syslog-ng Premium Edition 7.0.32 - Administration Guide

This driver sends messages to a named pipe like /dev/xconsole.

The pipe() destination has the following options:

flags()

Type:	no-multi-line, syslog-protocol
Default:	empty set

Description: Flags influence the behavior of the destination driver.

no-multi-line: The no-multi-line flag disables line-breaking in the messages: the entire message is converted to a single line.
syslog-protocol: The syslog-protocol flag instructs the driver to format the messages according to the new IETF syslog protocol standard (RFC5424), but without the frame header. If this flag is enabled, macros used for the message have effect only for the text of the message, the message header is formatted to the new standard. Note that this flag is not needed for the syslog driver, and that the syslog driver automatically adds the frame header to the messages.

flush-lines()

Type:	number
Default:	Use global setting.

Description: Specifies how many lines are flushed to a destination at a time. The syslog-ng PE application waits for this number of lines to accumulate and sends them off in a single batch. Increasing this number increases throughput as more messages are sent in a single batch, but also increases message latency.

The syslog-ng PE application flushes the messages if it has sent flush-lines() number of messages, or the queue became empty. If you stop or reload syslog-ng PE or in case of network sources, the connection with the client is closed, syslog-ng PE automatically sends the unsent messages to the destination.

For optimal performance when sending messages to a syslog-ng PE server, make sure that the flush-lines() is smaller than the window size set using the log-iw-size() option in the source of your server.

flush-timeout() (DEPRECATED)

Type:	time in milliseconds
Default:	Use global setting.

Description: This is a deprecated option. Specifies the time syslog-ng waits for lines to accumulate in its output buffer. For details, see the flush-lines() option.

frac-digits()

Type:	number
Default:	0

Description: The syslog-ng PE application can store fractions of a second in the timestamps according to the ISO8601 format. The frac-digits() parameter specifies the number of digits stored. The digits storing the fractions are padded by zeros if the original timestamp of the message specifies only seconds. Fractions can always be stored for the time the message was received.

NOTE: The syslog-ng PE application can add the fractions to non-ISO8601 timestamps as well.

NOTE: As syslog-ng PE is precise up to the microsecond, when the frac-digits() option is set to a value higher than 6, syslog-ng PE will truncate the fraction seconds in the timestamps after 6 digits.

group()

Type:	string
Default:	Use the global settings

Description: Set the group of the created file to the one specified. To preserve the original properties of an existing file, use the option without specifying an attribute: group().

log-fifo-size()

Type:	number
Default:	Use global setting.

Description: The number of messages that the output queue can store.

mark-freq()

Accepted values:	number [seconds]
Default:	1200

Description: An alias for the obsolete mark() option, retained for compatibility with syslog-ng version 1.6.x.

The number of seconds between two MARK messages. MARK messages are generated when there was no message traffic to inform the receiver that the connection is still alive. If set to zero (0), no MARK messages are sent. The mark-freq() can be set for global option and/or every MARK capable destination driver if mark-mode() is periodical or dst-idle or host-idle. If mark-freq() is not defined in the destination, then the mark-freq() will be inherited from the global options. If the destination uses internal mark-mode(), then the global mark-freq() will be valid (does not matter what mark-freq() set in the destination side).

mark-mode()

Accepted values:

Default:

internal for pipe, program drivers

none for file, unix-dgram, unix-stream drivers

global for syslog, tcp, udp destinations

host-idle for global option

Description: The mark-mode() option can be set for the following destination drivers: file(), program(), unix-dgram(), unix-stream(), network(), pipe(), syslog() and in global option.

internal: When internal mark mode is selected, internal source should be placed in the log path as this mode does not generate mark by itself at the destination. This mode only yields the mark messages from internal source. This is the mode as syslog-ng PE 3.x worked. MARK will be generated by internal source if there was NO traffic on local sources:

file(), pipe(), unix-stream(), unix-dgram(), program()
dst-idle: Sends MARK signal if there was NO traffic on destination drivers. MARK signal from internal source will be dropped.

