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NAME
os_sup - Interface to OS System Messages
DESCRIPTION
os_sup is a process providing a message passing service from the operating 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 suitable 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 syslogd. 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 nteventlog(3erl). Note that the
start functions of nteventlog does not need to be used, as 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, Severity, 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 Erlang. 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 messages from certain applications, the
version number of the application may have to be accounted for. This is what the NT
event viewer calls "source".
Severity = string():
One of "Error", "Warning", "Informational", "Audit_Success", "Audit_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 disabled) inside (true) or
outside (false) os_sup. For backwards compatibility 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 contains 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 arguments 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 contains 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.