Overview

This tutorial is for anyone who is actively using logback in their JVM applications. For those who are not familiar with the framework, I strongly recommend checking out its documentation.

Out-of-the-box logback can send WARNING and ERROR logging events via email. Sometimes receiving those events is the best way to monitor and debug remote applications. However, email as notifications channel isn't that attractive. That's why the SIP3 team wrote a handy logback extension that uses webhooks and makes it possible to send the same events to unlimited amount of channels including the most popular - Slack and Telegram.

In this tutorial we will build a simple Spring Boot application and configure it to start sending ERROR messages via Incoming Webhook for Slack.

1. Creating Spring Boot Application

Open Spring Initializr project to create a dummy Spring Boot application:

Let's choose Kotlin and press the GENERATE button.

For this showcase we will add some code in the DemoApplication class:

@SpringBootApplication
class DemoApplication {

    private val logger: Logger = LoggerFactory.getLogger(DemoApplication::class.java)

    @PostConstruct
    fun init() {
        try {
            throw RuntimeException("Houston, we have a problem!")
        } catch (e: Exception) {
            logger.error("Got exception...", e)
        }       
    }
}

fun main(args: Array<String>) {
    runApplication<DemoApplication>(*args)
}

As you can see the code above throws RuntimeException every time we start the application.

2. Adding logback-webhook-appender

Let's pull logback-webhook-appender and install it to a local Maven repository using mvn clean install.

Now we can add it as a dependency to the project's pom.xml(in some cases you will have to resolve a conflict with okhttp3 library by explicitly specifying its version):

<properties>
    ...
    <okhttp3.version>4.5.0</okhttp3.version>
</properties>

<dependencies>
    ...     
    <dependency>
        <groupId>io.sip3</groupId>
        <artifactId>logback-webhook-appender</artifactId>
        <version>1.0.0-SNAPSHOT</version>
    </dependency>   
    ...
</dependencies>

3. Configuring logback-webhook-appender

Prior to the next step we need to set up an Incoming Webhook for our Slack.

Once it's done we can create and configure src/main/resources/logback-spring.xml:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <appender name="webhook" class="io.sip3.logback.WebhookAppender">
        <url>https://hooks.slack.com/services/%YOUR_WEBHOOK_URI%</url>     // (1)
        <json>                                                             // (2)
            {
                "text": ":fire: Houston, we have a problem! :fire:",
                "attachments": [
                    {
                        "text": "{message}"                                // (3)
                    }
                ]
            }
        </json>
        <encoder>
            <pattern>%d{dd-MM-yyyy HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
        </encoder>
    </appender>

    <root level="ERROR">
        <appender-ref ref="webhook"/>
    </root>
</configuration>

• (1) - Use <url> to set up a webhook URL
• (2) - Use <json> to set up a payload template
• (3) - Use {message} as a placeholder for encoded logging event

4. Testing logback-webhook-appender

So far so good. Let's start our application using mvn spring-boot:run command. Then open the configured Slack channel to receive an ERROR notification:

And that is how you setup a very simple but useful monitoring in a matter of 2-5 minutes.

I hope you loved the approach and will start using it in your projects. If you have any questions, just leave me a message :)

Cheers...