We are trying to connect to IBMMQ using CCDT file and JMS configuration.
We are able to connect to it but we have an issue here:
since we are using spring to set connection factory with CCDT file, this is initialized once at the start of the application, but unfortunately it picks only one queue manager at a time,i.e it sends all the messages to same queue manager and it does not load balance.
Though i observed, if i manually set the CCDT file before every request then its able to load balance the Queue Managers, ideally it looks to me Queue Manager is decided whenever i set the URL to CCDT file. which is wrong practice. My expectation was to initialize the connection factory with CCDT file and then this configuration will be able to load balance on its own.
Can you help me this?
This is the expected behavior. MQ does not load balance clients, it connection balances them. The connection is the single most time consuming API call and in the case of a mutually authenticated TLS connection can take seconds to complete. Therefore a good application design will attempt to connect once, then maintain that connection for the duration of the session. The JMS architecture and Spring framework both expect this pattern.
The way that MQ provides load distribution (again, not true balancing, but rather round-robin distribution) is that the client connects a hop away from a clustered destination queue. A message addressed to that clustered destination queue will round-robin among all the instances of that queue.
If it is a request-reply application, the thing listening for requests on these clustered queue instances addresses the reply message using the Reply-To QMgr and Reply-To Queue name from the requesting message. In this scenario the requestors can fail over QMgr to QMgr if they lose their connection. The systems of record listening on the clustered queues generally do not fail over across queue managers in order to ensure all queue instances are served and because of transaction recovery.
Short answer is that CCDT and MQ client in general are not where MQ load distribution occurs. The client should make a connection and hold it as long as possible. Client reconnect and CCDT are for connection balancing only.
Load distribution is a feature of the MQ cluster. It requires multiple instances of a clustered queue and these are normally a network hop away from the client app that puts the message.
Does it make sense to perform producer/consumer connection pooling of kafka clients?
Does kafka internally maintain a list of connection objects initialized and ready to use?
We'd like to minimize time of connection creation, so that there is no additional overhead when it comes to send/receive messages.
Currently we're using apache commons-pool library GenericObjectPool to keep connections around.
Any help will be appreciated.
Kafka clients maintain their own connections to the clusters.
Both the Producer and Consumer keep connections alive to the brokers they are interacting with. In case they stop interacting, after connections.max.idle.ms the connection will be closed. This setting also exists on the broker so you may want to verify with your admin if they changed this value.
So in most cases, once started Kafka clients don't create many new connections but just use the ones created at startup
Spring integration has excellent example to TCP Server. But it seems to be using single thread for every socket connection.
Is there any example on how to create TCP Server which can process requests with multiple threads? Better yet, is there any example to use thread pooling in TCP Server.
I would appreciate if you can provide any links.
Thanks
Set using-nio="true" when processing a large number of sockets and a thread pool is shared across the connections.
For a small number of sockets it's generally faster to use a single thread per socket.
The RabbitMQ Java client has the following concepts:
Connection - a connection to a RabbitMQ server instance
Channel - ???
Consumer thread pool - a pool of threads that consume messages off the RabbitMQ server queues
Queue - a structure that holds messages in FIFO order
I'm trying to understand the relationship, and more importantly, the associations between them.
I'm still not quite sure what a Channel is, other than the fact that this is the structure that you publish and consume from, and that it is created from an open connection. If someone could explain to me what the "Channel" represents, it might help clear a few things up.
What is the relationship between Channel and Queue? Can the same Channel be used to communicate to multiples Queues, or does it have to be 1:1?
What is the relationship between Queue and the Consumer Pool? Can multiple Consumers be subscribed to the same Queue? Can multiple Queues be consumed by the same Consumer? Or is the relationship 1:1?
A Connection represents a real TCP connection to the message broker, whereas a Channel is a virtual connection (AMQP connection) inside it. This way you can use as many (virtual) connections as you want inside your application without overloading the broker with TCP connections.
You can use one Channel for everything. However, if you have multiple threads, it's suggested to use a different Channel for each thread.
Channel thread-safety in Java Client API Guide:
Channel instances are safe for use by multiple threads. Requests into
a Channel are serialized, with only one thread being able to run a
command on the Channel at a time. Even so, applications should prefer
using a Channel per thread instead of sharing the same Channel across
multiple threads.
There is no direct relation between Channel and Queue. A Channel is used to send AMQP commands to the broker. This can be the creation of a queue or similar, but these concepts are not tied together.
Each Consumer runs in its own thread allocated from the consumer thread pool. If multiple Consumers are subscribed to the same Queue, the broker uses round-robin to distribute the messages between them equally. See Tutorial two: "Work Queues".
It is also possible to attach the same Consumer to multiple Queues.
You can understand Consumers as callbacks. These are called everytime a message arrives on a Queue the Consumer is bound to. For the case of the Java Client, each Consumers has a method handleDelivery(...), which represents the callback method. What you typically do is, subclass DefaultConsumer and override handleDelivery(...). Note: If you attach the same Consumer instance to multiple queues, this method will be called by different threads. So take care of synchronization if necessary.
A good conceptual understanding of what the AMQP protocol does "under the hood" is useful here. I would offer that the documentation and API that AMQP 0.9.1 chose to deploy makes this particularly confusing, so the question itself is one which many people have to wrestle with.
TL;DR
A connection is the physical negotiated TCP socket with the AMQP server. Properly-implemented clients will have one of these per application, thread-safe, sharable among threads.
A channel is a single application session on the connection. A thread will have one or more of these sessions. AMQP architecture 0.9.1 is that these are not to be shared among threads, and should be closed/destroyed when the thread that created it is finished with it. They are also closed by the server when various protocol violations occur.
