feat: syslog option

metricq/cli/decorator.py

@@ -1,11 +1,12 @@
 import logging
-from typing import Callable, Optional, cast
+from typing import Callable, Optional, cast, Any
 
 import click
 import click_log  # type: ignore
-from click import option
+from click import option, Context
 from dotenv import find_dotenv, load_dotenv
 
+from .syslog import get_syslog_handler, SyslogFormatter
 from .. import get_logger
 from .params import MetricParam, TemplateStringParam
 from .types import FC
@@ -20,6 +21,41 @@
 load_dotenv(dotenv_path=find_dotenv(".metricq"), interpolate=False, override=False)
 
 
+def metricq_syslog_option() -> Callable[[FC], FC]:
+    """
+    Exposes the -\\-syslog option as a click param.
+
+    The program will try read the 'token' from the click params.
+    if the token is not set, the default value of 'metricq.program' will be used.
+    That's why the @metricq_syslog_option should be the 2nd decorator in the chain.
+
+    It is recommended to use the :py:func:`~metricq.cli.decorator.metricq_command` decorator instead of using this
+    function directly.
+    """
+
+    def enable_syslog(ctx: Context, param: Any | None, value: Optional[str]) -> None:
+        if value is not None:
+            logger = get_logger()
+            if value == "":
+                value = None
+
+            program_name = ctx.params.get("token", "metricq.program")
+
+            handler = get_syslog_handler(value)
+            handler.setFormatter(SyslogFormatter(name=program_name))
+            logger.addHandler(handler)
+
+    return option(
+        "--syslog",
+        help="Enable syslog logging by specifying the a Unix socket or host:port for the logger. If --syslog is set "
+        "but no value is specified, the default of localhost:514 will be used.",
+        callback=enable_syslog,
+        expose_value=False,
+        is_flag=False,
+        flag_value="",
+    )
+
+
 def metricq_server_option() -> Callable[[FC], FC]:
     """
     Allows the User to provide a -\\-server option. This option has no input validation and therefore can be any string.
@@ -140,10 +176,20 @@ def metricq_command(
     -  -\\-token:
         The Token is used to identify each program on the metricq network. for example: sink-py-dummy
 
-        The token param can be set using the environment variable METRICQ_TOKEN or adding the --token {value} option to the cli command
+        The token param can be set using the environment variable METRICQ_TOKEN or adding the --token {value} option
+        to the cli command
+
+    -  -\\-syslog:
+        The Syslog param is used to enable syslog. It can be used with or without parameter.
+
+        If used without parameter (for example: ``metricq-check --syslog`` ) the Syslog will default to localhost:514.
+
+        You can also specify a Unix socket (for example: /dev/log) or a custom host (for example: example.com:5114)
+        by adding the value to the syslog flag (for example: ``metricq-check --syslog example.com:5114``)
+
 
     Full example:
-    ``metricq-check --server amqp://localhost/ --token sink-py-dummy``
+    ``metricq-check --server amqp://localhost/ --token sink-py-dummy --syslog``
 
     **Example**::
 
@@ -181,8 +227,10 @@ def decorator(func: FC) -> click.Command:
             log_decorator(
                 metricq_token_option(default_token)(
                     metricq_server_option()(
-                        click.command(context_settings=context_settings, epilog=epilog)(
-                            func
+                        metricq_syslog_option()(
+                            click.command(
+                                context_settings=context_settings, epilog=epilog
+                            )(func)
                         )
                     )
                 )

metricq/cli/syslog.py

@@ -0,0 +1,32 @@
+import logging
+import socket
+import time
+from logging.handlers import SysLogHandler
+
+
+class SyslogFormatter(logging.Formatter):
+    def __init__(self, *args, name: str = "metricq", **kwargs):  # type: ignore
+        super().__init__(*args, **kwargs)
+        self.program = name
+
+    def format(self, record: logging.LogRecord) -> str:
+        timestamp = time.strftime("%Y-%m-%d %H:%M:%S", time.localtime(record.created))
+        hostname = socket.gethostname()
+        pid = record.process
+        program = self.program
+        # Custom Formatter based on rfc3164
+        # Format the header as "<PRI> TIMESTAMP HOSTNAME PROGRAM[PID]: MESSAGE"
+        # <PRI> is already beeing set by the SysLogHanlder, we only need to add the rest
+        syslog_header = f"{timestamp} {hostname} {program}[{pid}]: "
+        message = super().format(record)
+        return syslog_header + message
+
+
+def get_syslog_handler(address: str|None) -> SysLogHandler:
+    if address is None:
+        return SysLogHandler()
+    elif ":" in address:
+        ip, port = address.split(":")
+        return SysLogHandler(address=(ip, int(port)))
+    else:
+        return SysLogHandler(address=address)