hanm commented on a change in pull request #1069: ZOOKEEPER-3056: Fails to load
database with missing snapshot file but with valid transaction log file.
URL: https://github.com/apache/zookeeper/pull/1069#discussion_r319679426
##########
File path:
zookeeper-server/src/main/java/org/apache/zookeeper/server/persistence/FileTxnSnapLog.java
##########
@@ -232,11 +240,19 @@ public long restore(DataTree dt, Map<Long, Integer>
sessions, PlayBackListener l
} else {
trustEmptyDB = autoCreateDB;
}
+
if (-1L == deserializeResult) {
/* this means that we couldn't find any snapshot, so we need to
* initialize an empty database (reported in ZOOKEEPER-2325) */
if (txnLog.getLastLoggedZxid() != -1) {
- throw new IOException("No snapshot found, but there are log
entries. " + "Something is broken!");
+ // ZOOKEEPER-3056: provides an escape hatch for users upgrading
+ // from old versions of zookeeper (3.4.x, pre 3.5.3).
+ if (!trustEmptySnapshot) {
+ throw new IOException(EMPTY_SNAPSHOT_WARNING + "Something
is broken!");
+ } else {
+ LOG.warn(EMPTY_SNAPSHOT_WARNING + "This should only be
allowed during upgrading.");
+ trustEmptySnapshot = false;
+ }
}
if (trustEmptyDB) {
Review comment:
One concrete example:
* Create a fresh zookeeper cluster with `zookeeper.db.autocreate` set to
false.
* Start a fresh cluster, create a client and issue some transactions.
* The default snap count is 100000 so no snapshot will be created;
`zookeeper.db.autocreate` is set to false so no snapshot will be created upon
server start up.
* Now restart all zookeeper servers. We can't load because there is no
snapshot.
Does this sound a reasonable example to demonstrate the problem with
`trustEmptyDB ` set to false?
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