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| -rw-r--r-- | lib/tevent/doc/tutorials.dox | 42 |
1 files changed, 38 insertions, 4 deletions
diff --git a/lib/tevent/doc/tutorials.dox b/lib/tevent/doc/tutorials.dox index ba1fd904e3..e8beed7dc0 100644 --- a/lib/tevent/doc/tutorials.dox +++ b/lib/tevent/doc/tutorials.dox @@ -1,9 +1,43 @@ /** - * @page tevent_queue_tutorial teven_queue tutorial + * @page tevent_queue_tutorial The tevent_queue tutorial * - * @section something Something + * @section Introduction * - * @todo Write down the logic how to use teven_queue + * A tevent_queue is used to queue up async requests that must be + * serialized. For example writing buffers into a socket must be + * serialized. Writing a large lump of data into a socket can require + * multiple write(2) or send(2) system calls. If more than one async + * request is outstanding to write large buffers into a socket, every + * request must individually be completed before the next one begins, + * even if multiple syscalls are required. * - * guru meditation + * To do this, every socket gets assigned a tevent_queue struct. + * + * Creating a serialized async request follows the usual convention to + * return a tevent_req structure with an embedded state structure. To + * serialize the work the requests is about to so, instead of directly + * starting or doing that work, tevent_queue_add must be called. When it + * is time for the serialized async request to do its work, the trigger + * callback function tevent_queue_add was given is called. In the example + * of writing to a socket, the trigger is called when the write request + * can begin accessing the socket. + * + * How does this engine work behind the scenes? When the queue is empty, + * tevent_queue_add schedules an immediate call to the trigger + * callback. The trigger callback starts its work, likely by starting + * other async subrequests. While these async subrequests are working, + * more requests can accumulate in the queue by tevent_queue_add. While + * there is no function to explicitly trigger the next waiter in line, it + * still works: When the active request in the queue is done, it will be + * destroyed by talloc_free. Talloc_free of an serialized async request + * that had been added to a queue will trigger the next request in the + * queue via a talloc destructor attached to a child of the serialized + * request. This way the queue will be kept busy when an async request + * finishes. + * + * @section Example + * + * @code + * Metze: Please add a code example here. + * @endcode */ |