The syslog-ng OSE application can automatically execute scripts when it is started, and can include the output of such script in the configuration file. To create and use a script that generates a part of the syslog-ng OSE configuration file (actually, a configuration block), complete the following steps. The steps include examples for collecting Apache access log files (access.log) from subdirectories, but you can create any script that creates a valid syslog-ng OSE configuration snippet.
Navigate to the directory where you have installed syslog-ng OSE (for example, /opt/syslog-ng/share/include/scl/), and create a new directory, for example, apache-access-logs. The name of the directory will be used in the syslog-ng OSE configuration file as well, so use a descriptive name.
Create a file called plugin.conf in this new directory.
Edit the plugin.conf file and add the following line:
@module confgen context(source) name(<directory-name>) exec("`scl-root`/<directory-name>/<my-script>")
Replace <directory-name> with the name of the directory (for example, apache-access-logs), and <my-script> with the filename of your script (for example, apache-access-logs.sh). You can reference the script in your syslog-ng OSE configuration file as a configuration block using the value name option.
The context option determines the type of the configuration snippet that the script generates, and must be one of the following: destination, filter, log, parser, rewrite, root, source. The root blocks can be used in the "root" context of the configuration file, that is, outside any other statements. In the example, context(source) means that the output of the script will be used within a source statement.
Write a script that generates the output you need, and formats it to a configuration snippet that syslog-ng OSE can use. The filename of the script must match with the filename used in plugin.conf, for example, apache-access-logs.sh.
The following example checks the /var/log/apache2/ directory and its subdirectories, and creates a source driver for every directory that contains an access.log file.
#!/bin/bash for i in `find /var/log/apache2/ -type d`; do echo "file(\"$i/access.log\" flags(no-parse) program-override(\"apache2\"));"; done;
The script generates an output similar to this one, where service* is the actual name of a subdirectory:
file("/var/log/apache2/service1/access.log" flags(no-parse) program-override("apache2")); file("/var/log/apache2/service2/access.log" flags(no-parse) program-override("apache2"));
Include the plugin.conf file in the syslog-ng.conf file — or a file already included into syslog-ng.conf. Version
Add the block you defined in the plugin.conf file to your syslog-ng OSE configuration file. You can reference the block using the value of the name option from the plugin.conf file, followed by parentheses, for example, apache-access-logs(). Make sure to use the block in the appropriate context of the configuration file, for example, within a source statement if the value of the context option in the plugin.conf file is source.
@include "scl.conf" ... source s_apache { file("/var/log/apache2/access.log" flags(no-parse) program-override("apache2")); file("/var/log/apache2/error.log" flags(no-parse) program-override("apache2")); file("/var/log/apache2/ssl.log" flags(no-parse) program-override("apache2")); apache-access-logs(); }; log { source(s_apache); destination(d_central); }; ...
Check if your modified syslog-ng OSE configuration file is syntactically correct using the syslog-ng --syntax-only command.
If your modified configuration is syntactically correct, load the new configuration file using the syslog-ng-ctl reload command.
You can extend and customize syslog-ng OSE easily by writing destinations, parsers, template functions, and sources in Python.
Instead of writing Python code into your syslog-ng OSE configuration file, you can store the Python code for your Python object in an external file. That way, it is easier to write, maintain, and debug the code. You can store the Python code in any directory in your system, but make sure to include it in your Python path.
When referencing a Python class from an external file in the class() option of a Python block in the syslog-ng OSE configuration file, the class name must include the name of the Python file containing the class, without the path and the .py extension. For example, if the MyDestination class is available in the /etc/syslog-ng/etc/pythonexample.py file, use class("pythonexample.MyDestination"):
destination d_python_to_file { python( class("pythonexample.MyDestination") ); }; log { source(src); destination(d_python_to_file); };
If you store the Python code in a separate Python file and only include it in the syslog-ng OSE configuration file, make sure that the PYTHON_PATH environment variable includes the path to the Python file, and export the PYTHON_PATH environment variable. For example, if you start syslog-ng OSE manually from a terminal and you store your Python files in the /opt/syslog-ng/etc directory, use the following command: export PYTHONPATH=/opt/syslog-ng/etc
In production, when syslog-ng OSE starts on boot, you must configure your startup script to include the Python path. The exact method depends on your operating system. For recent Red Hat Enterprise Linux, Fedora, and CentOS distributions that use systemd, the systemctl command sources the /etc/sysconfig/syslog-ng file before starting syslog-ng OSE. (On openSUSE and SLES, /etc/sysconfig/syslog file.) Append the following line to the end of this file: PYTHONPATH="<path-to-your-python-file>", for example, PYTHONPATH="/opt/syslog-ng/etc"
To help debugging and troubleshooting your Python code, you can send log messages to the internal() source of syslog-ng OSE. For details, see Logging from your Python code.
You can extend and customize syslog-ng OSE easily by writing destinations, parsers, template functions, and sources in Python.
To debug and troubleshoot your Python code, syslog-ng OSE allows you to use the logger() method to send log messages to the internal() source of syslog-ng OSE. That way the diagnostic messages of your Python code are treated the same way as other such log messages of syslog-ng OSE. This has the following benefits:
The logger() method respects the log level settings of syslog-ng OSE. You can write error, warning, info, debug, and trace level messages.
You can follow what your Python code is doing even if syslog-ng OSE is running as a daemon in the background.
Logging to the internal() source is available in syslog-ng OSE version
To send log messages to the internal() source from Python
Add the following import to your Python code:
import syslogng
Create a logger object:
logger = syslogng.Logger()
Use the logger object in your Python code, for example:
logger.info("This is a sample log message send from the Python code.")
You can use the following log levels: logger.error, logger.warning, logger.info, logger.debug, logger.trace
Make sure that your syslog-ng OSE configuration includes the internal() source, for example:
source s_internal { internal(); }; destination d_internal { file("/var/log/internal.txt"); }; log {source(s_internal); destination(d_internal); };
default-network-drivers: Receive and parse common syslog messages
default-network-drivers() source options
internal: Collecting internal messages
file: Collecting messages from text files
Notes on reading kernel messages
wildcard-file: Collecting messages from multiple text files
wildcard-file() source options
linux-audit: Collecting messages from Linux audit logs
network: Collecting messages using the RFC3164 protocol (network() driver)
nodejs: Receiving JSON messages from nodejs applications
mbox: Converting local e-mail messages to log messages
osquery: Collect and parse osquery result logs
pipe: Collecting messages from named pipes
pacct: Collecting process accounting logs on Linux
program: Receiving messages from external applications
python: writing server-style Python sources
python() and python-fetcher() source options
python-fetcher: writing fetcher-style Python sources
sun-streams: Collecting messages on Sun Solaris
syslog: Collecting messages using the IETF syslog protocol (syslog() driver)
system: Collecting the system-specific log messages of a platform
systemd-journal: Collecting messages from the systemd-journal system log storage
systemd-journal() source options
systemd-syslog: Collecting systemd messages using a socket
tcp, tcp6, udp, udp6: Collecting messages from remote hosts using the BSD syslog protocol— OBSOLETE
tcp(), tcp6(), udp() and udp6() source options: OBSOLETE
unix-stream, unix-dgram: Collecting messages from UNIX domain sockets
UNIX credentials and other metadata
unix-stream() and unix-dgram() source options
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