A consumer is a virtual construct that represents the presence of a "mailbox" on a particular channel. The use of a consumer tells the broker to push messages from a particular queue to that channel endpoint.
Connection Facts
First, as others have correctly pointed out, a connection is the object that represents the actual TCP connection to the server. Connections are specified at the protocol level in AMQP, and all communication with the broker happens over one or more connections.
Since it's an actual TCP connection, it has an IP Address and Port #.
Protocol parameters are negotiated on a per-client basis as part of setting up the connection (a process known as the handshake.
It is designed to be long-lived; there are few cases where connection closure is part of the protocol design.
From an OSI perspective, it probably resides somewhere around Layer 6
Heartbeats can be set up to monitor the connection status, as TCP does not contain anything in and of itself to do this.
It is best to have a dedicated thread manage reads and writes to the underlying TCP socket. Most, if not all, RabbitMQ clients do this. In that regard, they are generally thread-safe.
Relatively speaking, connections are "expensive" to create (due to the handshake), but practically speaking, this really doesn't matter. Most processes really will only need one connection object. But, you can maintain connections in a pool, if you find you need more throughput than a single thread/socket can provide (unlikely with current computing technology).
Channel Facts
A Channel is the application session that is opened for each piece of your app to communicate with the RabbitMQ broker. It operates over a single connection, and represents a session with the broker.
As it represents a logical part of application logic, each channel usually exists on its own thread.
Typically, all channels opened by your app will share a single connection (they are lightweight sessions that operate on top of the connection). Connections are thread-safe, so this is OK.
Most AMQP operations take place over channels.
From an OSI Layer perspective, channels are probably around Layer 7.
Channels are designed to be transient; part of the design of AMQP is that the channel is typically closed in response to an error (e.g. re-declaring a queue with different parameters before deleting the existing queue).
Since they are transient, channels should not be pooled by your app.
The server uses an integer to identify a channel. When the thread managing the connection receives a packet for a particular channel, it uses this number to tell the broker which channel/session the packet belongs to.
Channels are not generally thread-safe as it would make no sense to share them among threads. If you have another thread that needs to use the broker, a new channel is needed.
Consumer Facts
A consumer is an object defined by the AMQP protocol. It is neither a channel nor a connection, instead being something that your particular application uses as a "mailbox" of sorts to drop messages.
"Creating a consumer" means that you tell the broker (using a channel via a connection) that you would like messages pushed to you over that channel. In response, the broker will register that you have a consumer on the channel and begin pushing messages to you.
Each message pushed over the connection will reference both a channel number and a consumer number. In that way, the connection-managing thread (in this case, within the Java API) knows what to do with the message; then, the channel-handling thread also knows what to do with the message.
Consumer implementation has the widest amount of variation, because it's literally application-specific. In my implementation, I chose to spin off a task each time a message arrived via the consumer; thus, I had a thread managing the connection, a thread managing the channel (and by extension, the consumer), and one or more task threads for each message delivered via the consumer.
Closing a connection closes all channels on the connection. Closing a channel closes all consumers on the channel. It is also possible to cancel a consumer (without closing the channel). There are various cases when it makes sense to do any of the three things.
Typically, the implementation of a consumer in an AMQP client will allocate one dedicated channel to the consumer to avoid conflicts with the activities of other threads or code (including publishing).
In terms of what you mean by consumer thread pool, I suspect that Java client is doing something similar to what I programmed my client to do (mine was based off the .Net client, but heavily modified).
I found this article which explains all aspects of the AMQP model, of which, channel is one. I found it very helpful in rounding out my understanding
https://www.rabbitmq.com/tutorials/amqp-concepts.html
Some applications need multiple connections to an AMQP broker. However, it is undesirable to keep many TCP connections open at the same time because doing so consumes system resources and makes it more difficult to configure firewalls. AMQP 0-9-1 connections are multiplexed with channels that can be thought of as "lightweight connections that share a single TCP connection".
For applications that use multiple threads/processes for processing, it is very common to open a new channel per thread/process and not share channels between them.
Communication on a particular channel is completely separate from communication on another channel, therefore every AMQP method also carries a channel number that clients use to figure out which channel the method is for (and thus, which event handler needs to be invoked, for example).
There is a relation between like A TCP connection can have multiple Channels.
Channel: It is a virtual connection inside a connection. When publishing or consuming messages from a queue - it's all done over a channel Whereas Connection: It is a TCP connection between your application and the RabbitMQ broker.
In multi-threading architecture, you may need a separate connection per thread. That may lead to underutilization of TCP connection, also it adds overhead to the operating system to establish as many TCP connections it requires during the peak time of the network. The performance of the system could be drastically reduced. This is where the channel comes handy, it creates virtual connections inside a TCP connection. It straightaway reduces the overhead of the OS, also it allows us to perform asynchronous operations in a more faster, reliable and simultaneously way.
I am unable to get connection to SonicMQ may be because of unavailable Producers/Consurmers. In this case is SonicMQ supports reconnecting after some time interval.
It doesn't matter if producers or consumers are available, you don't directly connect to them or topics or queues; you connect to the SonicMQ broker. Just use the connection factory to handle reconnect, and if you have multiple brokers, configure them like this...the factory handles reconnection on behalf of the client...
QueueConnectionFactory factory =
QueueConnectionFactory("broker1:2506;broker2:2506");
I have not tried this but may be you can have a look at this link Generic Resource Adapter for JMS. It provide options for defining connection pool, with reconnection.
It's not sonic MQ that may support reconnecting it's your client applications.
If you develop it to provide such feature it will work.