If I listen event in redis, just like command below,
$ redis-cli --csv psubscribe '__key*__:*'
Reading messages... (press Ctrl-C to quit)
I can get things like
"pmessage","__key*__:*","__keyspace#0__:exipre","xxx"
"pmessage","__key*__:*","__keyevent#0__:expired","xxx"
So, when I use spring-data-redis to listen events in redis, how can I get the specific event name(like keyspace#0:expire), so that not only get the key value like "xxx", but also get the event like expire or expired, as I don't want to build two topic listener respectively like below:
RedisMessageListenerContainer container = new RedisMessageListenerContainer();
container.setConnectionFactory(connectionFactory);
//one for expire
container.addMessageListener(listenerAdapter1, new PatternTopic(//topic 1));
//another for expired
container.addMessageListener(listenerAdapter2, new PatternTopic(//topic 2));
You might want to have a look at KeyspaceEventMessageListener that subscribes to __keyevent#* and then just implement doHandleMessage. Message.getChannel() holds the raw information about the event type like __keyevent#0__:expired.
KeyspaceEventMessageListener eventListener = new KeyspaceEventMessageListener(container) {
#Override
protected void doHandleMessage(Message message) {
String channelInfo = new String(message.getChannel()); // __keyevent#0__:expired
// ...
}
};
Related
I'm trying to delete a scheduled job in ActiveMQ, and so far no luck.
Schedule is created among with the message using either NMS API or Amqpnetlite (except openwire lib as that one is not updated and can't be used on netstandard/netcore)
Sample code used to create the schedule with NMS, same thing done with AMQP lib:
var factory = new Apache.NMS.ActiveMQ.ConnectionFactory(brokerUri);
IConnection connection = factory.CreateConnection(user, password);
connection.Start();
ISession session = connection.CreateSession(AcknowledgementMode.AutoAcknowledge);
IDestination dest = session.GetQueue(destination);
IMessageProducer producer = session.CreateProducer(dest);
producer.DeliveryMode = MsgDeliveryMode.NonPersistent;
var msg = session.CreateTextMessage("Sample text message");
msg.Properties.SetString("AMQ_SCHEDULED_CRON", "* * * * *");
producer.Send(msg);
connection.Close();
This part produces the following result in browser console, and that's what I am willing to delete:
I've read this other question and answer, also active mq system constants but no way the schedule gets deleted. Also tried to browse over the documentation but can't find anything useful so far
Does ActiveMQ even supports a programmative way of managing schedules? An AMQP solution would be great, but NMS is also appreciated.
You can manage scheduled jobs in ActiveMQ over STOMP, AMQP or simply from a JMS client. I've written about this before showing how to do it using the ActiveMQ Java client but the principle is the same. You can send messages with specific headers set that will operate on the scheduled messages.
To browse the collection of scheduled message you'd do something like the following:
Connection connection = createConnection();
Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
// Create the Browse Destination and the Reply To location
Destination requestBrowse = session.createTopic(ScheduledMessage.AMQ_SCHEDULER_MANAGEMENT_DESTINATION);
Destination browseDest = session.createTemporaryQueue();
// Create the "Browser"
MessageConsumer browser = session.createConsumer(browseDest);
connection.start();
// Send the browse request
MessageProducer producer = session.createProducer(requestBrowse);
Message request = session.createMessage();
request.setStringProperty(ScheduledMessage.AMQ_SCHEDULER_ACTION,
ScheduledMessage.AMQ_SCHEDULER_ACTION_BROWSE);
request.setJMSReplyTo(browseDest);
producer.send(request);
Message scheduled = browser.receive(5000);
while (scheduled != null) {
// Do something clever...
}
The returned messages contain the information on the actual scheduled message jobs that have been previously added. Obtaining the job Id allows you to completely cancel the delivery of said message.
To remove a scheduled message send that was scheduled using the Java client, AMQP client or other procotol client you'd do the following:
Message remove = session.createMessage();
remove.setStringProperty(ScheduledMessage.AMQ_SCHEDULER_ACTION,
ScheduledMessage.AMQ_SCHEDULER_ACTION_REMOVE);
remove.setStringProperty(ScheduledMessage.AMQ_SCHEDULED_ID,
scheduled.getStringProperty(ScheduledMessage.AMQ_SCHEDULED_ID));
producer.send(remove);
The full set of message property values that can be used when working with the scheduler are documented here, in AMQP just use the string literal of each as the Application Property value you set with the job Id to remote, or in the NMS client it'd just be a string key message property with the job Id that you want to remove.
There is one caveat though when doing this over AMQP and that would be that you'd need to ensure that the broker is using the JMS transformer ?transport.transformer=jms"see the AMQP documentation for ActiveMQ 5.
Accepted answer is working and correct. Turns out scheduledMessage.NMSMessageId was not holding the scheduler id.
