Introduce a trivial querier for configured java.util.logging.FileHand…

…ler.

For use as a backup for the new server_log info option when using the old log
handler setup in Bazel - in case we would need to temporarily roll back the
migration to SimpleLogHandler.

RELNOTES: None.
PiperOrigin-RevId: 211288834

src/main/java/com/google/devtools/build/lib/util/FileHandlerQuerier.java

@@ -0,0 +1,87 @@
+// Copyright 2018 The Bazel Authors. All rights reserved.
+//
+// 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 com.google.devtools.build.lib.util;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Supplier;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Optional;
+import java.util.logging.FileHandler;
+import java.util.logging.Handler;
+import java.util.logging.Level;
+import java.util.logging.LogManager;
+import java.util.logging.LogRecord;
+
+/**
+ * A {@link LogHandlerQuerier} for working with {@link java.util.logging.FileHandler} instances.
+ *
+ * <p>This querier is intended for situations where the logging handler is configured on the JVM
+ * command line to be {@link java.util.logging.FileHandler}, but where the code which needs to query
+ * the handler does not know the handler's class or cannot import it. The command line then should
+ * in addition specify {@code
+ * -Dcom.google.devtools.build.lib.util.LogHandlerQuerier.class=com.google.devtools.build.lib.util.FileHandlerQuerier}
+ * and an instance of FileHandlerQuerier class can then be obtained from {@code
+ * LogHandlerQuerier.getInstance()}.
+ *
+ * <p>Due to limitations of java.util.logging API, this querier only supports obtaining the log file
+ * path when it's specified in java.util.logging.config with no % variables.
+ *
+ * <p>TODO: is intended that this class be removed once Bazel is no longer using
+ * {@link java.util.logging.FileHandler}.
+ */
+public class FileHandlerQuerier extends LogHandlerQuerier {
+  /** Wrapper around LogManager.getLogManager() for testing. */
+  private final Supplier<LogManager> logManagerSupplier;
+
+  @VisibleForTesting
+  FileHandlerQuerier(Supplier<LogManager> logManagerSupplier) {
+    this.logManagerSupplier = logManagerSupplier;
+  }
+
+  public FileHandlerQuerier() {
+    this(() -> LogManager.getLogManager());
+  }
+
+  @Override
+  protected boolean canQuery(Handler handler) {
+    return handler instanceof FileHandler;
+  }
+
+  @Override
+  protected Optional<Path> getLogHandlerFilePath(Handler handler) {
+    // Hack: java.util.logging.FileHandler has no API for getting the current file path. Instead, we
+    // try to parse the configured path and check that it has no % variables.
+    String pattern = logManagerSupplier.get().getProperty("java.util.logging.FileHandler.pattern");
+    if (pattern == null) {
+      throw new IllegalStateException(
+          "java.util.logging.config property java.util.logging.FileHandler.pattern is undefined");
+    }
+    if (pattern.matches(".*%[thgu].*")) {
+      throw new IllegalStateException(
+          "resolving %-coded variables in java.util.logging.config property "
+              + "java.util.logging.FileHandler.pattern is not supported");
+    }
+    Path path = Paths.get(pattern.trim());
+
+    // Hack: java.util.logging.FileHandler has no API for checking if a log file is currently open.
+    // Instead, we try to query whether the handler can log a SEVERE level record - which for
+    // expected configurations should be true iff a log file is open.
+    if (!handler.isLoggable(new LogRecord(Level.SEVERE, ""))) {
+      return Optional.empty();
+    }
+    return Optional.of(path);
+  }
+}

src/test/java/com/google/devtools/build/lib/BUILD

@@ -325,6 +325,7 @@ java_test(
         "//src/main/java/com/google/devtools/build/lib/vfs",
         "//src/main/java/com/google/devtools/build/lib/vfs/inmemoryfs",
         "//src/main/java/com/google/devtools/common/options",
+        "//third_party:mockito",
         "//third_party:truth8",
     ],
 )

