releasenotes.md 22 KB
ZooKeeper 3.0.0 Release Notes
These release notes include new developer and user facing incompatibilities, features, and major improvements.
Migration Instructions when Upgrading to 3.0.0
You should only have to read this section if you are upgrading from a previous version of ZooKeeper to version 3.0.0, otw skip down to changes
A small number of changes in this release have resulted in non-backward compatible Zookeeper client user code and server instance data. The following instructions provide details on how to migrate code and date from version 2.2.1 to version 3.0.0.
Note: ZooKeeper increments the major version number (major.minor.fix) when backward incompatible changes are made to the source base. As part of the migration from SourceForge we changed the package structure (com.yahoo.zookeeper.* to org.apache.zookeeper.*) and felt it was a good time to incorporate some changes that we had been withholding. As a result the following will be required when migrating from 2.2.1 to 3.0.0 version of ZooKeeper.
Migrating Client Code
The underlying client-server protocol has changed in version 3.0.0 of ZooKeeper. As a result clients must be upgraded along with serving clusters to ensure proper operation of the system (old pre-3.0.0 clients are not guaranteed to operate against upgraded 3.0.0 servers and vice-versa).
Watch Management
In previous releases of ZooKeeper any watches registered by clients were lost if the client lost a connection to a ZooKeeper server. This meant that developers had to track watches they were interested in and reregister them if a session disconnect event was received. In this release the client library tracks watches that a client has registered and reregisters the watches when a connection is made to a new server. Applications that still manually reregister interest should continue working properly as long as they are able to handle unsolicited watches. For example, an old application may register a watch for /foo and /goo, lose the connection, and reregister only /goo. As long as the application is able to receive a notification for /foo, (probably ignoring it) it does not need to be changed. One caveat to the watch management: it is possible to miss an event for the creation and deletion of a znode if watching for creation and both the create and delete happens while the client is disconnected from ZooKeeper.
This release also allows clients to specify call specific watch functions. This gives the developer the ability to modularize logic in different watch functions rather than cramming everything in the watch function attached to the ZooKeeper handle. Call specific watch functions receive all session events for as long as they are active, but will only receive the watch callbacks for which they are registered.
Java API
- The java package structure has changed from com.yahoo.zookeeper* to org.apache.zookeeper*. This will probably effect all of your java code which makes use of ZooKeeper APIs (typically import statements)
- A number of constants used in the client ZooKeeper API were re-specified using enums (rather than ints). See ZOOKEEPER-7, ZOOKEEPER-132 and ZOOKEEPER-139 for full details
- ZOOKEEPER-18 removed KeeperStateChanged, use KeeperStateDisconnected instead
Also see the current java API
C API
- A number of constants used in the client ZooKeeper API were renamed in order to reduce namespace collision, see ZOOKEEPER-6 for full details
Migrating Server Data
The following issues resulted in changes to the on-disk data format (the snapshot and transaction log files contained within the ZK data directory) and require a migration utility to be run.
- ZOOKEEPER-27 Unique DB identifiers for servers and clients
- ZOOKEEPER-32 CRCs for ZooKeeper data
- ZOOKEEPER-33 Better ACL management
- ZOOKEEPER-38 headers (version+) in log/snap files
The following must be run once, and only once, when upgrading the ZooKeeper server instances to version 3.0.0.
Note
The and directories referenced below are specified by the dataLogDir and dataDir specification in your ZooKeeper config file respectively. dataLogDir defaults to the value of dataDir if not specified explicitly in the ZooKeeper server config file (in which case provide the same directory for both parameters to the upgrade utility).
- Shutdown the ZooKeeper server cluster.
- Backup your and directories
Run upgrade using
bin/zkServer.sh upgrade <dataLogDir> <dataDir>or
java -classpath pathtolog4j:pathtozookeeper.jar UpgradeMain <dataLogDir> <dataDir>where is the directory where all transaction logs (log.) are stored. is the directory where all the snapshots (snapshot.) are stored.
Restart the cluster.
If you have any failure during the upgrade procedure keep reading to sanitize your database.
This is how upgrade works in ZooKeeper. This will help you troubleshoot in case you have problems while upgrading
- Upgrade moves files from
<dataLogDir>and<dataDir>to<dataLogDir>/version-1/and<dataDir>/version-1respectively (version-1 sub-directory is created by the upgrade utility).- Upgrade creates a new version sub-directory
<dataDir>/version-2and<dataLogDir>/version-2- Upgrade reads the old database from
<dataDir>/version-1and<dataLogDir>/version-1into the memory and creates a new upgraded snapshot.- Upgrade writes the new database in
<dataDir>/version-2.Troubleshooting.
