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 3.20 and later.
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); };
source: Read, receive, and collect log messages
A source is where syslog-ng receives log messages. Sources consist of one or more drivers, each defining where and how messages are received.
To define a source, add a source statement to the syslog-ng configuration file using the following syntax:
source <identifier> {
source-driver(params); source-driver(params); ...
};
Example: A simple source statement
The following source statement receives messages on the TCP port 1999 of the interface having the 10.1.2.3 IP address.
source s_demo_tcp {
network(ip(10.1.2.3) port(1999));
};
Example: A source statement using two source drivers
The following source statement receives messages on the 1999 TCP port and the 1999 UDP port of the interface having the 10.1.2.3 IP address.
source s_demo_two_drivers {
network(ip(10.1.2.3) port(1999));
network(ip(10.1.2.3) port(1999) transport("udp"));
};
Example: Setting default priority and facility
If the message received by the source does not have a proper syslog header, you can use the default-facility() and default-priority() options to set the facility and priority of the messages. Note that these values are applied only to messages that do not set these parameters in their header.
source headerless_messages { network(default-facility(syslog) default-priority(emerg)); };
Define a source only once. The same source can be used in several log paths. Duplicating sources causes syslog-ng to open the source (TCP/IP port, file, and so on) more than once, which might cause problems. For example, include the /dev/log file source only in one source statement, and use this statement in more than one log path if needed.
To collect log messages on a specific platform, it is important to know how the native syslogd communicates on that platform. The following table summarizes the operation methods of syslogd on some of the tested platforms:
Table 6: Communication methods used between the applications and syslogd
| Linux |
A SOCK_DGRAM unix socket named /dev/log. Newer distributions that use systemd collect log messages into a journal file. |
| BSD flavors |
A SOCK_DGRAM unix socket named /var/run/log. |
| Solaris (2.5 or below) |
An SVR4 style STREAMS device named /dev/log. |
| Solaris (2.6 or above) |
In addition to the STREAMS device used in earlier versions, 2.6 uses a new multithreaded IPC method called door. By default the door used by syslogd is /etc/.syslog_door. |
| HP-UX 11 or later |
HP-UX uses a named pipe called /dev/log that is padded to 2048 bytes, for example, source s_hp-ux {pipe ("/dev/log" pad-size(2048)}. |
| AIX 5.2 and 5.3 |
A SOCK_STREAM or SOCK_DGRAM unix socket called /dev/log. |
Each possible communication mechanism has a corresponding source driver in syslog-ng. For example, to open a unix socket with SOCK_DGRAM style communication use the driver unix-dgram. The same socket using the SOCK_STREAM style — as used under Linux — is called unix-stream.
Example: Source statement on a Linux based operating system
The following source statement collects the following log messages:
-
internal(): Messages generated by syslog-ng.
-
network(transport("udp")): Messages arriving to the 514/UDP port of any interface of the host.
-
unix-dgram("/dev/log");: Messages arriving to the /dev/log socket.
source s_demo {
internal();
network(transport("udp"));
unix-dgram("/dev/log");
};
The following table lists the source drivers available in syslog-ng.
