fix #438

问题：edge模式，推流时异常断开。
    解决方法：增加edge模式推流检测。

@@ -806,6 +806,11 @@ int SrsPublishEdge::initialize(SrsSource* source, SrsRequest* req)
     return ret;
 }
 
+bool SrsPublishEdge::can_publish()
+{
+    return state != SrsEdgeStatePublish;
+}
+
 int SrsPublishEdge::on_client_publish()
 {
     int ret = ERROR_SUCCESS;

@@ -207,6 +207,7 @@ public:
     virtual void set_queue_size(double queue_size);
 public:
     virtual int initialize(SrsSource* source, SrsRequest* req);
+    virtual bool can_publish();
     /**
     * when client publish stream on edge.
     */

@@ -423,27 +423,20 @@ int SrsRtmpConn::stream_service_cycle()
         }
     }
     srs_assert(source != NULL);
-    
+
+    // check ASAP, to fail it faster if invalid.
+    if (type != SrsRtmpConnPlay) {
+        if ((ret = prepare_publish(source, vhost_is_edge)) != ERROR_SUCCESS) {
+            return ret;
+        }
+    }
+
     // update the statistic when source disconveried.
     SrsStatistic* stat = SrsStatistic::instance();
     if ((ret = stat->on_client(_srs_context->get_id(), req)) != ERROR_SUCCESS) {
         srs_error("stat client failed. ret=%d", ret);
         return ret;
     }
-
-    // check ASAP, to fail it faster if invalid.
-    if (type != SrsRtmpConnPlay && !vhost_is_edge) {
-        // check publish available
-        // for edge, never check it, for edge use proxy mode.
-        if (!source->can_publish()) {
-            ret = ERROR_SYSTEM_STREAM_BUSY;
-            srs_warn("stream %s is already publishing. ret=%d", 
-                req->get_stream_url().c_str(), ret);
-            // to delay request
-            st_usleep(SRS_STREAM_BUSY_SLEEP_US);
-            return ret;
-        }
-    }
     
     bool enabled_cache = _srs_config->get_gop_cache(req->vhost);
     srs_trace("source url=%s, ip=%s, cache=%d, is_edge=%d, source_id=%d[%d]",
@@ -1260,6 +1253,31 @@ int SrsRtmpConn::do_token_traverse_auth(SrsRtmpClient* client)
     return ret;
 }
 
+int SrsRtmpConn::prepare_publish(SrsSource* source, bool vhost_is_edge)
+{
+    int ret = ERROR_SUCCESS;
+    srs_assert(source);
+
+    // check publish available
+    bool can_publish = false;
+    if (vhost_is_edge) {
+        can_publish = source->proxy_can_publish();
+    } else {
+        can_publish = source->can_publish();
+    }
+    
+    if (!can_publish) {
+        ret = ERROR_SYSTEM_STREAM_BUSY;
+        srs_warn("stream %s is already publishing. ret=%d", 
+            req->get_stream_url().c_str(), ret);
+        // to delay request
+        st_usleep(SRS_STREAM_BUSY_SLEEP_US);
+        return ret;
+    }
+
+    return ret;
+}
+
 int SrsRtmpConn::http_hooks_on_connect()
 {
     int ret = ERROR_SUCCESS;

@@ -123,6 +123,7 @@ private:
     virtual int check_edge_token_traverse_auth();
     virtual int connect_server(int origin_index, st_netfd_t* pstsock);
     virtual int do_token_traverse_auth(SrsRtmpClient* client);
+    virtual int prepare_publish(SrsSource* source, bool vhost_is_edge);
 private:
     virtual int http_hooks_on_connect();
     virtual void http_hooks_on_close();

@@ -1355,6 +1355,11 @@ bool SrsSource::can_publish()
     return _can_publish;
 }
 
+bool SrsSource::proxy_can_publish()
+{
+    return publish_edge->can_publish();
+}
+
 int SrsSource::on_meta_data(SrsCommonMessage* msg, SrsOnMetaDataPacket* metadata)
 {
     int ret = ERROR_SUCCESS;

@@ -538,6 +538,7 @@ public:
 // logic data methods
 public:
     virtual bool can_publish();
+    virtual bool proxy_can_publish();
     virtual int on_meta_data(SrsCommonMessage* msg, SrsOnMetaDataPacket* metadata);
 public:
     virtual int on_audio(SrsCommonMessage* audio);