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Optionally measure filesystem timestamp resolution asynchronously 

In order to avoid blocking on the main thread during measurement
interactive applications like EGit may want to measure the filesystem
timestamp resolution asynchronously.

In order to enable measurement in the background call
FileStoreAttributeCache.setAsyncfileStoreAttrCache(true)
before the first access to cached FileStore attributes.

Bug: 548188
Change-Id: I8c9a2dbfc3f1d33441edea18b90e36b1dc0156c7
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
This commit is contained in:
Matthias Sohn 2019-06-21 13:37:32 +02:00
parent a024759cf5
commit a950eac23b
2 changed files with 148 additions and 55 deletions
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6
org.eclipse.jgit/.settings/.api_filters
View File

@ -115,6 +115,12 @@
<message_argument value="fileAttributes(File)"/>
</message_arguments>
</filter>
<filter id="1142947843">
<message_arguments>
<message_argument value="5.1.9"/>
<message_argument value="setAsyncfileStoreAttrCache(boolean)"/>
</message_arguments>
</filter>
<filter id="1142947843">
<message_arguments>
<message_argument value="5.2.3"/>

197
org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java
View File

@ -55,7 +55,6 @@
import java.io.OutputStream;
import java.io.PrintStream;
import java.nio.charset.Charset;
import java.nio.file.AccessDeniedException;
import java.nio.file.FileStore;
import java.nio.file.Files;
import java.nio.file.Path;
@ -71,12 +70,17 @@
import java.util.Objects;
import java.util.Optional;
import java.util.UUID;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.stream.Collectors;
import org.eclipse.jgit.annotations.NonNull;
@ -197,74 +201,143 @@ private static final class FileStoreAttributeCache {
private static final Map<FileStore, FileStoreAttributeCache> attributeCache = new ConcurrentHashMap<>();
static Duration getFsTimestampResolution(Path file) {
private static AtomicBoolean background = new AtomicBoolean();
private static Map<FileStore, Lock> locks = new ConcurrentHashMap<>();
private static void setBackground(boolean async) {
background.set(async);
}
private static Duration getFsTimestampResolution(Path file) {
Path dir = Files.isDirectory(file) ? file : file.getParent();
FileStore s;
try {
Path dir = Files.isDirectory(file) ? file : file.getParent();
if (!dir.toFile().canWrite()) {
// can not determine FileStore of an unborn directory or in
// a read-only directory
if (Files.exists(dir)) {
s = Files.getFileStore(dir);
FileStoreAttributeCache c = attributeCache.get(s);
if (c != null) {
return c.getFsTimestampResolution();
}
if (!Files.isWritable(dir)) {
// cannot measure resolution in a read-only directory
return FALLBACK_TIMESTAMP_RESOLUTION;
}
} else {
// cannot determine FileStore of an unborn directory
return FALLBACK_TIMESTAMP_RESOLUTION;
}
FileStore s = Files.getFileStore(dir);
FileStoreAttributeCache c = attributeCache.get(s);
if (c == null) {
c = new FileStoreAttributeCache(s, dir);
attributeCache.put(s, c);
if (LOG.isDebugEnabled()) {
LOG.debug(c.toString());
CompletableFuture<Optional<Duration>> f = CompletableFuture
.supplyAsync(() -> {
Lock lock = locks.computeIfAbsent(s,
l -> new ReentrantLock());
if (!lock.tryLock()) {
return Optional.empty();
}
Optional<Duration> resolution;
try {
// Some earlier future might have set the value
// and removed itself since we checked for the
// value above. Hence check cache again.
FileStoreAttributeCache c = attributeCache
.get(s);
if (c != null) {
return Optional
.of(c.getFsTimestampResolution());
}
resolution = measureFsTimestampResolution(s,
dir);
if (resolution.isPresent()) {
FileStoreAttributeCache cache = new FileStoreAttributeCache(
resolution.get());
attributeCache.put(s, cache);
if (LOG.isDebugEnabled()) {
LOG.debug(cache.toString());
}
}
} finally {
lock.unlock();
locks.remove(s);
}
return resolution;
});