MARK signal can be sent by the following destination drivers: network(), syslog(), program(), file(), pipe(), unix-stream(), unix-dgram().
host-idle: Sends MARK signal if there was NO local message on destination drivers. For example, MARK is generated even if messages were received from tcp. MARK signal from internal source will be dropped.

MARK signal can be sent by the following destination drivers: network(), syslog(), program(), file(), pipe(), unix-stream(), unix-dgram().
periodical: Sends MARK signal perodically, regardless of traffic on destination driver. MARK signal from internal source will be dropped.

MARK signal can be sent by the following destination drivers: network(), syslog(), program(), file(), pipe(), unix-stream(), unix-dgram().
none: Destination driver drops all MARK messages. If an explicit mark-mode() is not given to the drivers where none is the default value, then none will be used.
global: Destination driver uses the global mark-mode() setting. Note that setting the global mark-mode() to global causes a syntax error in syslog-ng PE.

NOTE: In case of dst-idle, host-idle and periodical, the MARK message will not be written in the destination, if it is not open yet.

Available in syslog-ng PE 4 LTS and later.

owner()

Type:	string
Default:	Use the global settings

Description: Set the owner of the created file to the one specified. To preserve the original properties of an existing file, use the option without specifying an attribute: owner().

pad-size()

Type:	number
Default:	0

Description: If set, syslog-ng PE will pad output messages to the specified size (in bytes). Some operating systems (such as HP-UX) pad all messages to block boundary. This option can be used to specify the block size. (HP-UX uses 2048 bytes).

Caution:

Hazard of data loss! If the size of the incoming message is larger than the previously set pad-size() value, syslog-ng will truncate the message to the specified size. Therefore, all message content above that size will be lost.

perm()

Type:	number (octal notation)
Default:	0600

Description: The permission mask of the pipe. For octal numbers prefix the number with '0', for example: use 0755 for rwxr-xr-x.

suppress()

Type:	seconds
Default:	0 (disabled)

Description: If several identical log messages would be sent to the destination without any other messages between the identical messages (for example, an application repeated an error message ten times), syslog-ng can suppress the repeated messages and send the message only once, followed by the Last message repeated n times. message. The parameter of this option specifies the number of seconds syslog-ng waits for identical messages.

template()

Type:	string
Default:	A format conforming to the default logfile format.

Description: Specifies a template defining the logformat to be used in the destination. Macros are described in Macros of syslog-ng PE. Please note that for network destinations it might not be appropriate to change the template as it changes the on-wire format of the syslog protocol which might not be tolerated by stock syslog receivers (like syslogd or syslog-ng itself). For network destinations make sure the receiver can cope with the custom format defined.

template-escape()

Type:	yes or no
Default:	no

Description: Turns on escaping for the ', ", and backspace characters in templated output files. This is useful for generating SQL statements and quoting string contents so that parts of the log message are not interpreted as commands to the SQL server.

throttle()

Type:	number
Default:	0

Description: Sets the maximum number of messages sent to the destination per second. Use this output-rate-limiting functionality only when using the disk-buffer option as well to avoid the risk of losing messages. Specifying 0 or a lower value sets the output limit to unlimited.

time-zone()

Type:	name of the timezone, or the timezone offset
Default:	unspecified

Description: Convert timestamps to the timezone specified by this option. If this option is not set, then the original timezone information in the message is used. Converting the timezone changes the values of all date-related macros derived from the timestamp, for example, HOUR. For the complete list of such macros, see Date-related macros.

