One way of creating JmDNS services is :
ServiceInfo.create(type, name, port, weight, priority, props);
where props is a Map which describes some propeties of the service. Does anybody have an example illustrating the use of theese properties, for instance how to use them in the reciever part.
I've tried :
Hashtable<String,String> settings = new Hashtable<String,String>();
settings.put("host", "hhgh");
settings.put("web_port", "hdhr");
settings.put("secure_web_port", "dfhdyhdh");
ServiceInfo info = ServiceInfo.create("_workstation._tcp.local.", "service6", 80, 0, 0, true, settings);
but, then in a machine receiving this service, what can I do to see those properties?
I would apreciate any help...
ServiceInfo info = jmDNS.getServiceInfo(serviceEvent.getType(), serviceEvent.getName());
Enumeration<String> ps = info.getPropertyNames();
while (ps.hasMoreElements()) {
String key = ps.nextElement();
String value = info.getPropertyString(key);
System.out.println(key + " " + value);
}
It has been a while since this was asked but I had the same question. One problem with the original question is that the host and ports should not be put into the text field, and in this case there should actually be two service types one secure and one insecure (or perhaps make use of subtypes).
Here is an incomplete example that gets a list of running workstation services:
ServiceInfo[] serviceInfoList = jmdns.list("_workstation._tcp.local.");
if(serviceInfoList != null) {
for (int index = 0; index < serviceInfoList.length; index++) {
int port = serviceInfoList[index].getPort();
int priority = serviceInfoList[index].getPriority();
int weight = serviceInfoList[index].getWeight();
InetAddress address = serviceInfoList[index].getInetAddresses()[0];
String someProperty = serviceInfoList[index].getPropertyString("someproperty");
// Build a UI or use some logic to decide if this service provider is the
// one you want to use based on prority, properties, etc.
...
}
}
Due to the way that JmDNS is implemented the first call to list() on a given type is slow (several seconds) but subsequent calls will be pretty fast. Providers of services can change the properties by calling info.setText(settings) and the changes will be propagated out to the listeners automatically.
Related
I would like to store values of event properties received from the server in a database. My problems are that in the event consumer:
I cant figure out which eventtype my client received.
I dont know how to map variant indexes to properties without knowing the EventType.
Events come with the property "EventType", which would solve my first problem. But since I am receiving many different event types, I do not know in which variant index it is located. Should I always relocate "EventType" at index 0 in the select clause whenever creating a new EventFilter?
For the second problem, item.getMonitoringFilter().decode(client.getSerializationContext())) offers a view on the property structure but I am not sure how to use it for mapping of variants to properties. Does anybody know how to solve those problems?
Here is the event consumer code that I use. It is taken from milo client examples.
for (UaMonitoredItem monitoredItem: mItems){
monitoredItem.setEventConsumer((item, vs) -> {
LOGGER.info(
"Event Received from: {}", item.getReadValueId().getNodeId());
LOGGER.info(
"getMonitoredItemId: {}", item.getMonitoredItemId());
LOGGER.info(
"getMonitoringFilter: {}", item.getMonitoringFilter().decode(client.getSerializationContext()));
for (int i = 0; i < vs.length; i++) {
LOGGER.info("variant[{}]:, datatype={}, value={}", i, vs[i].getDataType(), vs[i].getValue());
}
});
}
Thank you in advance.
Update:
Seems I have figured it out, by typcasting to EventFilter. Further information such as qName for event properties or event type node IDs can then be derived:
ExtensionObject eObject = item.getMonitoringFilter();
EventFilter eFilter = ((EventFilter) eObject.decode(client.getSerializationContext()));
QualifiedName qName = eFilter.getSelectClauses()[0].getBrowsePath()[0];
LiteralOperand literalOperand = (LiteralOperand) eFilter.getWhereClause().getElements()[0]
.getFilterOperands()[1].decode(client.getSerializationContext());
NodeId eventTypeNodeId = (NodeId) literalOperand.getValue().getValue();
Didn't you supply the filter in the first place when you created the MonitoredItem? Why do you need to "reverse engineer" the filter result to get back to what you did in the first place?
The properties you receive in the event data and the order they come in are defined by the select clause you used when creating the MonitoredItem. If you choose to select the EventId field then it will always be at the same corresponding index.
