Using Alarms and Conditions Server

Besides the usage of monitored items and events to observe the changes in the server, it is also important to make use of the Alarms and Conditions Server Model. Alarms are events which are triggered automatically by the server dependent on internal server logic or user specific logic when the state of server components change. The state of a component is represented through a condition. So the values of all the condition children (Fields) are the actual state of the component.

Trigger Alarm events by changing States

The following example will be based on the server events tutorial. Please make sure to understand the principle of normal events before proceeding with this example!

static UA_NodeId conditionSource;
static UA_NodeId conditionInstance_1;
static UA_NodeId conditionInstance_2;

static UA_StatusCode
addConditionSourceObject(UA_Server *server) {
    UA_ObjectAttributes object_attr = UA_ObjectAttributes_default;
    object_attr.eventNotifier = 1;

    object_attr.displayName = UA_LOCALIZEDTEXT("en", "ConditionSourceObject");
    UA_StatusCode retval =  UA_Server_addObjectNode(server, UA_NODEID_NULL,
                                      UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER),
                                      UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES),
                                      UA_QUALIFIEDNAME(0, "ConditionSourceObject"),
                                      UA_NODEID_NUMERIC(0, UA_NS0ID_BASEOBJECTTYPE),
                                      object_attr, NULL, &conditionSource);

    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "Creating Condition Source failed. StatusCode %s",
                     UA_StatusCode_name(retval));
    }

    /* ConditionSource should be EventNotifier of another Object (usually the
     * Server Object). If this Reference is not created by user then the A&C
     * Server will create "HasEventSource" reference to the Server Object
     * automatically when the condition is created*/
    retval = UA_Server_addReference(server, UA_NODEID_NUMERIC(0, UA_NS0ID_SERVER),
                                     UA_NODEID_NUMERIC(0, UA_NS0ID_HASNOTIFIER),
                                     UA_EXPANDEDNODEID_NUMERIC(conditionSource.namespaceIndex,
                                                               conditionSource.identifier.numeric),
                                     UA_TRUE);

    return retval;
}

Create a condition instance from OffNormalAlarmType. The condition source is the Object created in addConditionSourceObject(). The condition will be exposed in Address Space through the HasComponent reference to the condition source.

static UA_StatusCode
addCondition_1(UA_Server *server) {
    UA_StatusCode retval = addConditionSourceObject(server);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "creating Condition Source failed. StatusCode %s",
                     UA_StatusCode_name(retval));
    }

    retval = UA_Server_createCondition(server,
                                       UA_NODEID_NULL,
                                       UA_NODEID_NUMERIC(0, UA_NS0ID_OFFNORMALALARMTYPE),
                                       UA_QUALIFIEDNAME(0, "Condition 1"), conditionSource,
                                       UA_NODEID_NUMERIC(0, UA_NS0ID_HASCOMPONENT),
                                       &conditionInstance_1);

    return retval;
}

Create a condition instance from OffNormalAlarmType. The condition source is the server Object. The condition won’t be exposed in Address Space.

static UA_StatusCode
addCondition_2(UA_Server *server) {
    UA_StatusCode retval =
        UA_Server_createCondition(server, UA_NODEID_NULL,
                                  UA_NODEID_NUMERIC(0, UA_NS0ID_OFFNORMALALARMTYPE),
                                  UA_QUALIFIEDNAME(0, "Condition 2"),
                                  UA_NODEID_NUMERIC(0, UA_NS0ID_SERVER),
                                  UA_NODEID_NULL, &conditionInstance_2);

    return retval;
}

static void
addVariable_1_triggerAlarmOfCondition_1(UA_Server *server, UA_NodeId* outNodeId) {
    UA_VariableAttributes attr = UA_VariableAttributes_default;
    attr.displayName = UA_LOCALIZEDTEXT("en", "Activate Condition 1");
    attr.accessLevel = UA_ACCESSLEVELMASK_READ | UA_ACCESSLEVELMASK_WRITE;
    UA_Boolean tboolValue = UA_FALSE;
    UA_Variant_setScalar(&attr.value, &tboolValue, &UA_TYPES[UA_TYPES_BOOLEAN]);