The timezone can be specified as using the name of the (for example, time-zone("Europe/Budapest")), or as the timezone offset in +/-HH:MM format (for example, +01:00). On Linux and UNIX platforms, the valid timezone names are listed under the /usr/share/zoneinfo directory.

ts-format()

Type:	rfc3164, bsd, rfc3339, iso
Default:	rfc3164

Description: Override the global timestamp format (set in the global ts-format() parameter) for the specific destination. For details, see ts-format().

program: Sending messages to external applications

The program() driver starts an external application or script and sends the log messages to its standard input (stdin). Usually, every message is a single line (ending with a newline character), which your script can process. Make sure that your script runs in a loop and keeps reading the standard input — it should not exit. (If your script exits, syslog-ng PE tries to restart it.)

The program() driver has a single required parameter, specifying a program name to start. The program is executed with the help of the current shell, so the command may include both file patterns and I/O redirections. For the list of available optional parameters, see program() destination options.

Declaration

program(command_to_run);

NOTE: When configuring the program() driver, consider the following:

The syslog-ng PE application must be able to start and restart the external program, and have the necessary permissions to do so. For example, if your host is running AppArmor, you might have to modify your AppArmor configuration to enable syslog-ng PE to execute external applications.
The syslog-ng PE application executes program destinations through the standard system shell. If the system shell is not bash and you experience problems with the program destination, try changing the /bin/sh link to /bin/bash.
If the external program exits, the syslog-ng PE application automatically restarts it. However it is not recommended to launch programs for single messages, because if the message rate is high, launching several instances of an application might overload the system, resulting in Denial of Service.
When the syslog-ng PE application stops, it will automatically stop the external program. To avoid restarting the application when syslog-ng PE is only reloaded, enable the keep-alive() option in the program destination.
Certain external applications buffer the log messages, which might cause unexpected latency and other problems. For example, if you send the log messages to an external Perl script, Perl uses a line buffer for terminal output and block buffer otherwise. You might want to disable buffering in the external application.

Example: Using the program() destination driver

The message format does not include the priority and facility values by default. To add these values, specify a template for the program destination, as shown in the following example. Make sure to end your template with a newline character (\n).

destination d_prog { program("/bin/script" template("<${PRI}>${DATE} ${HOST} ${MESSAGE}\n") ); };

The following shell script writes the incoming messages into the /tmp/testlog file.

#!/bin/bash
while read line ; do
echo $line >> /tmp/testlog
done

program() destination options

This driver starts an external application or script and sends the log messages to its standard input (stdin).

The program() destination has the following options:

disk-buffer()

Description: This option enables putting outgoing messages into the disk-buffer file of the destination to avoid message loss in case of a system failure on the destination side. It has the following options:

dir()

Type:

string

Default:

N/A

Description: Defines the folder where the disk-buffer files are stored.

Note that changing the value the dir() option will not move or copy existing files from the old directory to the new one.

Caution:

When creating a new dir() option for a disk-buffer file, or modifying an existing one, make sure you delete the persist file.

syslog-ng PE creates disk-buffer files based on the path recorded in the persist file. Therefore, if the persist file is not deleted after modifying the dir() option, then following a restart, syslog-ng PE will look for or create disk-buffer files in their old location. To ensure that syslog-ng PE uses the new dir() setting, the persist file must not contain any information about the destinations which the disk-buffer file in question belongs to.

disk-buf-size()
Type:	number [bytes]
Default:
Description: This is a required option. The maximum size of the disk-buffer file in bytes. The minimum value is 1048576 bytes. If you set a smaller value, the minimum value will be used automatically. It replaces the old log-disk-fifo-size() option.

mem-buf-length()
Type:	number [messages]
Default:	10000
Description: Use this option if the option reliable() is set to no. This option contains the number of messages stored in overflow queue. It replaces the old log-fifo-size() option. It inherits the value of the global log-fifo-size() option if provided. If it is not provided, the default value is 10000 messages. Note that this option will be ignored if the option reliable() is set to yes.