Here's the clean C# source in case one is interested:
var factory = new Apache.NMS.ActiveMQ.ConnectionFactory(brokerUri);
IConnection connection = factory.CreateConnection(userName, password);
var session = connection.CreateSession(AcknowledgementMode.AutoAcknowledge);
var requestBrowse = session.GetTopic("ActiveMQ.Scheduler.Management");
var queue = session.GetQueue(queueName);
var consumer = session.CreateConsumer(queue);
connection.Start();
var producer = session.CreateProducer(requestBrowse);
var scheduledMessage = consumer.Receive(TimeSpan.FromSeconds(10));
if (scheduledMessage != null)
{
// do check with persistent storage, if schedule is canceled, remove it:
var remove = session.CreateMessage();
// get prop names from : http://activemq.apache.org/maven/apidocs/constant-values.htm
remove.Properties["AMQ_SCHEDULER_ACTION"] = "REMOVE";
remove.Properties["scheduledJobId"] = scheduledMessage.Properties.GetString("scheduledJobId");
producer.Send(remove);
}
producer.Close();
session.Close();
connection.Close();
Flow is like this: Get messages from some queue, in case some condition is met, drop the schedule entirely.
After a connection to the socket.io server a socket.id is given for the connection. When the socket connection has not been used after some time a new socket id is generated.
I have read a lot of tutorials that do a "hello world" connection that just gets you connected, but, there is not much literature on messaging peer-to-peer/group. The docs give a 3 line paragraph on rooms/namespaces and every question related to this is just given a link to the same 3 line paragraph.
I understand that you can create and object/array of chats(in this example). For this example, let's say it is an object. That Object looks something like this:
const connections = {
"randomSocketID1": {
recipient: "Mom",
messages: [Array of Objects]
//more information
}
}
I then send a message to randomSocketID1 --> 'Hello'. Then next day I want to send another message to "Mom". Is that socketID going to be the same OR AT LEAST will "randomSocketID1" be updated under the hood, to its updated ID(which sounds improbable)? Is the regeneration of the socketID a product of garbage collection or a socket/engine/websocket protocol?
thanks for any clarification
So I was still unable to find an actual answer to this and by the 0 responses i see that no one knows. So what I have done in order to make sure that user and socket id are maintained is whenever a user enters the component that connects to the socketio server an automatic 'update-user' is emitted and the back end then just finds the user and assigns it the value.
So I have something like this:
chat.component.ts:
ngOnInit(){
this.socket.emit('update-user', 'Ctfrancia');
}
then in the back end:
const users = {};
io.on('connection', socket => {
socket.on('update-user', user => {
if (user in users) users[user] = socket.id;
else users[user] = socket.id
});
});
Is it possible to publish a message to only one client subscribed to channel? I know how to get the address (client list). Is it possible to get the address and publish to only that client?
In Redis you publish to a channel, not to a subscriber.
So the only way should be having one channel per client.
You can probably have one common channel to share the address, and then use the addresses as the channels name.
http://redis.io/topics/pubsub
As an example, using C# and StackExchange.Redis library:
//SERVER
var cnn = ConnectionMultiplexer.Connect("localhost");
var sub = cnn.GetSubscriber();
sub.Subscribe("common", (channel, value) =>
{
Console.WriteLine("SERVER Received in common: {0}", value);
sub.Publish("channel:" + value, "private from server to " + value);
});
//CLIENT
var cnn = ConnectionMultiplexer.Connect("localhost");
var address = "client1";
var sub = cnn.GetSubscriber();
sub.Subscribe("channel:" + address, (channel, value) =>
{
Console.WriteLine("Private: {0}", value);
});
sub.Publish("common", address);
Another solution: what I was trying to do was to have all subscribers listen but only one handle the message. The way I did this was create a stack in redis and have all subscribe to a key's list command notifications. So I would RPUSH a new value onto the key, the subscribers would get the keyspace notification and the fist to LPOP the value would handle it.
I'm new to RabbitMQ and was wondering of a good approach to this problem I'm mulling over. I want to create a service that subscribes to a queue and only pulls messages that meet a specific criteria; for instance, if a specific subject header is in the message.
I'm still learning about RabbitMQ, and was looking for tips on how to approach this. My questions include: how can the consumer pull only specific messages from the queue? How can the producer set a subject header in the message (if that's even the right term?)
RabbitMQ is perfect for this situation. You have a number of options to do what you want. I suggest reading the documentation to get a better understanding. I would suggest that you use a topic or direct exchange. Topic is more flexible. It goes like this.
Producer code connects to the RabbitMQ Broker and creates and Exchange with a specific name.
Producer publishes to exchange. Each message published will be published with a routing key.
Consumer connects to RabbitMQ broker.
Consumer creates Queue
Consumer binds Queue to the exchange, the same exchange defined in the producer. The binding also includes the routing keys for each message require for this particular consumer.