    UA_QualifiedName CallbackTestVariableName = UA_QUALIFIEDNAME(0, "Activate Condition 1");
    UA_NodeId parentNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER);
    UA_NodeId parentReferenceNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES);
    UA_NodeId variableTypeNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_BASEDATAVARIABLETYPE);
    UA_Server_addVariableNode(server, UA_NODEID_NULL, parentNodeId,
                              parentReferenceNodeId, CallbackTestVariableName,
                              variableTypeNodeId, attr, NULL, outNodeId);
}

static void
addVariable_2_changeSeverityOfCondition_2(UA_Server *server,
                                          UA_NodeId* outNodeId) {
    UA_VariableAttributes attr = UA_VariableAttributes_default;
    attr.displayName = UA_LOCALIZEDTEXT("en", "Change Severity Condition 2");
    attr.accessLevel = UA_ACCESSLEVELMASK_READ | UA_ACCESSLEVELMASK_WRITE;
    UA_UInt16 severityValue = 0;
    UA_Variant_setScalar(&attr.value, &severityValue, &UA_TYPES[UA_TYPES_UINT16]);

    UA_QualifiedName CallbackTestVariableName =
        UA_QUALIFIEDNAME(0, "Change Severity Condition 2");
    UA_NodeId parentNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER);
    UA_NodeId parentReferenceNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES);
    UA_NodeId variableTypeNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_BASEDATAVARIABLETYPE);
    UA_Server_addVariableNode(server, UA_NODEID_NULL, parentNodeId,
                              parentReferenceNodeId, CallbackTestVariableName,
                              variableTypeNodeId, attr, NULL, outNodeId);
}

static void
addVariable_3_returnCondition_1_toNormalState(UA_Server *server,
                                              UA_NodeId* outNodeId) {
    UA_VariableAttributes attr = UA_VariableAttributes_default;
    attr.displayName = UA_LOCALIZEDTEXT("en", "Return to Normal Condition 1");
    attr.accessLevel = UA_ACCESSLEVELMASK_READ | UA_ACCESSLEVELMASK_WRITE;
    UA_Boolean rtn = 0;
    UA_Variant_setScalar(&attr.value, &rtn, &UA_TYPES[UA_TYPES_BOOLEAN]);

    UA_QualifiedName CallbackTestVariableName =
        UA_QUALIFIEDNAME(0, "Return to Normal Condition 1");
    UA_NodeId parentNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER);
    UA_NodeId parentReferenceNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES);
    UA_NodeId variableTypeNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_BASEDATAVARIABLETYPE);
    UA_Server_addVariableNode(server, UA_NODEID_NULL, parentNodeId,
                              parentReferenceNodeId, CallbackTestVariableName,
                              variableTypeNodeId, attr, NULL, outNodeId);
}

static void
afterWriteCallbackVariable_1(UA_Server *server, const UA_NodeId *sessionId,
                             void *sessionContext, const UA_NodeId *nodeId,
                             void *nodeContext, const UA_NumericRange *range,
                             const UA_DataValue *data) {
    UA_QualifiedName activeStateField = UA_QUALIFIEDNAME(0,"ActiveState");
    UA_QualifiedName activeStateIdField = UA_QUALIFIEDNAME(0,"Id");
    UA_Variant value;

    UA_StatusCode retval =
        UA_Server_writeObjectProperty_scalar(server, conditionInstance_1,
                                             UA_QUALIFIEDNAME(0, "Time"),
                                             &data->sourceTimestamp,
                                             &UA_TYPES[UA_TYPES_DATETIME]);

    if(*(UA_Boolean *)(data->value.data) == true) {
        /* By writing "true" in ActiveState/Id, the A&C server will set the
         * related fields automatically and then will trigger event
         * notification. */
        UA_Boolean activeStateId = true;
        UA_Variant_setScalar(&value, &activeStateId, &UA_TYPES[UA_TYPES_BOOLEAN]);
        retval |= UA_Server_setConditionVariableFieldProperty(server, conditionInstance_1,
                                                              &value, activeStateField,
                                                              activeStateIdField);
        if(retval != UA_STATUSCODE_GOOD) {
            UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                         "Setting ActiveState/Id Field failed. StatusCode %s",
                         UA_StatusCode_name(retval));
            return;
        }
    } else {
        /* By writing "false" in ActiveState/Id, the A&C server will set only
         * the ActiveState field automatically to the value "Inactive". The user
         * should trigger the event manually by calling
         * UA_Server_triggerConditionEvent inside the application or call
         * ConditionRefresh method with client to update the event notification. */
        UA_Boolean activeStateId = false;
        UA_Variant_setScalar(&value, &activeStateId, &UA_TYPES[UA_TYPES_BOOLEAN]);
        retval = UA_Server_setConditionVariableFieldProperty(server, conditionInstance_1,
                                                             &value, activeStateField,
                                                             activeStateIdField);
        if(retval != UA_STATUSCODE_GOOD) {
            UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                         "Setting ActiveState/Id Field failed. StatusCode %s",
                         UA_StatusCode_name(retval));
            return;
        }

        retval = UA_Server_triggerConditionEvent(server, conditionInstance_1,
                                                 conditionSource, NULL);
        if(retval != UA_STATUSCODE_GOOD) {
            UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                           "Triggering condition event failed. StatusCode %s",
                           UA_StatusCode_name(retval));
            return;
        }
    }
}