mem-buf-size()
Type:	number [bytes]
Default:	163840000
Description: Use this option if the option reliable() is set to yes. This option contains the size of the messages in bytes that is used in the memory part of the disk-buffer file. It replaces the old log-fifo-size() option. It does not inherit the value of the global log-fifo-size() option, even if it is provided. Note that this option will be ignored if the option reliable() is set to no.

quot-size()
Type:	number [messages]
Default:	1000
Description: The number of messages stored in the output buffer of the destination. Note that if you change the value of this option and the disk-buffer file already exists, the change will take effect when the disk-buffer file becomes empty.

reliable()

Type:

yes|no

Default:

Description: If set to yes, syslog-ng PE cannot lose logs in case of reload/restart, unreachable destination or syslog-ng PE crash. This solution provides a slower, but reliable disk-buffer option. It is created and initialized at startup and gradually grows as new messages arrive. If set to no, the normal disk-buffer option will be used. This provides a faster, but less reliable disk-buffer option.

Caution: Hazard of data loss!

If you change the value of reliable() option when there are messages in the disk-buffer file, the messages stored in the disk-buffer file will be lost.

truncate-size-ratio()

Type:

number (for percentage) between 0 and 1

Default:

0.1 (10%)

Description: Limits the truncation of the disk-buffer file. Truncating the disk-buffer file can slow down disk I/O operations, but it saves disk space. As a result, syslog-ng PE only truncates the file if the possible disk gain is more than truncate-size-ratio() times disk-buf-size().

Caution:

One Identity recommends that you do not modify the value of the truncate-size-ratio() option unless you are fully aware of the potential performance implications.

Example: Examples for using disk-buffer()

In the following case, reliable disk-buffer() is used.

destination d_demo {
    network("127.0.0.1"
        port(3333)
        disk-buffer(
            mem-buf-size(10000)
            disk-buf-size(2000000)
            reliable(yes)
            dir("/tmp/disk-buffer")
        )
    );
};

In the following case normal disk-buffer() is used.

destination d_demo {
    network("127.0.0.1"
        port(3333)
        disk-buffer(
            mem-buf-length(10000)
            disk-buf-size(2000000)
            reliable(no)
            dir("/tmp/disk-buffer")
        )
    );
};

flags()

Type:	no-multi-line, syslog-protocol
Default:	empty set

Description: Flags influence the behavior of the destination driver.

no-multi-line: The no-multi-line flag disables line-breaking in the messages: the entire message is converted to a single line.
syslog-protocol: The syslog-protocol flag instructs the driver to format the messages according to the new IETF syslog protocol standard (RFC5424), but without the frame header. If this flag is enabled, macros used for the message have effect only for the text of the message, the message header is formatted to the new standard. Note that this flag is not needed for the syslog driver, and that the syslog driver automatically adds the frame header to the messages.

flush-lines()

Type:	number
Default:	Use global setting.

flush-timeout() (DEPRECATED)

Type:	time in milliseconds
Default:	Use global setting.

Description: This is a deprecated option. Specifies the time syslog-ng waits for lines to accumulate in its output buffer. For details, see the flush-lines() option.

frac-digits()

Type:	number
Default:	0

NOTE: The syslog-ng PE application can add the fractions to non-ISO8601 timestamps as well.

log-fifo-size()

Type:	number
Default:	Use global setting.

Description: The number of messages that the output queue can store.

inherit-environment()

Type:	yes\|no
Default:	yes

Description: By default, when program() starts an external application or script, it inherits the entire environment of the parent process (that is, syslog-ng PE). Use inherit-environment(no) to prevent this.

keep-alive()

Type:	yes or no
Default:	no

Description: Specifies whether the external program should be closed when syslog-ng PE is reloaded.

mark-freq()

Accepted values:	number [seconds]
Default:	1200

Description: An alias for the obsolete mark() option, retained for compatibility with syslog-ng version 1.6.x.

mark-mode()

Accepted values:

Default:

internal for pipe, program drivers

none for file, unix-dgram, unix-stream drivers

global for syslog, tcp, udp destinations

host-idle for global option

Description: The mark-mode() option can be set for the following destination drivers: file(), program(), unix-dgram(), unix-stream(), network(), pipe(), syslog() and in global option.

internal: When internal mark mode is selected, internal source should be placed in the log path as this mode does not generate mark by itself at the destination. This mode only yields the mark messages from internal source. This is the mode as syslog-ng PE 3.x worked. MARK will be generated by internal source if there was NO traffic on local sources:

file(), pipe(), unix-stream(), unix-dgram(), program()
dst-idle: Sends MARK signal if there was NO traffic on destination drivers. MARK signal from internal source will be dropped.

MARK signal can be sent by the following destination drivers: network(), syslog(), program(), file(), pipe(), unix-stream(), unix-dgram().
host-idle: Sends MARK signal if there was NO local message on destination drivers. For example, MARK is generated even if messages were received from tcp. MARK signal from internal source will be dropped.

MARK signal can be sent by the following destination drivers: network(), syslog(), program(), file(), pipe(), unix-stream(), unix-dgram().
periodical: Sends MARK signal perodically, regardless of traffic on destination driver. MARK signal from internal source will be dropped.

MARK signal can be sent by the following destination drivers: network(), syslog(), program(), file(), pipe(), unix-stream(), unix-dgram().
none: Destination driver drops all MARK messages. If an explicit mark-mode() is not given to the drivers where none is the default value, then none will be used.
global: Destination driver uses the global mark-mode() setting. Note that setting the global mark-mode() to global causes a syntax error in syslog-ng PE.

NOTE: In case of dst-idle, host-idle and periodical, the MARK message will not be written in the destination, if it is not open yet.

Available in syslog-ng PE 4 LTS and later.

Note that in earlier versions of syslog-ng PE, the default for the mark-mode of the program destination was none. Now it defaults to the global setting, so the program destination will emit a MARK message every mark-freq interval. To avoid such messages, set the mark-mode() option of the destination to none.

suppress()

Type:	seconds
Default:	0 (disabled)

template()

Type:	string
Default:	A format conforming to the default logfile format.

Make sure to end your template with a newline character (\n).

template-escape()

Type:	yes or no
Default:	no

throttle()

Type:	number
Default:	0

time-zone()

Type:	name of the timezone, or the timezone offset
Default:	unspecified

ts-format()

Type:	rfc3164, bsd, rfc3339, iso
Default:	rfc3164

Description: Override the global timestamp format (set in the global ts-format() parameter) for the specific destination. For details, see ts-format().

python: writing custom Python destinations

The Python destination allows you to write your own destination in Python.

Only the default Python modules are available (that is, you cannot import external Python modules, and One Identity does not support using external Python modules).
The syslog-ng PE application uses its own Python interpreter (shipped with the default syslog-ng PE installation) instead of the system's Python interpreter.
The syslog-ng PE application is shipped with Python version 3.8.
The Python block must be a top-level block in the syslog-ng PE configuration file.
If you store the Python code in a separate Python file and only include it in the syslog-ng PE 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 PE 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 PE 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 PE. (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"

The Python object is initiated every time when syslog-ng PE is started or reloaded.

Caution:

If you reload syslog-ng PE, existing Python objects are destroyed, therefore the context and state information of Python blocks is lost. Log rotation and updating the configuration of syslog-ng PE typically involves a reload.

The Python block can contain multiple Python functions.
Using Python code in syslog-ng PE can significantly decrease the performance of syslog-ng PE, especially if the Python code is slow. In general, the features of syslog-ng PE are implemented in C, and are faster than implementations of the same or similar features in Python.
Validate and lint the Python code before using it. The syslog-ng PE application does not do any of this.
Python error messages are available in the internal() source of syslog-ng PE.
You can access the name-value pairs of syslog-ng PE directly through a message object or a dictionary.
To help debugging and troubleshooting your Python code, you can send log messages to the internal() source of syslog-ng PE. For details, see Logging from your Python code.

