From 06b446057cb964a78b49497a2f5fb14f68e84577 Mon Sep 17 00:00:00 2001 From: Martin Fick Date: Wed, 19 Aug 2015 15:05:54 -0600 Subject: [PATCH] Handle stale file handles on packed-refs file On a local filesystem the packed-refs file will be orphaned if it is replaced by another client while the current client is reading the old one. However, since NFS servers do not keep track of open files, instead of orphaning the old packed-refs file, such a replacement will cause the old file to be garbage collected instead. A stale file handle exception will be raised on NFS servers if the file is garbage collected (deleted) on the server while it is being read. Since we no longer have access to the old file in these cases, the previous code would just fail. However, in these cases, reopening the file and rereading it will succeed (since it will reopen the new replacement file). So retrying the read is a viable strategy to deal with stale file handles on the packed-refs file, implement such a strategy. Since it is possible that the packed-refs file could be replaced again while rereading it (multiple consecutive updates can easily occur with ref deletions), loop on stale file handle exceptions, up to 5 extra times, trying to read the packed-refs file again, until we either read the new file, or find that the file no longer exists. The limit of 5 is arbitrary, and provides a safe upper bounds to prevent infinite loops consuming resources in a potential unforeseen persistent error condition. Change-Id: I085c472bafa6e2f32f610a33ddc8368bb4ab1814 Signed-off-by: Martin Fick Signed-off-by: Matthias Sohn --- .../eclipse/jgit/internal/JGitText.properties | 1 + .../org/eclipse/jgit/internal/JGitText.java | 1 + .../internal/storage/file/RefDirectory.java | 52 +++++++++++++------ 3 files changed, 38 insertions(+), 16 deletions(-) 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 d8a0fc7f3..8ca3d9ae8 100644 --- a/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties +++ b/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties @@ -440,6 +440,7 @@ outputHasAlreadyBeenStarted=Output has already been started. packChecksumMismatch=Pack checksum mismatch detected for pack file {0} packCorruptedWhileWritingToFilesystem=Pack corrupted while writing to filesystem packDoesNotMatchIndex=Pack {0} does not match index +packedRefsHandleIsStale=packed-refs handle is stale, {0}. retry packetSizeMustBeAtLeast=packet size {0} must be >= {1} packetSizeMustBeAtMost=packet size {0} must be <= {1} packfileCorruptionDetected=Packfile corruption detected: {0} 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 31be94c71..c227884d5 100644 --- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java +++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java @@ -499,6 +499,7 @@ public static JGitText get() { /***/ public String packChecksumMismatch; /***/ public String packCorruptedWhileWritingToFilesystem; /***/ public String packDoesNotMatchIndex; + /***/ public String packedRefsHandleIsStale; /***/ public String packetSizeMustBeAtLeast; /***/ public String packetSizeMustBeAtMost; /***/ public String packfileCorruptionDetected; diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java index c7b60882a..6a04a538e 100644 --- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java +++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java @@ -98,6 +98,8 @@ import org.eclipse.jgit.util.RawParseUtils; import org.eclipse.jgit.util.RefList; import org.eclipse.jgit.util.RefMap; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; /** * Traditional file system based {@link RefDatabase}. @@ -115,6 +117,9 @@ * overall size of a Git repository on disk. */ public class RefDirectory extends RefDatabase { + private final static Logger LOG = LoggerFactory + .getLogger(RefDirectory.class); + /** Magic string denoting the start of a symbolic reference file. */ public static final String SYMREF = "ref: "; //$NON-NLS-1$ @@ -746,22 +751,37 @@ private PackedRefList getPackedRefs() throws IOException { } private PackedRefList readPackedRefs() throws IOException { - final FileSnapshot snapshot = FileSnapshot.save(packedRefsFile); - final BufferedReader br; - final MessageDigest digest = Constants.newMessageDigest(); - try { - br = new BufferedReader(new InputStreamReader( - new DigestInputStream(new FileInputStream(packedRefsFile), - digest), CHARSET)); - } catch (FileNotFoundException noPackedRefs) { - // Ignore it and leave the new list empty. - return PackedRefList.NO_PACKED_REFS; - } - try { - return new PackedRefList(parsePackedRefs(br), snapshot, - ObjectId.fromRaw(digest.digest())); - } finally { - br.close(); + int maxStaleRetries = 5; + int retries = 0; + while (true) { + final FileSnapshot snapshot = FileSnapshot.save(packedRefsFile); + final BufferedReader br; + final MessageDigest digest = Constants.newMessageDigest(); + try { + br = new BufferedReader(new InputStreamReader( + new DigestInputStream(new FileInputStream(packedRefsFile), + digest), CHARSET)); + } catch (FileNotFoundException noPackedRefs) { + // Ignore it and leave the new list empty. + return PackedRefList.NO_PACKED_REFS; + } + try { + return new PackedRefList(parsePackedRefs(br), snapshot, + ObjectId.fromRaw(digest.digest())); + } catch (IOException e) { + if (FileUtils.isStaleFileHandle(e) && retries < maxStaleRetries) { + if (LOG.isDebugEnabled()) { + LOG.debug(MessageFormat.format( + JGitText.get().packedRefsHandleIsStale, + Integer.valueOf(retries)), e); + } + retries++; + continue; + } + throw e; + } finally { + br.close(); + } } }