Table 7: Source drivers available in syslog-ng
| file() |
Opens the specified file and reads messages. |
| internal() |
Messages generated internally in syslog-ng. |
| network() |
Receives messages from remote hosts using the BSD-syslog protocol over IPv4 and IPv6. Supports the TCP, UDP, and TLS network protocols. |
| nodejs() |
Receives JSON messages from nodejs applications. |
| mbox() |
Read email messages from local mbox files, and convert them to multiline log messages. |
| osquery() |
Run osquery queries, and convert their results into log messages. |
| pacct() |
Reads messages from the process accounting logs on Linux. |
| pipe() |
Opens the specified named pipe and reads messages. |
| program() |
Opens the specified application and reads messages from its standard output. |
| python() and python-fetcher() |
Receive or fetch messages using a custom source written in Python. |
| snmptrap() |
Read and parse the SNMP traps of the Net-SNMP's snmptrapd application. |
| sun-stream(), sun-streams() |
Opens the specified STREAMS device on Solaris systems and reads incoming messages. |
| syslog() |
Listens for incoming messages using the new IETF-standard syslog protocol. |
| system() |
Automatically detects which platform syslog-ng OSE is running on, and collects the native log messages of that platform. |
| systemd-journal() |
Collects messages directly from the journal of platforms that use systemd. |
| systemd-syslog() |
Collects messages from the journal using a socket on platforms that use systemd. |
| unix-dgram() |
Opens the specified unix socket in SOCK_DGRAM mode and listens for incoming messages. |
| unix-stream() |
Opens the specified unix socket in SOCK_STREAM mode and listens for incoming messages. |
| stdin() |
Collects messages from the standard input stream. |
| wildcard-file() |
Reads messages from multiple files and directories. |
The default-network-drivers() source is a special source that uses multiple source drivers to receive and parse several different types of syslog messages from the network. Available in version 3.16 and later.
To use the default-network-drivers() source, the scl.conf file must be included in your syslog-ng OSE configuration:
@include "scl.conf"
Also, make sure that your SELinux, AppArmor, and firewall settings permit syslog-ng Open Source Edition to access the ports where you want to receive messages, and that no other application is using these ports. By default, the default-network-drivers() source accepts messages on the following ports:
-
514, both TCP and UDP, for RFC3164 (BSD-syslog) formatted traffic
-
601 TCP, for RFC5424 (IETF-syslog) formatted traffic
-
6514 TCP, for TLS-encrypted traffic
In addition to receiving messages on different ports and in different formats, this source tries to parse the messages automatically. If successful, it sets the ${.app.name} name-value pair to the name of the application that sent the log message. Currently it uses the following procedures.
|
|
Caution:
If you do not configure the TLS keys to dislay to the clients, syslog-ng OSE cannot accept encrypted connections. The application starts and listens on TCP:6514, and can receive messages on other ports, but will display a warning messages about missing keys. |
Parsing RFC3164-formatted messages
For RFC3164-formatted messages (that is, messages received on the ports set in options udp-port() and tcp-port() which default to port 514), syslog-ng OSE attempts to use the following parsers. If a parser cannot parse the message, it passes the original message to the next parser.
-
Parse the incoming raw message as a message from a Cisco device.
-
Parse the incoming message as an RFC3164-formatted message.
-
If the incoming message was sent by a syslog-ng OSE client using the syslog-ng() destination, parse its fields as a syslog-ng message.
The Enterprise-wide message model or EWMM allows you to deliver structured messages from the initial receiving syslog-ng component right up to the central log server, through any number of hops. It does not matter if you parse the messages on the client, on a relay, or on the central server, their structured results will be available where you store the messages. Optionally, you can also forward the original raw message as the first syslog-ng component in your infrastructure has received it, which is important if you want to forward a message for example, to a SIEM system. To make use of the enterprise-wide message model, you have to use the syslog-ng() destination on the sender side, and the default-network-drivers() source on the receiver side.
-
Otherwise, apply the application adapters if the message was sent from an application that already has a specific parser in syslog-ng OSE (for example, Splunk Common Information Model (CIM), iptables, or sudo).
Parsing RFC5424-formatted messages
For RFC5424-formatted messages (that is, messages received on the ports set in options rfc5424-tls-port() and rfc5424-tcp-port(), which default to port 601 and 6514), syslog-ng OSE parses the message according to RFC5424, then attempts apply the application adapters if the message was sent from an application that already has a specific parser in syslog-ng OSE (for example, Splunk Common Information Model (CIM), iptables, or sudo).
Example: Using the default-network-drivers() driver
The following example uses only the default settings.
source s_network {
default-network-drivers();
};
The following example can receive TLS-encrypted connections on the default port (port 6514).
source s_network {
default-network-drivers(
tls(
key-file("/path/to/ssl-private-key")
cert-file("/path/to/ssl-cert")
)
);
};
