os_sup(3erl) Erlang Module Definition os_sup(3erl)
NAME
os_sup - Interface to OS System Messages
DESCRIPTION
os_sup is a process providing a message passing service from the oper-
ating system to the error logger in the Erlang runtime system. It is
part of the OS_Mon application, see os_mon(7). Available for Solaris
and Windows.
Messages received from the operating system results in an user defined
callback function being called. This function can do whatever filtering
and formatting is necessary and then deploy any type of logging suit-
able for the user's application.
SOLARIS OPERATION
The Solaris (SunOS 5.x) messages are retrieved from the syslog-daemon,
syslogd.
Enabling the service includes actions which require root privileges,
such as change of ownership and file privileges of an executable binary
file, and creating a modified copy of the configuration file for sys-
logd. When os_sup is terminated, the service must be disabled, meaning
the original configuration must be restored. Enabling/disabling can be
done either outside or inside os_sup, see Configuration below.
Warning:
This process cannot run in multiple instances on the same hardware.
OS_Mon must be configured to start os_sup on one node only if two or
more Erlang nodes execute on the same machine.
The format of received events is not defined.
WINDOWS OPERATION
The Windows messages are retrieved from the eventlog file.
The nteventlog module is used to implement os_sup. See ntevent-
log(3erl). Note that the start functions of nteventlog does not need to
be used, in this case the process is started automatically as part of
the OS_Mon supervision tree.
OS messages are formatted as a tuple {Time, Category, Facility, Sever-
ity, Message}:
Time = {MegaSecs, Secs, MicroSecs}:
A time stamp as returned by the BIF now().
Category = string():
Usually one of "System", "Application" or "Security". Note that the
NT eventlog viewer has another notion of category, which in most
cases is totally meaningless and therefore not imported into Er-
lang. What is called a category here is one of the main three types
of events occurring in a normal NT system.
Facility = string():
The source of the message, usually the name of the application that
generated it. This could be almost any string. When matching mes-
sages from certain applications, the version number of the applica-
tion may have to be accounted for. This is what the NT event viewer
calls "source".
Severity = string():
One of "Error", "Warning", "Informational", "Audit_Success", "Au-
dit_Faulure" or, in case of a currently unknown Windows NT version
"Severity_Unknown".
Message = string():
Formatted exactly as it would be in the NT eventlog viewer. Binary
data is not imported into Erlang.
CONFIGURATION
os_sup_mfa = {Module, Function, Args}:
The callback function to use. Module and Function are atoms and
Args is a list of terms. When an OS message Msg is received, this
function is called as apply(Module, Function, [Msg | Args]).
Default is {os_sup, error_report, [Tag]} which will send the event
to the error logger using error_logger:error_report(Tag, Msg). Tag
is the value of os_sup_errortag, see below.
os_sup_errortag = atom():
This parameter defines the error report type used when messages are
sent to error logger using the default callback function. Default
is std_error, which means the events are handled by the standard
event handler.
os_sup_enable = bool():
Solaris only. Defines if the service should be enabled (and dis-
abled) inside (true) or outside (false) os_sup. For backwards com-
patibility reasons, the default is true. The recommended value is
false, as the Erlang emulator should normally not be run with root
privileges, as is required for enabling the service.
os_sup_own = string():
Solaris only. Defines the directory which contains the backup copy
and the Erlang specific configuration files for syslogd, and a
named pipe to receive the messages from syslogd. Default is "/etc".
os_sup_syslogconf = string():
Solaris only. Defines the full name of the configuration file for
syslogd. Default is "/etc/syslog.conf".
EXPORTS
enable() -> ok | {error, Res}
enable(Dir, Conf) -> ok | {error, Error}
Types:
Dir = Conf = Res = string()
Enables the os_sup service. Needed on Solaris only.
If the configuration parameter os_sup_enable is false, this
function is called automatically by os_sup, using the values of
os_sup_own and os_sup_syslogconf as arguments.
If os_sup_enable is true, this function must be called before
OS_Mon/os_sup is started. Dir defines the directory which con-
tains the backup copy and the Erlang specific configuration
files for syslogd, and a named pipe to receive the messages from
syslogd. Defaults to "/etc". Conf defines the full name of the
configuration file for syslogd. Default is "/etc/syslog.conf".
Results in a OS call to:
<PRIVDIR>/bin/mod_syslog otp Dir Conf
where <PRIVDIR> is the priv directory of OS_Mon,
code:priv_dir(os_mon).
Returns ok if this yields the expected result "0", and {error,
Res} if it yields anything else.
Note:
This function requires root privileges to succeed.
disable() -> ok | {error, Res}
disable(Dir, Conf) -> ok | {error, Error}
Types:
Dir = Conf = Res = string()
Disables the os_sup service. Needed on Solaris only.
If the configuration parameter os_sup_enable is false, this
function is called automatically by os_sup, using the same argu-
ments as when enable/2 was called.
If os_sup_enable is true, this function must be called after
OS_Mon/os_sup is stopped. Dir defines the directory which con-
tains the backup copy and the Erlang specific configuration
files for syslogd, and a named pipe to receive the messages from
syslogd. Defaults to "/etc". Conf defines the full name of the
configuration file for syslogd. Default is "/etc/syslog.conf".
Results in a OS call to:
<PRIVDIR>/bin/mod_syslog nootp Dir Conf
where <PRIVDIR> is the priv directory of OS_Mon,
code:priv_dir(os_mon).
Returns ok if this yields the expected result "0", and {error,
Res} if it yields anything else.
Note:
This function requires root privileges to succeed.
SEE ALSO
error_logger(3erl), os_mon(3erl)
syslogd(1M), syslog.conf(5) in the Solaris documentation.
Ericsson AB os_mon 2.5.2 os_sup(3erl)