I get what appears to me to be incorrect session handling when the Apache
Wicket session size of my application approaches my self-imposed limit of
900kB (which itself is near the Google App Engine (GAE) limit of 1MB).
I see flash messages set during the composition of a web response using
org.apache.wicket.Session#info(Serializable message)
occur again after the subsequent web response, even though no flash message
was set subsequently.
I believe that this effect might be due to the large session size and
either:
· the Wicket app's interplay of:
· IStoreSettings#setMaxSizePerSession(...)
· DefaultPageManagerProvider
· MemorySizeEvictionStrategy
or
· GAE's session handling
causing incorrect operation.
Has anyone else encountered this problem or does anyone have any suggestion
as to what I can do?
*My code*
public class MyApplication extends WebApplication
{
...
// GAE has a maximum session size of 1MB
private static final Bytes G_BY_MAXIMUM_SIZE_SESSION_PAGE_INSTANCES =
Bytes.kilobytes(900);
@Override
protected void init()
{
super.init();
...
IStoreSettings ssStoreSettings = getStoreSettings();
ssStoreSettings.setMaxSizePerSession(
G_BY_MAXIMUM_SIZE_SESSION_PAGE_INSTANCES);
// This prevents use of a new AsynchronousDataStore instance,
// which attempts to start a new thread. This is forbidden by GAE.
ssStoreSettings.setAsynchronous(false);
IPageManagerContext pmcPageManagerContext = getPageManagerContext();
DataStoreEvictionStrategy dsevEvictionStrategy =
new
MemorySizeEvictionStrategy(G_BY_MAXIMUM_SIZE_SESSION_PAGE_INSTANCES);
GaePageManagerProvider pmpPageManagerProvider = new
GaePageManagerProvider(
this, pmcPageManagerContext, dsevEvictionStrategy);
setPageManagerProvider(pmpPageManagerProvider);
...
}
...
}
...
/**
* This class extends <code>DefaultPageManagerProvider</code> as required to
* conform to Google App Engine restrictions.
*/
public class GaePageManagerProvider extends DefaultPageManagerProvider
{
private static final Logger m_logger = Logger.getLogger(
GaePageManagerProvider.class.getName());
private IPageManagerContext m_pmcPageManagerContext = null;
private DataStoreEvictionStrategy m_dsevEvictionStrategy = null;
/**
* The constructor.
* @param app
* The instance of the application.
* This must not be <code>null</code>.
* @param pmcPageManagerContext
* The application's page manager context.
* @param dsevEvictionStrategy
* The data store eviction strategy to be used.
*/
public GaePageManagerProvider(Application app,
IPageManagerContext pmcPageManagerContext,
DataStoreEvictionStrategy dsevEvictionStrategy)
{
super(app);
m_pmcPageManagerContext = pmcPageManagerContext;
m_dsevEvictionStrategy = dsevEvictionStrategy;
}
@Override
protected IDataStore newDataStore()
{
IDataStore dsResult = null;
dsResult = new HttpSessionDataStore(m_pmcPageManagerContext,
m_dsevEvictionStrategy)
{
// This method override is for logging purposes only
@Override
public void storeData(String sessionId, int pageId,
byte[] pageAsBytes)
{
int nPageSize = -1;
if (pageAsBytes != null)
nPageSize = pageAsBytes.length;
final int N_SIZE_FINE = 100000;
final int N_SIZE_INFO = 500000;
final int N_SIZE_WARNING = 800000;
if (nPageSize >= N_SIZE_FINE)
{
Level lvl;
if (nPageSize >= N_SIZE_WARNING)
lvl = Level.WARNING;
else if (nPageSize >= N_SIZE_INFO)
lvl = Level.INFO;
else
lvl = Level.FINE;
m_logger.log(lvl, String.format("Storing a page in the"
+ " application's DefaultPageManagerProvider's"
+ " HttpSessionDataStore with parameters:"
+ "\n sessionId = %s,"
+ "\n pageId = %d,"
+ "\n pageAsBytes.length = %d", sessionId, pageId, nPageSize));
}
super.storeData(sessionId, pageId, pageAsBytes);
}
};
return dsResult;
}
}
*My development environment*
Java: 1.6.0_35; Java HotSpot(TM) Client VM 20.10-b01
GAE/J SDK: 1.7.2
Web framework: Apache Wicket 1.5.8
Web browser: Mozilla Firefox 15.0.1
Operating system: Windows XP version 5.1 running on x86; Cp1252; en_GB (nb)
IDE: NetBeans 7.2 (build 201207171143)
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