Remove Exponential Backoff for Retry Until Up (skypilot-org#2821)

* remove exponential backoff

* add back random jitter

* format

* use backoff

* format

* add comment

* rerun checks

* format

* pylint

* form

* change to 30

sky/backends/cloud_vm_ray_backend.py

@@ -87,7 +87,7 @@
 
 # Time gap between retries after failing to provision in all possible places.
 # Used only if --retry-until-up is set.
-_RETRY_UNTIL_UP_INIT_GAP_SECONDS = 60
+_RETRY_UNTIL_UP_INIT_GAP_SECONDS = 30
 
 # The maximum retry count for fetching IP address.
 _FETCH_IP_MAX_ATTEMPTS = 3
@@ -2873,7 +2873,13 @@ def _provision(
                 # TODO(suquark): once we have sky on PyPI, we should directly
                 # install sky from PyPI.
                 local_wheel_path, wheel_hash = wheel_utils.build_sky_wheel()
-            backoff = common_utils.Backoff(_RETRY_UNTIL_UP_INIT_GAP_SECONDS)
+                # The most frequent reason for the failure of a provision
+                # request is resource unavailability instead of rate
+                # limiting; to make users wait shorter, we do not make
+                # backoffs exponential.
+                backoff = common_utils.Backoff(
+                    initial_backoff=_RETRY_UNTIL_UP_INIT_GAP_SECONDS,
+                    max_backoff_factor=1)
             attempt_cnt = 1
             while True:
                 # For on-demand instances, RetryingVmProvisioner will retry
@@ -2927,7 +2933,7 @@ def _provision(
                             f'{colorama.Style.BRIGHT}=== Retry until up ==='
                             f'{colorama.Style.RESET_ALL}\n'
                             f'Retrying provisioning after {gap_seconds:.0f}s '
-                            '(exponential backoff with random jittering). '
+                            '(backoff with random jittering). '
                             f'Already tried {attempt_cnt} attempt{plural}.')
                         attempt_cnt += 1
                         time.sleep(gap_seconds)