The callback only changes the severity field of the condition 2. The severity field is of ConditionVariableType, so changes in it triggers an event notification automatically by the server.

static void
afterWriteCallbackVariable_2(UA_Server *server, const UA_NodeId *sessionId,
                             void *sessionContext, const UA_NodeId *nodeId,
                             void *nodeContext, const UA_NumericRange *range,
                             const UA_DataValue *data) {
   /* Another way to set fields of conditions */
    UA_Server_writeObjectProperty_scalar(server, conditionInstance_2,
                                         UA_QUALIFIEDNAME(0, "Severity"),
                                         (UA_UInt16 *)data->value.data,
                                         &UA_TYPES[UA_TYPES_UINT16]);
}

RTN = return to normal.

Retain will be set to false, thus no events will be generated for condition 1 (although EnabledState/=true). To set Retain to true again, the disable and enable methods should be called respectively.

static void
afterWriteCallbackVariable_3(UA_Server *server,
               const UA_NodeId *sessionId, void *sessionContext,
               const UA_NodeId *nodeId, void *nodeContext,
               const UA_NumericRange *range, const UA_DataValue *data) {

    //UA_QualifiedName enabledStateField = UA_QUALIFIEDNAME(0,"EnabledState");
    UA_QualifiedName ackedStateField = UA_QUALIFIEDNAME(0,"AckedState");
    UA_QualifiedName confirmedStateField = UA_QUALIFIEDNAME(0,"ConfirmedState");
    UA_QualifiedName activeStateField = UA_QUALIFIEDNAME(0,"ActiveState");
    UA_QualifiedName severityField = UA_QUALIFIEDNAME(0,"Severity");
    UA_QualifiedName messageField = UA_QUALIFIEDNAME(0,"Message");
    UA_QualifiedName commentField = UA_QUALIFIEDNAME(0,"Comment");
    UA_QualifiedName retainField = UA_QUALIFIEDNAME(0,"Retain");
    UA_QualifiedName idField = UA_QUALIFIEDNAME(0,"Id");

    UA_StatusCode retval =
        UA_Server_writeObjectProperty_scalar(server, conditionInstance_1,
                                             UA_QUALIFIEDNAME(0, "Time"),
                                             &data->serverTimestamp,
                                             &UA_TYPES[UA_TYPES_DATETIME]);
    UA_Variant value;
    UA_Boolean idValue = false;
    UA_Variant_setScalar(&value, &idValue, &UA_TYPES[UA_TYPES_BOOLEAN]);
    retval |= UA_Server_setConditionVariableFieldProperty(server, conditionInstance_1,
                                                          &value, activeStateField,
                                                          idField);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "Setting ActiveState/Id Field failed. StatusCode %s",
                     UA_StatusCode_name(retval));
        return;
    }

    retval = UA_Server_setConditionVariableFieldProperty(server, conditionInstance_1,
                                                         &value, ackedStateField,
                                                         idField);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "Setting AckedState/Id Field failed. StatusCode %s",
                     UA_StatusCode_name(retval));
        return;
    }

    retval = UA_Server_setConditionVariableFieldProperty(server, conditionInstance_1,
                                                         &value, confirmedStateField,
                                                         idField);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "Setting ConfirmedState/Id Field failed. StatusCode %s",
                     UA_StatusCode_name(retval));
        return;
    }

    UA_UInt16 severityValue = 100;
    UA_Variant_setScalar(&value, &severityValue, &UA_TYPES[UA_TYPES_UINT16]);
    retval = UA_Server_setConditionField(server, conditionInstance_1,
                                         &value, severityField);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "Setting Severity Field failed. StatusCode %s",
                     UA_StatusCode_name(retval));
        return;
    }

    UA_LocalizedText messageValue =
        UA_LOCALIZEDTEXT("en", "Condition returned to normal state");
    UA_Variant_setScalar(&value, &messageValue, &UA_TYPES[UA_TYPES_LOCALIZEDTEXT]);
    retval = UA_Server_setConditionField(server, conditionInstance_1,
                                         &value, messageField);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "Setting Message Field failed. StatusCode %s",
                     UA_StatusCode_name(retval));
        return;
    }

