Log Web Config

A simple runtime REST-based configuration of the logging facility. You can query and modify the log levels of each and every logger inclusive the root logger with one HTTP PUT request.

Target scenarios

The library comes handy for the following scenarios:

• Non-JEE application. JEE servers usually have frontends for configuring the log levels.
• Applications of which you control the source.
• Long-running server application.
• Java 8+ application runtime.

Features

The features of this small library are:

• Get (HTTP GET) and modify (HTTP PUT) the log levels of loggers of your logging framework.
• Can interoperate with multiple logging frameworks. At the moment log4j1 and log4j2 is implemented.
• Small footprint using a mini http server.

Pros and cons

The advantages of configuring the log levels at runtime are:

• Changes get active promptly. No need to copy config files to many servers in a cluster.
• Changes get active smoothly. No need to restart applications.
• Changes can be configured easily. No long XML, JSON or properties files.
• Safe configuration. No risk of logging configuration files to be malformed.

The disadvantages are:

• There's a http server thread running besides your application.
• There's one more TCP/IP port to worry about. One more iptables / ACL to write if your organisation does whitelisting of ports.

Including it in your projects

The recommended way of including the library into your project is adding the following Apache Maven dependency:

---

<dependency>
    <groupId>de.sfuhrm</groupId>
    <artifactId>logwebconfig</artifactId>
    <version>0.8.1</version>
</dependency>

---

At program start you need to call the service once so the server starts up:

---

import de.sfuhrm.logwebconfig.LogWebConfig;

public class MyApp {
    public static void main(String args[]) {
        LogWebConfig.start();
        
        // your program comes here
    }
}

---

Startup time: Configuring the server

Configuration of the server is done using Java system properties. By default the server listens on TCP/IP port 19293.

The following properties are there for configuration:

• LOGWEBCONFIG_PORT: The TCP/IP port for the HTTP-server to listen to. Example value is 19293 which is also the default port.
• LOGWEBCONFIG_HOST: The IP address to bind the listening socket to. Defaults to "127.0.0.1" which is only reachable from localhost. This can be used to restrict the accessibility of the configuration from outside. Exposing the service to the internet by listening to all addresses ("0.0.0.0") might be a security risk because you can put the root logging level of your application to debug.
• LOGWEBCONFIG_ENABLE: Whether to enable the server. Defaults to true.
• LOGWEBCONFIG_USER: Username to use for HTTP basic authentication of the client. Defaults to no authentication.
• LOGWEBCONFIG_PASSWORD: Password to use for HTTP basic authentication of the client. Defaults to no authentication.

Example for listening on all interface addresses on port 54321:

---

java -DLOGWEBCONFIG_PORT=54321 -DLOGWEBCONFIG_HOST=0.0.0.0 -jar myjar.jar ...

---

Run time: Configuring log4j1

Log4j1 is configured by simply issueing PUT requests with the logger seen as a resource and the log level as a request parameter.

Example for setting the root logger level:

---

curl -X PUT -d WARN http://localhost:19293/log4j1//level

---

Example for setting the logger level for class 'com.company.my.Class':

---

curl -X PUT -d WARN http://localhost:19293/log4j1/com.company.my.Class/level

---

Example for getting the root logger level:

---

curl -X GET  http://localhost:19293/log4j1//level
ERROR

---

Run time: Configuring log4j2

Log4j2 is configured by simply issueing PUT requests with the logger seen as a resource and the log level as a request parameter.

Example for setting the root logger level:

---

curl -X PUT -d WARN http://localhost:19293/log4j2//level

---

Example for setting the logger level for class 'com.company.my.Class':

---

curl -X PUT -d WARN http://localhost:19293/log4j2/com.company.my.Class/level

---

Example for getting the root logger level:

---

curl -X GET  http://localhost:19293/log4j2//level
ERROR

---

Versions

The version numbers are chosen according to the semantic versioning schema. Especially major version changes come with breaking API changes.

Author

Written 2018 by Stephan Fuhrmann. You can reach me via email to s (at) sfuhrm.de

License

Copyright 2018 Stephan Fuhrmann

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.