@Marvin How do I specify the serializer that is used for task caching?

It appears there's no single, explicit method to specify a serializer for task caching in Prefect. Here's the overall view from both the documentation and GitHub issues: ### Documentation Insights 1. Cache Keys and Expiration: - Caching in Prefect allows task runs to use cached states based on "cache keys." - You can enable caching by specifying a

cache_key_fn

and optionally a

cache_expiration

. 2. Task Input Hashing: - You can cache a task based on its inputs using

task_input_hash

, which hashes all the inputs to create a cache key. ### GitHub Insights 1. Current Behavior and Use Case: - Prefect uses a

WritableFileSystem

object where serialized data is written as a single file. - It uses the

PersistedResultBlob

structure, which contains details about the

serializer

,

data

, and Prefect version. 2. Proposed Enhancements: - There are requests to handle cache metadata and task results separately, providing more granularity and control over the caching mechanism. To use and manage task caching with custom serialization, you'll need to customize your

WritableFileSystem

implementation. Here’s a rudimentary example based on Prefect’s current capabilities:

python
from prefect import task, flow
from prefect.orion.schemas.states import Cached
from prefect.tasks.collections import SendEmail
import hashlib

def cache_key_fn(params):
    # Custom logic for creating a cache key
    key = str(params)
    return hashlib.sha256(key.encode()).hexdigest()

@task(cache_key_fn=cache_key_fn, cache_expiration=timedelta(days=1))
def my_task(data):
    return data

@flow
def my_flow(data):
    result = my_task(data)
    print(result)

# Run the flow
my_flow({"sample": "data"})

### Sources - Prefect Task Caching Documentation - GitHub Issues on Task Caching If you have specific needs for the serializer, you’ll need to dive into the internal structures Prefect uses and possibly extend them for your requirements. While this can be cumbersome, it grants flexibility to suit diverse use cases. I hope this helps, but don't get your hopes too high - it's just another feature that may or may not work flawlessly.