aws_iot_mqtt_client_yield.cpp

00001 /*
00002 * Copyright 2015-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
00003 *
00004 * Licensed under the Apache License, Version 2.0 (the "License").
00005 * You may not use this file except in compliance with the License.
00006 * A copy of the License is located at
00007 *
00008 * http://aws.amazon.com/apache2.0
00009 *
00010 * or in the "license" file accompanying this file. This file is distributed
00011 * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
00012 * express or implied. See the License for the specific language governing
00013 * permissions and limitations under the License.
00014 */
00015 
00016 // Based on Eclipse Paho.
00017 /*******************************************************************************
00018  * Copyright (c) 2014 IBM Corp.
00019  *
00020  * All rights reserved. This program and the accompanying materials
00021  * are made available under the terms of the Eclipse Public License v1.0
00022  * and Eclipse Distribution License v1.0 which accompany this distribution.
00023  *
00024  * The Eclipse Public License is available at
00025  *    http://www.eclipse.org/legal/epl-v10.html
00026  * and the Eclipse Distribution License is available at
00027  *   http://www.eclipse.org/org/documents/edl-v10.php.
00028  *
00029  * Contributors:
00030  *    Allan Stockdill-Mander/Ian Craggs - initial API and implementation and/or initial documentation
00031  *******************************************************************************/
00032 
00033 /**
00034  * @file aws_iot_mqtt_client_yield.c
00035  * @brief MQTT client yield API definitions
00036  */
00037 
00038 #ifdef __cplusplus
00039 extern "C" {
00040 #endif
00041 
00042 #include "aws_iot_mqtt_client_common_internal.h"
00043 
00044 /**
00045   * This is for the case when the aws_iot_mqtt_internal_send_packet Fails.
00046   */
00047 static void _aws_iot_mqtt_force_client_disconnect(AWS_IoT_Client *pClient) {
00048     pClient->clientStatus.clientState = CLIENT_STATE_DISCONNECTED_ERROR;
00049     pClient->networkStack.disconnect(&(pClient->networkStack));
00050     pClient->networkStack.destroy(&(pClient->networkStack));
00051 }
00052 
00053 static IoT_Error_t _aws_iot_mqtt_handle_disconnect(AWS_IoT_Client *pClient) {
00054     IoT_Error_t rc;
00055 
00056     FUNC_ENTRY;
00057 
00058     rc = aws_iot_mqtt_disconnect(pClient);
00059     if(rc != IOT_SUCCESS) {
00060         // If the aws_iot_mqtt_internal_send_packet prevents us from sending a disconnect packet then we have to clean the stack
00061         _aws_iot_mqtt_force_client_disconnect(pClient);
00062     }
00063 
00064     if(NULL != pClient->clientData.disconnectHandler) {
00065         pClient->clientData.disconnectHandler(pClient, pClient->clientData.disconnectHandlerData);
00066     }
00067 
00068     /* Reset to 0 since this was not a manual disconnect */
00069     pClient->clientStatus.clientState = CLIENT_STATE_DISCONNECTED_ERROR;
00070     FUNC_EXIT_RC(NETWORK_DISCONNECTED_ERROR);
00071 }
00072 
00073 
00074 static IoT_Error_t _aws_iot_mqtt_handle_reconnect(AWS_IoT_Client *pClient) {
00075     IoT_Error_t rc;
00076 
00077     FUNC_ENTRY;
00078 
00079     if(!has_timer_expired(&(pClient->reconnectDelayTimer))) {
00080         /* Timer has not expired. Not time to attempt reconnect yet.
