implement new runtime framework for bootstrapping localstack #10942

thrau · 2024-06-03T09:57:29Z

Motivation

This is part of the effort to generalize certain aspects of the codebase to make them more re-usable (see #10946). One concept that was difficult to re-use was infra.py, which is responsible for starting what we now call the localstack Runtime. The reason is that it imports all sorts of aws-specific code.

The Runtime is roughly responsible for

running runtime lifecycle hooks
managing the localstack filesystem (creating directories and cleaning up afterwards)
clean up thread and process pools
serving the main Gateway

Another annoying thing with the previous runtime is that the server (either hypercorn or twisted), couldn't properly register signal handlers, such as a code reloader, because it can only do that from the main thread, and we were starting the server in a separate thread. Now the runtime server, i.e., the control/event loop of the underlying I/O framework, now (imo correctly) blocks the main thread.

💡 The primary change though is that you now have a dynamic and re-usable python -m localstack.runtime.main bootstrapping procedure, which follows the open-closed principle.

Usage

Here is an example to build a new localstack runtime distribution without needing to define a new main or new bootstrapping procedure. All you need to do is expose a Components plugin, and (provisionally) disable AWS plugins that the currently leaking from localstack-core using localstack/plux#22.

Then, in your distribution, you can python -m localstack.runtime.main, and instead of starting AWS, it will start the my-emulator.

from functools import cached_property

from localstack.runtime import components, hooks
from plux.runtime.filter import global_plugin_filter
from rolo import Response
from rolo.gateway import Gateway, HandlerChain, RequestContext


@hooks.on_runtime_create()  # <- new hook that this PR introduces
def _disable_aws_plugins():
    # disable unwanted plugins from localstack aws
    global_plugin_filter.add_exclusion(namespace="localstack.runtime.components", name="aws")
    global_plugin_filter.add_exclusion(namespace="localstack.aws.*")
    global_plugin_filter.add_exclusion(value="localstack.aws.*")
    global_plugin_filter.add_exclusion(value="localstack.services*")


class MyEmulatorComponents(components.BaseComponents):
    namespace = "localstack.runtime.components"
    name = "my-emulator"

    @cached_property
    def gateway(self) -> Gateway:
        def _dummy_handler(chain: HandlerChain, context: RequestContext, response: Response):
            chain.respond(200, "ok")

        return Gateway(request_handlers=[
            _dummy_handler
        ])

Architecture

This is a high-level diagram to help explain the components. It's an ad-hoc notation, I hope it helps to get the gist though 😅

Components

One critical aspect to add was an IoC mechanism to dynamically load, specifically the Gateway instance, but more generally a type of application context (now the Components).
We assume that, within a runtime, there is only one Components plugin. For instance, there are now AwsComponents which is a Components plugin. Within the context of the AWS emulator, only this plugin should be available and loaded.

RuntimeServer

The RuntimeServer represents the lower-level IO control loop that should block the main thread. In the case of twisted, this is the twisted reactor. In the case of hypercorn, this is the asyncio event loop.
There was no need to limit the RuntimeServer to serve only one Gateway instance. Basically an IO control loop should be able to serve multiple server sockets, so in the future we could serve TCP proxies for instance through the main control loop, rather than instantiating new threads. Thus, the register(Gateway, ...) method was conceived. Other than register, the RuntimeServer only has a run and a shutdown method.

Instantiation

Which type of RuntimeServer is instantiated is currently governed by config.GATEWAY_SERVER. The different server implementations are now registered as plugins instead of using static imports as we do in serve_gateway.

Global access

There are situations where you need global access to the runtime and runtime components (for instance in the in-memory client, we need access to the Gateway instance we inject the request into).
To this end, the runtime package provides a localstack.runtime.get_current_runtime() method, that represents global (or in the future: scoped) access to the current LocalstackRuntime object.

Bootstrapping

Bootstrapping (the process of creating a localstack runtime and starting it), is done by localstack.runtime.main. The idea is that this is generalized. Whether we start AWS, Snowflake, or Azure, we always run the generalized localstack.runtime.main, which gets its application context from the Components explained above.
Bootstrapping also involves setting the current runtime (as described above), and registering exit handlers. The runtime and subsequently the RuntimeServer's event loop, should now always block the main thread.

A special case is the in_memory_localstack.py for testing, which works similarly, only that it creates a new runtime running in a thread, which still works.

