<@ULVA73B9P> we're currently using ECS push pool f...
# ask-marvin
a
@Marvin we're currently using ECS push pool for our work pool. This is fine but we find that we have some tasks that we wish to start more quickly than the ECS startup time. We're thinking of running a hybrid system where we continue with ECS push but also have a long-running service running with a pull/subprocess runner that we can fire off quick tasks to. Does this make sense? is there any tooling which allows us to easily set up this infrastructure? I assue it's as "simple" as just setting up a new workpool and making a worker poll on it?
m
thought for 162.7 seconds
Yes — that does make sense, and your mental model is basically right. Short version: - Keep your existing
ecs:push
pool for jobs where startup latency is acceptable - Add a second work pool for lower-latency jobs - Run a long-lived worker against that second pool - Point specific deployments at the pool that fits their needs So yes, it can be as simple as “create another work pool and run a worker that polls it”. A couple of important clarifications though: ### 1. If you want faster than ECS task startup, an ECS worker may not help much If the worker is polling a normal
ecs
work pool, it still launches ECS tasks for flow runs. That removes the push mechanism, but not the underlying ECS startup latency. So there are two different patterns: #### Option A:
ecs:push
+
ecs
worker - Both ultimately run flow runs on ECS - Useful if you want more control over infra / networking / credentials / execution model - Does not fundamentally eliminate ECS startup time #### Option B:
ecs:push
+
process
/
docker
/
kubernetes
worker on always-on infra - Worker runs continuously on a VM, ECS service, K8s pod, etc. - Flow runs start as subprocesses or containers on already-running infrastructure - This is the pattern that usually helps with low-latency execution Based on your goal, Option B sounds more like what you want. ### Recommended architecture For your case, I’d usually suggest: - Pool 1: existing
ecs:push
pool - for heavier / bursty / less latency-sensitive jobs - Pool 2: a
process
or
docker
work pool - backed by a long-running worker on always-on compute - for quick jobs you want to start fast Then each deployment chooses its pool via
work_pool_name
. ### Good choices for the “fast” side ####
process
pool Best if: - the worker machine already has your code + dependencies - you want the fastest startup - you’re okay running flows as subprocesses on that machine ####
docker
pool Best if: - you want container isolation - you still want fairly fast startup - you have a host running Docker continuously ####
kubernetes
pool Best if: - you already have K8s - pod startup is acceptable - you want stronger orchestration/isolation ### What setup looks like conceptually 1. Create a new work pool 2. Start a worker polling that pool 3. Create deployments that target that pool For example, your quick jobs would use one pool, and your existing ECS-backed jobs would continue using the other. Example deployment idea:
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python
from prefect import flow

@flow
def quick_task():
    print("run quickly")

@flow
def heavy_task():
    print("run on ECS push")

if __name__ == "__main__":
    quick_task.deploy(
        name="quick-task",
        work_pool_name="fast-process-pool",
    )

    heavy_task.deploy(
        name="heavy-task",
        work_pool_name="ecs-push-pool",
        image="your-image:latest",
    )
### Operational caveat If you use a
process
worker, that worker host becomes part of your runtime: - it needs your code available - it needs Python deps installed - you’ll want to think about concurrency limits and resource contention - HA usually means running more than one worker / more than one host ### Tooling Prefect supports this natively with work pools + workers; you don’t need special orchestration beyond that. Useful docs: - Work pools - Workers - Deployments - Manage work pools - Deploy via Python - Serverless / push pools - ECS worker guide ### Practical recommendation
If your only problem is startup time, I would not make the second pool another ECS-based pool unless you specifically need ECS for those jobs too. Instead, I’d test: -
process
work pool on a small always-on instance, or -
docker
work pool on an always-on Docker host That usually gives the “quick lane” you’re looking for. ### Bottom line Yes, a hybrid setup is a normal Prefect pattern. But the key distinction is: - new work pool + worker is the right mechanism - using ECS again probably won’t solve the latency issue - for true fast-start jobs, prefer a long-running
process
or
docker
worker on warm infrastructure If you want, I can sketch a concrete setup for: - ECS push + process worker, or - ECS push + docker worker, including how to structure the deployments cleanly so you don’t duplicate config.
a
@Marvin yes, I plan to use the process work pool. We'll run it as a long-running ECS task based on our ecs:push docker image, but that's an implementation detail. Does prefect come with any tooling to set up such a task on an existing ecs cluster?
m
thought for 102.8 seconds
Not directly for a process worker, no. Prefect does have ECS deployment tooling via
prefect-aws
, but that tooling is for deploying an ECS worker that polls an
ecs
work pool — i.e. a worker whose job is to launch other ECS tasks for flow runs. That is not the same as: - running a generic Prefect worker on ECS - polling a
process
work pool - executing flow runs as local subprocesses inside that long-running ECS task For your design, Prefect’s role is basically just: 1. create a
process
work pool 2. run a worker with:
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bash
prefect worker start --pool <your-process-pool>
and you choose where that worker process lives. ### So what tooling exists? #### Built-in Prefect tooling - Yes for: deploying/managing an ECS worker for an
ecs
work pool via
prefect-aws
- No for: “take this generic worker and create an ECS service for it on my existing cluster” So if you want a long-running ECS task that runs a
process
worker, you’d generally provision that ECS service/task definition yourself using your normal AWS/IaC tooling: - Terraform - CloudFormation / CDK - Copilot - console/manual ECS service setup ### What your ECS task would do Your container entrypoint/command is just the worker start command, something like:
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bash
prefect worker start --pool fast-process-pool
with environment variables such as: -
PREFECT_API_URL
-
PREFECT_API_KEY
and of course your image needs: - your flow code - your Python dependencies - Prefect installed ### Important caveat for
process
on ECS This setup works, but remember what
process
means: - flow runs execute as subprocesses inside the same ECS task/container that is running the worker - so the worker container is also the execution environment - concurrency means multiple subprocesses on that same task, subject to CPU/memory limits That’s why this can be great for low-latency jobs, but you’ll want to size that worker task appropriately and probably set a worker concurrency limit. ### When this pattern makes sense It’s a good fit if you want: - warm always-on runtime - minimal startup overhead - code/image already present - “quick lane” execution It’s less ideal if you want: - strong per-run isolation - per-run autoscaling - very different resource shapes per job ### If you want the cleanest setup Your architecture would look like: -
ecs-push-pool
- for normal/heavier jobs -
fast-process-pool
- polled by a long-running ECS service running
prefect worker start --pool fast-process-pool
That’s a very reasonable hybrid design. ### Relevant docs - Work pools - Workers - Deployments - ECS worker integration ### Bottom line No, Prefect does not currently provide a dedicated “deploy a generic/process worker as an ECS service on my cluster” tool. For your case, the usual path is: - create the
process
work pool in Prefect - create an ECS service yourself using your existing infra tooling - have that service run
prefect worker start --pool ...
If you want, I can sketch: - the minimal ECS task definition/service shape for this, or - the tradeoffs between running one process worker task with concurrency vs multiple worker tasks with low concurrency each.