[core] fix worker launch time formatting (ray-project#43516)

Signed-off-by: hongchaodeng <[email protected]>

python/ray/util/state/common.py

@@ -90,7 +90,7 @@ class Humanify:
  convert units into a human readable string."""
 
  def timestamp(x: float):
- """Converts miliseconds to a datetime object."""
+ """Converts milliseconds to a datetime object."""
  return str(datetime.datetime.fromtimestamp(x / 1000))
 
  def memory(x: int):
@@ -104,7 +104,7 @@ def memory(x: int):
  return str(format(x, ".3f")) + " B"
 
  def duration(x: int):
- """Converts miliseconds to a human readable duration."""
+ """Converts milliseconds to a human readable duration."""
  return str(datetime.timedelta(milliseconds=x))
 
  def events(events: List[dict]):
@@ -630,12 +630,16 @@ class WorkerState(StateSchema):
  #: -> start_time_ms (worker is ready to be used).
  #: -> end_time_ms (worker is destroyed).
  worker_launch_time_ms: Optional[int] = state_column(
- filterable=False, detail=True, format_fn=Humanify.timestamp
+ filterable=False,
+ detail=True,
+ format_fn=lambda x: "" if x == -1 else Humanify.timestamp(x),
  )
  #: The time worker is succesfully launched
  #: -1 if the value doesn't exist.
  worker_launched_time_ms: Optional[int] = state_column(
- filterable=False, detail=True, format_fn=Humanify.timestamp
+ filterable=False,
+ detail=True,
+ format_fn=lambda x: "" if x == -1 else Humanify.timestamp(x),
  )
  #: The time when the worker is started and initialized.
  #: 0 if the value doesn't exist.