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# frozen_string_literal: true
module Gitlab
module Metrics
# Module for gathering system/process statistics such as the memory usage.
#
# This module relies on the /proc filesystem being available. If /proc is
# not available the methods of this module will be stubbed.
module System
PROC_STATUS_PATH = '/proc/self/status'
PROC_SMAPS_ROLLUP_PATH = '/proc/self/smaps_rollup'
PROC_LIMITS_PATH = '/proc/self/limits'
PROC_FD_GLOB = '/proc/self/fd/*'
PRIVATE_PAGES_PATTERN = /^(Private_Clean|Private_Dirty|Private_Hugetlb):\s+(?<value>\d+)/.freeze
PSS_PATTERN = /^Pss:\s+(?<value>\d+)/.freeze
RSS_PATTERN = /VmRSS:\s+(?<value>\d+)/.freeze
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_rss
sum_matches(PROC_STATUS_PATH, rss: RSS_PATTERN)[:rss].kilobytes
end
# Returns the current process' USS/PSS (unique/proportional set size) in bytes.
def self.memory_usage_uss_pss
sum_matches(PROC_SMAPS_ROLLUP_PATH, uss: PRIVATE_PAGES_PATTERN, pss: PSS_PATTERN)
.transform_values(&:kilobytes)
end
def self.file_descriptor_count
Dir.glob(PROC_FD_GLOB).length
end
def self.max_open_file_descriptors
sum_matches(PROC_LIMITS_PATH, max_fds: MAX_OPEN_FILES_PATTERN)[:max_fds]
end
def self.cpu_time
Process.clock_gettime(Process::CLOCK_PROCESS_CPUTIME_ID, :float_second)
end
# Returns the current real time in a given precision.
#
# Returns the time as a Float for precision = :float_second.
def self.real_time(precision = :float_second)
Process.clock_gettime(Process::CLOCK_REALTIME, precision)
end
# Returns the current monotonic clock time as seconds with microseconds precision.
#
# Returns the time as a Float.
def self.monotonic_time
Process.clock_gettime(Process::CLOCK_MONOTONIC, :float_second)
end
def self.thread_cpu_time
# Not all OS kernels are supporting `Process::CLOCK_THREAD_CPUTIME_ID`
# Refer: https://gitlab.com/gitlab-org/gitlab/issues/30567#note_221765627
return unless defined?(Process::CLOCK_THREAD_CPUTIME_ID)
Process.clock_gettime(Process::CLOCK_THREAD_CPUTIME_ID, :float_second)
end
def self.thread_cpu_duration(start_time)
end_time = thread_cpu_time
return unless start_time && end_time
end_time - start_time
end
# Given a path to a file in /proc and a hash of (metric, pattern) pairs,
# sums up all values found for those patterns under the respective metric.
def self.sum_matches(proc_file, **patterns)
results = patterns.transform_values { 0 }
begin
File.foreach(proc_file) do |line|
patterns.each do |metric, pattern|
match = line.match(pattern)
value = match&.named_captures&.fetch('value', 0)
results[metric] += value.to_i
end
end
rescue Errno::ENOENT
# This means the procfile we're reading from did not exist;
# this is safe to ignore, since we initialize each metric to 0
end
results
end
end
end
end
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