Change from Network Latency to Step Processing Latency. Closes #239

[edavalosanaya]

fix(latency of step): Changed the logic of the profiler to instead focus on the out-going data chunk's and their latency.

[edavalosanaya]

Here is an overview of the changes:

Instead of computing latency and payload in the pre-step of a Node, we compute these metrics after the completion of step function. Instead of computing latency in terms of transmitted - received, the Node performs a tic-toc approach by wrapping the step function.

async def post_step(self, data_chunk: DataChunk):
        # assert self.process
        if not self.process:
            return None

        # Computing the diagnostics metrics per step
        payload_size = 0.0

        # Containers to compute metrics
        payload_sizes: List[float] = []

        # Obtain the meta data of the data chunk
        meta = data_chunk.get("meta")["value"]

        # Get the payload size (of all keys)
        total_size = 0.0
        for key in data_chunk.contains():
            payload = data_chunk.get(key)["value"]
            total_size += self.get_object_kilobytes(payload)
        payload_sizes.append(total_size)

        # After processing all data_chunk keys, get payload total
        payload_size = sum(payload_sizes)

        # Store results
        self.deques["latency(ms)"].append(meta['delta'])
        self.deques["payload_size(KB)"].append(payload_size)

The deltais the step processing time, stored in the added field in the data chunk:

class DataChunk:
    def __init__(self):
        # Removed code to show the change

        # Adding default key-value pair
        self._container["meta"] = {
            "value": {
                "ownership": [],
                "created": datetime.datetime.now(),
                "delta": 0, # ms <---- THIS IS THE NEW FIELD
                "transmitted": None,
                "received": None,
            },
            "content-type": "meta",
        }

With these changes, the profiling makes more sense, as now all the metrics (resources, payload, latency) are 100% about the current Node running the ProfilingService.