<Container id="myStatelessContainer" type="STATELESS">
accessTimeout = 30 seconds
callbackThreads = 5
closeTimeout = 5 minutes
garbageCollection = false
idleTimeout = 0 minutes
maxAge = 0 hours
maxAgeOffset = -1
maxSize = 10
minSize = 0
replaceAged = true
replaceFlushed = false
strictPooling = true
sweepInterval = 5 minutes
</Container>StatelessContainer Configuration
A StatelessContainer can be declared via xml in the
<tomee-home>/conf/tomee.xml file or in a WEB-INF/resources.xml file
using a declaration like the following. All properties in the element
body are optional.
Alternatively, a StatelessContainer can be declared via properties in
the <tomee-home>/conf/system.properties file or via Java
VirtualMachine -D properties. The properties can also be used when
embedding TomEE via the javax.ejb.embeddable.EJBContainer API or
InitialContext
myStatelessContainer = new://Container?type=STATELESS
myStatelessContainer.accessTimeout = 30 seconds
myStatelessContainer.callbackThreads = 5
myStatelessContainer.closeTimeout = 5 minutes
myStatelessContainer.garbageCollection = false
myStatelessContainer.idleTimeout = 0 minutes
myStatelessContainer.maxAge = 0 hours
myStatelessContainer.maxAgeOffset = -1
myStatelessContainer.maxSize = 10
myStatelessContainer.minSize = 0
myStatelessContainer.replaceAged = true
myStatelessContainer.replaceFlushed = false
myStatelessContainer.strictPooling = true
myStatelessContainer.sweepInterval = 5 minutesProperties and xml can be mixed. Properties will override the xml allowing for easy configuration change without the need for $\{} style variable substitution. Properties are not case sensitive. If a property is specified that is not supported by the declared StatelessContainer a warning will be logged. If a StatelessContainer is needed by the application and one is not declared, TomEE will create one dynamically using default settings. Multiple StatelessContainer declarations are allowed. # Supported Properties
Property
Type
Default
Description
accessTimeout
time
30 seconds
Specifies the time an invokation should wait for an instance of the pool to become available.
callbackThreads
int
5
The number of threads for constructing and destroying beans.
closeTimeout
time
5 minutes
Maximum time to wait for instances to be destroyed when shutting down the pool
garbageCollection
boolean
false
Allows Garbage Collection to be used as a mechanism for shrinking the pool.
idleTimeout
time
0 minutes
Specifies the maximum time that an instance should be allowed to sit idly in the pool without use before it should be retired and removed.
maxAge
time
0 hours
Specifies the maximum time that an instance should live before it should be retired and removed from use.
maxAgeOffset
int
-1
Applies to MaxAge usage and would rarely be changed, but is a nice feature to understand.
maxSize
int
10
Specifies the size of the instance pool for this stateless SessionBean container.
minSize
int
0
Specifies the minimum number of bean instances that should be in the pool for each bean.
replaceAged
boolean
true
When ReplaceAged is enabled, any instances in the pool that expire due
to reaching their MaxAge will be replaced immediately so that the pool
will remain at its current size.
replaceFlushed
boolean
false
When ReplaceFlushed is enabled, any instances in the pool that are
flushed will be replaced immediately so that the pool will remain at its
current size.
strictPooling
boolean
true
StrictPooling tells the container what to do when the pool reaches it’s maximum size and there are incoming requests that need instances.
sweepInterval
time
5 minutes
The frequency in which the container will sweep the pool and evict expired instances.
accessTimeout
Specifies the time an invokation should wait for an instance of the pool to become available.
After the timeout is reached, if an instance in the pool cannot be obtained, the method invocation will fail.
Usable time units: nanoseconds, microsecons, milliseconds, seconds, minutes, hours, days. Or any combination such as "1 hour and 27 minutes and 10 seconds"
Any usage of the javax.ejb.AccessTimeout annotation will override this
setting for the bean or method where the annotation is used.
callbackThreads
The number of threads for constructing and destroying beans.
