Module: OsCtld::CGroup

Includes:
OsCtl::Lib::Utils::Log
Defined in:
lib/osctld/cgroup.rb,
lib/osctld/cgroup/param.rb

Defined Under Namespace

Classes: ContainerParams, Param, Params

Constant Summary collapse

FS = 
'/sys/fs/cgroup'

Class Method Summary collapse

Class Method Details

.freeze_tree(path) ⇒ Object

Freeze cgroup at path

Parameters:

  • path (String) 


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# File 'lib/osctld/cgroup.rb', line 173

def self.freeze_tree(path)
  abs_path = File.join(FS, real_subsystem('freezer'), path)
  state = File.join(abs_path, 'freezer.state')

  begin
    File.open(state, 'w') { |f| f.write('FROZEN') }
  rescue SystemCallError => e
    log(:warn, "Unable to freeze #{abs_path}: #{e.message} (#{e.class})")
  end
end

.inherit_param(base, cgroup, param) ⇒ Object

Inherit cgroup parameter from the parent cgroup

The parameter is considered to be set if it isn't empty. If the parent cgroup does not have the parameter set, it is inherited from its own parent and so on, all the way to the root cgroup defined by `base`. All parents will inherit the parameter as well.

Parameters:

  • base (String) —

    absolute path to the root cgroup

  • cgroup (String) —

    absolute path of the created cgroup

  • param (String) —

    parameter name



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# File 'lib/osctld/cgroup.rb', line 115

def self.inherit_param(base, cgroup, param)
  v = File.read(File.join(cgroup, param)).strip
  return v unless v.empty?
  fail "parameter #{param} not set in root cgroup #{base}" if base == cgroup

  v = inherit_param(base, File.dirname(cgroup), param)
  set_param(File.join(cgroup, param), [v])
  v
end

.init_cgroup(type, base, cgroup) ⇒ Object

Initialize cgroup after it was created.

This is used to ensure that `cpuset` cgroups have parameters `cpuset.cpus` and `cpuset.mems` set.

Parameters:

  • type (String) —

    cgroup subsystem

  • base (String) —

    absolute path to the root cgroup

  • cgroup (String) —

    absolute path of the created cgroup



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# File 'lib/osctld/cgroup.rb', line 96

def self.init_cgroup(type, base, cgroup)
  case type
  when 'cpuset'
    inherit_param(base, cgroup, 'cpuset.cpus')
    inherit_param(base, cgroup, 'cpuset.mems')
    set_param(File.join(cgroup, 'cgroup.clone_children'), ['1'])
  end
end

.mkpath(type, path, chown: nil, attach: false) ⇒ Boolean

Create CGroup a path, optionally chowning the last CGroup or attaching the current process into it.

For example, `path` `['osctl', 'subgroup', 'subsubgroup']` will create `osctl/subgroup/subsubgroup` in the chosen subsystem. If `chown` or `attach` is set, it has an effect on the last group, i.e. `subsubgroup`,

Parameters:

  • type (String) —

    subsystem

  • path (Array<String>) —

    paths to create

  • chown (Integer) (defaults to: nil) —

    chown the last group to `chown`:`chown`

  • attach (Boolean) (defaults to: false) —

    attach the current process to the last group

Returns:

  • (Boolean) —

    `true` if the last component was created, `false` if it already existed



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# File 'lib/osctld/cgroup.rb', line 36

def self.mkpath(type, path, chown: nil, attach: false)
  base = File.join(FS, type)
  tmp = []
  created = false

  path.each do |name|
    tmp << name
    cgroup = File.join(base, *tmp)

    next if Dir.exist?(cgroup)

    # Prevent an error if multiple processes attempt to create this cgroup
    # at a time
    begin
      Dir.mkdir(cgroup)
      created = true

    rescue Errno::EEXIST
      created = false
      next
    end

    init_cgroup(type, base, cgroup)
  end

  cgroup = File.join(base, *path)

  if chown
    File.chown(chown, chown, cgroup)
    File.chown(chown, chown, File.join(cgroup, 'cgroup.procs'))

    if type == 'unified'
      %w(cgroup.threads cgroup.subtree_control).each do |f|
        File.chown(chown, chown, File.join(cgroup, f))
      end
    end
  end

  if attach
    ['tasks', 'cgroup.procs'].each do |tasks|
      tasks_path = File.join(cgroup, tasks)
      next unless File.exist?(tasks_path)

      File.open(tasks_path, 'a') do |f|
        f.write("#{Process.pid}\n")
      end
    end
  end

  created
end

.real_subsystem(subsys) ⇒ Object

Convert a single subsystem name to the mountpoint name, because some CGroup subsystems are mounted in a shared mountpoint.



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# File 'lib/osctld/cgroup.rb', line 11

def self.real_subsystem(subsys)
  return 'cpu,cpuacct' if %w(cpu cpuacct).include?(subsys)
  return 'net_cls,net_prio' if %w(net_cls net_prio).include?(subsys)
  subsys
end

.rmpath(subsystem, path) ⇒ Object

Remove cgroup path

Parameters:

  • subsystem (String)
  • path (String) —

    path to remove, relative to the subsystem



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# File 'lib/osctld/cgroup.rb', line 147

def self.rmpath(subsystem, path)
  abs_path = File.join(FS, subsystem, path)

  # Remove subdirectories recursively
  Dir.entries(abs_path).each do |dir|
    next if dir == '.' || dir == '..'
    next unless Dir.exist?(File.join(abs_path, dir))

    rmpath(subsystem, File.join(path, dir))
  end

  # Remove directory
  Dir.rmdir(abs_path)

rescue Errno::ENOENT
  # pass
end

.rmpath_all(path) ⇒ Object

Remove cgroup path in all subsystems

Parameters:

  • path (String) —

    path to remove, relative to subsystem



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# File 'lib/osctld/cgroup.rb', line 167

def self.rmpath_all(path)
  subsystems.each { |subsys| rmpath(subsys, path) }
end

.set_param(path, value) ⇒ Object

Raises:



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# File 'lib/osctld/cgroup.rb', line 125

def self.set_param(path, value)
  raise CGroupFileNotFound.new(path, value) unless File.exist?(path)

  value.each do |v|
    log(:info, :cgroup, "Set #{path}=#{v}")

    begin
      File.write(path, v.to_s)

    rescue => e
      log(
        :warn,
        :cgroup,
        "Unable to set #{path}=#{v}: #{e.message}"
      )
    end
  end
end

.subsystems ⇒ Array<String>

Returns a list of mounted CGroup subsystems on the system

Returns:

  • (Array<String>) 


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# File 'lib/osctld/cgroup.rb', line 19

def self.subsystems
  Dir.entries(FS) - ['.', '..']
end

.thaw_tree(path) ⇒ Object

Thaw all frozen cgroups under path

Parameters:

  • path (String) 


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# File 'lib/osctld/cgroup.rb', line 186

def self.thaw_tree(path)
  abs_path = File.join(FS, real_subsystem('freezer'), path)

  Dir.entries(abs_path).each do |dir|
    next if dir == '.' || dir == '..'
    next unless Dir.exist?(File.join(abs_path, dir))

    thaw_tree(File.join(path, dir))
  end

  state = File.join(abs_path, 'freezer.state')

  begin
    if %w(FREEZING FROZEN).include?(File.read(state).strip)
      log(:info, "Thawing #{abs_path}")
      File.open(state, 'w') { |f| f.write('THAWED') }
    end
  rescue SystemCallError => e
    log(:warn, "Unable to thaw #{abs_path}: #{e.message} (#{e.class})")
  end
end