Support disclaimer

Caution:

This is a Preview Feature, which provides an insight to planned enhancements to functionality in the product. Consider this Preview Feature a work in progress, as it may not represent the final design and functionality.

This feature has completed QA release testing, but its full impact on production systems has not been determined yet, and potential future changes in functionality and the user interface may result in compatibility issues in your current settings.

One Identity recommends the following:

Consider the potential risks when using this functionality in a production environment.
Consider the Support Policy on Product Preview Features before using this functionality in a production environment.
Closely and regularly keep track of official One Identity announcements about potential changes in functionality and the user interface. If these potential changes affect your configuration, check the changes you have to make in your configuration, otherwise your syslog-ng PE application may not start after upgrade.
Always perform tests prior to upgrades in order to avoid the risks mentioned.

However, you are welcome to try this feature and if you have any feedback, Contact One Identity.

Support Policy on Product Preview Features

The One Identity Support Team will:

Accept and review each service request opened regarding a Preview Feature.
Consider all service requests relating to a Preview Features as severity level 3.
Provide best effort support to resolve any issues relating to a Preview Feature.
Work with customers to log any product defects or enhancements relating to Preview Features.
Not accept requests for escalations regarding Preview Features.
Not provide after-hours support for Preview Features.

Using Python in syslog-ng PE is recommended only if you are familiar with both Python and syslog-ng PE. One Identity is not responsible for the quality, resource requirements, or any bugs in the Python code, nor any syslog-ng PE crashes, message losses, or any other damage caused by the improper use of this feature, unless explicitly stated in a contract with One Identity.

NOTE: Starting with 7.0.19, syslog-ng PE assigns a persist name to Python sources and destinations. The persist name is generated from the class name. If you want to use the same Python class multiple times in your syslog-ng PE configuration, add a unique persist-name() to each source or destination, otherwise syslog-ng PE will not start. For example:

log {
    source { python(class(PyNetworkSource) options("port" "8080") persist-name("<unique-string>); };
    source { python(class(PyNetworkSource) options("port" "8081")); };
  };

Alternatively, you can include the following line in the Python package: @staticmethod generate_persist_name. For example:

from syslogng import LogSource
  class PyNetworSource(LogSource):
    @staticmethod
    def generate_persist_name(options):
        return options["port"]
    def run(self):
        pass
    def request_exit(self):
        pass

Declaration

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

destination <name_of_the_python_destination>{
    python(
        class("<name_of_the_python_class_executed_by_the_destination>")
    );
};

python {
class <name_of_the_python_class_executed_by_the_destination>(object):

    def open(self):
        """Open a connection to the target service

        Should return False if opening fails"""
        return True

    def close(self):
        """Close the connection to the target service"""
        pass

    def is_opened(self):
        """Check if the connection to the target is able to receive messages"""
        return True

    def init(self, options):
        """This method is called at initialization time

        Should return false if initialization fails"""
        return True

    def deinit(self):
        """This method is called at deinitialization time"""
        pass

    def send(self, msg):
        """Send a message to the target service

        It should return True to indicate success. False will suspend the
        destination for a period specified by the time-reopen() option.
        This will be repeated for the same message retries() times.

        Alternatively, it can return the following integer values:
        self.SUCCESS: message sending was successful (same as boolean True)
        self.ERROR: message sending was unsuccessful (same as boolean False)
        self.DROP: the message cannot be sent, it should be dropped immediately
        self.QUEUED: the message is not sent immediately, it will be sent in a batch with the flush method
        self.NOT_CONNECTED: the message is put back into the queue, the open method will be called until it succeeds
        self.RETRY: the message is put back into the queue, to retry send it retries() times, then fallback to self.NOT_CONNECTED
        """
        return True
};

Methods of the python() destination

init(self, options) method (optional)

The syslog-ng PE application initializes Python objects every time when it is started or reloaded. The init method is executed as part of the initialization. You can perform any initialization steps that are necessary for your source to work.

