From 24d6d605388c82201092cf1699b51095299380a2 Mon Sep 17 00:00:00 2001 From: Antonio Barone Date: Wed, 2 Jun 2021 18:13:17 +0300 Subject: [PATCH] Retry loose object read upon "Stale file handle" exception When reading loose objects over NFS it is possible that the OS syscall would fail with ESTALE errors: This happens when the open file descriptor no longer refers to a valid file. Notoriously it is possible to hit this scenario when git data is shared among multiple clients, for example by multiple gerrit instances in HA. If one of the two clients performs a GC operation that would cause the packing and then the pruning of loose objects, the other client might still hold a reference to those objects, which would cause an exception to bubble up the stack. The Linux NFS FAQ[1] (at point A.10), suggests that the proper way to handle such ESTALE scenarios is to: "[...] close the file or directory where the error occurred, and reopen it so the NFS client can resolve the pathname again and retrieve the new file handle." In case of a stale file handle exception, we now attempt to read the loose object again (up to 5 times), until we either succeed or encounter a FileNotFoundException, in which case the search can continue to Packfiles and alternates. The limit of 5 provides an arbitrary upper bounds that is consistent to the one chosen when handling stale file handles for packed-refs files (see [2] for context). [1] http://nfs.sourceforge.net/ [2] https://git.eclipse.org/r/c/jgit/jgit/+/54350 Bug: 573791 Change-Id: I9950002f772bbd8afeb9c6108391923be9d0ef51 --- .../storage/file/ObjectDirectoryTest.java | 41 +++++++++ .../eclipse/jgit/internal/JGitText.properties | 1 + .../org/eclipse/jgit/internal/JGitText.java | 1 + .../storage/file/ObjectDirectory.java | 84 +++++++++++++++---- 4 files changed, 111 insertions(+), 16 deletions(-) diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/ObjectDirectoryTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/ObjectDirectoryTest.java index d269457eb1..a0bc63a698 100644 --- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/ObjectDirectoryTest.java +++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/ObjectDirectoryTest.java @@ -44,8 +44,12 @@ package org.eclipse.jgit.internal.storage.file; import static java.nio.charset.StandardCharsets.UTF_8; import static org.junit.Assert.assertFalse; +import static org.junit.Assert.assertNull; import static org.junit.Assert.assertThrows; import static org.junit.Assert.assertTrue; +import static org.mockito.ArgumentMatchers.any; +import static org.mockito.Mockito.mock; +import static org.mockito.Mockito.verify; import java.io.File; import java.io.IOException; @@ -69,6 +73,7 @@ import org.eclipse.jgit.storage.file.FileBasedConfig; import org.eclipse.jgit.util.FS; import org.junit.Assume; import org.junit.Test; +import org.mockito.Mockito; public class ObjectDirectoryTest extends RepositoryTestCase { @@ -194,6 +199,42 @@ public class ObjectDirectoryTest extends RepositoryTestCase { assertTrue(shallowCommits.isEmpty()); } + @Test + public void testOpenLooseObjectSuppressStaleFileHandleException() + throws Exception { + ObjectId id = ObjectId + .fromString("873fb8d667d05436d728c52b1d7a09528e6eb59b"); + WindowCursor curs = new WindowCursor(db.getObjectDatabase()); + + ObjectDirectory mock = mock(ObjectDirectory.class); + UnpackedObjectCache unpackedObjectCacheMock = mock( + UnpackedObjectCache.class); + + Mockito.when(mock.getObjectLoader(any(), any(), any())) + .thenThrow(new IOException("Stale File Handle")); + Mockito.when(mock.openLooseObject(curs, id)).thenCallRealMethod(); + Mockito.when(mock.unpackedObjectCache()) + .thenReturn(unpackedObjectCacheMock); + + assertNull(mock.openLooseObject(curs, id)); + verify(unpackedObjectCacheMock).remove(id); + } + + @Test + public void testOpenLooseObjectPropagatesIOExceptions() throws Exception { + ObjectId id = ObjectId + .fromString("873fb8d667d05436d728c52b1d7a09528e6eb59b"); + WindowCursor curs = new WindowCursor(db.getObjectDatabase()); + + ObjectDirectory mock = mock(ObjectDirectory.class); + + Mockito.when(mock.getObjectLoader(any(), any(), any())) + .thenThrow(new IOException("some IO failure")); + Mockito.when(mock.openLooseObject(curs, id)).thenCallRealMethod(); + + assertThrows(IOException.class, () -> mock.openLooseObject(curs, id)); + } + @Test public void testShallowFileCorrupt() throws Exception { FileRepository repository = createBareRepository(); diff --git a/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties b/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties index c5e7dc3efa..2f3520de50 100644 --- a/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties +++ b/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties @@ -416,6 +416,7 @@ logInconsistentFiletimeDiff={}: inconsistent duration from file timestamps on {} logLargerFiletimeDiff={}: inconsistent duration from file timestamps on {}, {}: diff = {} > {} (last good value). Aborting measurement. logSmallerFiletime={}: got smaller file timestamp on {}, {}: {} < {}. Aborting measurement at resolution {}. logXDGConfigHomeInvalid=Environment variable XDG_CONFIG_HOME contains an invalid path {} +looseObjectHandleIsStale=loose-object {0} file handle is stale. retry {1} of {2} maxCountMustBeNonNegative=max count must be >= 0 mergeConflictOnNonNoteEntries=Merge conflict on non-note entries: base = {0}, ours = {1}, theirs = {2} mergeConflictOnNotes=Merge conflict on note {0}. base = {1}, ours = {2}, theirs = {2} diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java index 814811d131..22200c26bc 100644 --- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java +++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java @@ -444,6 +444,7 @@ public class JGitText extends TranslationBundle { /***/ public String logLargerFiletimeDiff; /***/ public String logSmallerFiletime; /***/ public String logXDGConfigHomeInvalid; + /***/ public String looseObjectHandleIsStale; /***/ public String maxCountMustBeNonNegative; /***/ public String mergeConflictOnNonNoteEntries; /***/ public String mergeConflictOnNotes; diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/ObjectDirectory.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/ObjectDirectory.java index 265b71dd2a..9d1d457369 100644 --- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/ObjectDirectory.java +++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/ObjectDirectory.java @@ -85,6 +85,10 @@ public class ObjectDirectory extends FileObjectDatabase { /** Maximum number of candidates offered as resolutions of abbreviation. */ private static final int RESOLVE_ABBREV_LIMIT = 256; + /** Maximum number of attempts to read a loose object for which a stale file + * handle exception is thrown */ + final static int MAX_LOOSE_OBJECT_STALE_READ_ATTEMPTS = 5; + private final AlternateHandle handle = new AlternateHandle(this); private final Config config; @@ -212,7 +216,7 @@ public class ObjectDirectory extends FileObjectDatabase { /** {@inheritDoc} */ @Override public void close() { - unpackedObjectCache.clear(); + unpackedObjectCache().clear(); final PackList packs = packList.get(); if (packs != NO_PACKS && packList.compareAndSet(packs, NO_PACKS)) { @@ -277,7 +281,7 @@ public class ObjectDirectory extends FileObjectDatabase { /** {@inheritDoc} */ @Override public boolean has(AnyObjectId objectId) { - return unpackedObjectCache.isUnpacked(objectId) + return