syslog-ng Open Source Edition 3.18 - Administration Guide

Declaration:

Python sources consist of two parts. The first is a syslog-ng OSE source object that you define in your syslog-ng OSE configuration and use in the log path. This object references a Python class, which is the second part of the Python source. The Python class receives or fetches the log messages, and can do virtually anything that you can code in Python. You can either embed the Python class into your syslog-ng OSE configuration file, or store it in an external Python file.

source <name_of_the_python_source>{
    python-fetcher(
        class("<name_of_the_python_class_executed_by_the_source>")
    );
};

python {
from syslogng import LogFetcher
from syslogng import LogMessage

class <name_of_the_python_class_executed_by_the_source>(LogFetcher):
    def init(self, options): # optional
        print("init")
        print(options)
        return True

    def deinit(self): # optional
        print("deinit")

    def open(self): # optional
        print("open")
        return True

    def fetch(self): # mandatory
        print("fetch")
        # return LogFetcher.FETCH_ERROR,
        # return LogFetcher.FETCH_NOT_CONNECTED,
        return LogFetcher.FETCH_SUCCESS, msg

    def request_exit(self):
        print("request_exit")
        # If your fetching method is blocking, do something to break it
        # For example, if it reads a socket: socket.shutdown()

    def close(self): # optional
        print("close")
};

Methods of the python-fetcher() source

Fetcher-style Python sources must be inherited from the syslogng.LogFetcher class, and must implement at least the fetch method. Multiple inheritance is allowed, but only for pure Python super classes.

For fetcher-style Python sources, syslog-ng OSE handles the event loop and the scheduling automatically. You can use simple blocking server/client libraries to receive or fetch logs.

You can retrieve messages using the fetch() method.

Limitations:

• The snmptrap() source has only the options listed in snmptrap() source options. Other options commonly available in other source drivers are not supported.

• In addition to traps, the log of snmptrapd may contain other messages (for example, daemon start/stop information, debug logs) as well. Currently syslog-ng OSE discards these messages.

• The syslog-ng OSE application cannot resolve OIDs, you have to configure snmptrapd to do so. Note that because of a bug, if snmptrapd does not escape String values in the VarBindList if it can resolve an OID to a symbolic name. As a result, syslog-ng OSE cannot process traps that contain the = in the value of the string. To overcome this problem, disable resolving OIDs in snmptrapd. For details, see the documentation of snmptrapd.

• The colon (:) character is commonly used in SNMP traps. However, this character cannot be used in the name of syslog-ng OSE macros (name-value pairs). Therefore, the syslog-ng OSE application automatically replaces all consecutive : characters with a single underscore (_) character. For example, you can reference the value of the NET-SNMP-EXAMPLES-MIB::netSnmpExampleString key using the ${NET-SNMP-EXAMPLES-MIB_netSnmpExampleString} macro.

  Note that this affects only name-value pairs (macros). The generated message always contains the original name of the key.

Prerequisites:

• Configure snmptrapd to log into a file.

• If you use SMIv1 traps, include the following format string in the configuration file of snmptrapd:

  format1 %.4y-%.2m-%.2l %.2h:%.2j:%.2k %B [%b]: %N\n\t%W Trap (%q) Uptime: %#T\n%v\n

• If you use SMIv2 traps, use the default format. The snmptrap() source of syslog-ng OSE expects this default format:

  format2 %.4y-%.2m-%.2l %.2h:%.2j:%.2k %B [%b]:\n%v\n

• Beacause of an snmptrapd bug, if you specify the filename in the configuration file with logOption, you must also specify another output as a command line argument (-Lf, -Ls). Otherwise, snmptrapd will not apply the the trap format.

To use the snmptrap() driver, the scl.conf file must be included in your syslog-ng OSE configuration:

@include "scl.conf"

filename()

Description: The log file of snmptrapd. The syslog-ng OSE application reads the traps from this file.

In addition to traps, the log of snmptrapd may contain other messages (for example, daemon start/stop information, debug logs) as well. Currently syslog-ng OSE discards these messages.

prefix()

Description: Insert a prefix before the name part of the parsed name-value pairs to help further processing. For example:

• To insert the my-parsed-data. prefix, use the prefix(my-parsed-data.) option.

• To refer to a particular data that has a prefix, use the prefix in the name of the macro, for example, ${my-parsed-data.name}.

• If you forward the parsed messages using the IETF-syslog protocol, you can insert all the parsed data into the SDATA part of the message using the prefix(.SDATA.my-parsed-data.) option.

Names starting with a dot (for example, .example) are reserved for use by syslog-ng OSE. If you use such a macro name as the name of a parsed value, it will attempt to replace the original value of the macro (note that only soft macros can be overwritten, see Hard vs. soft macros for details). To avoid such problems, use a prefix when naming the parsed values, for example, prefix(my-parsed-data.)

Default value: .snmp. option.

set-message-macro()

Description: The snmptrap() source automatically parses the traps into name-value pairs, so you can handle the content of the trap as a structured message. Consequently, you might not even need the ${MESSAGE} part of the log message. If set-message-macro() is set to no, syslog-ng OSE leaves the ${MESSAGE} part empty. If set-message-macro() is set to yes, syslog-ng OSE generates a regular log message from the trap.

Declaration:

sun-streams(<name_of_the_streams_device> door(<filename_of_the_door>));