nRF Cloud Log backend (REST API) not pushing logs to cloud

Question

I'm trying to configure the nRF cloud log backend to aid with debugging of devices during field tests without the need for bulky UART harnesses to capture logs from the serial output of the board. Relevant prj.conf excerpts below: ``` CONFIG_LOG=y CONFIG_LOG_PROCESS_THREAD=y CONFIG_LOG_PROCESS_THREAD_STACK_SIZE=4096 CONFIG_LOG_BUFFER_SIZE=1024 CONFIG_LOG_PROCESS_THREAD_SLEEP_MS=10000 CONFIG_LOG_PROCESS_TRIGGER_THRESHOLD=5 CONFIG_LOG_DEFAULT_LEVEL=3 CONFIG_NRF_CLOUD=y CONFIG_NRF_CLOUD_REST=y CONFIG_NRF_CLOUD_REST_AUTOGEN_JWT=y CONFIG_LOG_BACKEND_NRF_CLOUD_OUTPUT_TEXT=y CONFIG_NRF_CLOUD_LOG_DIRECT=y CONFIG_NRF_CLOUD_LOG_BACKEND=y CONFIG_NRF_CLOUD_LOG_OUTPUT_LEVEL=3 CONFIG_NRF_CLOUD_LOG_LOG_LEVEL_DBG=y CONFIG_NRF_CLOUD_LOG_BUF_SIZE=1024 CONFIG_LOG_MODE_DEFERRED=y ``` At the very start of main.c, a buffer for REST responses is allocated, and a rest context passed to the cloud log backend: ``` 
 int main(void) { boot_write_img_confirmed(); uint8_t *rx_buf = calloc(2048, sizeof(uint8_t)); struct nrf_cloud_rest_context ctx = { .connect_socket = -1, .keep_alive = true, .timeout_ms = 10000, .auth = NULL, .rx_buf = rx_buf, .rx_buf_len = 2048, }; nrf_cloud_log_rest_context_set(&ctx, "LOG_TEST"); ``` This configuration appears to have some effect, as the format of log lines on the UART output are changed after enabling the cloud log backend, however no data is actually pushed to the cloud for this device. Besides log line format changes, the only indication that the cloud logger is present is occasional debug output between application logs: `[00:00:24.045,135] <dbg> nrf_cloud_log_backend: logger_notify: Buffered lines:0, bytes:0; logged lines:0, bytes:0; sent lines:0, bytes:0; dropped lines:0` This is the only message received from the nrf_cloud_log_backend module, and it never indicates any buffered or sent data. I know this device can use the nRF Cloud API, as we're using the LTE location API without issue. Please let me know how I should adjust our firmware to allow logs to be properly pushed to the cloud Kaitlyn

Syed Maysum Abbas Zaidi · Accepted Answer

Hi, 
 Thanks for your logs. The secure fault in strlen() from the logging thread suggests that an invalid string pointer is being accessed. In the snippet you shared, both device_id and the REST context ctx are defined as local (stack) variables. Since the cloud log backend runs asynchronously in its own thread, it may continue to use these pointers after the initialization code has completed, at which point the memory is no longer valid. 
 Could you please try making the REST context and the device_id buffer persistent (for example static or global) and then retest? For example: 
 static uint8_t rx_buf[2048];
static struct nrf_cloud_rest_context ctx = {
 .connect_socket = -1,
 .keep_alive = true,
 .timeout_ms = 10000,
 .auth = NULL,
 .rx_buf = rx_buf,
 .rx_buf_len = sizeof(rx_buf),
};

static char device_id[128];

void cloud_log_setup(void)
{
 char imei[32] = {0};

 modem_info_string_get(MODEM_INFO_IMEI, imei, sizeof(imei));
 snprintk(device_id, sizeof(device_id), "nrf-%s", imei);

 nrf_cloud_log_rest_context_set(&ctx, device_id);
 nrf_cloud_log_init();
 nrf_cloud_log_enable(true);
 nrf_cloud_log_level_set(3);
} 
 If the issue persists after this change, please let us know the NCS version you’re using and share the back trace so we can investigate further. 
 Best regards, Syed Maysum