// even if measuring in background wait a little - if the result
// arrives, it's better than returning the large fallback
Optional<Duration> d = f.get(background.get() ? 50 : 2000,
TimeUnit.MILLISECONDS);
if (d.isPresent()) {
return d.get();
}
// return fallback until measurement is finished
} catch (IOException | InterruptedException
| ExecutionException e) {
LOG.error(e.getMessage(), e);
} catch (TimeoutException e) {
// use fallback
}
return FALLBACK_TIMESTAMP_RESOLUTION;
}
private static Optional<Duration> measureFsTimestampResolution(
FileStore s, Path dir) {
Path probe = dir.resolve(".probe-" + UUID.randomUUID()); //$NON-NLS-1$
try {
Files.createFile(probe);
long wait = 512;
long start = System.nanoTime();
FileTime t1 = Files.getLastModifiedTime(probe);
FileTime t2 = t1;
while (t2.compareTo(t1) <= 0) {
TimeUnit.NANOSECONDS.sleep(wait);
checkTimeout(s, start);
FileUtils.touch(probe);
t2 = Files.getLastModifiedTime(probe);
if (wait < 100_000_000L) {
wait = wait * 2;
}
}
return c.getFsTimestampResolution();
return Optional
.of(Duration.between(t1.toInstant(), t2.toInstant()));
} catch (IOException | TimeoutException e) {
LOG.error(e.getLocalizedMessage(), e);
} catch (InterruptedException e) {
LOG.error(e.getLocalizedMessage(), e);
Thread.currentThread().interrupt();
} finally {
deleteProbe(probe);
}
return Optional.empty();
}
} catch (IOException | InterruptedException e) {
LOG.warn(e.getMessage(), e);
return FALLBACK_TIMESTAMP_RESOLUTION;
private static void checkTimeout(FileStore s, long start)
throws TimeoutException {
if (System.nanoTime() - start >= FALLBACK_TIMESTAMP_RESOLUTION
.toNanos()) {
throw new TimeoutException(MessageFormat.format(JGitText
.get().timeoutMeasureFsTimestampResolution,
s.toString()));
}
}
private static void deleteProbe(Path probe) {
if (Files.exists(probe)) {
try {
Files.delete(probe);
} catch (IOException e) {
LOG.error(e.getLocalizedMessage(), e);
}
}
}
private Duration fsTimestampResolution;
private final @NonNull Duration fsTimestampResolution;
@NonNull
Duration getFsTimestampResolution() {
return fsTimestampResolution;
}
private FileStoreAttributeCache(FileStore s, Path dir)
throws IOException, InterruptedException {
Path probe = dir.resolve(".probe-" + UUID.randomUUID()); //$NON-NLS-1$
Files.createFile(probe);
try {
long start = System.nanoTime();
FileTime startTime = Files.getLastModifiedTime(probe);
FileTime actTime = startTime;
long sleepTime = 512;
while (actTime.compareTo(startTime) <= 0) {
TimeUnit.NANOSECONDS.sleep(sleepTime);
if (timeout(start)) {
LOG.warn(MessageFormat.format(JGitText
.get().timeoutMeasureFsTimestampResolution,
s.toString()));
fsTimestampResolution = FALLBACK_TIMESTAMP_RESOLUTION;
return;
}
FileUtils.touch(probe);
actTime = Files.getLastModifiedTime(probe);
// limit sleep time to max. 100ms
if (sleepTime < 100_000_000L) {
sleepTime = sleepTime * 2;
}
}
fsTimestampResolution = Duration.between(startTime.toInstant(),
actTime.toInstant());
} catch (AccessDeniedException e) {
LOG.error(e.getLocalizedMessage(), e);
} finally {
Files.delete(probe);
}
}
private static boolean timeout(long start) {
return System.nanoTime() - start >= FALLBACK_TIMESTAMP_RESOLUTION
.toNanos();
private FileStoreAttributeCache(
@NonNull Duration fsTimestampResolution) {
this.fsTimestampResolution = fsTimestampResolution;
}
@SuppressWarnings("nls")
@ -292,6 +365,20 @@ public static FS detect() {
return detect(null);
}
/**
* Whether FileStore attribute cache entries should be determined
* asynchronously
*
* @param asynch
* whether FileStore attribute cache entries should be determined
* asynchronously. If false access to cached attributes may block
* for some seconds for the first call per FileStore
* @since 5.1.9
*/
public static void setAsyncfileStoreAttrCache(boolean asynch) {
FileStoreAttributeCache.setBackground(asynch);
}
/**
* Auto-detect the appropriate file system abstraction, taking into account
* the presence of a Cygwin installation on the system. Using jgit in