How do I invoke and wait for 1,000 AWS Lambdas running in parallel from Python?

Question

When I use third party aiobotocore it works up to NUM_WORKERS=500 and If I want to go up to a 1000 I get this error:

    r, w, _ = self._select(self._readers, self._writers, [], timeout)
  File ".....\lib\selectors.py", line 314, in _select
    r, w, x = select.select(r, w, w, timeout)
ValueError: too many file descriptors in select()

If there a way to execute 1000 in parallel?

Source:

import os, sys, time, json
import asyncio
from itertools import chain
from typing import List
import logging
from functools import partial
from pprint import pprint 



# Third Party
import asyncpool
import aiobotocore.session
import aiobotocore.config

_NUM_WORKERS=500

async def execute_lambda( lambda_name: str, key: str, client):
    # Get json content from s3 object
    if 1:
        name=lambda_name
        response = await client.invoke(
            InvocationType='RequestResponse',
            FunctionName=name,
            LogType='Tail',
            Payload=json.dumps({
                'exec_id':key,
                })
            )
    out=[]
    async for event in response['Payload']:
        out.append(event.decode())

    #await asyncio.sleep(1)
    return out


async def submit(lambda_name: str) -> List[dict]:
    """
    Returns list of AWS Lambda outputs executed in parallel

    :param name: name of lambda function
    :return: list of lambda returns
    """
    logging.basicConfig(level=logging.INFO)
    logger = logging.getLogger()

    session = aiobotocore.session.AioSession()
    config = aiobotocore.config.AioConfig(max_pool_connections=_NUM_WORKERS)
    contents = []
    #client = boto3.client('lambda', region_name='us-west-2')
    async with session.create_client('lambda', region_name='us-west-2', config=config) as client:
        worker_co = partial(execute_lambda, lambda_name)
        async with asyncpool.AsyncPool(None, _NUM_WORKERS, 'lambda_work_queue', logger, worker_co,
                                       return_futures=True, raise_on_join=True, log_every_n=10) as work_pool:
            for x in range(_NUM_WORKERS):
                contents.append(await work_pool.push(x, client))

    # retrieve results from futures
    contents = [c.result() for c in contents]
    return list(chain.from_iterable(contents))



def main(name, files):
    s = time.perf_counter()
    _loop = asyncio.get_event_loop()
    _result = _loop.run_until_complete(submit(name))
    pprint(_result)
    elapsed = time.perf_counter() - s
    print(f"{__file__} executed in {elapsed:0.2f} seconds.")

Lambda function:

import time
def lambda_handler(event, context):
    time.sleep(10)
    return {'code':0, 'exec_id':event['exec_id']}

Result:

 '{"code": 0, "exec_id": 0}',
 '{"code": 0, "exec_id": 1}',
 '{"code": 0, "exec_id": 2}',
 '{"code": 0, "exec_id": 3}',
...
 '{"code": 0, "exec_id": 496}',
 '{"code": 0, "exec_id": 497}',
 '{"code": 0, "exec_id": 498}',
 '{"code": 0, "exec_id": 499}']
my_cli_script.py executed in 14.56 seconds.

Answer 1

In response to the question asked in the comments here, here's the code I use to spin up 100 lambda instances in parallel:

import boto3
import json
from concurrent.futures import ThreadPoolExecutor

# AWS credentials are exported in my env variables
# so region and account-id are fetched from there
lambda_ = boto3.client('lambda')

def invoke_lambda(payload):
    payload = {'body': json.dumps(payload)}

    response = lambda_.invoke(
        FunctionName='my-func',
        # I need to receive a response back from lambda
        # so I use sync invocation
        InvocationType='RequestResponse',
        LogType='Tail',
        Payload=json.dumps(payload)
    )

    res_payload = response.get('Payload').read()
    body = json.loads(res_payload).get('body')
    
    return body


MAX_WORKERS = 100  # how many lambdas you want to spin up concurrently

with ThreadPoolExecutor(max_workers=MAX_WORKERS) as executor:
    result = list(executor.map(invoke_lambda, data))
# data is a list of dicts, each element is a single "payload"

Two last notes:

1. a dozen milliseconds to spawn 100 concurrent lambdas was probably an exaggeration. For some reason if I set a higher granularity in cloudwatch metrics it plots nothing so I can't say for sure how long it took exactly. To thread safely I would say within 2 seconds.
2. this piece of code has only been run in my local environment so far. It's pretty vanilla so I don't see why it wouldn't work elsewhere (for example, another parent lambda), but as a word of warning, I haven't tested it online yet.

Answer 2

found this post: python-asyncio-aiohttp-valueerror-too-many-file-descriptors-in-select-on-win

After change it started to work

# 1000 is a soft concurrency limit
_NUM_WORKERS=990  

def main(name, files):
    if sys.platform == 'win32':
        _loop = asyncio.ProactorEventLoop()
        asyncio.set_event_loop(_loop)
        _result = _loop.run_until_complete(submit(name))
    else:
        _loop = asyncio.get_event_loop()
        _result = _loop.run_until_complete(submit(name))
    process = psutil.Process(os.getpid())
    print(f"{__file__}: memory[{process.memory_info().rss/1024:7,.2f}], elapsed {elapsed:0.2f} sec")

Result:

...
 '{"code": 0, "exec_id": 986}',
 '{"code": 0, "exec_id": 987}',
 '{"code": 0, "exec_id": 988}',
 '{"code": 0, "exec_id": 989}']
my_cli_script.py: memory[201,064.00], elapsed 16.53 sec