1 files changed, 105 insertions, 0 deletions
diff --git a/python/knot_resolver_manager/manager/log.py b/python/knot_resolver_manager/manager/log.py
new file mode 100644
index 00000000..95043f89
--- /dev/null
+++ b/python/knot_resolver_manager/manager/log.py
@@ -0,0 +1,105 @@
+import logging
+import logging.handlers
+import os
+import sys
+from typing import Optional
+
+from knot_resolver_manager.manager.config_store import ConfigStore, only_on_real_changes_update
+from knot_resolver_manager.manager.constants import STARTUP_LOG_LEVEL
+from knot_resolver_manager.manager.datamodel.config_schema import KresConfig
+from knot_resolver_manager.manager.datamodel.logging_schema import LogTargetEnum
+
+logger = logging.getLogger(__name__)
+
+
+def get_log_format(config: KresConfig) -> str:
+    """
+    Based on an environment variable $KRES_SUPRESS_LOG_PREFIX, returns the appropriate format string for logger.
+    """
+
+    if os.environ.get("KRES_SUPRESS_LOG_PREFIX") == "true":
+        # In this case, we are running under supervisord and it's adding prefixes to our output
+        return "[%(levelname)s] %(name)s: %(message)s"
+    else:
+        # In this case, we are running standalone during inicialization and we need to add a prefix to each line
+        # by ourselves to make it consistent
+        assert config.logging.target != "syslog"
+        stream = ""
+        if config.logging.target == "stderr":
+            stream = " (stderr)"
+
+        pid = os.getpid()
+        return f"%(asctime)s manager[{pid}]{stream}: [%(levelname)s] %(name)s: %(message)s"
+
+
+async def _set_log_level(config: KresConfig) -> None:
+    levels_map = {
+        "crit": "CRITICAL",
+        "err": "ERROR",
+        "warning": "WARNING",
+        "notice": "WARNING",
+        "info": "INFO",
+        "debug": "DEBUG",
+    }
+
+    # when logging group is set to make us log with DEBUG
+    if config.logging.groups and "manager" in config.logging.groups:
+        target = "DEBUG"
+    # otherwise, follow the standard log level
+    else:
+        target = levels_map[config.logging.level]
+
+    # expect exactly one existing log handler on the root
+    logger.warning(f"Changing logging level to '{target}'")
+    logging.getLogger().setLevel(target)
+
+
+async def _set_logging_handler(config: KresConfig) -> None:
+    target: Optional[LogTargetEnum] = config.logging.target
+
+    if target is None:
+        target = "stdout"
+
+    handler: logging.Handler
+    if target == "syslog":
+        handler = logging.handlers.SysLogHandler(address="/dev/log")
+        handler.setFormatter(logging.Formatter("%(name)s: %(message)s"))
+    elif target == "stdout":
+        handler = logging.StreamHandler(sys.stdout)
+        handler.setFormatter(logging.Formatter(get_log_format(config)))
+    elif target == "stderr":
+        handler = logging.StreamHandler(sys.stderr)
+        handler.setFormatter(logging.Formatter(get_log_format(config)))
+    else:
+        raise RuntimeError(f"Unexpected value '{target}' for log target in the config")
+
+    root = logging.getLogger()
+
+    # if we had a MemoryHandler before, we should give it the new handler where we can flush it
+    if isinstance(root.handlers[0], logging.handlers.MemoryHandler):
+        root.handlers[0].setTarget(handler)
+
+    # stop the old handler
+    root.handlers[0].flush()
+    root.handlers[0].close()
+    root.removeHandler(root.handlers[0])
+
+    # configure the new handler
+    root.addHandler(handler)
+
+
+@only_on_real_changes_update(lambda config: config.logging)
+async def _configure_logger(config: KresConfig) -> None:
+    await _set_logging_handler(config)
+    await _set_log_level(config)
+
+
+async def logger_init(config_store: ConfigStore) -> None:
+    await config_store.register_on_change_callback(_configure_logger)
+
+
+def logger_startup() -> None:
+    logging.getLogger().setLevel(STARTUP_LOG_LEVEL)
+    err_handler = logging.StreamHandler(sys.stderr)
+    err_handler.setFormatter(logging.Formatter(logging.BASIC_FORMAT))
+    logging.getLogger().addHandler(logging.handlers.MemoryHandler(10_000, logging.ERROR, err_handler))