When sweeping the pool for expired instances a thread pool is used to
process calling @PreDestroy on expired instances as well as creating
new instances as might be required to fill the pool to the minimum after
a Flush or MaxAge expiration. The CallbackThreads setting dictates
the size of the thread pool and is shared by all beans deployed in the
container.
closeTimeout
Maximum time to wait for instances to be destroyed when shutting down the pool
PostConstruct methods are invoked on all instances in the pool when the
bean is undeployed and its pool is closed. The CloseTimeout specifies
the maximum time to wait for the pool to close and PostConstruct
methods to be invoked.
Usable time units: nanoseconds, microsecons, milliseconds, seconds,
minutes, hours, days. Or any combination such as
1 hour and 27 minutes and 10 seconds
garbageCollection
Allows Garbage Collection to be used as a mechanism for shrinking the pool.
When set to true all instances in the pool, excluding the minimum, are
eligible for garbage collection by the virtual machine as per the rules
of java.lang.ref.SoftReference and can be claimed by the JVM to free
memory. Instances garbage collected will have their @PreDestroy
methods called during finalization.
In the OpenJDK VM the -XX:SoftRefLRUPolicyMSPerMB flag can adjust how
aggressively SoftReferences are collected. The default OpenJDK setting
is 1000, resulting in inactive pooled instances living one second of
lifetime per free megabyte in the heap, which is very aggressive. The
setting should be increased to get the most out of the
GarbageCollection feature of the pool. Much higher settings are safe.
Even a setting as high as 3600000 (1 hour per free MB in the heap) does
not affect the ability for the VM to garbage collect SoftReferences in
the event that memory is needed to avoid an OutOfMemoryException.
idleTimeout
Specifies the maximum time that an instance should be allowed to sit idly in the pool without use before it should be retired and removed.
Only instances in surplus of the pool’s MinSize are eligible to expire
via IdleTimeout Instances that expire due to IdleTimeout will have
their @PreDestroy methods invoked before being completely destroyed.
Usable time units: nanoseconds, microsecons, milliseconds, seconds, minutes, hours, days. Or any combination such as "1 hour and 27 minutes and 10 seconds"
maxAge
Specifies the maximum time that an instance should live before it should be retired and removed from use.
This will happen gracefully. Useful for situations where bean instances are designed to hold potentially expensive resources such as memory or file handles and need to be periodically cleared out.
Usable time units: nanoseconds, microsecons, milliseconds, seconds,
minutes, hours, days. Or any combination such as
1 hour and 27 minutes and 10 seconds
maxAgeOffset
Applies to MaxAge usage and would rarely be changed, but is a nice feature to understand.
When the container first starts and the pool is filled to the minimum
size, all those "minimum" instances will have the same creation time and
therefore all expire at the same time dictated by the MaxAge setting.
To protect against this sudden drop scenario and provide a more gradual
expiration from the start the container will spread out the age of the
instances that fill the pool to the minimum using an offset.
The MaxAgeOffset is not the final value of the offset, but rather it
is used in creating the offset and allows the spreading to push the
initial ages into the future or into the past. The pool is filled at
startup as follows:
for (int i = 0; i < poolMin; i++) {
long ageOffset = (maxAge / poolMin * i * maxAgeOffset) % maxAge;
pool.add(new Bean(), ageOffset));
}The default MaxAgeOffset is -1 which causes the initial instances in
the pool to live a bit longer before expiring. As a concrete example,
let’s say the MinSize is 4 and the MaxAge is 100 years. The generated
offsets for the four instances created at startup would be 0, -25, -50,
-75. So the first instance would be "born" at age 0, die at 100, living
100 years. The second instance would be born at -25, die at 100, living
a total of 125 years. The third would live 150 years. The fourth 175
years.
A MaxAgeOffset of 1 would cause instances to be "born" older and
therefore die sooner. Using the same example MinSize of 4 and MaxAge
of 100 years, the life spans of these initial four instances would be
100, 75, 50, and 25 years respectively.