unpackedObjectCache().isUnpacked(objectId) || hasPackedInSelfOrAlternate(objectId, null) || hasLooseInSelfOrAlternate(objectId, null); } @@ -395,7 +399,7 @@ public class ObjectDirectory extends FileObjectDatabase { @Override ObjectLoader openObject(WindowCursor curs, AnyObjectId objectId) throws IOException { - if (unpackedObjectCache.isUnpacked(objectId)) { + if (unpackedObjectCache().isUnpacked(objectId)) { ObjectLoader ldr = openLooseObject(curs, objectId); if (ldr != null) { return ldr; @@ -473,23 +477,71 @@ public class ObjectDirectory extends FileObjectDatabase { @Override ObjectLoader openLooseObject(WindowCursor curs, AnyObjectId id) throws IOException { - File path = fileFor(id); + int readAttempts = 0; + while (readAttempts < MAX_LOOSE_OBJECT_STALE_READ_ATTEMPTS) { + readAttempts++; + File path = fileFor(id); + try { + return getObjectLoader(curs, path, id); + } catch (FileNotFoundException noFile) { + if (path.exists()) { + throw noFile; + } + break; + } catch (IOException e) { + if (!FileUtils.isStaleFileHandleInCausalChain(e)) { + throw e; + } + if (LOG.isDebugEnabled()) { + LOG.debug(MessageFormat.format( + JGitText.get().looseObjectHandleIsStale, id.name(), + Integer.valueOf(readAttempts), Integer.valueOf( + MAX_LOOSE_OBJECT_STALE_READ_ATTEMPTS))); + } + } + } + unpackedObjectCache().remove(id); + return null; + } + + /** + * Provides a loader for an objectId + * + * @param curs + * cursor on the database + * @param path + * the path of the loose object + * @param id + * the object id + * @return a loader for the loose file object + * @throws IOException + * when file does not exist or it could not be opened + */ + ObjectLoader getObjectLoader(WindowCursor curs, File path, AnyObjectId id) + throws IOException { try (FileInputStream in = new FileInputStream(path)) { - unpackedObjectCache.add(id); + unpackedObjectCache().add(id); return UnpackedObject.open(in, path, id, curs); - } catch (FileNotFoundException noFile) { - if (path.exists()) { - throw noFile; - } - unpackedObjectCache.remove(id); - return null; } } + /** + *

+ * Getter for the field unpackedObjectCache. + *

+ * This accessor is particularly useful to allow mocking of this class for + * testing purposes. + * + * @return the cache of the objects currently unpacked. + */ + UnpackedObjectCache unpackedObjectCache() { + return unpackedObjectCache; + } + @Override long getObjectSize(WindowCursor curs, AnyObjectId id) throws IOException { - if (unpackedObjectCache.isUnpacked(id)) { + if (unpackedObjectCache().isUnpacked(id)) { long len = getLooseObjectSize(curs, id); if (0 <= len) { return len; @@ -567,13 +619,13 @@ public class ObjectDirectory extends FileObjectDatabase { throws IOException { File f = fileFor(id); try (FileInputStream in = new FileInputStream(f)) { - unpackedObjectCache.add(id); + unpackedObjectCache().add(id); return UnpackedObject.getSize(in, id, curs); } catch (FileNotFoundException noFile) { if (f.exists()) { throw noFile; } - unpackedObjectCache.remove(id); + unpackedObjectCache().remove(id); return -1; } } @@ -667,7 +719,7 @@ public class ObjectDirectory extends FileObjectDatabase { boolean createDuplicate) throws IOException { // If the object is already in the repository, remove temporary file. // - if (unpackedObjectCache.isUnpacked(id)) { + if (unpackedObjectCache().isUnpacked(id)) { FileUtils.delete(tmp, FileUtils.RETRY); return InsertLooseObjectResult.EXISTS_LOOSE; } @@ -723,7 +775,7 @@ public class ObjectDirectory extends FileObjectDatabase { Files.move(FileUtils.toPath(tmp), FileUtils.toPath(dst), StandardCopyOption.ATOMIC_MOVE); dst.setReadOnly(); - unpackedObjectCache.add(id); + unpackedObjectCache().add(id); return InsertLooseObjectResult.INSERTED; } -- 2.39.5