namespace s4u {
/** @brief Mailboxes: Network rendez-vous points.
- * @ingroup s4u_api
*
- * @tableofcontents
- *
- * @section s4u_mb_what What are mailboxes
+ * <b>What are mailboxes?</b>
*
* Rendez-vous point for network communications, similar to URLs on
* which you could post and retrieve data. Actually, the mailboxes are
* find the receiver. The twitter hashtag, which help senders and
* receivers to find each others. In TCP, the pair {host name, host
* port} to which you can connect to find your interlocutor. In HTTP,
- * URLs through which the clients can connect to the servers.
+ * URLs through which the clients can connect to the servers. In ZeroMQ
+ * and other queuing systems, the queues are used to match senders
+ * and receivers.
*
- * One big difference with most of these systems is that usually, no
- * actor is the exclusive owner of a mailbox, neither in sending nor
- * in receiving. Many actors can send into and/or receive from the
+ * One big difference with most of these systems is that no actor is
+ * the exclusive owner of a mailbox, neither in sending nor in
+ * receiving. Many actors can send into and/or receive from the
* same mailbox. This is a big difference to the socket ports for
* example, that are definitely exclusive in receiving.
*
+ * Mailboxes can optionally have a @i receiver with `simgrid::s4u::Mailbox::set_receiver()`.
+ * It means that the data exchange starts as soon as the sender has
+ * done the `put()`, even before the corresponding `get()`
+ * (usually, it starts as soon as both `put()` and `get()` are posted).
+ * This is closer to the BSD semantic and can thus help to improve
+ * the timing accuracy, but this is not mandatory at all.
+ *
* A big difference with twitter hashtags is that SimGrid does not
* offer easy support to broadcast a given message to many
* receivers. So that would be like a twitter tag where each message
* is consumed by the first coming receiver.
*
+ * A big difference with the ZeroMQ queues is that you cannot filter
+ * on the data you want to get from the mailbox. To model such settings
+ * in SimGrid, you'd have one mailbox per potential topic, and subscribe
+ * to each topic individually with a `get_async()` on each mailbox.
+ * Then, use `Comm::wait_any()` to get the first message on any of the
+ * mailbox you are subscribed onto.
+ *
* The mailboxes are not located on the network, and you can access
* them without any latency. The network delay are only related to the
* location of the sender and receiver once the match between them is
* done on the mailbox. This is just like the phone number that you
* can use locally, and the geographical distance only comes into play
- * once you start the communication by dialling this number.
+ * once you start the communication by dialing this number.
*
- * @section s4u_mb_howto How to use mailboxes?
+ * <b>How to use mailboxes?</b>
*
* Any existing mailbox can be retrieve from its name (which are
* unique strings, just like with twitter tags). This results in a
*
* For something close to classical socket communications, use
* "hostname:port" as mailbox names, and make sure that only one actor
- * reads into that mailbox. It's hard to build a prefectly realistic
+ * reads into that mailbox. It's hard to build a perfectly realistic
* model of the TCP sockets, but most of the time, this system is too
* cumbersome for your simulations anyway. You probably want something
* simpler, that turns our to be easy to build with the mailboxes.
* the first relevant actor that can deal with the request will handle
* it.
*
- * @section s4u_mb_matching How are sends and receives matched?
+ * <b>How are sends and receives matched?</b>
*
* The matching algorithm is as simple as a first come, first
* serve. When a new send arrives, it matches the oldest enqueued
- * receive. If no receive is currently enqueued, then the incomming
+ * receive. If no receive is currently enqueued, then the incoming
* send is enqueued. As you can see, the mailbox cannot contain both
* send and receive requests: all enqueued requests must be of the
* same sort.
*
- * @section s4u_mb_receiver Declaring a receiving actor
+ * <b>Declaring a receiving actor</b>
*
* The last twist is that by default in the simulator, the data starts
* to be exchanged only when both the sender and the receiver are
* start as soon as possible, and the data will already be there on
* the receiver host when the receiver actor posts its receive().
*
- * @section s4u_mb_api The API
+ * <b>The API</b>
+ *
*/
class XBT_PUBLIC Mailbox {
- friend Comm;
+ friend simgrid::s4u::Comm;
friend simgrid::kernel::activity::MailboxImpl;
simgrid::kernel::activity::MailboxImpl* pimpl_;
*
* It means that the communications sent to this mailbox will start flowing to
* its host even before he does a recv(). This models the real behavior of TCP
- * and MPI communications, amongst other.
+ * and MPI communications, amongst other. It will improve the accuracy of
+ * predictions, in particular if your application exhibits swarms of small messages.
+ *
+ * SimGrid does not enforces any kind of ownership over the mailbox. Even if a receiver
+ * was declared, any other actors can still get() data from the mailbox. The timings
+ * will then probably be off tracks, so you should strive on your side to not get data
+ * from someone else's mailbox.
*/
void set_receiver(ActorPtr actor);
