitedArray.log_limited_array(job['args']) if job['args']
+
+        if job['args']
+          job['args'].map!(&:to_s)
+          job['args'] = Gitlab::Utils::LogLimitedArray.log_limited_array(job['args'])
+        end
 
         job
       end

spec/lib/gitlab/sidekiq_logging/structured_logger_spec.rb

@@ -30,6 +30,7 @@ describe Gitlab::SidekiqLogging::StructuredLogger do
     let(:clock_thread_cputime_end) { 1.333333799 }
     let(:start_payload) do
       job.except('error_backtrace', 'error_class', 'error_message').merge(
+        'args' => job['args'].map(&:to_s),
         'message' => 'TestWorker JID-da883554ee4fe414012f5f42: start',
         'job_status' => 'start',
         'pid' => Process.pid,
@@ -99,13 +100,29 @@ describe Gitlab::SidekiqLogging::StructuredLogger do
         end
       end
 
+      context 'when the job args contain non-string objects' do
+        it 'converts them to strings' do
+          Timecop.freeze(timestamp) do
+            job['args'] = [2, true, 'foo', { "foo" => "bar" }]
+            expected_args = ['2', 'true', 'foo', '{"foo"=>"bar"}']
+
+            expect(logger).to receive(:info).with(start_payload.merge('args' => expected_args)).ordered
+            expect(logger).to receive(:info).with(end_payload.merge('args' => expected_args)).ordered
+            expect(subject).to receive(:log_job_start).and_call_original
+            expect(subject).to receive(:log_job_done).and_call_original
+
+            subject.call(job, 'test_queue') { }
+          end
+        end
+      end
+
       context 'when the job args are bigger than the maximum allowed' do
         it 'keeps args from the front until they exceed the limit' do
           Timecop.freeze(timestamp) do
             half_limit = Gitlab::Utils::LogLimitedArray::MAXIMUM_ARRAY_LENGTH / 2
             job['args'] = [1, 2, 'a' * half_limit, 'b' * half_limit, 3]
 
-            expected_args = job['args'].take(3) + ['...']
+            expected_args = job['args'].map(&:to_s).take(3) + ['...']
 
             expect(logger).to receive(:info).with(start_payload.merge('args' => expected_args)).ordered
             expect(logger).to receive(:info).with(end_payload.merge('args' => expected_args)).ordered