Add execution stats docs

[aitorarjona]

• Added a section to the futures API documentation where the different methods of obtaining execution metrics and statistics are explained.

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[aitorarjona]

Plase @JosepSampe could you review the description of the statis parameters and tell me if they are correct? I would need to know what exactly host_result_query_count and host_status_query_count indicate as I am not sure (left them blank).

[JosepSampe]

@aitorarjona *_query_count is the amount of attempts to download the file. For example host_status_query_count=2 and host_result_query_count=1 means that the status file was download at the second try, and the result file was downloaded at the first try

[aitorarjona]

@JosepSampe For this example:

import lithops
import time
from pprint import pprint

def my_function(x):
    time.sleep(10)  # Do some work...
    return x + 7

if __name__ == '__main__':
    fexec = lithops.FunctionExecutor()
    future = fexec.call_async(my_function, 3)
    fexec.wait(fs=future)
    result = fexec.get_result(fs=future)
    pprint(future.stats)

I get this output:

{'chunksize': 1,
 'data_size_bytes': 21,
 'func_module_size_bytes': 611,
 'func_result_size': 26.0,
 'host_data_upload_time': 0,
 'host_func_upload_time': 0.588293,
 'host_job_create_tstamp': 1647287154.5765412,
 'host_job_created_time': 0.590769,
 'host_job_serialize_time': 0.001758,
 'host_result_done_tstamp': 1647287169.3160923,
 'host_result_query_count': 1,
 'host_status_done_tstamp': 1647287168.708364,
 'host_status_query_count': 0,
 'host_submit_tstamp': 1647287155.1686838,
 'warm_container': True,
 'worker_end_tstamp': 1647287166.442059,
 'worker_exec_time': 10.52488446,
 'worker_func_end_tstamp': 1647287166.314035,
 'worker_func_exec_time': 10.01008964,
 'worker_func_start_tstamp': 1647287156.3039453,
 'worker_result_upload_time': 0.12039733,
 'worker_start_tstamp': 1647287155.9171746}

Should not host_status_query_count be at least 1? And another question: So the 404-ed GET request for the status.json to synchronize finished functions do not count for the host_status_query_count? Should it do?

[JosepSampe]

Yes, host_status_query_count should be at least 1. These stats were inherited from pywren. Now in lithops the logic for syncronizing finsihed functions is completely diferent and the status file is check in the monitor component, so here the value will be always 1 (except if you call future.result() directly). Not sure if we really need this stats right now, as we never used them

[aitorarjona]

You decide ;)

[JosepSampe]

@aitorarjona There is no need to delete them. I think this is enough