- In case you start ZooKeeper 3.0 without upgrading from 2.0 on a 2.0 database - the servers will start up with an empty database. This is because the servers assume that
<dataDir>/version-2and<dataLogDir>/version-2will have the database to start with. Since this will be empty in case of no upgrade, the servers will start with an empty database. In such a case, shutdown the ZooKeeper servers, remove the version-2 directory (remember this will lead to loss of updates after you started 3.0.) and then start the upgrade procedure.- If the upgrade fails while trying to rename files into the version-1 directory, you should try and move all the files under
<dataDir>/version-1and<dataLogDir>/version-1to<dataDir>and<dataLogDir>respectively. Then try upgrade again.- If you do not wish to run with ZooKeeper 3.0 and prefer to run with ZooKeeper 2.0 and have already upgraded - you can run ZooKeeper 2 with the
<dataDir>and<dataLogDir>directories changed to<dataDir>/version-1and<dataLogDir>/version-1. Remember that you will lose all the updates that you made after the upgrade.Migrating Server Configuration
There is a significant change to the ZooKeeper server configuration file.
The default election algorithm, specified by the electionAlg configuration attribute, has changed from a default of 0 to a default of 3. See Cluster Options section of the administrators guide, specifically the electionAlg and server.X properties.
You will either need to explicitly set electionAlg to it's previous default value of 0 or change your server.X options to include the leader election port.
Changes Since ZooKeeper 2.2.1
Version 2.2.1 code, documentation, binaries, etc... are still accessible on SourceForge
Issue Notes ZOOKEEPER-43 Server side of auto reset watches. ZOOKEEPER-132 Create Enum to replace CreateFlag in ZooKepper.create method ZOOKEEPER-139 Create Enums for WatcherEvent's KeeperState and EventType ZOOKEEPER-18 keeper state inconsistency ZOOKEEPER-38 headers in log/snap files ZOOKEEPER-8 Stat enchaned to include num of children and size ZOOKEEPER-6 List of problem identifiers in zookeeper.h ZOOKEEPER-7 Use enums rather than ints for types and state ZOOKEEPER-27 Unique DB identifiers for servers and clients ZOOKEEPER-32 CRCs for ZooKeeper data ZOOKEEPER-33 Better ACL management ZOOKEEPER-203 fix datadir typo in releasenotes ZOOKEEPER-145 write detailed release notes for users migrating from 2.x to 3.0 ZOOKEEPER-23 Auto reset of watches on reconnect ZOOKEEPER-191 forrest docs for upgrade. ZOOKEEPER-201 validate magic number when reading snapshot and transaction logs ZOOKEEPER-200 the magic number for snapshot and log must be different ZOOKEEPER-199 fix log messages in persistence code ZOOKEEPER-197 create checksums for snapshots ZOOKEEPER-198 apache license header missing from FollowerSyncRequest.java ZOOKEEPER-5 Upgrade Feature in Zookeeper server. ZOOKEEPER-194 Fix terminology in zookeeperAdmin.xml ZOOKEEPER-151 Document change to server configuration ZOOKEEPER-193 update java example doc to compile with latest zookeeper ZOOKEEPER-187 CreateMode api docs missing ZOOKEEPER-186 add new "releasenotes.xml" to forrest documentation ZOOKEEPER-190 Reorg links to docs and navs to docs into related sections ZOOKEEPER-189 forrest build not validated xml of input documents ZOOKEEPER-188 Check that election port is present for all servers ZOOKEEPER-185 Improved version of FLETest ZOOKEEPER-184 tests: An explicit include derective is needed for the usage of memcpy functions ZOOKEEPER-183 Array subscript is above array bounds in od_completion, src/cli.c. ZOOKEEPER-182 zookeeper_init accepts empty host-port string and returns valid pointer to zhandle_t. ZOOKEEPER-17 zookeeper_init doc needs clarification ZOOKEEPER-181 Some Source Forge Documents did not get moved over: javaExample, zookeeperTutorial, zookeeperInternals ZOOKEEPER-180 Placeholder sections needed in document for new topics that the umbrella jira discusses ZOOKEEPER-179 Programmer's Guide "Basic Operations" section is missing content ZOOKEEPER-178 FLE test. ZOOKEEPER-159 Cover two corner cases of leader election ZOOKEEPER-156 update programmer guide with acl details from old wiki page ZOOKEEPER-154 reliability graph diagram in overview doc needs context ZOOKEEPER-157 Peer can't find existing leader