I'm writing a server application in D, who should be able to manage n connections simultaneously.
To achieve this i am using std.socket.Socket.select. This works fine. But I can't bind session specific data to the socket and i don't see any way to do this, cause Socket does not allow to save a handle to user specific data. After
Socket.select(socketSet, null, null);
I'm able to get all affected sockets, but I can't assign this sockets to my user specific session data. What's my mistake? Is it possible to reach my goal in this way? Or should I choose another way for my requirements?
My relevant code:
ushort port = 5010;
stoprequest = false;
auto listener = new TcpSocket();
assert(listener.isAlive);
listener.blocking = false;
listener.bind(new InternetAddress(port));
listener.listen(10);
enum MAX_CONNECTIONS = 100;
auto socketSet = new SocketSet(MAX_CONNECTIONS + 1);
Socket[] reads;
Session[] sessions;
while (true)
{
socketSet.add(listener);
foreach (session; sessions)
socketSet.add(session.socket);
Socket.select(socketSet, null, null);
for (size_t i = 0; i < reads.length; i++)
{
if (socketSet.isSet(reads[i]))
{
// Now i should acces to session related data, but how?
char[1024] buf;
auto datLength = reads[i].receive(buf[]);
if (datLength == Socket.ERROR)
writeln("Connection error.");
else if (datLength != 0)
{
writefln("Received %d bytes from %s: \"%s\"", datLength, reads[i].remoteAddress().toString(), buf[0..datLength]);
continue;
}
else { // Error Handling. Shortened, since unimportant for the example}
reads[i].close();
reads = reads.remove(i);
i--;
}
}
if (socketSet.isSet(listener))
{
Socket sn = null;
sn = listener.accept();
if (reads.length < MAX_CONNECTIONS)
{
Session session = new Session();
session.socket = sn;
sessions ~= session;
}
else { // Error Handling for too many connection. Shortened, since unimportant for the example}}
}
socketSet.reset();
}
The hint to use poll() was helpful. After reading https://daniel.haxx.se/docs/poll-vs-select.html I think that both variants work and neither of them are the real thing. For an efficient way, I should better deal with libev. Fortunately, efficiency is not my problem in this particular project. For this reason I will use select(), because i found out, that accessing handle gives me a unique number which can be passed to a own lookup table. This allows me to assign session data to a socket. So I prefer to stick with the encapsulated functionality of std.socket.Socket and don't work around it.
My concrete question can therefore be answered with :
Use Socket.handle to identify the socket and manage session related
data
A few other alternatives you can consider:
1) use a subclass of Socket. You can make your own class that inherits from it and adds more stuff.
2) The poll function is found in import core.sys.posix.poll;, and you can pass socket.handle to that as well. But note it will not work on Windows without modification.
or indeed 3) do your own lookup table, that works too.
Note that the std.socket.Socket is a very thin wrapper around the bsd socket api, just internally it does conveniently handle the slight differences between Windows and posix. Still it is pretty easy to adapt code to use the other apis with it (or tutorials on C language stuff to D) since it is all basically the same thing - and literally the same functions if you import core.sys stuff.
i need to provide a H/A mechanism.
i understand thet zookeeper can be chosen as a leader election
i'm looking for the right pattern for this flow:
i need to implement a service that invoke a flow.
when it starting the flow [the flow is a looping flow], it must validate that it is the leader. (say by it's ip address).
i understand that i can put a value into a zookeeper that define that entering
instance, and dispose it when 1 loop end, or for a period of time.
it is that the right pattern?
also it seems that race condition issues if i use something like:
...
...
List<String> names = zk.getChildren( path, false );
String id = null;
// See whether we have already run for election in this process
for ( String name : names ) {
{
if ( name.startsWith( myIP ) ) {
id = name;
break;
}
}
if ( id == null ) {
id = zk.create( path + "/" + myIP, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
}
boolean isLeader = id != null;
for example:
2 services read null
and than 2nd overrides the 1st signature, and both of them running the task.
can you help?
thanks
Using ZooKeeper correctly can be difficult and takes some studying of its APIs and semantics. There are some nice high-level libraries such as Curator that already have implemented common algorithms such as leader election. The ZooKeeper documentation also has a recipe for leader election.
