<html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns="http://www.w3.org/TR/REC-html40"> <head> <meta http-equiv=Content-Type content="text/html; charset=us-ascii"> <meta name=Generator content="Microsoft Word 11 (filtered medium)"> <style>  </style> </head> <body lang=EN-US link=blue vlink=purple> <div class=Section1> I am trying to determine the recommended approach to handle a DBus request to a service that takes a “long” time to complete. From the client-side (e.g. the DBus service “proxy”) most of the DBus language bindings allow the client to either block waiting for a response or register a callback function to handle the response asynchronously at a later time.<o:p></o:p> <o:p> </o:p> If I am writing a DBus service, however, I have not run across a binding that allows the server side callback to defer handling the request to a time beyond the scope of the service callback (e.g. beyond the “return” at the end of the callback). For example, suppose I provide a service that has a method which query’s a huge database. Typically querys may take several seconds and during the time the service is waiting on the response from an internal database, I don’t want to block the mainloop of the DBus service. In fact, I want to be able to handle multiple overlapping requests (or at least queue these requests up for later processing). So my server has a DBus method that looks like this:<o:p></o:p> <o:p> </o:p> void getResults(const char* cmd, char** results)<o:p></o:p> {<o:p></o:p>             // Issue request to the internal DB<o:p></o:p> <o:p> </o:p>             // Either block (do NOT want to do this), or better yet, somehow defer replying to<o:p></o:p>             // this request at some point in the future.<o:p></o:p> <o:p> </o:p>             // I don’t want the binding/wrapper code to immediately return a result<o:p></o:p>             return;<o:p></o:p> }<o:p></o:p> <o:p> </o:p> If I block waiting on the response from the database, it ties up the DBus main loop which is not what I want to do. Spawning a thread to wait on the database doesn’t help much either since when the function returns most bindings (I think) expect the result to be filled in. Ideally, I’d like to copy what state information I need related to the request and on-going database query, stash that somewhere, register a callback for the internal database to indicate completion, and return WITHOUT the DBus binding immediately replying to the request.  In other proprietary frameworks I have used there has been a method to “detach” the request in the service handler and then later re-associate that request with the results. I *think* the lowest level DBus library fundamentally supports this notion of deferring a response but I am not sure how the more mature DBus bindings/wrappers handle this. I’d rather NOT have to use a one-way call where there is no immediate response but a signal is issued later time containing the results and a key/token used to associate the earlier request with the later response. It’s cumbersome to design such services.<o:p></o:p> <o:p> </o:p> Can anyone suggest the appropriate way to architect this pattern (preferably using either the C++ or Glib binding to DBus)?<o:p></o:p> </div> </body> </html>