Upgrade guide

The purpose of this guide is to detail changes made by successive versions of the Java driver.

2.0.11

2.0.11 preserves binary compatibility with previous versions. There are a few changes in the driver’s behavior:

  1. The DefaultRetryPolicy‘s behaviour has changed in the case of an Unavailable exception received from a request. The new behaviour will cause the driver to process a Retry on a different node at most once, otherwise an exception will be thrown. This change makes sense in the case where the node tried initially for the request happens to be isolated from the rest of the cluster (e.g. because of a network partition) but can still answer to the client normally. In this case, trying another node has a chance of success. The previous behaviour was to always throw an exception.

  2. A BuiltStatement is now considered non-idempotent whenever a fcall() or raw() is used to build a value to be inserted in the database. If you know that the CQL functions or expressions are safe, use setIdempotent(true) on the statement.

  3. The list of contact points provided at startup is now shuffled before trying to open the control connection, so that multiple clients with the same contact points don’t all pick the same control host. As a result, you can’t assume that the driver will try contact points in a deterministic order. In particular, if you use the DCAwareRoundRobinPolicy without specifying a primary datacenter name, make sure that you only provide local hosts as contact points.

2.0.x to 2.0.10

We try to avoid breaking changes within a branch (2.0.x to 2.0.y), but 2.0.10 saw a lot of new features and internal improvements. There is one breaking change:

  1. LatencyTracker#update now has a different signature and takes two new parameters: the statement that has been executed (never null), and the exception thrown while executing the query (or null, if the query executed successfully). Existing implementations of this interface, once upgraded to the new method signature, should continue to work as before.

The following might also be of interest:

  1. SocketOptions#getTcpNoDelay() is now TRUE by default (it was previously undefined). This reflects the new behavior of Netty (which was upgraded from version 3.9.0 to 4.0.27): TCP_NODELAY is now turned on by default, instead of depending on the OS default like in previous versions.

  2. Netty is not shaded anymore in the default Maven artifact. However we publish a shaded artifact under a different classifier.

  3. The internal initialization sequence of the Cluster object has been slightly changed: some fields that were previously initialized in the constructor are now set when the init() method is called. In particular, Cluster#getMetrics() will return null until the cluster is initialized.

1.0 to 2.0

We used the opportunity of a major version bump to incorporate your feedback and improve the API, to fix a number of inconsistencies and remove cruft. Unfortunately this means there are some breaking changes, but the new API should be both simpler and more complete.

The following describes the changes for 2.0 that are breaking changes of the 1.0 API. For ease of use, we distinguish two categories of API changes: the “main” ones and the “other” ones.

The “main” API changes are the ones that are either likely to affect most upgraded apps or are incompatible changes that, even if minor, will not be detected at compile time. Upgraders are highly encouraged to check this list of “main” changes while upgrading their application to 2.0 (even though most applications are likely to be affected by only a handful of changes).

The “other” list is, well, other changes: those that are likely to affect a minor number of applications and will be detected by compile time errors anyway. It is ok to skip those initially and only come back to them if you have trouble compiling your application after an upgrade.

Main API changes

  1. The Query class has been renamed into Statement (it was confusing to some that the BoundStatement was not a Statement). To allow this, the old Statement class has been renamed to RegularStatement.

  2. The Cluster and Session shutdown API has changed. There is now a closeAsync that is asynchronous but returns a Future on the completion of the shutdown process. There is also a close shortcut that does the same but blocks. Also, close now waits for ongoing queries to complete by default (but you can force the closing of all connections if you want to).

  3. NoHostAvailableException#getErrors now returns the full exception objects for each node instead of just a message. In other words, it returns a Map<InetAddress, Throwable> instead of a Map<InetAddress, String>.

  4. Statement#getConsistencyLevel (previously Query#getConsistencyLevel, see first point) will now return null by default (instead of CL.ONE), with the meaning of “use the default consistency level”. The default consistency level can now be configured through the new QueryOptions object in the cluster Configuration.

  5. The Metrics class now uses the Codahale metrics library version 3 (version 2 was used previously). This new major version of the library has many API changes compared to its version 2 (see the release notes for details), which can thus impact consumers of the Metrics class. Furthermore, the default JmxReporter now includes a name specific to the cluster instance (to avoid conflicts when multiple Cluster instances are created in the same JVM). As a result, tools that were polling JMX info will have to be updated accordingly.

  6. The QueryBuilder#in method now has the following special case: using QueryBuilder.in(QueryBuilder.bindMarker()) will generate the string IN ?, not IN (?) as was the case in 1.0. The reasoning being that the former syntax, made valid by CASSANDRA-4210 is a lot more useful than IN (?), as the latter can more simply use an equality. Note that if you really want to output IN (?) with the query builder, you can use QueryBuilder.in(QueryBuilder.raw("?")).