I'm finding this incredibly frustrating. I'm trying to use the InventoryFacadeClient to call either the Change or Sync web services to update product availability. The issue I'm facing is that I can't seem to instantiate all of the required DataTypes to populate the request.
It's quite confusing, I wanted to call ChangeInventory but can't compose the request, and started down SyncProductAvailability but again, can't compose the request.
The problem below is that the ProductIdentifierType is null, and there's no corresponding "createProductIdentifierType" on the Factory....I'm not sure what I"m missing here, the factory seems to be half baked...
If someone can help me complete this code, it would be great?
public void setUp() throws Exception {
String METHOD_NAME = "setUp";
logger.info("{} entering", METHOD_NAME);
super.setUp();
InventoryFacadeClient iClient = super.initializeInventoryClient(false);
InventoryFactory f = com.ibm.commerce.inventory.datatypes.InventoryFactory.eINSTANCE;
com.ibm.commerce.inventory.facade.datatypes.InventoryFactory cf = iClient.getInventoryFactory();
CommerceFoundationFactory fd = iClient.getCommerceFoundationFactory();
// we must have customised the SyncProductAvailability web service to
// handle ATP inventory model.
SyncProductAvailabilityDataAreaType dataArea = f.createSyncProductAvailabilityDataAreaType();
SyncProductAvailabilityType sat = f.createSyncProductAvailabilityType();
sat.setDataArea(dataArea);
DocumentRoot root = cf.createDocumentRoot();
sat.setVersionID(root.getInventoryAvailabilityBODVersion());
ProductAvailabilityType pat = f.createProductAvailabilityType();
ProductIdentifierType pid = pat.getProductIdentifier();
I found the answer to this on another forum. I was missing the right CommerceFoundationFactory - the class the ProductIdentifierType is created from is:
com.ibm.commerce.foundation.datatypes.CommerceFoundationFactory fd2 = com.ibm.commerce.foundation.datatypes.CommerceFoundationFactory.eINSTANCE;
fd2.createProductIdentifierType
I want to delete all the messages in a queue configured in Websphere 8.5 SIB. Below are two approaches I tried, but none of them seem to be working and each throws a different exception. Can someone please advise on what is the correct way to achieve this.
Approach 1
MBeanServerConnection connection = getServerConnection();
connection.invoke(new ObjectName("WebSphere:*,type=SIBQueuePoint,name=jms.queue.MY_QUEUE"), "deleteAllQueuedMessages", null, null);
This approach throws the below exception.
javax.management.InstanceNotFoundException: WebSphere:type=SIBQueuePoint,name=jms.queue.MY_QUEUE
Approach 2
MBeanServerConnection connection = getServerConnection();
ObjectName objQueue = new ObjectName(WAS85_RESOURCE_URL + ",type=SIBQueuePoint");
Set<ObjectName> objNames = connection.queryNames(objQueue, null);
for(ObjectName objName: objNames) {
String qName = connection.getAttribute(objName,"identifier").toString();
if(qName.equals("jms.queue.MY_QUEUE")) {
connection.invoke(objName, "deleteAllQueuedMessages", null, null);
}
}
This approach throws the below exception.
javax.management.ReflectionException: Target method not found: com.ibm.ws.sib.admin.impl.JsQueuePoint.deleteAllQueuedMessages
Figured out the issue.
The 2nd approach works. The issue was with my invocation of the deleteAllQueuedMessages message. The method takes a boolean argument which indicates the messages should be moved to the Exception Destination. I was not passing this argument !!!
I corrected the implementation as below and it works now.
connection.invoke(objName, "deleteAllQueuedMessages", new Object[]{false}, new String[]{"java.lang.Boolean"});
A better way to delete all Messages is something like that:
String queryString = "WebSphere:*,type=JMSAdministration";
ObjectName queryServer = new ObjectName(queryString);
String serverStr = "";
Set pet = aClient.queryNames(queryServer, null);
Iterator itsServer = pet.iterator();
if (itsServer.hasNext())
serverStr = itsServer.next().toString();
ObjectName obj = new ObjectName(serverStr);
Object param[] = { "jms/messageQueue","jms/messageCF" };
String signature[] = { "java.lang.String","java.lang.String" };
aClient.invoke(obj, "clear", param, signature);
Using MBean JMSAdministration is better because you can set Query exacly.