Lets say you were publishing log messages. The routing key might be something like "log.info", "log.warn", "log.error". Each message published by the producer will have the relevant routing key attached. You will then have a consumer that sends and email for all the error messages and another one that writes all the error messages to a file. So the emailer will define the binding from its queue to the exchange with the routing key "log.error". This way though the exchange receives all messages, the queue defined for the emailer will only contain the error messages. The filelogger will define a new separate queue bound to the same exchange and set up a different routing key. You could do three separate bindings for the three different routing keys require or just use the wildcard "log.*" to request all messages from the exchange starting with log.
This is a simple example that shows how you can achieve what you want to do.
look here for code examples specifically number tutorial number 5.
Making the best of exchange/routing of rabbitmq is recommended. If you do want to check according to the message content, the following code is a viable solution.
Retrieve messages from a queue and check, selectively ack the messages in which you're interested.
pull one message
GetResponse resp = channel.basicGet(QUEUE_NAME, false);
ack one message
channel.basicAck(resp.getEnvelope().getDeliveryTag(), false);
Example
import com.rabbitmq.client.*;
public class ReceiveLogs {
private final static String QUEUE_NAME = "hello";
public static void main(String[] argv) throws Exception {
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("localhost");
try(Connection connection = factory.newConnection();
Channel channel = connection.createChannel();){
channel.queueDeclare(QUEUE_NAME, true, false, false, null);
// pull one message and ack manually and exit
GetResponse resp = channel.basicGet(QUEUE_NAME, false);
if( resp != null ){
String message = new String(resp.getBody(), "UTF-8");
System.out.println(" [x] Received '" + message + "'");
channel.basicAck(resp.getEnvelope().getDeliveryTag(), false);
}
System.out.println();
}
}
}
dependency
compile group: 'com.rabbitmq', name: 'amqp-client', version: '5.8.0'
To Retrieve Message from RabbitMQ we need to first connect with RabbitMQ server
public WebClient GetRabbitMqConnection(string userName, string password)
{
var client = new WebClient();
client.Credentials = new NetworkCredential(userName, password);
return client;
}
Now retrieve message from RabbitMQ using below code.
public string GetRabbitMQMessages(string domainName, string port,
string queueName, string virtualHost, WebClient client, string methodType)
{
string messageResult = string.Empty;
string strUri = "http://" + domainName + ":" + port +
"/api/queues/" + virtualHost + "/";
var data = client.DownloadString(strUri + queueName + "/");
var queueInfo = JsonConvert.DeserializeObject<QueueInfo>(data);
if (queueInfo == null || queueInfo.messages == 0)
return string.Empty;
if (methodType == "POST")
{
string postbody = "
{\"ackmode\":\"ack_requeue_true\",\"count\":
\"$totalMessageCount\",\"name\":\"${DomainName}\",
\"requeue\":\"false\",\"encoding\":\"auto\",\"vhost\" :
\"${QueueName}\"}";
postbody = postbody
.Replace("$totalMessageCount", queueInfo.messages.ToString())
.Replace("${DomainName}", domainName)
.Replace("${QueueName}", queueName);
messageResult = client.UploadString(strUri + queueName +
"/get", "POST", postbody);
}
return messageResult;
}
I think this will help you to implement RabbitMQ.
If you want to retrieve single message at a time please add the following properties with your Retrieving code .
Boolean autoAck = false;
model.BasicConsume(Queuename, autoAck);
model.BasicGet("Queuename", false);
model.BasicGet("Queuename", false);
By adding this properties of RabbitMQ you can retrieve the message one by one from the queue .Same like FIFO criteria
i am trying to setup Redis on appharbor. I have followed their instructions and again i have an issue with the Booksleeve API. Here is the code i am using to make it work initially:
var connectionUri = new Uri(url);
using (var redis = new RedisConnection(connectionUri.Host, connectionUri.Port, password: connectionUri.UserInfo.Split(new[] { ':' }, 2)[1]))
{
redis.Strings.Set(1, "greeting", "welcome to remember your stuff!");
try
{
var task = redis.Strings.GetString(1, "greeting");
redis.Wait(task);
ViewBag.Message = task.Result;
}
catch (Exception)
{
// It throws an exception trying to wait for the task?
}
}
However, the issue is that it sets the string correctly, but when trying to retrieve the same string from the key value store, it throws a timeout exception waiting for the task to eexecute. However, this code works on my local redis server connection.
Am i using the API in a wrong way? or is this something related to Appharbor?
Thanks
Like a SqlConnection, you need to call Open() (otherwise your messages are queued for delivery).
Unlike SqlConnection, you should not fire up a RedisConnection each time you need it - it is intended to be used as a shared, thread-safe, multiplexer - i.e. a single connection is held somewhere and used by lots and lots of unrelated callers. Unless of course you only need to do one thing!