Allow to dynamically change log filename

configuration/spotbugs-filters.xml

@@ -82,4 +82,10 @@
 		<!-- Performance of inner anonymous class is the purpose of a benchmark -->
 		<Bug pattern="SIC_INNER_SHOULD_BE_STATIC_ANON" />
 	</Match>
+	<Match>
+		<!-- Dynamic Name Policy -->
+		<Class name="org.tinylog.policies.DynamicNamePolicy" />
+		<!-- Allow writing to static field org.tinylog.policies.DynamicNamePolicy.reset from instance method org.tinylog.policies.DynamicNamePolicy.reset -->
+		<Bug pattern="ST_WRITE_TO_STATIC_FROM_INSTANCE_METHOD" />
+	</Match>
 </FindBugsFilter>

tinylog-impl/src/main/java/org/tinylog/path/DynamicNameSegment.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2021 Martin Winandy
+ *
+ * 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.
+ */
+
+package org.tinylog.path;
+
+import org.tinylog.policies.DynamicNamePolicy;
+import org.tinylog.policies.Policy;
+import org.tinylog.runtime.Timestamp;
+
+/**
+ * Path segment that represents the log filename from {@link DynamicNamePolicy}.
+ */
+public class DynamicNameSegment implements Segment {
+
+	private static String dynamicName;
+
+	DynamicNameSegment(final String defaultValue) {
+		setDynamicName(defaultValue);
+	}
+
+	/**
+	 * Returns the current dynamic name.
+	 *
+	 * @return the current dynamic name
+	 */
+	public static String getDynamicName() {
+		return dynamicName;
+	}
+
+	/**
+	 * Sets a new dynamic name.
+	 * When used together with {@link DynamicNamePolicy} and the dynamic name differs from the current one,
+	 * a {@linkplain Policy#reset() reset} is triggered.
+	 *
+	 * @param newDynamicName the dynamic name to set
+	 */
+	public static void setDynamicName(final String newDynamicName) {
+		if (dynamicName != null && dynamicName.equals(newDynamicName)) {
+			return;
+		}
+		dynamicName = newDynamicName;
+		DynamicNamePolicy.setReset();
+	}
+
+	@Override
+	public String getStaticText() {
+		return getDynamicName();
+	}
+
+	@Override
+	public boolean validateToken(final String token) {
+		return dynamicName != null && dynamicName.equals(token);
+	}
+
+	@Override
+	public String createToken(final String prefix, final Timestamp timestamp) {
+		return getDynamicName();
+	}
+}

tinylog-impl/src/main/java/org/tinylog/path/DynamicPath.java

@@ -29,6 +29,7 @@
 public final class DynamicPath {
 
 	private static final String DEFAULT_DATE_FORMAT_PATTERN = "yyyy-MM-dd_HH-mm-ss";
+	private static final String DEFAULT_LOG_FILENAME = "log";
 
 	private final List<Segment> segments;
 	private final File folder;
@@ -280,6 +281,8 @@ private static Segment parseSegment(final String path, final String token) {
 			return new CountSegment();
 		} else if ("pid".equals(name) && parameter == null) {
 			return new ProcessIdSegment();
+		} else if ("dynamic name".equals(name)) {
+			return new DynamicNameSegment(parameter == null ? DEFAULT_LOG_FILENAME : parameter);
 		} else {
 			throw new IllegalArgumentException("Invalid token '" + token + "' in '" + path + "'");
 		}

