Merge branch '216584-drop-ruby-memory-bytes' into 'master'

Drop redundant `memory_bytes` metrics from ruby_sampler

Closes #216584

See merge request gitlab-org/gitlab!31705

changelogs/unreleased/216584-drop-ruby-memory-bytes.yml

+---
+title: Remove ruby_memory_bytes metric, duplicate of ruby_process_resident_memory_bytes
+merge_request: 31705
+author:
+type: removed

doc/administration/monitoring/prometheus/gitlab_metrics.md

@@ -183,7 +183,6 @@ Some basic Ruby runtime metrics are available:
 | `ruby_gc_duration_seconds`           | Counter   | 11.1  | Time spent by Ruby in GC |
 | `ruby_gc_stat_...`                   | Gauge     | 11.1  | Various metrics from [GC.stat](https://ruby-doc.org/core-2.6.5/GC.html#method-c-stat) |
 | `ruby_file_descriptors`              | Gauge     | 11.1  | File descriptors per process |
-| `ruby_memory_bytes`                  | Gauge     | 11.1  | Memory usage by process |
 | `ruby_sampler_duration_seconds`      | Counter   | 11.1  | Time spent collecting stats |
 | `ruby_process_cpu_seconds_total`     | Gauge     | 12.0  | Total amount of CPU time per process |
 | `ruby_process_max_fds`               | Gauge     | 12.0  | Maximum number of open file descriptors per process |

lib/gitlab/metrics/samplers/influx_sampler.rb

@@ -31,7 +31,7 @@ module Gitlab
         end
 
         def sample_memory_usage
-          add_metric('memory_usage', value: System.memory_usage)
+          add_metric('memory_usage', value: System.memory_usage_rss)
         end
 
         def sample_file_descriptors

lib/gitlab/metrics/samplers/ruby_sampler.rb

@@ -35,7 +35,6 @@ module Gitlab
         def init_metrics
           metrics = {
             file_descriptors:                  ::Gitlab::Metrics.gauge(with_prefix(:file, :descriptors), 'File descriptors used', labels),
-            memory_bytes:                      ::Gitlab::Metrics.gauge(with_prefix(:memory, :bytes), 'Memory used (RSS)', labels),
             process_cpu_seconds_total:         ::Gitlab::Metrics.gauge(with_prefix(:process, :cpu_seconds_total), 'Process CPU seconds total'),
             process_max_fds:                   ::Gitlab::Metrics.gauge(with_prefix(:process, :max_fds), 'Process max fds'),
             process_resident_memory_bytes:     ::Gitlab::Metrics.gauge(with_prefix(:process, :resident_memory_bytes), 'Memory used (RSS)', labels),
@@ -87,9 +86,7 @@ module Gitlab
         end
 
         def set_memory_usage_metrics
-          memory_rss = System.memory_usage
-          metrics[:memory_bytes].set(labels, memory_rss)
-          metrics[:process_resident_memory_bytes].set(labels, memory_rss)
+          metrics[:process_resident_memory_bytes].set(labels, System.memory_usage_rss)
 
           if Gitlab::Utils.to_boolean(ENV['enable_memory_uss_pss'])
             memory_uss_pss = System.memory_usage_uss_pss

lib/gitlab/metrics/system.rb

@@ -18,7 +18,7 @@ module Gitlab
       MAX_OPEN_FILES_PATTERN = /Max open files\s*(?<value>\d+)/.freeze
 
       # Returns the current process' RSS (resident set size) in bytes.
-      def self.memory_usage
+      def self.memory_usage_rss
         sum_matches(PROC_STATUS_PATH, rss: RSS_PATTERN)[:rss].kilobytes
       end
 

lib/gitlab/metrics/transaction.rb

@@ -55,13 +55,13 @@ module Gitlab
       def run
         Thread.current[THREAD_KEY] = self
 
-        @memory_before = System.memory_usage
+        @memory_before = System.memory_usage_rss
         @started_at = System.monotonic_time
         @thread_cputime_start = System.thread_cpu_time
 
         yield
       ensure
-        @memory_after = System.memory_usage
+        @memory_after = System.memory_usage_rss
         @finished_at = System.monotonic_time
 
         self.class.gitlab_transaction_cputime_seconds.observe(labels, thread_cpu_duration)

lib/gitlab/utils/measuring.rb

@@ -36,7 +36,7 @@ module Gitlab
           gc_stats: gc_stats,
           time_to_finish: time_to_finish,
           number_of_sql_calls: sql_calls_count,
-          memory_usage: "#{Gitlab::Metrics::System.memory_usage.to_f / 1024 / 1024} MiB",
+          memory_usage: "#{Gitlab::Metrics::System.memory_usage_rss.to_f / 1024 / 1024} MiB",
           label: ::Prometheus::PidProvider.worker_id
         )
 

spec/lib/gitlab/metrics/samplers/influx_sampler_spec.rb

@@ -37,7 +37,7 @@ describe Gitlab::Metrics::Samplers::InfluxSampler do
 
   describe '#sample_memory_usage' do
     it 'adds a metric containing the memory usage' do
-      expect(Gitlab::Metrics::System).to receive(:memory_usage)
+      expect(Gitlab::Metrics::System).to receive(:memory_usage_rss)
         .and_return(9000)
 
       expect(sampler).to receive(:add_metric)

spec/lib/gitlab/metrics/samplers/ruby_sampler_spec.rb

@@ -21,7 +21,7 @@ describe Gitlab::Metrics::Samplers::RubySampler do
 
   describe '#sample' do
     it 'adds a metric containing the process resident memory bytes' do
-      expect(Gitlab::Metrics::System).to receive(:memory_usage).and_return(9000)
+      expect(Gitlab::Metrics::System).to receive(:memory_usage_rss).and_return(9000)
 
       expect(sampler.metrics[:process_resident_memory_bytes]).to receive(:set).with({}, 9000)
 

spec/lib/gitlab/metrics/system_spec.rb

@@ -64,11 +64,11 @@ describe Gitlab::Metrics::System do
       SNIP
     end
 
-    describe '.memory_usage' do
+    describe '.memory_usage_rss' do
       it "returns the process' resident set size (RSS) in bytes" do
         mock_existing_proc_file('/proc/self/status', proc_status)
 
-        expect(described_class.memory_usage).to eq(2527232)
+        expect(described_class.memory_usage_rss).to eq(2527232)
       end
     end
 
@@ -103,9 +103,9 @@ describe Gitlab::Metrics::System do
       mock_missing_proc_file
     end
 
-    describe '.memory_usage' do
+    describe '.memory_usage_rss' do
       it 'returns 0' do
-        expect(described_class.memory_usage).to eq(0)
+        expect(described_class.memory_usage_rss).to eq(0)
       end
     end