def get_cached_result(params: inputs.Inputs, context: LambdaContext,
cache: Cache):
''' Backing job is already running. So just query cached data from and return result '''
def wait_for_backing_job_to_exit_batch_phase(
keepalive_state: KeepaliveState, cache: Cache,
cache_keys: CacheKeys, wait_until_ms: int):
print("wait_for_backing_job_to_exit_batch_phase: started",
cache_keys.keepalive)
while not keepalive_state or not keepalive_state.in_streaming_phase:
# wait for backing job to be running and advance to streaming state
if utils.millitime() > wait_until_ms:
raise Exception(
"wait_for_backing_job_to_exit_batch_phase: timed out")
print(
"get_cached_result: waiting for batch phase to end. keepalive_state=",
keepalive_state)
time.sleep(1)
try:
keepalive_state: KeepaliveState = pickle.loads(
cache.get(cache_keys.keepalive))
except Exception as e:
print(
"wait_for_backing_job_to_exit_batch_phase: failed to read keepalive from cache",
cache_keys.keepalive, e)
print("wait_for_backing_job_to_exit_batch_phase: backing job is ready",
keepalive_state)
return keepalive_state
print("get_cached_result: started")
# Update 'lastaccess' timestamp in memcache to indicate the corresponding backing job's data was recently queried
cache_keys: CacheKeys = CacheKeys(params.cache_key_prefix())
now_ms = params.invoke_time_ms
try:
cache.set(cache_keys.lastaccess, now_ms)
except Exception as e:
print(
"get_cached_result: failed to set lastaccess cache key {}={}, {}".
format(cache_keys.lastaccess, now_ms, e))
# start the backing job if one is not running, or if the backing job's keepalive timestamp is stale
keepalive_state: KeepaliveState = start_backing_job_if_necessary(
params, context, cache)
# now that backing job is surely running, wait for it to become 'ready' - i.e. go from batch to streaming phase
keepalive_state = wait_for_backing_job_to_exit_batch_phase(
keepalive_state, cache, cache_keys, now_ms + defaults.API_TIMEOUT_MS)
# compute which cache keys need to be fetched
if not params.is_streaming():
tstart = params.absolute_ms(params.start_time_ms)
tend = params.absolute_ms(params.end_time_ms)
else:
tend = now_ms
tstart = tend - params.duration_ms()
timestamps = sorted([
ts for ts in keepalive_state.data_timestamps
if ts >= tstart and ts <= tend
])
data_keys = [cache_keys.data_prefix + str(ts) for ts in timestamps]
# retrieve metadata and data from cache. retry if necessary
metadata = cache.get(cache_keys.metadata)
if len(timestamps):
print(
"get_cached_result: fetching {} timestamps {} - {} @ {}ms".format(
len(timestamps), time.ctime(timestamps[0] / 1000),
time.ctime(timestamps[-1] / 1000),
keepalive_state.resolution_ms))
data = cache.multiget(data_keys)
missing_keys = set(data_keys) - set(data.keys())
if (len(missing_keys)):
print("get_cached_result: retrying fetch of {}/{} keys: {}".format(
len(missing_keys), len(data_keys), sorted(missing_keys)))
data.update(cache.multiget(list(missing_keys)))
# Fill in results in results struct
result = {
"start_time_ms": tstart,
"end_time_ms": tend,
"earliest_result_ms": 0,
"latest_result_ms": 0,
"resolution_ms": keepalive_state.resolution_ms,
"metadata": metadata,
"data": {},
"missing_timestamps_ms": []
}
# First fill in retrieved data
tsids = set()
missing_timestamps = []
for timestamp in timestamps:
k = cache_keys.data_prefix + str(timestamp)
if k in data.keys():
for tsid, value in data[k].items():
if not result["earliest_result_ms"]:
result["earliest_result_ms"] = timestamp
if timestamp > result["latest_result_ms"]:
result["latest_result_ms"] = timestamp
tsids.add(tsid)
result["data"].setdefault(tsid, [])
result["data"][tsid].append([timestamp, value])
else:
missing_timestamps.append(timestamp)
# Second, fill in metadata of only the relevant mts that have data
remove_metadata_ids = set(metadata.keys()).difference(tsids)
for tsid in remove_metadata_ids:
metadata.pop(tsid)
result["missing_timestamps_ms"] = missing_timestamps
return result
