diff options
Diffstat (limited to 'cpp/include')
| -rw-r--r-- | cpp/include/qpid/agent/ManagementAgent.h | 29 |
1 files changed, 18 insertions, 11 deletions
diff --git a/cpp/include/qpid/agent/ManagementAgent.h b/cpp/include/qpid/agent/ManagementAgent.h index b0f0f1cec4..41b6423624 100644 --- a/cpp/include/qpid/agent/ManagementAgent.h +++ b/cpp/include/qpid/agent/ManagementAgent.h @@ -155,17 +155,24 @@ class ManagementAgent // virtual uint32_t pollCallbacks(uint32_t callLimit = 0) = 0; - // If "useExternalThread" was set to true in the constructor, this method provides - // a callback that is invoked whenever there is work to be done by pollCallbacks. - // This function is invoked on the agent's thread and should not perform any work - // except to signal the application's thread. - // - // There are two flavors of callback: - // A C version that uses a pointer to a function with a void* context - // A C++ version that uses a class derived from Notifyable - // - // Either type of callback may be used. If they are both provided, the C++ callback - // will be the only one invoked. + // In the "useExternalThread" scenario, there are three ways that an application can + // use to be notified that there is work to do. Of course the application may periodically + // call pollCallbacks if it wishes, but this will cause long latencies in the responses + // to method calls. + // + // The notification methods are: + // + // 1) Register a C-style callback by providing a pointer to a function + // 2) Register a C++-style callback by providing an object of a class that is derived + // from Notifyable + // 3) Call getSignalFd() to get a file descriptor that can be used in a select + // call. The file descriptor shall become readable when the agent has work to + // do. Note that this mechanism is specific to Posix-based operating environments. + // getSignalFd will probably not function correctly on Windows. + // + // If a callback is registered, the callback function will be called on the agent's + // thread. The callback function must perform no work other than to signal the application + // thread to call pollCallbacks. // typedef void (*cb_t)(void*); virtual void setSignalCallback(cb_t callback, void* context) = 0; |