The Python destination allows you to write your own destination in Python. You can import external Python modules to process the messages, and send them to other services or servers. Since many services have a Python library, the Python destination makes integrating syslog-ng PE very easy and quick.
The following points apply to using Python blocks in syslog-ng PE in general.
Python parsers and template functions are available in syslog-ng PE version
Python destinations and sources are available in syslog-ng PE version
Supported Python versions: 2.7
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.
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 dict.
Using Python in syslog-ng PE is recommended only if you are familiar with both Python and syslog-ng PE. Product support applies only to syslog-ng PE: that is, until the entry point of the Python code and passing the specified arguments to the Python code. 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.
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 };
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.
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 dict.
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.
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.
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 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.
This method is executed when syslog-ng PE is stopped or reloaded. This method does not return a value.
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.
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.
The Python destination allows you to write your own destination in Python. The python() destination has the following options. The class() option is mandatory. For details on writing destinations in Python, see python: writing custom Python destinations.
Type: | string |
Default: | N/A |
Description: The name of the Python class that implements the destination, for example:
python( class("MyPythonDestination") );
If you want to store the Python code in an external Python file, the class() option must include the name of the Python file containing the class, without the path and the .py extension, for example:
python( class("MyPythonfilename.MyPythonDestination") );
For details, see Python code in external files
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:
reliable() | |||
Type: | yes|no | ||
Default: | no | ||
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.
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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. |
qout-size() | |
Type: | number (messages) |
Default: | 64 |
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. |
Options reliable() and disk-buf-size() are required options.
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") ) ); };
Type: | number |
Default: | 0 |
Description: The syslog-ng 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 that syslog-ng can add the fractions to non-ISO8601 timestamps as well.
Type: | number |
Default: | Use global setting. |
Description: The number of messages that the output queue can store.
Accepted values: |
drop-message|drop-property|fallback-to-string| silently-drop-message|silently-drop-property|silently-fallback-to-string |
Default: | Use the global setting (which defaults to drop-message) |
Description: Controls what happens when type-casting fails and syslog-ng PE cannot convert some data to the specified type. By default, syslog-ng PE drops the entire message and logs the error. Currently the value-pairs() option uses the settings of on-error().
drop-message: Drop the entire message and log an error message to the internal() source. This is the default behavior of syslog-ng PE.
drop-property: Omit the affected property (macro, template, or message-field) from the log message and log an error message to the internal() source.
fallback-to-string: Convert the property to string and log an error message to the internal() source.
silently-drop-message: Drop the entire message silently, without logging the error.
silently-drop-property: Omit the affected property (macro, template, or message-field) silently, without logging the error.
silently-fallback-to-string: Convert the property to string silently, without logging the error.
Type: | string |
Default: | N/A |
Description: This option allows you to pass custom values from the configuration file to the Python code. Enclose both the option names and their values in double-quotes. The Python code will receive these values during initialization as the options dictionary. For example, you can use this to set the IP address of the server from the configuration file, so it is not hard-coded in the Python object.
python( class("MyPythonClass") options( "host" "127.0.0.1" "port" "1883" "otheroption" "value") );
For example, you can refer to the value of the host field in the Python code as options["host"]. Note that the Python code receives the values as strings, so you might have to cast them to the type required, for example: int(options["port"])
Type: | string |
Default: |
None |
Description:If you receive the following error message during syslog-ng PE startup, set the persist-name() option of the duplicate drivers:
Error checking the uniqueness of the persist names, please override it with persist-name option. Shutting down.
This error happens if you use identical drivers in multiple sources, for example, if you configure two file sources to read from the same file. In this case, set the persist-name() of the drivers to a custom string, for example, persist-name("example-persist-name1").
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.
Type: | parameter list of the value-pairs() option |
Default: | scope("selected-macros" "nv-pairs") |
Description: The value-pairs() option creates structured name-value pairs from the data and metadata of the log message. For details on using value-pairs(), see Structuring macros, metadata, and other value-pairs.
|
NOTE:
Empty keys are not logged. |
You can use this option to limit which name-value pairs are passed to the Python code for each message. Note that if you use the value-pairs() option, the Python code receives the specified value-pairs as a Python dict. Otherwise, it receives the message object. In the following example, only the text of the log message is passed to Python.
destination d_python_to_file { python( class("pythonexample.TextDestination") value-pairs(key(MESSAGE)) ); };
The destination is aimed at a fully controlled local, or near-local, trusted SMTP server. The goal is to send mail to trusted recipients, through a controlled channel. It hands mails over to an SMTP server, and that is all it does, therefore the resulting solution is as reliable as sending an e-mail in general. For example, syslog-ng PE does not verify whether the recipient exists.
The smtp() driver sends e-mail messages triggered by log messages. The smtp() driver uses SMTP, without needing external applications. You can customize the main fields of the e-mail, add extra headers, send the e-mail to multiple recipients, and so on.
The subject(), body(), and header() fields may include macros which get expanded in the e-mail. For more information on available macros see Macros of syslog-ng PE.