00081          * Return attempting reconnect */
00082         FUNC_EXIT_RC(NETWORK_ATTEMPTING_RECONNECT);
00083     }
00084 
00085     rc = NETWORK_PHYSICAL_LAYER_DISCONNECTED;
00086     if(NULL != pClient->networkStack.isConnected) {
00087         rc = pClient->networkStack.isConnected(&(pClient->networkStack));
00088     }
00089 
00090     if(NETWORK_PHYSICAL_LAYER_CONNECTED == rc) {
00091         rc = aws_iot_mqtt_attempt_reconnect(pClient);
00092         if(NETWORK_RECONNECTED == rc) {
00093             rc = aws_iot_mqtt_set_client_state(pClient, CLIENT_STATE_CONNECTED_IDLE,
00094                                                CLIENT_STATE_CONNECTED_YIELD_IN_PROGRESS);
00095             if(IOT_SUCCESS != rc) {
00096                 FUNC_EXIT_RC(rc);
00097             }
00098             FUNC_EXIT_RC(NETWORK_RECONNECTED);
00099         }
00100     }
00101 
00102     pClient->clientData.currentReconnectWaitInterval *= 2;
00103 
00104     if(AWS_IOT_MQTT_MAX_RECONNECT_WAIT_INTERVAL < pClient->clientData.currentReconnectWaitInterval) {
00105         FUNC_EXIT_RC(NETWORK_RECONNECT_TIMED_OUT_ERROR);
00106     }
00107     countdown_ms(&(pClient->reconnectDelayTimer), pClient->clientData.currentReconnectWaitInterval);
00108     FUNC_EXIT_RC(rc);
00109 }
00110 
00111 static IoT_Error_t _aws_iot_mqtt_keep_alive(AWS_IoT_Client *pClient) {
00112     IoT_Error_t rc = IOT_SUCCESS;
00113     TimerAWS timer;
00114     size_t serialized_len;
00115 
00116     FUNC_ENTRY;
00117 
00118     if(NULL == pClient) {
00119         FUNC_EXIT_RC(NULL_VALUE_ERROR);
00120     }
00121 
00122     if(0 == pClient->clientData.keepAliveInterval) {
00123         FUNC_EXIT_RC(IOT_SUCCESS);
00124     }
00125 
00126     if(!has_timer_expired(&pClient->pingTimer)) {
00127         FUNC_EXIT_RC(IOT_SUCCESS);
00128     }
00129 
00130     if(pClient->clientStatus.isPingOutstanding) {
00131         rc = _aws_iot_mqtt_handle_disconnect(pClient);
00132         FUNC_EXIT_RC(rc);
00133     }
00134 
00135     /* there is no ping outstanding - send one */
00136     init_timer(&timer);
00137 
00138     countdown_ms(&timer, pClient->clientData.commandTimeoutMs);
00139     serialized_len = 0;
00140     rc = aws_iot_mqtt_internal_serialize_zero(pClient->clientData.writeBuf, pClient->clientData.writeBufSize,
00141                                               PINGREQ, &serialized_len);
00142     if(IOT_SUCCESS != rc) {
00143         FUNC_EXIT_RC(rc);
00144     }
00145 
00146     /* send the ping packet */
00147     rc = aws_iot_mqtt_internal_send_packet(pClient, serialized_len, &timer);
00148     if(IOT_SUCCESS != rc) {
00149         //If sending a PING fails we can no longer determine if we are connected.  In this case we decide we are disconnected and begin reconnection attempts
00150         rc = _aws_iot_mqtt_handle_disconnect(pClient);
00151         FUNC_EXIT_RC(rc);
00152     }
00153 
00154     pClient->clientStatus.isPingOutstanding = true;
00155     /* start a timer to wait for PINGRESP from server */
00156     countdown_sec(&pClient->pingTimer, pClient->clientData.keepAliveInterval);
00157 
00158     FUNC_EXIT_RC(IOT_SUCCESS);
00159 }
00160 
00161 /**
00162  * @brief Yield to the MQTT client
00163  *
00164  * Called to yield the current thread to the underlying MQTT client.  This time is used by
00165  * the MQTT client to manage PING requests to monitor the health of the TCP connection as
00166  * well as periodically check the socket receive buffer for subscribe messages.  Yield()
00167  * must be called at a rate faster than the keepalive interval.  It must also be called
00168  * at a rate faster than the incoming message rate as this is the only way the client receives
00169  * processing time to manage incoming messages.
