open62541/examples/tutorial_server_alarms_conditions.c

/* This work is licensed under a Creative Commons CCZero 1.0 Universal License.
 * See http://creativecommons.org/publicdomain/zero/1.0/ for more information. */

#include <open62541/plugin/log_stdout.h>
#include <open62541/server.h>
#include <open62541/server_config_default.h>

#include <signal.h>
#include <stdlib.h>

/**
 * 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_NULL,
                                      UA_NODEID_NULL,
                                      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 = UA_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;
}