<lazyDeserialization enabled="true"/>
Marshalling is the process of converting Java POJOs into something that can be written in a format that can be transfered over the wire. Unmarshalling is the reverse process whereby data read from a wire format is transformed back into Java POJOs. Infinispan uses marshalling/unmarshalling in order to:
Transform data so that it can be send over to other Infinispan nodes in a cluster.
Transform data so that it can be stored in underlying cache stores.
Store data in Infinispan in a wire format to provide lazy deserialization capabilities.
Since performance is a very important factor in this process, Infinispan uses JBoss Marshalling framework instead of standard Java Serialization in order to marshall/unmarshall Java POJOs. Amongst other things, this framework enables Infinispan to provide highly efficient ways to marshall internal Infinispan Java POJOs that are constantly used. Apart from providing more efficient ways to marshall Java POJOs, including internal Java classes, JBoss Marshalling uses highly performant java.io.ObjectOutput and java.io.ObjectInput implementations compared to standard java.io.ObjectOutputStream and java.io.ObjectInputStream.
From a users perspective, a very common concern is whether Infinispan supports storing non-Serializable objects. In 4.0, an Infinispan cache instance can only store non-Serializable key or value objects if, and only if:
cache is configured to be a local cache and...
cache is not configured with lazy serialization and...
cache is not configured with any write-behind cache store
If either of these options is true, key/value pairs in the cache will need to be marshalled and currently they require to either to extend java.io.Serializable or java.io.Externalizable. However, since Infinispan 5.0, marshalling non-Serializable key/value objects is supported as long as users can to provide meaningful Externalizer implementations for these non-Seralizable objects, see this article to find out more.
If you're unable to retrofit Serializable or Externalizable into the classes whose instances are stored in Infinispan, you could alternatively use something like XStream to convert your Non-Serializable objects into an String that can be stored into Infinispan. You can find an example on how to use XStream here. The one caveat about using XStream is that it slows down the process of storing key/value objects due to the XML transformation that it needs to do.
Lazy deserialization is the mechanism by which Infinispan by which serialization and deserialization of objects is deferred till the point in time in which they are used and needed. This typically means that any deserialization happens using the thread context class loader of the invocation that requires deserialization, and is an effective mechanism to provide classloader isolation. By default lazy deserialization is disabled but if you want to enable it, you can do it like this:
Via XML at the Cache level, either under <namedCache> or <default> elements:
<lazyDeserialization enabled="true"/>
Programmatically:
Configuration configuration = ... configuration.setUseLazyDeserialization(true);
Note: Since 5.0 onwards, lazyDeserialization has been renamed to storeAsBinary to better represent its functionality:
<storeAsBinary enabled="true"/>
The programmatic configuration has changed as well together with a move towards more fluent configuration:
Configuration configuration = ... configuration.fluent().storeAsBinary();
When using lazy deserialization/storing as binary, keys and values are wrapped as MarshalledValues. It is this wrapper class that transparently takes care of serialization and deserialization on demand, and internally may have a reference to the object itself being wrapped, or the serialized, byte array representation of this object
This has a particular effect on the behavior of equality. The equals() method of this class will either compare binary representations (byte arrays) or delegate to the wrapped object instance's equals() method, depending on whether both instances being compared are in serialized or deserialized form at the time of comparison. If one of the instances being compared is in one form and the other in another form, then one instance is either serialized or deserialized. The preference will be to compare object representations, unless the cache is compacted, in which case byte array comparison is favored.
This will affect the way keys stored in the cache will work, when storeAsBinary is used, since comparisons happen on the key which will be wrapped by a MarshalledValue. Implementers of equals() methods on their keys need to be aware of the behavior of equality comparison, when a key is wrapped as a MarshalledValue, as detailed above.
Internally, Infinispan uses an implementation of this Marshaller interface in order to marshall/unmarshall Java objects so that they're sent other nodes in the grid, or so that they're stored in a cache store, or even so to transform them into byte arrays for lazy deserialization.
