[GitHub] [qpid-dispatch] kgiusti commented on a change in pull request #693: DISPATCH-1579: open dedicated inter-router sessions for data and control links

[GitBox <gi...@apache.org>]

kgiusti commented on a change in pull request #693: DISPATCH-1579: open dedicated inter-router sessions for data and control links
URL: https://github.com/apache/qpid-dispatch/pull/693#discussion_r389857365
 
 

 ##########
 File path: src/router_node.c
 ##########
 @@ -786,18 +786,47 @@ static int AMQP_link_attach_handler(void* context, qd_link_t *link)
 
 
 /**
- * Handler for flow events on links
+ * Handler for flow events on links.  Flow updates include session window
+ * state, which needs to be checked for unblocking Q3.
  */
 static int AMQP_link_flow_handler(void* context, qd_link_t *link)
 {
-    qd_router_t *router = (qd_router_t*) context;
-    qdr_link_t  *rlink  = (qdr_link_t*) qd_link_get_context(link);
-    pn_link_t   *pnlink = qd_link_pn(link);
-
-    if (!rlink)
-        return 0;
+    qd_router_t *router  = (qd_router_t*) context;
+    pn_link_t   *pnlink  = qd_link_pn(link);
+    pn_session_t *pn_ssn = pn_link_session(pnlink);
+
+    bool link_flowed = false;
+    if (pn_ssn) {
+        qd_session_t *qd_ssn = pn_session_get_context(pn_ssn);
+        if (qd_ssn && qd_session_is_q3_blocked(qd_ssn)) {
+            // Q3 blocked - have we drained enough outgoing bytes?
+            const size_t q3_lower = BUFFER_SIZE * QD_QLIMIT_Q3_LOWER;
+            if (pn_session_outgoing_bytes(pn_ssn) < q3_lower) {
+                // yes.  We must now unblock all links that have been blocked by Q3
+                qd_link_list_t *blinks = qd_session_q3_blocked_links(qd_ssn);
+                qd_link_t *blink = DEQ_HEAD(*blinks);
+                while (blink) {
+                    qd_link_q3_unblock(blink);  // removes from blinks list!
+                    qdr_link_t *qdr_link = (qdr_link_t *) qd_link_get_context(blink);
+                    if (qdr_link) {
+                        pn_link_t *pn_link = qd_link_pn(blink);
+                        // signalling flow to the core causes the link to be activated
+                        qdr_link_flow(router->router_core, qdr_link, pn_link_remote_credit(pn_link), pn_link_get_drain(pn_link));
+                        if (blink == link)
+                            link_flowed = true;  // original link flowed - do not flow again
+                    }
+                    blink = DEQ_HEAD(*blinks);
+                }
+            }
+        }
+    }
 
-    qdr_link_flow(router->router_core, rlink, pn_link_remote_credit(pnlink), pn_link_get_drain(pnlink));
+    if (!link_flowed) {
 
 Review comment:
   will do

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