Other Features

The Logger provides only two types of loggers: default_logger and msg_logger.

• default_logger: Logs information generated during API execution, including serialization errors, network connection errors, etc.

import dolphindb as ddb
ddb.logger.default_logger

• msg_logger: Controls the print output from scripts executed via Session.run. Each Session corresponds to a msg_logger.

import dolphindb as ddb
s = ddb.Session()
s.msg_logger

Set the log level by modifying the min_level attribute. The log values from low to high are: DEBUG, INFO (default), WARNING, and ERROR.

import dolphindb as ddb
ddb.logger.default_logger.min_level = ddb.logger.Level.ERROR

The Logger offers the following interfaces to enable or disable standard output (stdout). The stdout is enabled by default.

enable_stdout_sink

def enable_stdout_sink(self) -> None: ...

Enable stdout.

disable_stdout_sink

def disable_stdout_sink(self) -> None: ...

Disable stdout.

File log output is disabled by default. Enable or disable it using the following interfaces.

enable_file_sink

def enable_file_sink(self, path: str) -> None: ...

• path: The path of the file log.

Enable file log output. This will overwrite the previously specified path.

disable_file_sink

def disable_file_sink(self) -> None: ...

Disable file log output.

Sink

The Logger offers the Sink class. Users can inherit it to implement custom log output. Users must specific a name when initializing a new instance of the Sink class.

add_sink

def add_sink(self, sink: Sink) -> None: ...

Add a custom Sink instance to a Logger object.

remove_sink

def remove_sink(self, name: str) -> None: ...

Remove a Sink instance from a Logger object based on the name.

list_links

def list_sinks(self) -> List[Sink]: ...

List all custom Sink instances currently in a Logger object.

The following example of modifying msg_logger shows how to redirect log output through a custom Sink.

import dolphindb as ddb
from dolphindb.logger import Sink

msg_list = []


class mySink(Sink):
    def handle(self, msg):
        msg_list.append(msg.log)


s = ddb.Session()
s.msg_logger.add_sink(mySink("test1"))

s.connect("localhost", 8848, "admin", "123456")
s.run("print(123)")

print("msg: ", msg_list)

""" output:

123
msg: ['123']
"""

Explanation:

• Inherit the Sink class to initialize a subclass mySink instance, and override handle method to save the received messages into msg_list.
• Add a customs Sink instance named "test1" to msg_logger.
• Execute print(123). With stdout enabled, the console displays two lines of output: the first line is default standard output; the second line is the contents of msg_list.