00170  * This is the internal function which is called by the yield API to perform the operation.
00171  * Not meant to be called directly as it doesn't do validations or client state changes
00172  *
00173  * @param pClient Reference to the IoT Client
00174  * @param timeout_ms Maximum number of milliseconds to pass thread execution to the client.
00175  *
00176  * @return An IoT Error Type defining successful/failed client processing.
00177  *         If this call results in an error it is likely the MQTT connection has dropped.
00178  *         iot_is_mqtt_connected can be called to confirm.
00179  */
00180 static IoT_Error_t _aws_iot_mqtt_internal_yield(AWS_IoT_Client *pClient, uint32_t timeout_ms) {
00181     IoT_Error_t yieldRc = IOT_SUCCESS;
00182 
00183     uint8_t packet_type;
00184     ClientState clientState;
00185     TimerAWS timer;
00186     init_timer(&timer);
00187     countdown_ms(&timer, timeout_ms);
00188 
00189     FUNC_ENTRY;
00190 
00191     // evaluate timeout at the end of the loop to make sure the actual yield runs at least once
00192     do {
00193         clientState = aws_iot_mqtt_get_client_state(pClient);
00194         if(CLIENT_STATE_PENDING_RECONNECT == clientState) {
00195             if(AWS_IOT_MQTT_MAX_RECONNECT_WAIT_INTERVAL < pClient->clientData.currentReconnectWaitInterval) {
00196                 yieldRc = NETWORK_RECONNECT_TIMED_OUT_ERROR;
00197                 break;
00198             }
00199             yieldRc = _aws_iot_mqtt_handle_reconnect(pClient);
00200             /* Network reconnect attempted, check if yield timer expired before
00201              * doing anything else */
00202             continue;
00203         }
00204 
00205         yieldRc = aws_iot_mqtt_internal_cycle_read(pClient, &timer, &packet_type);
00206         if(IOT_SUCCESS == yieldRc) {
00207             yieldRc = _aws_iot_mqtt_keep_alive(pClient);
00208         } else {
00209             // SSL read and write errors are terminal, connection must be closed and retried
00210             if(NETWORK_SSL_READ_ERROR == yieldRc || NETWORK_SSL_READ_TIMEOUT_ERROR == yieldRc
00211                 || NETWORK_SSL_WRITE_ERROR == yieldRc || NETWORK_SSL_WRITE_TIMEOUT_ERROR == yieldRc) {
00212                 yieldRc = _aws_iot_mqtt_handle_disconnect(pClient);
00213             }
00214         }
00215 
00216         if(NETWORK_DISCONNECTED_ERROR == yieldRc) {
00217             pClient->clientData.counterNetworkDisconnected++;
00218             if(1 == pClient->clientStatus.isAutoReconnectEnabled) {
00219                 yieldRc = aws_iot_mqtt_set_client_state(pClient, CLIENT_STATE_DISCONNECTED_ERROR,
00220                                                         CLIENT_STATE_PENDING_RECONNECT);
00221                 if(IOT_SUCCESS != yieldRc) {
00222                     FUNC_EXIT_RC(yieldRc);
00223                 }
00224 
00225                 pClient->clientData.currentReconnectWaitInterval = AWS_IOT_MQTT_MIN_RECONNECT_WAIT_INTERVAL;
00226                 countdown_ms(&(pClient->reconnectDelayTimer), pClient->clientData.currentReconnectWaitInterval);
00227                 /* Depending on timer values, it is possible that yield timer has expired
00228                  * Set to rc to attempting reconnect to inform client that autoreconnect
00229                  * attempt has started */
00230                 yieldRc = NETWORK_ATTEMPTING_RECONNECT;
00231             } else {
00232                 break;
00233             }
00234         } else if(IOT_SUCCESS != yieldRc) {
00235             break;
00236         }
00237     } while(!has_timer_expired(&timer));
00238 
00239     FUNC_EXIT_RC(yieldRc);
00240 }
00241 
00242 /**
00243  * @brief Yield to the MQTT client
00244  *
00245  * Called to yield the current thread to the underlying MQTT client.  This time is used by
00246  * the MQTT client to manage PING requests to monitor the health of the TCP connection as
00247  * well as periodically check the socket receive buffer for subscribe messages.  Yield()
00248  * must be called at a rate faster than the keepalive interval.  It must also be called
00249  * at a rate faster than the incoming message rate as this is the only way the client receives
00250  * processing time to manage incoming messages.