    UA_LocalizedText commentValue = UA_LOCALIZEDTEXT("en", "Normal State");
    UA_Variant_setScalar(&value, &commentValue, &UA_TYPES[UA_TYPES_LOCALIZEDTEXT]);
    retval = UA_Server_setConditionField(server, conditionInstance_1,
                                         &value, commentField);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "Setting Comment Field failed. StatusCode %s",
                     UA_StatusCode_name(retval));
        return;
    }

    UA_Boolean retainValue = false;
    UA_Variant_setScalar(&value, &retainValue, &UA_TYPES[UA_TYPES_BOOLEAN]);
    retval = UA_Server_setConditionField(server, conditionInstance_1,
                                         &value, retainField);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "Setting Retain Field failed. StatusCode %s",
                     UA_StatusCode_name(retval));
        return;
    }

    retval = UA_Server_triggerConditionEvent(server, conditionInstance_1,
                                             conditionSource, NULL);
    if (retval != UA_STATUSCODE_GOOD) {
     UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                    "Triggering condition event failed. StatusCode %s",
                    UA_StatusCode_name(retval));
     return;
    }
}

static UA_StatusCode
enteringEnabledStateCallback(UA_Server *server, const UA_NodeId *condition) {
    UA_Boolean retain = true;
    return UA_Server_writeObjectProperty_scalar(server, *condition,
                                                UA_QUALIFIEDNAME(0, "Retain"),
                                                &retain,
                                                &UA_TYPES[UA_TYPES_BOOLEAN]);
}

This is user specific function which will be called upon acknowledging an alarm notification. In this example we will set the Alarm to Inactive state. The server is responsible of setting standard fields related to Acknowledge Method and triggering the alarm notification.

static UA_StatusCode
enteringAckedStateCallback(UA_Server *server, const UA_NodeId *condition) {
    /* deactivate Alarm when acknowledging*/
    UA_Boolean activeStateId = false;
    UA_Variant value;
    UA_QualifiedName activeStateField = UA_QUALIFIEDNAME(0,"ActiveState");
    UA_QualifiedName activeStateIdField = UA_QUALIFIEDNAME(0,"Id");

    UA_Variant_setScalar(&value, &activeStateId, &UA_TYPES[UA_TYPES_BOOLEAN]);
    UA_StatusCode retval =
        UA_Server_setConditionVariableFieldProperty(server, *condition,
                                                    &value, activeStateField,
                                                    activeStateIdField);

    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "Setting ActiveState/Id Field failed. StatusCode %s",
                     UA_StatusCode_name(retval));
    }

    return retval;
}

static UA_StatusCode
enteringConfirmedStateCallback(UA_Server *server, const UA_NodeId *condition) {
     /* Deactivate Alarm and put it out of the interesting state (by writing
     * false to Retain field) when confirming*/
    UA_Boolean activeStateId = false;
    UA_Boolean retain = false;
    UA_Variant value;
    UA_QualifiedName activeStateField = UA_QUALIFIEDNAME(0,"ActiveState");
    UA_QualifiedName activeStateIdField = UA_QUALIFIEDNAME(0,"Id");
    UA_QualifiedName retainField = UA_QUALIFIEDNAME(0,"Retain");

    UA_Variant_setScalar(&value, &activeStateId, &UA_TYPES[UA_TYPES_BOOLEAN]);
    UA_StatusCode retval =
        UA_Server_setConditionVariableFieldProperty(server, *condition,
                                                    &value, activeStateField,
                                                    activeStateIdField);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "Setting ActiveState/Id Field failed. StatusCode %s",
                     UA_StatusCode_name(retval));
        return retval;
    }

    UA_Variant_setScalar(&value, &retain, &UA_TYPES[UA_TYPES_BOOLEAN]);
    retval = UA_Server_setConditionField(server, *condition,
                                         &value, retainField);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "Setting ActiveState/Id Field failed. StatusCode %s",
                     UA_StatusCode_name(retval));
    }

    return retval;
}

static UA_StatusCode
setUpEnvironment(UA_Server *server) {
    UA_NodeId variable_1;
    UA_NodeId variable_2;
    UA_NodeId variable_3;
    UA_ValueCallback callback;
    callback.onRead = NULL;

    /* Exposed condition 1. We will add to it user specific callbacks when
     * entering enabled state, when acknowledging and when confirming. */
    UA_StatusCode retval = addCondition_1(server);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "adding condition 1 failed. StatusCode %s",
                     UA_StatusCode_name(retval));
        return retval;
    }

