Conflict/race between makeWebRequest and Storage.setValue called from onUpdate on a watchface.

So, I did the test you suggest (test for having storage and register on onExitSleep).

Same issue. (tested with sdk 4.0.7)

output: 

we have storage
onUpdate 8
we have storage
onUpdate 9
onExitSleep
we have storage
onUpdate 10
we have storage
[...]
we have storage
onUpdate 15
Background: Before query
we have storage
onUpdate 16
we have storage
onUpdate 17
we have storage
onUpdate 18
we have storage
onUpdate 19

Error: Symbol Not Found Error
Details: Failed invoking <symbol>
Stack: 
we have storage
onUpdate 20
we have storage

source: 

using Toybox.Application;
using Toybox.Background;
using Toybox.System;
using Toybox.WatchUi;
using Toybox.Time;
using Toybox.Communications;
using Toybox.Application.Storage;

(:background)
class PiServiceDelegate extends Toybox.System.ServiceDelegate {
  function initialize() {
    System.ServiceDelegate.initialize();
  }
  function onTemporalEvent() {
    // That URI takes about 3 seconds to answer
    var uri = "">https://wb.elaine.fi/pi_slow";
    System.println("Before query");
    var options = {
      :methods => Communications.HTTP_REQUEST_METHOD_GET,
      :responseType => Communications.HTTP_RESPONSE_CONTENT_TYPE_JSON
    };
    Communications.makeWebRequest(uri, null, options,
                                  method(:pi_received));
  }
  function pi_received(code, data) {
    System.println(code);
    System.println(data);
  }
}

(:background)
class PiWatch extends Application.AppBase {
  public function initialize() {
    AppBase.initialize();
  }
  function getServiceDelegate() {
    return [new PiServiceDelegate()];
  }
  function getInitialView() {
    return [new PiWatchView(), new PiWatchDelegate()];
  }
}

class PiWatchView extends WatchUi.WatchFace {
  var i = 1;
  public function initialize() {
    WatchFace.initialize();
  }
  public function onUpdate(dc) {
    i += 1;
    if (Toybox.Application has :Storage) {
      System.println("we have storage");
      Storage.setValue("foo", "bar");
    }
    System.println("onUpdate " + i.format("%d"));
  }
  public function onExitSleep() {
    System.println("onExitSleep");
    Background.registerForTemporalEvent(new Time.Duration(5 * 60));
  }
}

class PiWatchDelegate extends WatchUi.WatchFaceDelegate {
  public function initialize() {
    WatchFaceDelegate.initialize();
  }
}

As I've said, setValue is expensive, and really not something you want to do all the time in onUpdate, as it will also impact your battery life,  Only call setValue when you need to - do it in onBackgroundDate instead for example.  The most it will be called then will be every 5 minutes.  Or, as I mentioned before you only really need to do it in onStop for the main app,

on sim it's to short probably to get watchdog

Have test "has  for storage" to exclude error in onUpdate?

Move

Background.registerForTemporalEvent(new Time.Duration(5 * 60));

to PiWatchVie.onShow or batter to onExitSleep()

So, now that the onPartialUpdate/budget exceeded case is cleared, I tested the following:

Long loop on onUpdate, just enough to not trigger the watchdog.

In that version, we do not call setValue, and there is no problem.

using Toybox.Application;
using Toybox.Background;
using Toybox.System;
using Toybox.WatchUi;
using Toybox.Time;
using Toybox.Communications;
using Toybox.Application.Storage;

(:background)
class PiServiceDelegate extends Toybox.System.ServiceDelegate {
  function initialize() {
    System.ServiceDelegate.initialize();
  }
  function onTemporalEvent() {
    // That URI takes about 3 seconds to answer
    var uri = "">https://wb.elaine.fi/pi_slow";
    System.println("Before query");
    var options = {
      :methods => Communications.HTTP_REQUEST_METHOD_GET,
      :responseType => Communications.HTTP_RESPONSE_CONTENT_TYPE_JSON
    };
    Communications.makeWebRequest(uri, null, options,
                                  method(:pi_received));
  }
  function pi_received(code, data) {
    System.println(code);
    System.println(data);
  }
}

(:background)
class PiWatch extends Application.AppBase {
  public function initialize() {
    AppBase.initialize();
  }
  function getServiceDelegate() {
    return [new PiServiceDelegate()];
  }
  function getInitialView() {
    Background.registerForTemporalEvent(new Time.Duration(5 * 60));
    return [new PiWatchView(), new PiWatchDelegate()];
  }
}

class PiWatchView extends WatchUi.WatchFace {
  var i = 1;
  public function initialize() {
    WatchFace.initialize();
  }
  public function onUpdate(dc) {
    i += 1;
    // 6000 is sweet spot, 7000 triggers the Watchdog
    for(var j = 0; j < 6000; j++) {
      var k = Math.sqrt(j);
    }
  }
}

class PiWatchDelegate extends WatchUi.WatchFaceDelegate {
  public function initialize() {
    WatchFaceDelegate.initialize();
  }
}

The order that these calls happen can vary, and it's something you need to account for in your code.  onAppUpdate/onAppInstall will happen before getInitialView, and even if you don't override them, getserviceDelate will be called.  And then there's the thing in your appBase (initialize(), onStart. onStop, etc,) that are called when the main app or the background service runs.