  7. When binding values by name in BoundStatement (i.e. using the setX(String, X) methods), if more than one variable have the same name, then all values corresponding to that variable name are set instead of just the first occurrence.

  8. The QueryBuilder#raw method does not automatically add quotes anymore, but rather output its result without any change (as the raw name implies). This means for instance that eq("x", raw(foo)) will output x = foo, not x = 'foo' (you don’t need the raw method to output the latter string).

  9. The QueryBuilder will now sometimes use the new ability to send value as bytes instead of serializing everything to string. In general the QueryBuilder will do the right thing, but if you were calling the getQueryString() method on a Statement created with a QueryBuilder (for other reasons than to prepare a query) then the returned string may contain bind markers in place of some of the values provided (and in that case, getValues() will contain the values corresponding to those markers). If need be, it is possible to force the old behavior by using the new setForceNoValues() method.

Other API Changes

  1. Creating a Cluster instance (through Cluster#buildFrom or the Cluster.Builder#build method) does not create any connection right away anymore (and thus cannot throw a NoHostAvailableException or an AuthenticationException). Instead, the initial contact points are checked the first time a call to Cluster#connect is done. If for some reason you want to emulate the previous behavior, you can use the new method Cluster#init: Cluster.builder().build() in 1.0 is equivalent to Cluster.builder().build().init() in 2.0.

  2. Methods from Metadata, KeyspaceMetadata and TableMetadata now use by default case insensitive identifiers (for keyspace, table and column names in parameter). You can double-quote an identifier if you want it to be a case sensitive one (as you would do in CQL) and there is a Metadata.quote helper method for that.

  3. The TableMetadata#getClusteringKey method has been renamed TableMetadata#getClusteringColumns to match the “official” vocabulary.

  4. The UnavailableException#getConsistency method has been renamed to UnavailableException#getConsistencyLevel for consistency with the method of QueryTimeoutException.

  5. The RegularStatement class (ex-Statement class, see above) must now implement two additional methods: RegularStatement#getKeyspace and RegularStatement#getValues. If you had extended this class, you will have to implement those new methods, but both can return null if they are not useful in your case.

  6. The Cluster.Initializer interface should now implement 2 new methods: Cluster.Initializer#getInitialListeners (which can return an empty collection) and Cluster.Initializer#getClusterName (which can return null).

  7. The Metadata#getReplicas method now takes 2 arguments. On top of the partition key, you must now provide the keyspace too. The previous behavior was buggy: it’s impossible to properly return the full list of replica for a partition key without knowing the keyspace since replication may depend on the keyspace).

  8. The method LoadBalancingPolicy#newQueryPlan() method now takes the currently logged keyspace as 2nd argument. This information is necessary to do proper token aware balancing (see preceding point).

  9. The ResultSetFuture#set and ResultSetFuture#setException methods have been removed (from the public API at least). They were never meant to be exposed publicly: a resultSetFuture is always set by the driver itself and should not be set manually.

  10. The deprecated since 1.0.2 Host.HealthMonitor class has been removed. You will now need to use Host#isUp and Cluster#register if you were using that class.

Features available only with Cassandra 2.0

This section details the biggest additions to 2.0 API wise. It is not an exhaustive list of new features in 2.0.

  1. The new BatchStatement class allows to group any type of insert Statements (BoundStatement or RegularStatement) for execution as a batch. For instance, you can do something like:

    List<String> values = ...;
PreparedStatement ps = session.prepare("INSERT INTO myTable(value) VALUES (?)");
BatchStatement bs = new BatchStatement();
for (String value : values)
   bs.add(ps.bind(value));
session.execute(bs);

  2. SimpleStatement can now take a list of values in addition to the query. This allows to do the equivalent of a prepare+execute but with only one round-trip to the server and without keeping the prepared statement after the execution.

    This is typically useful if a given query should be executed only once (i.e. you don’t want to prepare it) but you also don’t want to serialize all values into strings. Shortcut Session#execute() and Session#executeAsync() methods are also provided so you that you can do:

    String imgName = ...;
ByteBuffer imgBytes = ...;
session.execute("INSERT INTO images(name, bytes) VALUES (?, ?)", imgName, imgBytes);

  3. SELECT queries are now “paged” under the hood. In other words, if a query yields a very large result, only the beginning of the ResultSet will be fetched initially, the rest being fetched “on-demand”. In practice, this means that:

    for (Row r : session.execute("SELECT * FROM mytable"))
   ... process r ...

    should not timeout or OOM the server anymore even if “mytable” contains a lot of data. In general paging should be transparent for the application (as in the example above), but the implementation provides a number of knobs to fine tune the behavior of that paging:

  • the size of each “page” can be set per-query (Statement#setFetchSize())
  • the ResultSet object provides 2 methods to check the state of paging (ResultSet#getAvailableWithoutFetching and ResultSet#isFullyFetched) as well as a mean to force the pre-fetching of the next page (ResultSet#fetchMoreResults).