(Why is) getLocalTime() taking several seconds to complete successfully

[marcelstoer]

I noticed that getLocalTime() is consistently taking 5-10+ seconds to complete. So far I haven't been able to find the root cause.

I am testing on a ESP32-WROVER-B module. On startup the device first connects to WiFi and then tries to sync time.

boolean initTime() {
  struct tm timeinfo;

  log_i("Synchronizing time.");
  // Connect to NTP server with 0 TZ offset, call setTimezone() later
  configTime(0, 0, "pool.ntp.org");
  // getLocalTime uses a default timeout of 5s -> the loop takes at most 3*5s to complete
  for (int i = 0; i < 3; i++) {
    if (getLocalTime(&timeinfo)) {
      log_i("UTC time: %s.", getCurrentTimestamp(SYSTEM_TIMESTAMP_FORMAT).c_str());
      return true;
    }
  }

  log_e("Failed to obtain time.");
  return false;
}

  ...
  10:12:28.118 > [  3634][I][connectivity.h:17] startWiFi(): ...done. IP: 192.168.0.57, WiFi RSSI: -55.
- 10:12:28.118 > [  3700][I][util.h:25] initTime(): Synchronizing time.
| 
->10:12:34.025 > [ 11572][I][util.h:37] initTime(): UTC time: 2023-09-19 08:12:34.
  10:12:34.037 > [ 11572][I][util.h:60] setTimezone(): Setting timezone to 'CET-1CEST,M3.5.0,M10.5.0/3'.
  10:12:34.042 > [ 11574][I][main.cpp:175] syncTime(): Current local time: 2023-09-19 10:12:34
  ...

In the above example it took ~6s for a "valid" timestamp to become available.

[marcelstoer]

Most likely caused by rate-limiting or throttling on either the NTP server or one of the intermediary players (e.g. my ISP).

-> https://arduino.stackexchange.com/a/94447/48623

[mrengineer7777]

In my project I wait 30 seconds (I use Ticker.once() to schedule the event) for WiFi to connect and be settled before getting NTP time. I haven't noticed any delays. Once SNTP is started, it automatically re-queries NTP servers for time at a reasonable rate. I think it's once an hour, but could be every 6 hours.

This is how I start SNTP:

void TimeUtils::SNTP_Start(void) {
    if(sntp_enabled()) {
        log_v("SNTP already started");
        return;
    }
    //sntp_set_time_sync_notification_cb(sntp_time_sync_notification_cb);
    configTime(0, 0, "time.cloudflare.com", "pool.ntp.org", "time.nist.gov");       //Use UTC time, no DST offset. May change later.  Using timeservers from different providers should guarantee a response.
}