tinylog-impl/src/main/java/org/tinylog/policies/DynamicNamePolicy.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2021 Martin Winandy
+ *
+ * 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.
+ */
+
+package org.tinylog.policies;
+
+import org.tinylog.Level;
+import org.tinylog.path.DynamicNameSegment;
+import org.tinylog.provider.InternalLogger;
+
+/**
+ * Policy for triggering a manual rollover by calling {@link #setReset()}.
+ * Might be used together with {@link DynamicNameSegment}.
+ */
+public final class DynamicNamePolicy implements Policy {
+
+	private static boolean reset;
+
+	/**
+	 *
+	 */
+	public DynamicNamePolicy() {
+		this(null);
+	}
+
+	/**
+	 * @param argument Should be always {@code null} as dynamic name policy does not support arguments
+	 */
+	public DynamicNamePolicy(final String argument) {
+		if (argument != null) {
+			InternalLogger.log(Level.WARN, "Dynamic name policy does not support arguments");
+		}
+	}
+
+	@Override
+	public boolean continueExistingFile(final String path) {
+		return !reset;
+	}
+
+	@Override
+	public boolean continueCurrentFile(final byte[] entry) {
+		return !reset;
+	}
+
+	@Override
+	public void reset() {
+		reset = false;
+	}
+
+	/**
+	 * Sets the reset flag to trigger a {@linkplain #reset() reset}.
+	 */
+	public static void setReset() {
+		reset = true;
+	}
+}

tinylog-impl/src/main/resources/META-INF/services/org.tinylog.policies.Policy

@@ -1,4 +1,5 @@
 org.tinylog.policies.DailyPolicy
+org.tinylog.policies.DynamicNamePolicy
 org.tinylog.policies.MonthlyPolicy
 org.tinylog.policies.StartupPolicy
 org.tinylog.policies.SizePolicy

tinylog-impl/src/test/java/org/tinylog/path/DynamicNameSegmentTest.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2021 Martin Winandy
+ *
+ * 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.
+ */
+
+package org.tinylog.path;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link DynamicNameSegment}.
+ */
+public final class DynamicNameSegmentTest {
+
+	/**
+	 * Verifies that the passed initial dynamic name text as well as the dynamic name set via
+	 * {@link DynamicNameSegment#setDynamicName(String)} will be returned as static text.
+	 */
+	@Test
+	public void doesHaveStaticText() {
+		DynamicNameSegment segment = new DynamicNameSegment("test");
+		assertThat(segment.getStaticText()).isEqualTo("test");
+		DynamicNameSegment.setDynamicName("foo");
+		assertThat(segment.getStaticText()).isEqualTo("foo");
+		DynamicNameSegment.setDynamicName("bar");
+		assertThat(segment.getStaticText()).isEqualTo("bar");
+	}
+
+	/**
+	 * Verifies that the passed initial dynamic name text as well as the dynamic name set via
+	 * {@link DynamicNameSegment#setDynamicName(String)} will be returned as generated token.
+	 */
+	@Test
+	public void createToken() {
+		DynamicNameSegment segment = new DynamicNameSegment("test");
+		assertThat(segment.createToken(null, null)).isEqualTo("test");
+		DynamicNameSegment.setDynamicName("foo");
+		assertThat(segment.getStaticText()).isEqualTo("foo");
+		DynamicNameSegment.setDynamicName("bar");
+		assertThat(segment.getStaticText()).isEqualTo("bar");
+	}
+
+	/**
+	 * Verifies that the dynamic name text will be accepted as valid token.
+	 */
+	@Test
+	public void validateValidToken() {
+		DynamicNameSegment segment = new DynamicNameSegment("test");
+		assertThat(segment.validateToken("test")).isTrue();
+		assertThat(segment.validateToken("foo")).isFalse();
+		DynamicNameSegment.setDynamicName("foo");
+		assertThat(segment.validateToken("test")).isFalse();
+		assertThat(segment.validateToken("foo")).isTrue();
+	}
+
+}

tinylog-impl/src/test/java/org/tinylog/path/DynamicPathTest.java

@@ -114,6 +114,32 @@ public void processIdToken() {
 		assertThat(path.resolve()).isEqualTo(folder.getRoot() + File.separator + RuntimeProvider.getProcessId() + ".log");
 	}
 