By default, Infinispan uses the VersionAwareMarshaller which, as the name suggests, adds a version short to the start of any stream when writing, enabling similar VersionAwareMarshaller instances to read the version short and know which specific marshaller implementation to delegate the call to. Using a VersionAwareMarshaller helps achieve wire protocol compatibility between minor releases but still affords us the flexibility to tweak and improve the wire protocol between minor or micro releases. Optionally, Infinispan users to optionally provide their own marshaller, for example:
Via XML at the CacheManager level, under <global> element:
<serialization marshallerClass="com.acme.MyMarshaller"/>
Programatically:
GlobalConfiguration globalConfiguration = ...
globalConfiguration.setMarshallerClass("com.acme.MyMarshaller")
Sometimes it might happen that the Infinispan marshalling layer, and in particular JBoss Marshalling, might have issues marshalling/unmarshalling some user object. In Infinispan 4.0, marshalling exceptions will contain further information on the objects that were being marshalled. Example:
<code class="jive-code jive-java">java.io.NotSerializableException: java.lang.Object at org.jboss.marshalling.river.RiverMarshaller.doWriteObject(RiverMarshaller.java:857) at org.jboss.marshalling.AbstractMarshaller.writeObject(AbstractMarshaller.java:407) at org.infinispan.marshall.exts.ReplicableCommandExternalizer.writeObject(ReplicableCommandExternalizer.java:54) at org.infinispan.marshall.jboss.ConstantObjectTable$ExternalizerAdapter.writeObject(ConstantObjectTable.java:267) at org.jboss.marshalling.river.RiverMarshaller.doWriteObject(RiverMarshaller.java:143) at org.jboss.marshalling.AbstractMarshaller.writeObject(AbstractMarshaller.java:407) at org.infinispan.marshall.jboss.JBossMarshaller.objectToObjectStream(JBossMarshaller.java:167) at org.infinispan.marshall.VersionAwareMarshaller.objectToBuffer(VersionAwareMarshaller.java:92) at org.infinispan.marshall.VersionAwareMarshaller.objectToByteBuffer(VersionAwareMarshaller.java:170) at org.infinispan.marshall.VersionAwareMarshallerTest.testNestedNonSerializable(VersionAwareMarshallerTest.java:415) Caused by: an exception which occurred: in object java.lang.Object@b40ec4 in object org.infinispan.commands.write.PutKeyValueCommand@df661da7 ... Removed 22 stack frames </code>
The way the "in object" messages are read is the same in which stacktraces are read. The highest "in object" being the most inner one and the lowest "in object" message being the most outer one. So, the above example indicates that a java.lang.Object instance contained in an instance of org.infinispan.commands.write.PutKeyValueCommand could not be serialized because java.lang.Object@b40ec4 is not serializable.
This is not all though! If you enable DEBUG or TRACE logging levels, marshalling exceptions will contain show the toString() representations of objects in the stacktrace. For example:
<code class="jive-code jive-java">java.io.NotSerializableException: java.lang.Object
...
Caused by: an exception which occurred:
in object java.lang.Object@b40ec4
-> toString = java.lang.Object@b40ec4
in object org.infinispan.commands.write.PutKeyValueCommand@df661da7
-> toString = PutKeyValueCommand{key=k, value=java.lang.Object@b40ec4, putIfAbsent=false, lifespanMillis=0, maxIdleTimeMillis=0}
</code>
With regards to unmarshalling exceptions, showing such level of information it's a lot more complicated but where possible. Infinispan will provide class type information. For example:
