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/***************************************************************************
* Copyright (c) 2024 Microsoft Corporation
* Copyright (c) 2025-present Eclipse ThreadX Contributors
*
* This program and the accompanying materials are made available under the
* terms of the MIT License which is available at
* https://opensource.org/licenses/MIT.
*
* SPDX-License-Identifier: MIT
**************************************************************************/
#include <stdio.h>
#include "nx_azure_iot_hub_client.h"
#ifndef SAMPLE_MAX_EXPONENTIAL_BACKOFF_IN_SEC
#define SAMPLE_MAX_EXPONENTIAL_BACKOFF_IN_SEC (10 * 60)
#endif /* SAMPLE_MAX_EXPONENTIAL_BACKOFF_IN_SEC */
#ifndef SAMPLE_INITIAL_EXPONENTIAL_BACKOFF_IN_SEC
#define SAMPLE_INITIAL_EXPONENTIAL_BACKOFF_IN_SEC (3)
#endif /* SAMPLE_INITIAL_EXPONENTIAL_BACKOFF_IN_SEC */
#ifndef SAMPLE_MAX_EXPONENTIAL_BACKOFF_JITTER_PERCENT
#define SAMPLE_MAX_EXPONENTIAL_BACKOFF_JITTER_PERCENT (60)
#endif /* SAMPLE_MAX_EXPONENTIAL_BACKOFF_JITTER_PERCENT */
VOID sample_connection_monitor(NX_IP *ip_ptr, NX_AZURE_IOT_HUB_CLIENT *iothub_client_ptr, UINT sample_status,
UINT (*iothub_init)(NX_AZURE_IOT_HUB_CLIENT *hub_client_ptr));
static UINT exponential_retry_count;
static UINT iothub_init_count = 0;
static UINT exponential_backoff_with_jitter()
{
double jitter_percent = (SAMPLE_MAX_EXPONENTIAL_BACKOFF_JITTER_PERCENT / 100.0) * (rand() / ((double)RAND_MAX));
UINT base_delay = SAMPLE_MAX_EXPONENTIAL_BACKOFF_IN_SEC;
uint64_t delay;
if (exponential_retry_count < (sizeof(UINT) * 8))
{
delay = (uint64_t)((1 << exponential_retry_count) * SAMPLE_INITIAL_EXPONENTIAL_BACKOFF_IN_SEC);
if (delay <= (UINT)(-1))
{
base_delay = (UINT)delay;
}
}
if (base_delay > SAMPLE_MAX_EXPONENTIAL_BACKOFF_IN_SEC)
{
base_delay = SAMPLE_MAX_EXPONENTIAL_BACKOFF_IN_SEC;
}
else
{
exponential_retry_count++;
}
return((UINT)(base_delay * (1 + jitter_percent)) * NX_IP_PERIODIC_RATE) ;
}
static VOID exponential_backoff_reset()
{
exponential_retry_count = 0;
}
/**
*
* Connection state
*
*
* +--------------+ +--------------+ +--------------+
* | | INIT | | NETWORK | |
* | | SUCCESS | | GOOD | |
* | INIT | | NETWORK | | CONNECT |
* | +-------------> CHECK +---------------------> +---------+
* | | | | | | |
* | | | | | | |
* +------^-------+ +------^-------+ +------+-------+ |
* | | | |
* | | CONNECT FAIL | |
* | | +--------------------------+ |
* | | | CONNECTED |
* | RECONNECT | | |
* | | | |
* | | +------v-------+ +--------------+ |
* | REINITIALIZE | | | | | |
* | +---+ | DISCONNECT | | |
* | | DISCONNECTED | | CONNECTED | |
* | | <--------------+ <------+
* +--------------------------------+ | | |
* | | | |
* +--------------+ +---^------+---+
* | |(TELEMETRY |
* | | C2D |
* | | COMMAND | METHOD |
* +------+ PROPERTIES | DEVICE TWIN)
*
*
*
*/
VOID sample_connection_monitor(NX_IP *ip_ptr, NX_AZURE_IOT_HUB_CLIENT *hub_client_ptr, UINT connection_status,
UINT (*iothub_init)(NX_AZURE_IOT_HUB_CLIENT *hub_client_ptr))
{
UINT loop = NX_TRUE;
ULONG gateway_address;
/* Check parameters. */
if ((ip_ptr == NX_NULL) || (hub_client_ptr == NX_NULL) || (iothub_init == NX_NULL))
{
return;
}
/* Check if connected. */
if (connection_status == NX_SUCCESS)
{
/* Reset the exponential. */
exponential_backoff_reset();
}
else
{
/* Disconnect. */
if (connection_status != NX_AZURE_IOT_NOT_INITIALIZED)
{
nx_azure_iot_hub_client_disconnect(hub_client_ptr);
}
/* Recover. */
while (loop)
{
switch (connection_status)
{
/* Something bad has happened with client state, we need to re-initialize it. */
case NX_DNS_QUERY_FAILED :
case NXD_MQTT_ERROR_BAD_USERNAME_PASSWORD :
case NXD_MQTT_ERROR_NOT_AUTHORIZED :
{
/* Deinitialize iot hub client. */
nx_azure_iot_hub_client_deinitialize(hub_client_ptr);
}
/* fallthrough */
case NX_AZURE_IOT_NOT_INITIALIZED:
{
if (iothub_init_count++)
{
printf("Re-initializing iothub connection, after backoff\r\n");
tx_thread_sleep(exponential_backoff_with_jitter());
}
/* Initialize iot hub. */
if (iothub_init(hub_client_ptr))
{
connection_status = NX_AZURE_IOT_NOT_INITIALIZED;
}
else
{
/* Wait for network. */
while (nx_ip_gateway_address_get(ip_ptr, &gateway_address))
{
tx_thread_sleep(NX_IP_PERIODIC_RATE);
}
/* Connect to iot hub. */
connection_status = nx_azure_iot_hub_client_connect(hub_client_ptr, NX_FALSE, NX_WAIT_FOREVER);
}
}
break;
case NX_AZURE_IOT_SAS_TOKEN_EXPIRED:
{
printf("SAS token expired\r\n");
}
/* fallthrough */
default :
{
printf("Reconnecting iothub, after backoff\r\n");
tx_thread_sleep(exponential_backoff_with_jitter());
/* Wait for network. */
while (nx_ip_gateway_address_get(ip_ptr, &gateway_address))
{
tx_thread_sleep(NX_IP_PERIODIC_RATE);
}
connection_status = nx_azure_iot_hub_client_connect(hub_client_ptr, NX_FALSE, NX_WAIT_FOREVER);
}
break;
}
/* Check status. */
if (connection_status == NX_SUCCESS)
{
return;
}
}
}
}
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