- Type Parameters:
T
- the type of value object stored in this oort object
- All Implemented Interfaces:
Iterable<OortObject.Info<T>>
,EventListener
,ConfigurableServerChannel.Initializer
,Oort.CometListener
,org.eclipse.jetty.util.component.Dumpable
,org.eclipse.jetty.util.component.LifeCycle
- Direct Known Subclasses:
OortContainer
An OortObject
represents a named composite entity that is distributed in an Oort cluster.
A typical example is an oort object that stores the number of users connected to an Oort node.
The entity in this case is a long
value representing the number of connected users.
Such oort object may be named 'user_count', and there will be an oort object instance with this name in each node.
Each oort object instance will have a different local value, along with all the values from the other nodes.
A particular OortObject
has a unique name across the node and is made of N parts,
where N is the number of active nodes. A part is represented by OortObject.Info
instances.
Each OortObject.Info
instance represents the contribution of that node to the whole OortObject
and stores the Oort URL of the node it represents along with the entity in that node.
+------------+
| user_count |
+---+---+----+---+--------------------+
| part1 | 13 | local - http://oort1/ |
+-------+----+------------------------+
| part2 | 19 | remote - http://oort2/ |
+-------+----+------------------------+
| part3 | 29 | remote - http://oort3/ |
+-------+----+------------------------+
An OortObject
must be created and then started
:
Oort oort1 = ...; OortObject userCount1 = new OortObject(oort1, "user_count", OortObjectFactories.forLong()); userCount1.start();
Once started, it connects via Oort facilities to the other nodes and communicates with the oort object
instances that have the same name that live in the other nodes.
The communication is performed on a channel constructed from the oort object's name and returned by
getChannelName()
.
Oort objects work best when the entity they hold is an immutable, value-type object: OortObject<Long>
works better than OortObject<AtomicLong>
because AtomicLong is mutable and its APIs
(for example, AtomicLong.compareAndSet(long, long)
) are not exposed by OortObject
.
Objects stored by an oort object are created using a OortObject.Factory
. This is necessary to recreate
objects that may be serialized differently when transmitted via JSON, without forcing a global JSON serializer.
A number of factories are available in OortObjectFactories
, and applications can write their own.
Applications can change the entity value of the oort object and broadcast the change to other nodes via
setAndShare(Object, Result)
. The other nodes will receive a message on the oort object's channel
and set the new entity value in the part that corresponds to the node that changed the entity.
The diagram below shows one oort object with name "user_count" in two nodes.
On the left of the arrow (A), the situation before calling:
userCount1.setAndShare(17, result -> { ... });
and on the right of the arrow (A) the situation afterwards, that shows how the value is first changed
(1) locally on node_1
, then a message (2) is broadcast on the cluster, reaches
node_2
, where it updates (3) the part corresponding to node_1
to the new value.
+-------------+ +-------------+ +-----------------+ +-----------------+
| node_1 | | node_2 | | node_1 | | node_2 |
+-------------+ +-------------+ +-----------------+ (2) +-----------------+
| user_count | | user_count | (A) | user_count | ----> | user_count |
+--------+----+ +--------+----+ ----> +--------+--------+ +--------+--------+
| local | 13 | | local | 19 | | local | 17 (1) | | local | 19 |
+--------+----+ +--------+----+ +--------+--------+ +--------+--------+
| remote | 19 | | remote | 13 | | remote | 19 | | remote | 17 (3) |
+--------+----+ +-------+----+ +--------+--------+ +-------+---------+
When an entity is updated, either locally or remotely, an event is fired to registered OortObject.Listener
s.
Oort objects can only update the entity they own; in the example above, node_1
can only update
the "local" value 13 to 17, but cannot modify the "remote" value 19, which is owned by node_2
.
Only update messages from node_1
can update the "remote" value on node_2
.
Every node has a part that belongs to a particular node, and only that particular node can update it.
Values of oort objects may be merged using a OortObject.Merger
via merge(Merger)
.
A number of mergers are available in OortObjectMergers
, and applications can write their own.
For example:
long totalUsersOnAllNodes = userCount1.merge(OortObjectMergers.longSum()); // yields 17+19=36
Oort objects implement a strategy where value objects are replicated in each node, trading increased memory
usage for reduced latency accessing the data.
An alternative strategy that trades reduced memory usage for increased latency is implemented by
OortService
.
