Enable reloading of Aviso configuration

Re ECFLOW-1986

libs/node/src/ecflow/node/AvisoAttr.cpp

@@ -93,6 +93,14 @@ void AvisoAttr::reset() {
     }
 }
 
+void AvisoAttr::reload() {
+    if (controller_) {
+        state_change_no_ = Ecf::incr_state_change_no();
+        finish();
+        start();
+    }
+}
+
 bool AvisoAttr::isFree() const {
 
     if (controller_ == nullptr) {

libs/node/src/ecflow/node/AvisoAttr.hpp

@@ -56,6 +56,8 @@ class AvisoAttr {
     static constexpr const char* default_polling = "%ECF_AVISO_POLLING%";
     static constexpr const char* default_auth    = "%ECF_AVISO_AUTH%";
 
+    static constexpr const char* reload_option_value = "reload";
+
     static bool is_valid_name(const std::string& name);
 
     /**
@@ -98,8 +100,19 @@ class AvisoAttr {
 
     bool why(std::string& theReasonWhy) const;
 
+    /**
+     * Initialises the Aviso procedure, which effectively starts the background polling mechanism.
+     * Typically, called when traversing the tree -- does nothing if Aviso service is already set up.
+     */
     void reset();
 
+    /**
+     * Restarts the Aviso procedure, which effectively stops before restarting the background polling mechanism.
+     * Typicallly, called explicitly via Alter command -- forces the reinitialisation of the Aviso service,
+     * guaranteeing that parameters, given as ECF variables, are reevaluated.
+     */
+    void reload();
+
     [[nodiscard]] bool isFree() const;
 
     void start() const;

libs/node/src/ecflow/node/NodeChange.cpp

@@ -172,7 +172,11 @@ void Node::changeAviso(const std::string& name, const std::string& value) {
         throw std::runtime_error("Node::changeAviso: Could not find aviso " + name);
     }
 
-    *found = AvisoParser::parse_aviso_line(value, name);
+    if (value == AvisoAttr::reload_option_value) {
+        found->reload();
+    } else {
+        *found = AvisoParser::parse_aviso_line(value, name);
+    }
 
     state_change_no_ = Ecf::incr_state_change_no();
 }