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From: lvfangmin <git@git.apache.org>
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Subject: [GitHub] zookeeper pull request #117: ZOOKEEPER-2325: Data inconsistency if all snaps...
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Message-Id: <20161201013753.99C22E04BB@git1-us-west.apache.org>
Date: Thu,  1 Dec 2016 01:37:53 +0000 (UTC)
archived-at: Thu, 01 Dec 2016 01:37:55 -0000

Github user lvfangmin commented on a diff in the pull request:

    https://github.com/apache/zookeeper/pull/117#discussion_r90368114
  
    --- Diff: src/java/main/org/apache/zookeeper/server/persistence/FileTxnSnapLog.java ---
    @@ -165,8 +165,22 @@ public File getSnapDir() {
          */
         public long restore(DataTree dt, Map<Long, Integer> sessions,
                 PlayBackListener listener) throws IOException {
    -        snapLog.deserialize(dt, sessions);
    +        long deserializeResult = snapLog.deserialize(dt, sessions);
             FileTxnLog txnLog = new FileTxnLog(dataDir);
    +        if (-1L == deserializeResult) {
    +            /* this means that we couldn't find any snapshot, so we need to
    +             * initialize an empty database */
    +            if (txnLog.getLastLoggedZxid() != -1) {
    +                throw new IOException(
    +                        "No snapshot found, but there are log entries. " +
    +                        "Something is broken!");
    +            }
    +            /* TODO: (br33d) we should either put a ConcurrentHashMap on restore()
    +             *       or use Map on save() */
    +            save(dt, (ConcurrentHashMap<Long, Integer>)sessions);
    --- End diff --
    
    n00b question, why we need to save here? I saw there is potential that the follower will sync with with leader just to send over the empty snapshot.


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