Class: OverSIP::PosixMQ

Inherits:
Object
  • Object
show all
Extended by:
Logger
Defined in:
lib/oversip/posix_mq.rb

Class Method Summary collapse

Methods included from Logger

close, fg_system_msg2str, init_logger_mq, load_methods, log_id, syslog_system_msg2str, syslog_user_msg2str

Class Method Details

.create_queue(options = {}) ⇒ Object 



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# File 'lib/oversip/posix_mq.rb', line 7

def self.create_queue options={}
  @log_id = "PosixMQ #{options[:name]}"

  # Queue attributes.
  mq_name = options[:name]
  mq_mode = case options[:mode]
    when :read       then ::IO::RDONLY
    when :write      then ::IO::WRONLY
    when :read_write then ::IO::RDWR
    end
  mq_group = options[:group]
  mq_attr = ::POSIX_MQ::Attr.new
  # NOTE: maximun value for maxmsg is 65536.
  mq_attr.maxmsg  = options[:maxmsg]
  mq_attr.msgsize = options[:msgsize]
  mq_attr.flags   = 0
  mq_attr.curmsgs = 0

  # Delete the queue if it exists.
  begin
    ::POSIX_MQ.unlink mq_name
  rescue ::Errno::ENOENT
  rescue ::Errno::EACCES => e
    ::OverSIP::Launcher.fatal "queue already exists and cannot remove it due file permissions"
  # Kernel has no support for posix message queues.
  rescue ::Errno::ENOSYS => e
    ::OverSIP::Launcher.fatal "the kernel has no support for posix messages queues, enable it (#{e.class}: #{e.message})"
  end

  # Set the UMASK in a way that the group has permission to delete the queue.
  orig_umask = ::File.umask(0007)

  # Change the effective group for the Posix queue. Keep the original
  # group.
  orig_gid = ::Process::GID.eid
  if mq_group
    gid = ::Etc.getgrnam(mq_group).gid
    ::Process::GID.change_privilege(gid)
  end

  # System limits required size (ulimit -q).
  mq_size = case 1.size
    # 32 bits OS.
    when 4 then mq_attr.maxmsg * 4 + mq_attr.maxmsg * mq_attr.msgsize
    # 64 bits OS.
    when 8 then mq_attr.maxmsg * 8 + mq_attr.maxmsg * mq_attr.msgsize
    end

  log_system_info "queue requires #{mq_size} bytes"

  # Set RLIMIT_MSGQUEUE (ulimit) in order to create the queue with required
  # ammount of memory.
  if ( current_rlimit = ::Process.getrlimit(::Process::RLIMIT_MSGQUEUE)[1] ) < mq_size
    log_system_info "incrementing rlimits for 'msgqueue' Posix Message Queues (currently #{current_rlimit} bytes) to #{mq_size} bytes (ulimit -q)"
    begin
      ::Process.setrlimit(::Process::RLIMIT_MSGQUEUE, mq_size, mq_size)
    rescue ::Errno::EPERM
      ::OverSIP::Launcher.fatal "current user has no permissions to increase 'msgqueue' rlimits to #{mq_size} bytes"
    rescue => e
      ::OverSIP::Launcher.fatal e
    end
  else
    log_system_info "rlimits for 'msgqueue' is #{current_rlimit} bytes (>= #{mq_size}), no need to increase it"
  end

  # Create the Posix message queue to write into it.
  # - IO::WRONLY   =>  Just write.
  # - IO::CREAT    =>  Create if it doesn't exist.
  # - IO::EXCL     =>  Raise if the queue already exists.
  # - IO::NONBLOCK =>  Don't block when sending (instead raise Errno::EAGAIN).
  # - mode: 00660  =>  User and group can write and read.
  # - mq_attr      =>  Set maxmsg and msgsize.
  begin
    mq = ::POSIX_MQ.new mq_name, mq_mode | ::IO::CREAT | ::IO::EXCL | ::IO::NONBLOCK, 00660, mq_attr

  # Kernel has no support for posix message queues.
  rescue ::Errno::ENOSYS => e
    ::OverSIP::Launcher.fatal "the kernel has no support for Posix Messages Queues, enable it (#{e.class}: #{e.message})"

  # http://linux.die.net/man/3/mq_open
  #
  # IO_CREAT was specified in oflag, and attr was not NULL, but attr->mq_maxmsg or attr->mq_msqsize was
  # invalid. Both of these fields must be greater than zero. In a process that is unprivileged (does not
  # have the CAP_SYS_RESOURCE capability), attr->mq_maxmsg must be less than or equal to the msg_max
  # limit, and attr->mq_msgsize must be less than or equal to the msgsize_max limit. In addition, even
  # in a privileged process, attr->mq_maxmsg cannot exceed the HARD_MAX limit. (See mq_overview(7) for
  # details of these limits.)
  rescue ::Errno::EINVAL
    log_system_warn "cannot set queue attributes due to user permissions, using system default values"
    mq = ::POSIX_MQ.new mq_name, mq_mode | ::IO::CREAT | ::IO::NONBLOCK, 00660
  rescue ::Errno::ENOMEM => e
    ::OverSIP::Launcher.fatal "insufficient memory (#{e.class}: #{e.message})"
  rescue ::Errno::EMFILE => e
    ::OverSIP::Launcher.fatal "the process already has the maximum number of files and message queues open (#{e.class}: #{e.message})"
  rescue Errno::ENFILE => e
    ::OverSIP::Launcher.fatal "the system limit on the total number of open files and message queues has been reached (#{e.class}: #{e.message})"
  rescue ::Errno::ENOSPC => e
    ::OverSIP::Launcher.fatal "insufficient space for the creation of a new message queue, probably occurred because the 'queues_max' limit was encountered (#{e.class}: #{e.message})"

  end

  # Recover the original Umask settings.
  ::File.umask(orig_umask)

  # Recover the original effective group.
  ::Process::GID.change_privilege(orig_gid)  if mq_group

  if mq.attr.maxmsg == mq_attr.maxmsg and mq.attr.msgsize == mq_attr.msgsize
    log_system_info "maxmsg=#{mq.attr.maxmsg}, msgsize=#{mq.attr.msgsize}"
  else
    log_system_warn "maxmsg=#{mq.attr.maxmsg}, msgsize=#{mq.attr.msgsize}, " \
                "but recommended values are maxmsg=#{mq_attr.maxmsg}, msgsize=#{mq_attr.msgsize}"
  end

  mq
end