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionprotected static class
static interface
Factory that creates objects stored byOortObject
s.static class
The oort object part holding the object and the metadata associated with it.static interface
Listener for events that update the value of aOortObject.Info
, either local or remote.static interface
A merge strategy for object values.static interface
An asynchronous result.Nested classes/interfaces inherited from class org.eclipse.jetty.util.component.AbstractLifeCycle
org.eclipse.jetty.util.component.AbstractLifeCycle.AbstractLifeCycleListener, org.eclipse.jetty.util.component.AbstractLifeCycle.StopException
Nested classes/interfaces inherited from interface org.cometd.bayeux.server.ConfigurableServerChannel.Initializer
ConfigurableServerChannel.Initializer.Persistent
Nested classes/interfaces inherited from interface org.eclipse.jetty.util.component.Dumpable
org.eclipse.jetty.util.component.Dumpable.DumpableContainer
Nested classes/interfaces inherited from interface org.cometd.oort.Oort.CometListener
Oort.CometListener.Event
-
Field Summary
FieldsFields inherited from class org.eclipse.jetty.util.component.AbstractLifeCycle
FAILED, STARTED, STARTING, STOPPED, STOPPING
Fields inherited from interface org.eclipse.jetty.util.component.Dumpable
KEY
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionvoid
addListener
(OortObject.Listener<T> listener) void
Callback method invoked when a new comet joins the cloudvoid
Callback method invoked when a comet leaves the cloudvoid
Configures the channel used by this oort object.protected Object
deserialize
(Object object) protected void
doStart()
protected void
doStop()
void
dump
(Appendable out, String indent) Returns the channel name used by this oort object for communication with other oort objects in other nodes.getInfoByObject
(T object) protected Collection
<OortObject.Info<T>> getInfos()
getName()
getOort()
iterator()
<R> R
merge
(OortObject.Merger<T, R> strategy) Merges the objects of all theOortObject.Info
s known to this oort object using the givenstrategy
.protected OortObject.Info
<T> protected void
notifyRemoved
(OortObject.Info<T> info) protected void
notifyUpdated
(OortObject.Info<T> oldInfo, OortObject.Info<T> newInfo) protected void
protected void
protected void
void
removeListener
(OortObject.Listener<T> listener) void
Removes all listeners.protected Object
void
setAndShare
(T newObject, OortObject.Result<T> callback) Sets the given new object on this oort object, and then broadcast the new object to all nodes in the cluster.toString()
Methods inherited from class org.eclipse.jetty.util.component.AbstractLifeCycle
addEventListener, getEventListeners, getState, getState, isFailed, isRunning, isStarted, isStarting, isStopped, isStopping, removeEventListener, setEventListeners, start, stop
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Methods inherited from interface org.eclipse.jetty.util.component.Dumpable
dump, dumpSelf
Methods inherited from interface java.lang.Iterable
forEach, spliterator
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Field Details
-
OORT_OBJECTS_CHANNEL
- See Also:
-
-
Constructor Details
-
OortObject
-
-
Method Details
-
doStart
protected void doStart()- Overrides:
doStart
in classorg.eclipse.jetty.util.component.AbstractLifeCycle
-
doStop
protected void doStop()- Overrides:
doStop
in classorg.eclipse.jetty.util.component.AbstractLifeCycle
-
configureChannel
Configures the channel used by this oort object. By default does nothing, but subclasses may override this method to make the channel lazy, for example.- Specified by:
configureChannel
in interfaceConfigurableServerChannel.Initializer
- Parameters:
channel
- the channel to configure- See Also:
-
getOort
-
getName
- Returns:
- the name of this oort object, that must be unique across the node.
-
getFactory
- Returns:
- the factory to create objects contained in this oort object
-
getLocalSession
- Returns:
- the local session that sends messages to other nodes
-
getChannelName
-
serialize
-
deserialize
-
newInfo
-
cometJoined
Description copied from interface:Oort.CometListener
Callback method invoked when a new comet joins the cloud- Specified by:
cometJoined
in interfaceOort.CometListener
- Parameters:
event
- the comet event
-
cometLeft
Description copied from interface:Oort.CometListener
Callback method invoked when a comet leaves the cloud- Specified by:
cometLeft
in interfaceOort.CometListener
- Parameters:
event
- the comet event
-
iterator
- Specified by:
iterator
in interfaceIterable<T>
- Returns:
- an iterator over the
OortObject.Info
known to this oort object
-
getInfo
- Parameters:
oortURL
- the oort URL used to search the correspondingOortObject.Info
- Returns:
- the
OortObject.Info
with the given oort URL, or null if no suchOortObject.Info
exists
-
getInfoByObject
- Parameters:
object
- the object used to search the correspondingOortObject.Info
- Returns:
- the first
OortObject.Info
whose object equals (via a possibly overriddenObject.equals(Object)
) the givenobject
-
merge
Merges the objects of all theOortObject.Info
s known to this oort object using the givenstrategy
.- Type Parameters:
R
- the merge result type- Parameters:
strategy
- the strategy to merge the objects- Returns:
- the merged result
-
addListener
- Parameters:
listener
- the listener to add- See Also:
-
removeListener
- Parameters:
listener
- the listener to remove- See Also:
-
removeListeners
public void removeListeners()Removes all listeners.- See Also:
-
notifyUpdated
-
notifyRemoved
-
onObject
-
pushInfo
-
pullInfo
-
getInfos
-
dump
- Specified by:
dump
in interfaceorg.eclipse.jetty.util.component.Dumpable
- Throws:
IOException
-
toString
- Overrides:
toString
in classorg.eclipse.jetty.util.component.AbstractLifeCycle
-