Caution:

When this method returns with False, syslog-ng PE does not start. It can be used to check options and return False when they prevent the successful start of the source.

options: This optional argument contains the contents of the options() parameter of the syslog-ng PE configuration object as a Python dictionary.

is_opened(self) method (optional)

Checks if the connection to the target is able to receive messages, and should return True if it is. For details, see Error handling in the python() destination.

open(self) method (optional)

The open(self) method opens the resources required for the destination, for example, it initiates a connection to the target service. It is called after init() when syslog-ng PE is started or reloaded. If send() returns with an error, syslog-ng PE calls close() and open() before trying to send again.

If open() fails, it should return the False value. In this case, syslog-ng PE retries it every time-reopen() seconds. By default, this is 1 second for Python sources and destinations, the value of time-reopen() is not inherited from the global option. For details, see Error handling in the python() destination.

send(self, message) method (mandatory)

The send method sends a message to the target service. It should return True to indicate success.

This is the only mandatory method of the destination.

If a message cannot be delivered after the number of times set in retries() (by default: 3), syslog-ng PE drops the message and continues with the next message. For details, see Error handling in the python() destination.

close(self) method (optional)

Close the connection to the target service. Usually it is called right before deinit() when stopping or reloading syslog-ng PE. It is also called when send() fails.

The deinit(self) method (optional)

This method is executed when syslog-ng PE is stopped or reloaded. This method does not return a value.

Caution:

Error handling in the python() destination

The Python destination handles errors as follows.

Currently syslog-ng PE ignores every error from the open method until the first log message arrives to the Python destination. If the fist message has arrived and there was an error in the open method, syslog-ng PE starts calling the open method every time-reopen() second, until opening the destination succeeds.
If the open method returns without error, syslog-ng PE calls the send method to send the first message.
If the send method returns with an error, syslog-ng PE calls the is_opened method.
- If the is_opened method returns an error, syslog-ng PE starts calling the open method every time-reopen() second, until opening the destination succeeds.
- Otherwise, syslog-ng PE calls the send method again.
If the send method has returned with an error retries() times and the is_opened method has not returned any errors, syslog-ng PE drops the message and attempts to process the next message.

Example: Write logs into a file

The purpose of this example is only to demonstrate the basics of the Python destination, if you really want to write log messages into text files, use the file destination instead.

The following sample code writes the body of log messages into the /tmp/example.txt file. Only the send() method is implemented, meaning that syslog-ng PE opens and closes the file for every message.

destination d_python_to_file {
    python(
        class("TextDestination")
    );
};
log {
    source(src);
    destination(d_python_to_file);
};
python {
class TextDestination(object):
    def send(self, msg):
        self.outfile = open("/tmp/example.txt", "a")
        self.outfile.write("MESSAGE = %s\n" % msg["MESSAGE"])
        self.outfile.flush()
        self.outfile.close();
        return True
};

The following code is similar to the previous example, but it opens and closes the file using the open() and close() methods.

destination d_python_to_file {
    python(
        class("TextDestination")
    );
};
log {
    source(src);
    destination(d_python_to_file);
};
python {
class TextDestination(object):
    def open(self):
        try:
            self.outfile = open("/tmp/example.txt", "a")
            return True
        except:
            return False

    def send(self, msg):
        self.outfile.write("MESSAGE = %s\n" % msg["MESSAGE"])
        self.outfile.flush()
        return True

    def close(self):
        try:
            self.outfile.flush()
            self.outfile.close();
            return True
        except:
            return False
};

For a more detailed example about sending log messages to an MQTT (Message Queuing Telemetry Transport) server, see the Writing Python destination in syslog-ng: how to send log messages to MQTT blog post.

For the list of available optional parameters, see python() destination options.

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Example: Write logs into a file