    UA_TwoStateVariableChangeCallback userSpecificCallback = enteringEnabledStateCallback;
    retval = UA_Server_setConditionTwoStateVariableCallback(server, conditionInstance_1,
                                                            conditionSource, false,
                                                            userSpecificCallback,
                                                            UA_ENTERING_ENABLEDSTATE);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "adding entering enabled state callback failed. StatusCode %s",
                     UA_StatusCode_name(retval));
        return retval;
    }

    userSpecificCallback = enteringAckedStateCallback;
    retval = UA_Server_setConditionTwoStateVariableCallback(server, conditionInstance_1,
                                                            conditionSource, false,
                                                            userSpecificCallback,
                                                            UA_ENTERING_ACKEDSTATE);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "adding entering acked state callback failed. StatusCode %s",
                     UA_StatusCode_name(retval));
        return retval;
    }

    userSpecificCallback = enteringConfirmedStateCallback;
    retval = UA_Server_setConditionTwoStateVariableCallback(server, conditionInstance_1,
                                                            conditionSource, false,
                                                            userSpecificCallback,
                                                            UA_ENTERING_CONFIRMEDSTATE);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "adding entering confirmed state callback failed. StatusCode %s",
                     UA_StatusCode_name(retval));
        return retval;
    }

    /* Unexposed condition 2. No user specific callbacks, so the server will
     * behave in a standard manner upon entering enabled state, acknowledging
     * and confirming. We will set Retain field to true and enable the condition
     * so we can receive event notifications (we cannot call enable method on
     * unexposed condition using a client like UaExpert or Softing). */
    retval = addCondition_2(server);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "adding condition 2 failed. StatusCode %s",
                     UA_StatusCode_name(retval));
        return retval;
    }

    UA_Boolean retain = UA_TRUE;
    UA_Server_writeObjectProperty_scalar(server, conditionInstance_2,
                                         UA_QUALIFIEDNAME(0, "Retain"),
                                         &retain, &UA_TYPES[UA_TYPES_BOOLEAN]);

    UA_Variant value;
    UA_Boolean enabledStateId = true;
    UA_QualifiedName enabledStateField = UA_QUALIFIEDNAME(0,"EnabledState");
    UA_QualifiedName enabledStateIdField = UA_QUALIFIEDNAME(0,"Id");
    UA_Variant_setScalar(&value, &enabledStateId, &UA_TYPES[UA_TYPES_BOOLEAN]);
    retval = UA_Server_setConditionVariableFieldProperty(server, conditionInstance_2,
                                                         &value, enabledStateField,
                                                         enabledStateIdField);

    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "Setting EnabledState/Id Field failed. StatusCode %s",
                     UA_StatusCode_name(retval));
        return retval;
    }


    /* Add 3 variables to trigger condition events */
    addVariable_1_triggerAlarmOfCondition_1(server, &variable_1);

    callback.onWrite = afterWriteCallbackVariable_1;
    retval = UA_Server_setVariableNode_valueCallback(server, variable_1, callback);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "Setting variable 1 Callback failed. StatusCode %s",
                     UA_StatusCode_name(retval));
        return retval;
    }

    /* Severity can change internally also when the condition disabled and
     * retain is false. However, in this case no events will be generated. */
    addVariable_2_changeSeverityOfCondition_2(server, &variable_2);

    callback.onWrite = afterWriteCallbackVariable_2;
    retval = UA_Server_setVariableNode_valueCallback(server, variable_2, callback);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "Setting variable 2 Callback failed. StatusCode %s",
                     UA_StatusCode_name(retval));
        return retval;
    }

    addVariable_3_returnCondition_1_toNormalState(server, &variable_3);

    callback.onWrite = afterWriteCallbackVariable_3;
    retval = UA_Server_setVariableNode_valueCallback(server, variable_3, callback);
    if(retval != UA_STATUSCODE_GOOD) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                     "Setting variable 3 Callback failed. StatusCode %s",
                     UA_StatusCode_name(retval));
    }

    return retval;
}

It follows the main server code, making use of the above definitions.

static UA_Boolean running = true;
static void stopHandler(int sig) {
    running = false;
}

int main (void) {
    /* default server values */
    signal(SIGINT, stopHandler);
    signal(SIGTERM, stopHandler);

    UA_Server *server = UA_Server_new();
    UA_ServerConfig_setDefault(UA_Server_getConfig(server));

    UA_StatusCode retval = setUpEnvironment(server);

    if(retval == UA_STATUSCODE_GOOD)
        retval = UA_Server_run(server, &running);

    UA_Server_delete(server);
    return retval == UA_STATUSCODE_GOOD ? EXIT_SUCCESS : EXIT_FAILURE;
}