<code class="jive-code jive-java">java.io.IOException: Injected failue! at org.infinispan.marshall.VersionAwareMarshallerTest$1.readExternal(VersionAwareMarshallerTest.java:426) at org.jboss.marshalling.river.RiverUnmarshaller.doReadNewObject(RiverUnmarshaller.java:1172) at org.jboss.marshalling.river.RiverUnmarshaller.doReadObject(RiverUnmarshaller.java:273) at org.jboss.marshalling.river.RiverUnmarshaller.doReadObject(RiverUnmarshaller.java:210) at org.jboss.marshalling.AbstractUnmarshaller.readObject(AbstractUnmarshaller.java:85) at org.infinispan.marshall.jboss.JBossMarshaller.objectFromObjectStream(JBossMarshaller.java:210) at org.infinispan.marshall.VersionAwareMarshaller.objectFromByteBuffer(VersionAwareMarshaller.java:104) at org.infinispan.marshall.VersionAwareMarshaller.objectFromByteBuffer(VersionAwareMarshaller.java:177) at org.infinispan.marshall.VersionAwareMarshallerTest.testErrorUnmarshalling(VersionAwareMarshallerTest.java:431) Caused by: an exception which occurred: in object of type org.infinispan.marshall.VersionAwareMarshallerTest$1 </code>
In this example, an IOException was thrown when trying to unmarshall a instance of the inner class org.infinispan.marshall.VersionAwareMarshallerTest$1. In similar fashion to marshalling exceptions, when DEBUG or TRACE logging levels are enabled, classloader information of the class type is provided. For example:
<code class="jive-code jive-java">java.io.IOException: Injected failue! ... Caused by: an exception which occurred: in object of type org.infinispan.marshall.VersionAwareMarshallerTest$1 -> classloader hierarchy: -> type classloader = sun.misc.Launcher$AppClassLoader@198dfaf ->...file:/opt/eclipse/configuration/org.eclipse.osgi/bundles/285/1/.cp/eclipse-testng.jar ->...file:/opt/eclipse/configuration/org.eclipse.osgi/bundles/285/1/.cp/lib/testng-jdk15.jar ->...file:/home/galder/jboss/infinispan/code/trunk/core/target/test-classes/ ->...file:/home/galder/jboss/infinispan/code/trunk/core/target/classes/ ->...file:/home/galder/.m2/repository/org/testng/testng/5.9/testng-5.9-jdk15.jar ->...file:/home/galder/.m2/repository/net/jcip/jcip-annotations/1.0/jcip-annotations-1.0.jar ->...file:/home/galder/.m2/repository/org/easymock/easymockclassextension/2.4/easymockclassextension-2.4.jar ->...file:/home/galder/.m2/repository/org/easymock/easymock/2.4/easymock-2.4.jar ->...file:/home/galder/.m2/repository/cglib/cglib-nodep/2.1_3/cglib-nodep-2.1_3.jar ->...file:/home/galder/.m2/repository/javax/xml/bind/jaxb-api/2.1/jaxb-api-2.1.jar ->...file:/home/galder/.m2/repository/javax/xml/stream/stax-api/1.0-2/stax-api-1.0-2.jar ->...file:/home/galder/.m2/repository/javax/activation/activation/1.1/activation-1.1.jar ->...file:/home/galder/.m2/repository/jgroups/jgroups/2.8.0.CR1/jgroups-2.8.0.CR1.jar ->...file:/home/galder/.m2/repository/org/jboss/javaee/jboss-transaction-api/1.0.1.GA/jboss-transaction-api-1.0.1.GA.jar ->...file:/home/galder/.m2/repository/org/jboss/marshalling/river/1.2.0.CR4-SNAPSHOT/river-1.2.0.CR4-SNAPSHOT.jar ->...file:/home/galder/.m2/repository/org/jboss/marshalling/marshalling-api/1.2.0.CR4-SNAPSHOT/marshalling-api-1.2.0.CR4-SNAPSHOT.jar ->...file:/home/galder/.m2/repository/org/jboss/jboss-common-core/2.2.14.GA/jboss-common-core-2.2.14.GA.jar ->...file:/home/galder/.m2/repository/org/jboss/logging/jboss-logging-spi/2.0.5.GA/jboss-logging-spi-2.0.5.GA.jar ->...file:/home/galder/.m2/repository/log4j/log4j/1.2.14/log4j-1.2.14.jar ->...file:/home/galder/.m2/repository/com/thoughtworks/xstream/xstream/1.2/xstream-1.2.jar ->...file:/home/galder/.m2/repository/xpp3/xpp3_min/1.1.3.4.O/xpp3_min-1.1.3.4.O.jar ->...file:/home/galder/.m2/repository/com/sun/xml/bind/jaxb-impl/2.1.3/jaxb-impl-2.1.3.jar -> parent classloader = sun.misc.Launcher$ExtClassLoader@1858610 ->...file:/usr/java/jdk1.5.0_19/jre/lib/ext/localedata.jar ->...file:/usr/java/jdk1.5.0_19/jre/lib/ext/sunpkcs11.jar ->...file:/usr/java/jdk1.5.0_19/jre/lib/ext/sunjce_provider.jar ->...file:/usr/java/jdk1.5.0_19/jre/lib/ext/dnsns.jar ... Removed 22 stack frames </code>
Finding the root cause of marshalling/unmarshalling exceptions can sometimes be really daunting but we hope that the above improvements would help get to the bottom of those in a more quicker and efficient manner.