require 'spec_helper' describe Gitlab::Metrics::Sampler do let(:sampler) { described_class.new(5) } after do Allocations.stop if Gitlab::Metrics.mri? end describe '#start' do it 'gathers a sample at a given interval' do expect(sampler).to receive(:sleep).with(a_kind_of(Numeric)) expect(sampler).to receive(:sample) expect(sampler).to receive(:loop).and_yield sampler.start.join end end describe '#sample' do it 'samples various statistics' do expect(sampler).to receive(:sample_memory_usage) expect(sampler).to receive(:sample_file_descriptors) expect(sampler).to receive(:sample_objects) expect(sampler).to receive(:sample_gc) expect(sampler).to receive(:flush) sampler.sample end it 'clears any GC profiles' do expect(sampler).to receive(:flush) expect(GC::Profiler).to receive(:clear) sampler.sample end end describe '#flush' do it 'schedules the metrics using Sidekiq' do expect(Gitlab::Metrics).to receive(:submit_metrics). with([an_instance_of(Hash)]) sampler.sample_memory_usage sampler.flush end end describe '#sample_memory_usage' do it 'adds a metric containing the memory usage' do expect(Gitlab::Metrics::System).to receive(:memory_usage). and_return(9000) expect(sampler).to receive(:add_metric). with(/memory_usage/, value: 9000). and_call_original sampler.sample_memory_usage end end describe '#sample_file_descriptors' do it 'adds a metric containing the amount of open file descriptors' do expect(Gitlab::Metrics::System).to receive(:file_descriptor_count). and_return(4) expect(sampler).to receive(:add_metric). with(/file_descriptors/, value: 4). and_call_original sampler.sample_file_descriptors end end describe '#sample_objects' do it 'adds a metric containing the amount of allocated objects' do expect(sampler).to receive(:add_metric). with(/object_counts/, an_instance_of(Hash), an_instance_of(Hash)). at_least(:once). and_call_original sampler.sample_objects end end describe '#sample_gc' do it 'adds a metric containing garbage collection statistics' do expect(GC::Profiler).to receive(:total_time).and_return(0.24) expect(sampler).to receive(:add_metric). with(/gc_statistics/, an_instance_of(Hash)). and_call_original sampler.sample_gc end end describe '#add_metric' do it 'prefixes the series name for a Rails process' do expect(sampler).to receive(:sidekiq?).and_return(false) expect(Gitlab::Metrics::Metric).to receive(:new). with('rails_cats', { value: 10 }, {}). and_call_original sampler.add_metric('cats', value: 10) end it 'prefixes the series name for a Sidekiq process' do expect(sampler).to receive(:sidekiq?).and_return(true) expect(Gitlab::Metrics::Metric).to receive(:new). with('sidekiq_cats', { value: 10 }, {}). and_call_original sampler.add_metric('cats', value: 10) end end describe '#sleep_interval' do it 'returns a Numeric' do expect(sampler.sleep_interval).to be_a_kind_of(Numeric) end # Testing random behaviour is very hard, so treat this test as a basic smoke # test instead of a very accurate behaviour/unit test. it 'does not return the same interval twice in a row' do last = nil 100.times do interval = sampler.sleep_interval expect(interval).to_not eq(last) last = interval end end end end