The Python source allows you to write your own source in Python.
You can write two different type of sources in Python:
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Server-style sources that receives messages. Write server-style sources if you want to use an event-loop based, nonblocking server framework in Python, or if you want to implement a custom loop.
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Fetcher-style sources that actively fetch messages. In general, write fetcher-style sources (for example, when using simple blocking APIs), unless you explicitly need a server-style source.
This section describes fetcher-style sources. For details on server-style sources, see python: writing server-style Python sources.
- The following points apply to using Python blocks in syslog-ng PE in general:
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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).
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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.
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The syslog-ng PE application is shipped with Python version 3.8.
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The Python block must be a top-level block in the syslog-ng PE configuration file.
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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"
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The Python object is initiated every time when syslog-ng PE is started or reloaded.
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The Python block can contain multiple Python functions.
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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.
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Validate and lint the Python code before using it. The syslog-ng PE application does not do any of this.
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Python error messages are available in the internal() source of syslog-ng PE.
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You can access the name-value pairs of syslog-ng PE directly through a message object or a dictionary.
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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.
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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:
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Accept and review each service request opened regarding a Preview Feature.
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Consider all service requests relating to a Preview Features as severity level 3.
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Provide best effort support to resolve any issues relating to a Preview Feature.
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Work with customers to log any product defects or enhancements relating to Preview Features.
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Not accept requests for escalations regarding Preview Features.
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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.
Declaration
Python sources consist of two parts. The first is a syslog-ng PE source 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 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 PE 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 PE 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.
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.
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.
open(self) method (optional)
The open(self) method opens the resources required for the source, for example, it initiates a connection to the target service. It is called after init() when syslog-ng PE is started or reloaded. If fetch() returns with an error, syslog-ng PE calls the close() and open() methods before trying to fetch a new message.
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.
fetch(self) method (mandatory)
Use the fetch method to fetch messages and pass them to the log paths.
For details on parsing messages, see Python LogMessage API.
The fetch method must return one of the following values:
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LogFetcher.FETCH_ERROR: Fetching new messages failed, syslog-ng PE calls the close and open methods.
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LogFetcher.FETCH_NOT_CONNECTED: Could not access the source, syslog-ng PE calls the open method.
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LogFetcher.FETCH_SUCCESS, msg: Post the message returned as the second argument.
request_exit(self) method (optional)
If you use blocking operations within the fetch() method, use request_exit() to interrupt those operations (for example, to shut down a socket), otherwise syslog-ng PE is not able to stop. Note that syslog-ng PE calls the request_exit method from a thread different from the source thread.
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 fecth() 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.
For the list of available optional parameters, see python() and python-fetcher() source options.