3 files changed, 178 insertions, 0 deletions
diff --git a/opendc-common/build.gradle.kts b/opendc-common/build.gradle.kts
index 2dd35d83..aeb9bc4d 100644
--- a/opendc-common/build.gradle.kts
+++ b/opendc-common/build.gradle.kts
@@ -36,5 +36,9 @@ dependencies {
     implementation(libs.kotlin.logging)
     implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:$serializationVersion")
 
+    api(libs.log4j.core)
+    api(libs.log4j.slf4j)
+    api(libs.kotlin.logging)
+
     testImplementation(projects.opendcSimulator.opendcSimulatorCore)
 }
diff --git a/opendc-common/src/main/kotlin/org/opendc/common/logger/Logger.kt b/opendc-common/src/main/kotlin/org/opendc/common/logger/Logger.kt
new file mode 100644
index 00000000..ee2f828a
--- /dev/null
+++ b/opendc-common/src/main/kotlin/org/opendc/common/logger/Logger.kt
@@ -0,0 +1,131 @@
+/*
+ * Copyright (c) 2024 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.common.logger
+
+import mu.KotlinLogging
+import org.slf4j.Logger
+
+/**
+ * @return a slf4j logger named as the calling class simple name.
+ * Can also be used in the companion object to limit the instances of loggers.
+ *
+ *
+ * ```kotlin
+ * class Foo {
+ *      val LOG by logger() // Same as: KotlinLogging.logger(name = "Foo")
+ *
+ *      companion object {
+ *          val LOG by logger() // Same as: KotlinLogging.logger(name = "Foo")
+ *          val LOG by logger("smth") // Same as: KotlinLogging.logger(name = "smth")
+ *      }
+ * }
+ * ```
+ */
+public fun <T : Any> T.logger(name: String? = null): Lazy<Logger> {
+    return lazy {
+        KotlinLogging.logger(
+            name
+                ?: runCatching { this::class.java.enclosingClass.simpleName }
+                    .getOrNull()
+                ?: "unknown",
+        )
+    }
+}
+
+/**
+ * Logs [msg] with WARN level and returns null.
+ * ```kotlin
+ * // Replace
+ * LOG.warn(<msg>)
+ * return null
+ * // With
+ * return LOG.warnAndNull(<msg>)
+ */
+public fun Logger.warnAndNull(msg: String): Nothing? {
+    this.warn(msg)
+    return null
+}
+
+/**
+ * Logs [msg] with ERROR level and returns null.
+ * ```kotlin
+ * // Replace
+ * LOG.error(<msg>)
+ * return null
+ * // With
+ * return LOG.errAndNull(<msg>)
+ */
+public fun Logger.errAndNull(msg: String): Nothing? {
+    this.error(msg)
+    return null
+}
+
+/**
+ * Logs [msg] with *WARN* level and returns [obj].
+ *
+ *
+ * ```kotlin
+ * // Replace
+ * if (<key> !in map) {
+ *      LOG.warn("warn-message")
+ *      return <default-value>
+ * } else map[<key>]
+ * // With
+ * map.getOrDefault(<key>, LOG.withWarn(<default-value>, "<warn-message>"))
+ * ```
+ */
+public fun <T> Logger.withWarn(
+    obj: T,
+    msg: String,
+): T {
+    this.warn(msg)
+    return obj
+}
+
+/**
+ * Logs [msg] with *ERROR* level and returns [obj].
+ */
+public fun <T> Logger.withErr(
+    obj: T,
+    msg: String,
+): T {
+    this.error(msg)
+    return obj
+}
+
+/**
+ * Logs [msg] with *INFO* level on a new line.
+ * ```console
+ *
+ * 09:28:08.830 [INFO] ScenariosSpec -
+ * | === Compute Export Config ===
+ * | Host Fields (columns)    : timestamp,
+ * ...
+ * // Instead of
+ * 09:28:08.830 [INFO] ScenariosSpec - | === Compute Export Config ===
+ * | Host Fields (columns)    : timestamp,
+ * ```
+ */
+public fun Logger.infoNewLine(msg: String) {
+    info("\n" + msg)
+}
diff --git a/opendc-common/src/main/resources/log4j2.xml b/opendc-common/src/main/resources/log4j2.xml
new file mode 100644
index 00000000..07389360
--- /dev/null
+++ b/opendc-common/src/main/resources/log4j2.xml
@@ -0,0 +1,43 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ MIT License
+  ~
+  ~ Copyright (c) 2020 atlarge-research
+  ~
+  ~ Permission is hereby granted, free of charge, to any person obtaining a copy
+  ~ of this software and associated documentation files (the "Software"), to deal
+  ~ in the Software without restriction, including without limitation the rights
+  ~ to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+  ~ copies of the Software, and to permit persons to whom the Software is
+  ~ furnished to do so, subject to the following conditions:
+  ~
+  ~ The above copyright notice and this permission notice shall be included in all
+  ~ copies or substantial portions of the Software.
+  ~
+  ~ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  ~ IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  ~ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  ~ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  ~ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  ~ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  ~ SOFTWARE.
+  -->
+
+<Configuration status="WARN">
+    <Appenders>
+        <Console name="Console" target="SYSTEM_OUT">
+            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%highlight{%-5level}] %logger{36} - %msg%n" disableAnsi="false"/>
+        </Console>
+    </Appenders>
+    <Loggers>
+        <Logger name="org.opendc" level="warn" additivity="false">
+            <AppenderRef ref="Console"/>
+        </Logger>
+        <Logger name="org.apache.hadoop" level="warn" additivity="false">
+            <AppenderRef ref="Console"/>
+        </Logger>
+        <Root level="warn">
+            <AppenderRef ref="Console"/>
+        </Root>
+    </Loggers>
+</Configuration>