+	/**
+	 * Verifies that a path with a log filename pattern can be resolved.
+	 */
+	@Test
+	public void dynamicName() {
+		String pattern = new File(folder.getRoot(), "{dynamic name}.log").getAbsolutePath();
+		DynamicPath path = new DynamicPath(pattern);
+		assertThat(path.resolve()).isEqualTo(folder.getRoot() + File.separator + "log.log");
+		DynamicNameSegment.setDynamicName("foo");
+		assertThat(path.resolve()).isEqualTo(folder.getRoot() + File.separator + "foo.log");
+		DynamicNameSegment.setDynamicName("bar");
+		assertThat(path.resolve()).isEqualTo(folder.getRoot() + File.separator + "bar.log");
+	}
+
+	/**
+	 * Verifies that a path with a log filename pattern including initial value can be resolved.
+	 */
+	@Test
+	public void dynamicNameParameter() {
+		String pattern = new File(folder.getRoot(), "{dynamic name: foobar}.log").getAbsolutePath();
+		DynamicPath path = new DynamicPath(pattern);
+		assertThat(path.resolve()).isEqualTo(folder.getRoot() + File.separator + "foobar.log");
+		DynamicNameSegment.setDynamicName("baz");
+		assertThat(path.resolve()).isEqualTo(folder.getRoot() + File.separator + "baz.log");
+	}
+
 	/**
 	 * Verifies that a path with an unknown pattern will be rejected.
 	 */

tinylog-impl/src/test/java/org/tinylog/policies/DynamicNamePolicyTest.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2021 Martin Winandy
+ *
+ * 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.
+ */
+
+package org.tinylog.policies;
+
+import java.io.IOException;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.tinylog.configuration.ServiceLoader;
+import org.tinylog.rules.SystemStreamCollector;
+import org.tinylog.util.FileSystem;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link DynamicNamePolicy}.
+ */
+public final class DynamicNamePolicyTest {
+
+	/**
+	 * Redirects and collects system output streams.
+	 */
+	@Rule
+	public final SystemStreamCollector systemStream = new SystemStreamCollector(true);
+
+	/**
+	 * Verifies that an existing log file will be never continued.
+	 * 
+	 * @throws IOException
+	 *             Failed creating temporary file
+	 */
+	@Test
+	public void discontinueExistingFile() throws IOException {
+		String file = FileSystem.createTemporaryFile();
+		final DynamicNamePolicy policy = new DynamicNamePolicy(null);
+		assertThat(policy.continueExistingFile(file)).isTrue();
+		DynamicNamePolicy.setReset();
+		assertThat(policy.continueExistingFile(file)).isFalse();
+		policy.reset();
+		assertThat(policy.continueExistingFile(file)).isTrue();
+	}
+
+	/**
+	 * Verifies that the current log file will be always continued.
+	 */
+	@Test
+	public void continueCurrentFile() {
+		final DynamicNamePolicy policy = new DynamicNamePolicy(null);
+		assertThat(policy.continueCurrentFile(new byte[0])).isTrue();
+		DynamicNamePolicy.setReset();
+		assertThat(policy.continueCurrentFile(new byte[0])).isFalse();
+		policy.reset();
+		assertThat(policy.continueCurrentFile(new byte[0])).isTrue();
+	}
+
+	/**
+	 * Verifies that the reset() method can be executed without throwing any exception.
+	 */
+	@Test
+	public void resetIsCallable() {
+		new DynamicNamePolicy(null).reset();
+	}
+
+	/**
+	 * Verifies that a warning will be output, if an argument is passed.
+	 */
+	@Test
+	public void warnIfArgumentIsSet() {
+		new DynamicNamePolicy("test");
+		assertThat(systemStream.consumeErrorOutput()).containsOnlyOnce("WARN").containsOnlyOnce("argument");
+	}
+
+	/**
+	 * Verifies that policy is registered as service under the name "startup".
+	 */
+	@Test
+	public void isRegistered() {
+		Policy policy = new ServiceLoader<>(Policy.class, String.class).create("dynamic name", (String) null);
+		assertThat(policy).isInstanceOf(DynamicNamePolicy.class);
+	}
+
+}