| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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.apache.bookkeeper.util; |
| |
| import com.sun.jna.LastErrorException; |
| import com.sun.jna.Native; |
| |
| import java.io.FileDescriptor; |
| import java.lang.reflect.Field; |
| |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| /** |
| * Native I/O operations. |
| */ |
| public final class NativeIO { |
| private static final Logger LOG = LoggerFactory.getLogger(NativeIO.class); |
| |
| private static final int POSIX_FADV_DONTNEED = 4; /* fadvise.h */ |
| |
| private static boolean initialized = false; |
| private static boolean fadvisePossible = true; |
| |
| static { |
| try { |
| Native.register("c"); |
| initialized = true; |
| } catch (NoClassDefFoundError e) { |
| LOG.info("JNA not found. Native methods will be disabled."); |
| } catch (UnsatisfiedLinkError e) { |
| LOG.info("Unable to link C library. Native methods will be disabled."); |
| } catch (NoSuchMethodError e) { |
| LOG.warn("Obsolete version of JNA present; unable to register C library"); |
| } |
| } |
| |
| // fadvice |
| public static native int posix_fadvise(int fd, long offset, long len, int flag) throws LastErrorException; |
| |
| private NativeIO() {} |
| |
| private static Field getFieldByReflection(Class cls, String fieldName) { |
| Field field = null; |
| |
| try { |
| field = cls.getDeclaredField(fieldName); |
| field.setAccessible(true); |
| } catch (Exception e) { |
| // We don't really expect this so throw an assertion to |
| // catch this during development |
| assert false; |
| LOG.warn("Unable to read {} field from {}", fieldName, cls.getName()); |
| } |
| |
| return field; |
| } |
| /** |
| * Get system file descriptor (int) from FileDescriptor object. |
| * @param descriptor - FileDescriptor object to get fd from |
| * @return file descriptor, -1 or error |
| */ |
| public static int getSysFileDescriptor(FileDescriptor descriptor) { |
| Field field = getFieldByReflection(descriptor.getClass(), "fd"); |
| try { |
| return field.getInt(descriptor); |
| } catch (Exception e) { |
| LOG.warn("Unable to read fd field from java.io.FileDescriptor"); |
| } |
| |
| return -1; |
| } |
| |
| /** |
| * Remove pages from the file system page cache when they wont |
| * be accessed again. |
| * |
| * @param fd The file descriptor of the source file. |
| * @param offset The offset within the file. |
| * @param len The length to be flushed. |
| */ |
| public static void bestEffortRemoveFromPageCache(int fd, long offset, long len) { |
| if (!initialized || !fadvisePossible || fd < 0) { |
| return; |
| } |
| try { |
| posix_fadvise(fd, offset, len, POSIX_FADV_DONTNEED); |
| } catch (UnsupportedOperationException uoe) { |
| LOG.warn("posix_fadvise is not supported : ", uoe); |
| fadvisePossible = false; |
| } catch (UnsatisfiedLinkError ule) { |
| // if JNA is unavailable just skipping Direct I/O |
| // instance of this class will act like normal RandomAccessFile |
| LOG.warn("Unsatisfied Link error: posix_fadvise failed on file descriptor {}, offset {} : ", |
| fd, offset, ule); |
| fadvisePossible = false; |
| } catch (Exception e) { |
| // This is best effort anyway so lets just log that there was an |
| // exception and forget |
| LOG.warn("Unknown exception: posix_fadvise failed on file descriptor {}, offset {} : ", |
| fd, offset, e); |
| } |
| } |
| |
| } |