The smtp() driver has the following required parameters: host(), port(), from(), to(), subject(), and body(). For the list of available optional parameters, see smtp() destination options.
|
NOTE:
In order to use this destination, syslog-ng Premium Edition must run in server mode. Typically, only the central syslog-ng Premium Edition server uses this destination. For details on the server mode, see Server mode. |
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NOTE:
The smtp() destination driver is available only in |
smtp(host() port() from() to() subject() body() options());
The following example defines an smtp() destination using only the required parameters.
destination d_smtp { smtp( host("localhost") port(25) from("syslog-ng alert service" "noreply@example.com") to("Admin #1" "admin1@example.com") subject("[ALERT] Important log message of $LEVEL condition received from $HOST/$PROGRAM!") body("Hi!\nThe syslog-ng alerting service detected the following important log message:\n $MSG\n-- \nsyslog-ng\n") ); };
The following example sets some optional parameters as well.
destination d_smtp { smtp( host("localhost") port(25) from("syslog-ng alert service" "noreply@example.com") to("Admin #1" "admin1@example.com") to("Admin #2" "admin2@example.com") cc("Admin BOSS" "admin.boss@example.com") bcc("Blind CC" "blindcc@example.com") subject("[ALERT] Important log message of $LEVEL condition received from $HOST/$PROGRAM!") body("Hi!\nThe syslog-ng alerting service detected the following important log message:\n $MSG\n-- \nsyslog-ng\n") header("X-Program", "$PROGRAM") ); };
The following example sends an e-mail alert if the eth0 network interface of the host is down.
filter f_linkdown { match("eth0: link down" value("MESSAGE")); }; destination d_alert { smtp( host("localhost") port(25) from("syslog-ng alert service" "syslog@localhost") reply-to("Admins" "root@localhost") to("Ennekem" "me@localhost") subject("[SYSLOG ALERT]: eth0 link down") body("Syslog received an alert:\n$MSG") ); }; log { source(s_local); filter(f_linkdown); destination(d_alert); };
The smtp() sends e-mail messages using SMTP, without needing external applications. The smtp() destination has the following options:
Type: | string |
Default: | n/a |
Description: The BODY field of the e-mail. You can also use macros in the string. Use \n to start a new line. For example:
body("syslog-ng PE received the following alert from $HOST:\n$MSG")
Type: | string |
Default: | n/a |
Description: The BCC recipient of the e-mail (contents of the BCC field). You can specify the e-mail address, or the name and the e-mail address. Set the bcc() option multiple times to send the e-mail to multiple recipients. For example: bcc("admin@example.com") or bcc("Admin" "admin@example.com") or bcc("Admin" "admin@example.com") bcc("Admin2" "admin2@example.com")
You can also use macros to set the value of this parameter.
Type: | string |
Default: | n/a |
Description: The CC recipient of the e-mail (contents of the CC field). You can specify the e-mail address, or the name and the e-mail address. Set the cc() option multiple times to send the e-mail to multiple recipients. For example: cc("admin@example.com") or cc("Admin" "admin@example.com") or cc("Admin" "admin@example.com") cc("Admin2" "admin2@example.com")
You can also use macros to set the value of this parameter.
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:
reliable() | |||
Type: | yes|no | ||
Default: | no | ||
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.
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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.
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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. |
qout-size() | |
Type: | number (messages) |
Default: | 64 |
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. |
Options reliable() and disk-buf-size() are required options.
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") ) ); };
Type: | string |
Default: | n/a |
Description: The sender of the e-mail (contents of the FROM field). You can specify the e-mail address, or the name and the e-mail address. For example:
from("admin@example.com")or
from("Admin" "admin@example.com")
If you specify the from() option multiple times, the last value will be used. Instead of the from() option, you can also use sender(), which is just an alias of the from() option.
You can also use macros to set the value of this parameter.
Type: | string |
Default: | n/a |
Description: Adds an extra header to the e-mail with the specified name and content. The first parameter sets the name of the header, the second one its value. The value of the header can contain macros. Set the header() option multiple times to add multiple headers. For example:
header("X-Program", "$PROGRAM")
When using the header option, note the following points:
Do not use the header() option to set the values of headers that have dedicated options. Use it only to add extra headers.
If you set the same custom header multiple times, only the first will be added to the e-mail, other occurrences will be ignored.
It is not possible to set the DATE, Return-Path, Original-Recipient, Content-*, MIME-*, Resent-*, Received headers.
Type: | hostname or IP address |
Default: | n/a |
Description: Hostname or IP address of the SMTP server.
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NOTE:
If you specify host="localhost", syslog-ng PE will use a socket to connect to the local SMTP server. Use host="127.0.0.1" to force TCP communication between syslog-ng PE and the local SMTP server. |
Type: | number |
Default: | Use global setting. |
Description: The number of messages that the output queue can store.
Type: | number |
Default: | 25 |
Description: The port number of the SMTP server.
Type: | string |
Default: | n/a |
Description: Replies of the recipient will be sent to this address (contents of the REPLY-TO field). You can specify the e-mail address, or the name and the e-mail address. Set the reply-to() option multiple times to send the e-mail to multiple recipients. For example: reply-to("admin@example.com") or reply-to("Admin" "admin@example.com") or reply-to("Admin" "admin@example.com") reply-to("Admin2" "admin2@example.com")
You can also use macros to set the value of this parameter.
Type: | number (of attempts) |
Default: | 3 |
Description: The number of times syslog-ng PE attempts to send a message to this destination. If syslog-ng PE could not send a message, it will try again until the number of attempts reaches retries, then drops the message.
Type: | string |
Default: | n/a |
Description: The SUBJECT field of the e-mail. You can also use macros. For example:
subject("[SYSLOG ALERT]: Critical error message received from $HOST")
If you specify the subject() option multiple times, the last value will be used.
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.
Type: | string |
Default: | localhost |
Description: The recipient of the e-mail (contents of the TO field). You can specify the e-mail address, or the name and the e-mail address. Set the to() option multiple times to send the e-mail to multiple recipients. For example: to("admin@example.com") or to("Admin" "admin@example.com") or to("Admin" "admin@example.com") to("Admin2" "admin2@example.com")
You can also use macros to set the value of this parameter.
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