src/test/java/com/google/devtools/build/lib/util/FileHandlerQuerierTest.java

@@ -0,0 +1,121 @@
+// Copyright 2018 The Bazel Authors. All rights reserved.
+//
+// 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 com.google.devtools.build.lib.util;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.common.truth.Truth8.assertThat;
+import static com.google.devtools.build.lib.testutil.MoreAsserts.assertThrows;
+import static org.mockito.Mockito.when;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Optional;
+import java.util.logging.FileHandler;
+import java.util.logging.LogManager;
+import java.util.logging.Logger;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+import org.mockito.Mockito;
+
+/** Tests for the {@link FileHandlerQuerier} class. */
+@RunWith(JUnit4.class)
+public class FileHandlerQuerierTest {
+  @Rule public TemporaryFolder tmp = new TemporaryFolder();
+
+  private Logger getLoggerWithFileHandler(FileHandler handler) {
+    Logger logger = Logger.getAnonymousLogger();
+    logger.addHandler(handler);
+    return logger;
+  }
+
+  private Logger getLoggerWithFileHandler(Path logPath) throws IOException {
+    return getLoggerWithFileHandler(new FileHandler(logPath.toString()));
+  }
+
+  @Test
+  public void getLoggerFilePath_onExpectedConfigurationOpenFile_returnsPath() throws Exception {
+    Path configuredLogPath = Paths.get(tmp.getRoot().toString(), "hello.log");
+    LogManager mockLogManager = Mockito.mock(LogManager.class);
+    when(mockLogManager.getProperty("java.util.logging.FileHandler.pattern"))
+        .thenReturn(configuredLogPath.toString());
+    Logger logger = getLoggerWithFileHandler(configuredLogPath);
+    FileHandlerQuerier handlerQuerier = new FileHandlerQuerier(() -> mockLogManager);
+
+    Optional<Path> retrievedLogPath = handlerQuerier.getLoggerFilePath(logger);
+
+    assertThat(retrievedLogPath).isPresent();
+    assertThat(retrievedLogPath.get().toString()).isEqualTo(configuredLogPath.toString());
+  }
+
+  @Test
+  public void getLoggerFilePath_onExpectedConfigurationClosedFile_returnsEmpty() throws Exception {
+    Path configuredLogPath = Paths.get(tmp.getRoot().toString(), "hello.log");
+    LogManager mockLogManager = Mockito.mock(LogManager.class);
+    when(mockLogManager.getProperty("java.util.logging.FileHandler.pattern"))
+        .thenReturn(configuredLogPath.toString());
+    FileHandler handler = new FileHandler(configuredLogPath.toString());
+    Logger logger = getLoggerWithFileHandler(handler);
+    FileHandlerQuerier handlerQuerier = new FileHandlerQuerier(() -> mockLogManager);
+    handler.close();
+
+    assertThat(handlerQuerier.getLoggerFilePath(logger)).isEmpty();
+  }
+
+  @Test
+  public void getLoggerFilePath_onMissingConfiguration_fails() throws Exception {
+    Path configuredLogPath = Paths.get(tmp.getRoot().toString(), "hello.log");
+    LogManager mockLogManager = Mockito.mock(LogManager.class);
+    when(mockLogManager.getProperty("java.util.logging.FileHandler.pattern")).thenReturn(null);
+    Logger logger = getLoggerWithFileHandler(configuredLogPath);
+    FileHandlerQuerier handlerQuerier = new FileHandlerQuerier(() -> mockLogManager);
+
+    assertThrows(IllegalStateException.class, () -> handlerQuerier.getLoggerFilePath(logger));
+  }
+
+  @Test
+  public void getLoggerFilePath_onVariablesInPath_fails() throws Exception {
+    LogManager mockLogManager = Mockito.mock(LogManager.class);
+    when(mockLogManager.getProperty("java.util.logging.FileHandler.pattern"))
+        .thenReturn(tmp.getRoot() + File.separator + "hello_%u.log");
+    Logger logger =
+        getLoggerWithFileHandler(Paths.get(tmp.getRoot().toString(), "hello_0.log"));
+    FileHandlerQuerier handlerQuerier = new FileHandlerQuerier();
+
+    assertThrows(IllegalStateException.class, () -> handlerQuerier.getLoggerFilePath(logger));
+  }
+
+  @Test
+  public void getLoggerFilePath_onUnsupportedLogHandler_fails() throws Exception {
+    FileHandlerQuerier handlerQuerier = new FileHandlerQuerier();
+    Logger logger = Logger.getAnonymousLogger();
+    logger.addHandler(
+        SimpleLogHandler.builder().setPrefix(tmp.getRoot() + File.separator + "hello.log").build());
+
+    assertThrows(IllegalArgumentException.class, () -> handlerQuerier.getLoggerFilePath(logger));
+  }
+
+  @Test
+  public void getLoggerFilePath_onMissingLogHandler_fails() throws Exception {
+    FileHandlerQuerier handlerQuerier = new FileHandlerQuerier();
+    Logger logger = Logger.getAnonymousLogger();
+
+    assertThrows(IllegalArgumentException.class, () -> handlerQuerier.getLoggerFilePath(logger));
+  }
+}