00251  * This is the outer function which does the validations and calls the internal yield above
00252  * to perform the actual operation. It is also responsible for client state changes
00253  *
00254  * @param pClient Reference to the IoT Client
00255  * @param timeout_ms Maximum number of milliseconds to pass thread execution to the client.
00256  *
00257  * @return An IoT Error Type defining successful/failed client processing.
00258  *         If this call results in an error it is likely the MQTT connection has dropped.
00259  *         iot_is_mqtt_connected can be called to confirm.
00260  */
00261 IoT_Error_t aws_iot_mqtt_yield(AWS_IoT_Client *pClient, uint32_t timeout_ms) {
00262     IoT_Error_t rc, yieldRc;
00263     ClientState clientState;
00264 
00265     if(NULL == pClient || 0 == timeout_ms) {
00266         FUNC_EXIT_RC(NULL_VALUE_ERROR);
00267     }
00268 
00269     clientState = aws_iot_mqtt_get_client_state(pClient);
00270     /* Check if network was manually disconnected */
00271     if(CLIENT_STATE_DISCONNECTED_MANUALLY == clientState) {
00272         FUNC_EXIT_RC(NETWORK_MANUALLY_DISCONNECTED);
00273     }
00274 
00275     /* If we are in the pending reconnect state, skip other checks.
00276      * Pending reconnect state is only set when auto-reconnect is enabled */
00277     if(CLIENT_STATE_PENDING_RECONNECT != clientState) {
00278         /* Check if network is disconnected and auto-reconnect is not enabled */
00279         if(!aws_iot_mqtt_is_client_connected(pClient)) {
00280             FUNC_EXIT_RC(NETWORK_DISCONNECTED_ERROR);
00281         }
00282 
00283         /* Check if client is idle, if not another operation is in progress and we should return */
00284         if(CLIENT_STATE_CONNECTED_IDLE != clientState) {
00285             FUNC_EXIT_RC(MQTT_CLIENT_NOT_IDLE_ERROR);
00286         }
00287 
00288         rc = aws_iot_mqtt_set_client_state(pClient, CLIENT_STATE_CONNECTED_IDLE,
00289                                            CLIENT_STATE_CONNECTED_YIELD_IN_PROGRESS);
00290         if(IOT_SUCCESS != rc) {
00291             FUNC_EXIT_RC(rc);
00292         }
00293     }
00294 
00295     yieldRc = _aws_iot_mqtt_internal_yield(pClient, timeout_ms);
00296 
00297     if(NETWORK_DISCONNECTED_ERROR != yieldRc && NETWORK_ATTEMPTING_RECONNECT != yieldRc) {
00298         rc = aws_iot_mqtt_set_client_state(pClient, CLIENT_STATE_CONNECTED_YIELD_IN_PROGRESS,
00299                                            CLIENT_STATE_CONNECTED_IDLE);
00300         if(IOT_SUCCESS == yieldRc && IOT_SUCCESS != rc) {
00301             yieldRc = rc;
00302         }
00303     }
00304 
00305     FUNC_EXIT_RC(yieldRc);
00306 }
00307 
00308 #ifdef __cplusplus
00309 }
00310 #endif
00311