ZOOKEEPER-155 improve "the zookeeper project" section of overview doc ZOOKEEPER-140 Deadlock in QuorumCnxManager ZOOKEEPER-147 This is version of the documents with most of the [tbd...] scrubbed out ZOOKEEPER-150 zookeeper build broken ZOOKEEPER-136 sync causes hang in all followers of quorum. ZOOKEEPER-134 findbugs cleanup ZOOKEEPER-133 hudson tests failing intermittently ZOOKEEPER-144 add tostring support for watcher event, and enums for event type/state ZOOKEEPER-21 Improve zk ctor/watcher ZOOKEEPER-142 Provide Javadoc as to the maximum size of the data byte array that may be stored within a znode ZOOKEEPER-93 Create Documentation for Zookeeper ZOOKEEPER-117 threading issues in Leader election ZOOKEEPER-137 client watcher objects can lose events ZOOKEEPER-131 Old leader election can elect a dead leader over and over again ZOOKEEPER-130 update build.xml to support apache release process ZOOKEEPER-118 findbugs flagged switch statement in followerrequestprocessor.run ZOOKEEPER-115 Potential NPE in QuorumCnxManager ZOOKEEPER-114 cleanup ugly event messages in zookeeper client ZOOKEEPER-112 src/java/main ZooKeeper.java has test code embedded into it. ZOOKEEPER-39 Use Watcher objects rather than boolean on read operations. ZOOKEEPER-97 supports optional output directory in code generator. ZOOKEEPER-101 Integrate ZooKeeper with "violations" feature on hudson ZOOKEEPER-105 Catch Zookeeper exceptions and print on the stderr. ZOOKEEPER-42 Change Leader Election to fast tcp. ZOOKEEPER-48 auth_id now handled correctly when no auth ids present ZOOKEEPER-44 Create sequence flag children with prefixes of 0's so that they can be lexicographically sorted. ZOOKEEPER-108 Fix sync operation reordering on a Quorum. ZOOKEEPER-25 Fuse module for Zookeeper. ZOOKEEPER-58 Race condition on ClientCnxn.java ZOOKEEPER-56 Add clover support to build.xml. ZOOKEEPER-75 register the ZooKeeper mailing lists with nabble.com ZOOKEEPER-54 remove sleeps in the tests. ZOOKEEPER-55 build.xml failes to retrieve a release number from SVN and the ant target "dist" fails ZOOKEEPER-89 invoke WhenOwnerListener.whenNotOwner when the ZK connection fails ZOOKEEPER-90 invoke WhenOwnerListener.whenNotOwner when the ZK session expires and the znode is the leader ZOOKEEPER-82 Make the ZooKeeperServer more DI friendly. ZOOKEEPER-110 Build script relies on svnant, which is not compatible with subversion 1.5 working copies ZOOKEEPER-111 Significant cleanup of existing tests. ZOOKEEPER-122 Fix NPE in jute's Utils.toCSVString. ZOOKEEPER-123 Fix the wrong class is specified for the logger. ZOOKEEPER-2 Fix synchronization issues in QuorumPeer and FastLeader election. ZOOKEEPER-125 Remove unwanted class declaration in FastLeaderElection. ZOOKEEPER-61 Address in client/server test cases. ZOOKEEPER-75 cleanup the library directory ZOOKEEPER-109 cleanup of NPE and Resource issue nits found by static analysis ZOOKEEPER-76 Commit 677109 removed the cobertura library, but not the build targets. ZOOKEEPER-63 Race condition in client close ZOOKEEPER-70 Add skeleton forrest doc structure for ZooKeeper ZOOKEEPER-79 Document jacob's leader election on the wiki recipes page ZOOKEEPER-73 Move ZK wiki from SourceForge to Apache ZOOKEEPER-72 Initial creation/setup of ZooKeeper ASF site. ZOOKEEPER-71 Determine what to do re ZooKeeper Changelog ZOOKEEPER-68 parseACLs in ZooKeeper.java fails to parse elements of ACL, should be lastIndexOf rather than IndexOf ZOOKEEPER-130 update build.xml to support apache release process. ZOOKEEPER-131 Fix Old leader election can elect a dead leader over and over again. ZOOKEEPER-137 client watcher objects can lose events ZOOKEEPER-117 threading issues in Leader election ZOOKEEPER-128 test coverage on async client operations needs to be improved ZOOKEEPER-127 Use of non-standard election ports in config breaks services ZOOKEEPER-53 tests failing on solaris. ZOOKEEPER-172 FLE Test ZOOKEEPER-41 Sample startup script ZOOKEEPER-33 Better ACL management ZOOKEEPER-49 SetACL does not work ZOOKEEPER-20 Child watches are not triggered when the node is deleted ZOOKEEPER-15 handle failure better in build.xml:test ZOOKEEPER-11 ArrayList is used instead of List ZOOKEEPER-45 Restructure the SVN repository after initial import ZOOKEEPER-1 Initial ZooKeeper code contribution from Yahoo!