// Copyright 2014 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.skyframe;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Function;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import com.google.devtools.build.lib.util.OS;
import com.google.devtools.build.lib.util.Preconditions;
import com.google.devtools.build.lib.vfs.ModifiedFileSet;
import com.google.devtools.build.lib.vfs.PathFragment;
import com.google.devtools.common.options.Option;
import com.google.devtools.common.options.OptionsBase;
import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.util.Set;
/**
* File system watcher for local filesystems. It's able to provide a list of changed files between
* two consecutive calls. On Linux, uses the standard Java WatchService, which uses 'inotify' and,
* on OS X, uses {@link MacOSXFsEventsDiffAwareness}, which use FSEvents.
*
* <p>
* This is an abstract class, specialized by {@link MacOSXFsEventsDiffAwareness} and
* {@link WatchServiceDiffAwareness}.
*/
public abstract class LocalDiffAwareness implements DiffAwareness {
/**
* Option to enable / disable local diff awareness.
*/
public static final class Options extends OptionsBase {
@Option(
name = "watchfs",
defaultValue = "false",
category = "server startup",
help = "If true, %{product} tries to use the operating system's file watch service for "
+ "local changes instead of scanning every file for a change."
)
public boolean watchFS;
}
/** Factory for creating {@link LocalDiffAwareness} instances. */
public static class Factory implements DiffAwareness.Factory {
private final ImmutableList<String> prefixBlacklist;
/**
* Creates a new factory; the file system watcher may not work on all file systems, particularly
* for network file systems. The prefix blacklist can be used to blacklist known paths that
* point to network file systems.
*/
public Factory(ImmutableList<String> prefixBlacklist) {
this.prefixBlacklist = prefixBlacklist;
}
@Override
public DiffAwareness maybeCreate(com.google.devtools.build.lib.vfs.Path pathEntry) {
com.google.devtools.build.lib.vfs.Path resolvedPathEntry;
try {
resolvedPathEntry = pathEntry.resolveSymbolicLinks();
} catch (IOException e) {
return null;
}
PathFragment resolvedPathEntryFragment = resolvedPathEntry.asFragment();
// There's no good way to automatically detect network file systems. We rely on a blacklist
// for now (and maybe add a command-line option in the future?).
for (String prefix : prefixBlacklist) {
if (resolvedPathEntryFragment.startsWith(PathFragment.create(prefix))) {
return null;
}
}
// On OSX uses FsEvents due to https://bugs.openjdk.java.net/browse/JDK-7133447
if (OS.getCurrent() == OS.DARWIN) {
return new MacOSXFsEventsDiffAwareness(resolvedPathEntryFragment.toString());
}
return new WatchServiceDiffAwareness(resolvedPathEntryFragment.toString());
}
}
/**
* A view that results in any subsequent getDiff calls returning
* {@link ModifiedFileSet#EVERYTHING_MODIFIED}. Use this if --watchFs is disabled.
*
* <p>The position is set to -2 in order for {@link #areInSequence} below to always return false
* if this view is passed to it. Any negative number would work; we don't use -1 as the other
* view may have a position of 0.
*/
protected static final View EVERYTHING_MODIFIED =
new SequentialView(/*owner=*/null, /*position=*/-2, ImmutableSet.<Path>of());
public static boolean areInSequence(SequentialView oldView, SequentialView newView) {
// Keep this in sync with the EVERYTHING_MODIFIED View above.
return oldView.owner == newView.owner && (oldView.position + 1) == newView.position;
}
private int numGetCurrentViewCalls = 0;
/** Root directory to watch. This is an absolute path. */
protected final Path watchRootPath;
protected LocalDiffAwareness(String watchRoot) {
this.watchRootPath = FileSystems.getDefault().getPath(watchRoot);
}
/**
* The WatchService is inherently sequential and side-effectful, so we enforce this by only
* supporting {@link #getDiff} calls that happen to be sequential.
*/
@VisibleForTesting
static class SequentialView implements DiffAwareness.View {
private final LocalDiffAwareness owner;
private final int position;
private final Set<Path> modifiedAbsolutePaths;
public SequentialView(LocalDiffAwareness owner, int position, Set<Path> modifiedAbsolutePaths) {
this.owner = owner;
this.position = position;
this.modifiedAbsolutePaths = modifiedAbsolutePaths;
}
@Override
public String toString() {
return String.format("SequentialView[owner=%s, position=%d, modifiedAbsolutePaths=%s]", owner,
position, modifiedAbsolutePaths);
}
}
/**
* Returns true on any call before first call to {@link #newView}.
*/
protected boolean isFirstCall() {
return numGetCurrentViewCalls == 0;
}
/**
* Create a new views using a list of modified absolute paths. This will increase the view
* counter.
*/
protected SequentialView newView(Set<Path> modifiedAbsolutePaths) {
numGetCurrentViewCalls++;
return new SequentialView(this, numGetCurrentViewCalls, modifiedAbsolutePaths);
}
@Override
public ModifiedFileSet getDiff(View oldView, View newView)
throws IncompatibleViewException, BrokenDiffAwarenessException {
SequentialView oldSequentialView;
SequentialView newSequentialView;
try {
oldSequentialView = (SequentialView) oldView;
newSequentialView = (SequentialView) newView;
} catch (ClassCastException e) {
throw new IncompatibleViewException("Given views are not from LocalDiffAwareness");
}
if (!areInSequence(oldSequentialView, newSequentialView)) {
return ModifiedFileSet.EVERYTHING_MODIFIED;
}
return ModifiedFileSet.builder()
.modifyAll(Iterables.transform(newSequentialView.modifiedAbsolutePaths,
nioAbsolutePathToPathFragment))
.build();
}
@Override
public String name() {
return "local";
}
/** Converts java.nio.file.Path objects to vfs.PathFragment. */
private final Function<Path, PathFragment> nioAbsolutePathToPathFragment =
new Function<Path, PathFragment>() {
@Override
public PathFragment apply(Path input) {
Preconditions.checkArgument(
input.startsWith(watchRootPath), "%s %s", input, watchRootPath);
return PathFragment.create(watchRootPath.relativize(input).toString());
}
};
}