A MaxAgeOffset of 0 will cause no "spreading" of the age of the first
instances used to fill the pool to the minimum and these instances will
of course reach their MaxAge at the same time. It is possible to set to
decimal values such as -0.5, 0.5, -1.2, or 1.2.
maxSize
Specifies the size of the instance pool for this stateless SessionBean container.
Each @Stateless bean will get its own instance pool. If StrictPooling
is not used, instances will still be created beyond this number if there
is demand, but they will not be returned to the pool and instead will be
immediately expire.
minSize
Specifies the minimum number of bean instances that should be in the pool for each bean.
Pools are prefilled to the minimum on startup. Note this will create
start order dependencies between other beans that also eagerly start,
such as other @Stateless beans with a minimum or @Singleton beans
using @Startup. The @DependsOn annotation can be used to
appropriately influence start order.
The minimum pool size is rigidly maintained. Instances in the minimum
side of the pool are not eligible for IdleTimeout or
GarbageCollection, but are subject to MaxAge and flushing.
If the pool is flushed it is immediately refilled to the minimum size
with MaxAgeOffset applied. If an instance from the minimum side of the
pool reaches its MaxAge, it is also immediately replaced. Replacement
is done in a background queue using the number of threads specified by
CallbackThreads.
replaceAged
When ReplaceAged is enabled, any instances in the pool that expire due
to reaching their MaxAge will be replaced immediately so that the pool
will remain at its current size.
Replacement is done in a background queue so that incoming threads will not have to wait for instance creation.
The aim of his option is to prevent user requests from paying the
instance creation cost as MaxAge is enforced, potentially while under
heavy load at peak hours.
Instances from the minimum side of the pool are always replaced when
they reach their MaxAge, this setting dictates the treatment of
non-minimum instances.
replaceFlushed
When ReplaceFlushed is enabled, any instances in the pool that are
flushed will be replaced immediately so that the pool will remain at its
current size.
Replacement is done in a background queue so that incoming threads will not have to wait for instance creation.
The aim of his option is to prevent user requests from paying the instance creation cost if a flush performed while under heavy load at peak hours.
Instances from the minimum side of the pool are always replaced when they are flushed, this setting dictates the treatment of non-minimum instances.
A bean may flush its pool by casting the SessionContext to Flushable
and calling flush(). See SweepInterval for details on how flush is
performed.
import javax.annotation.Resource;
import javax.ejb.SessionContext;
import javax.ejb.Stateless;
import java.io.Flushable;
import java.io.IOException;
public class MyBean {
private SessionContext sessionContext;
public void flush() throws IOException {
((Flushable) sessionContext).flush();
}
}strictPooling
StrictPooling tells the container what to do when the pool reaches it’s maximum size and there are incoming requests that need instances.
With strict pooling, requests will have to wait for instances to become
available. The pool size will never grow beyond the the set MaxSize
value. The maximum amount of time a request should wait is specified via
the AccessTimeout setting.
Without strict pooling, the container will create temporary instances to meet demand. The instances will last for just one method invocation and then are removed.
Setting StrictPooling to false and MaxSize to 0 will result in
no pooling. Instead instances will be created on demand and live for
exactly one method call before being removed.
sweepInterval
The frequency in which the container will sweep the pool and evict expired instances.
Eviction is how the IdleTimeout, MaxAge, and pool "flush"
functionality is enforced. Higher intervals are better.
Instances in use are excluded from sweeping. Should an instance expire
while in use it will be evicted immediately upon return to the pool.
Effectively MaxAge and flushes will be enforced as a part of normal
activity or sweeping, while IdleTimeout is only enforcable via sweeping.
This makes aggressive sweeping less important for a pool under moderate
load.
Usable time units: nanoseconds, microsecons, milliseconds, seconds,
minutes, hours, days. Or any combination such as
1 hour and 27 minutes and 10 seconds