Changes

Introduce a new runtime that can be enabled with LEGACY_RUNTIME=0 (changed in the future)
The runtime server (twisted reactor or hypercorn eventloop) now blocks the main thread.
Integration tests already use the new runtime

Testing

Simply run make entrypoints and then python -m localstack.runtime.main - should already use the new runtime.
You can also test that different gateway servers are instantiated correctly by setting GATEWAY_SERVER=hypercorn

Limitations / Future work

We still have a lot of import errors when running the example in "Usage". This is mostly because of localstack.services.plugins which contains the Service and ServiceManager framework, but also imports from botocore. In a second step, we need to generalize the Service concept similar to what I've done in this PR.
There are a few provisional concepts like localstack.runtime.legacy that I don't like, but were necessary to decouple the new runtime from localstack.services.infra while maintaining backwards compatibility
I would like to remove the legacy runtime very soon, and start replacing global access to it with get_current_runtime(). maybe we can make the switch to the new runtime with 3.5, and then remove LEGACY_RUNTIME with 3.6

TODO

What's left to do:

Extend PR description
Greenify pipeline
Set default config back to LEGACY_RUNTIME (maybe?)

github-actions · 2024-06-03T10:05:37Z

S3 Image Test Results (AMD64 / ARM64)

2 files 2 suites 3m 23s ⏱️
404 tests 352 ✅ 52 💤 0 ❌
808 runs 704 ✅ 104 💤 0 ❌

Results for commit 7639225.

♻️ This comment has been updated with latest results.

github-actions · 2024-06-03T10:52:03Z

LocalStack Community integration with Pro

2 files ±0 2 suites ±0 1h 35m 42s ⏱️ - 1m 44s
3 080 tests +6 2 735 ✅ +9 345 💤 ±0 0 ❌ - 3
3 082 runs +6 2 735 ✅ +9 347 💤 ±0 0 ❌ - 3

Results for commit 7639225. ± Comparison against base commit de41959.

This pull request removes 2 and adds 8 tests. Note that renamed tests count towards both.

tests.aws.services.support.test_support.TestConfigService ‑ test_create_support_case
tests.aws.services.support.test_support.TestConfigService ‑ test_resolve_case

tests.aws.services.lambda_.test_lambda_api.TestPartialARNMatching ‑ test_cross_region_arn_function_access
tests.aws.services.lambda_.test_lambda_api.TestPartialARNMatching ‑ test_update_function_configuration_full_arn
tests.aws.services.stepfunctions.v2.services.test_aws_sdk_task_service.TestTaskServiceAwsSdk ‑ test_s3_put_object[bool]
tests.aws.services.stepfunctions.v2.services.test_aws_sdk_task_service.TestTaskServiceAwsSdk ‑ test_s3_put_object[dict]
tests.aws.services.stepfunctions.v2.services.test_aws_sdk_task_service.TestTaskServiceAwsSdk ‑ test_s3_put_object[list]
tests.aws.services.stepfunctions.v2.services.test_aws_sdk_task_service.TestTaskServiceAwsSdk ‑ test_s3_put_object[num]
tests.aws.services.stepfunctions.v2.services.test_aws_sdk_task_service.TestTaskServiceAwsSdk ‑ test_s3_put_object[str]
tests.aws.services.support.test_support.TestConfigService ‑ test_support_case_lifecycle

♻️ This comment has been updated with latest results.

thrau · 2024-06-06T15:48:52Z

current state: i think everything works, except i believe the runtime shuts down too eagerly and therefore a CFn cleanup isn't working correctly.

alexrashed

Wow! This is truly great, and an awesome push towards a proper separation between the runtime and the emulator specific code.
Currently, these parts are a bit intertwined, which you can see when you think about what code this PR supersedes:

localstack.aws.serving.*
localstack.aws.gateway

The separation into a Runtime, a RuntimeServer, as well as a Component is great!
However, I am not 100% sure if the current separation of concerns is the best way forward (but it's definitely a great step and this thinking should not block a merge of this PR):
You mentioned in the code that at some point it would be great to have the possibility to run multiple components in a single process (I know, it's quite far away from now).
These Component instances would then be served via different Gateway instances on a single RuntimeServer.
But the RuntimeServer is currently managed by the Component which basically means there's a 1:1 mapping between the Component and the RuntimeServer.
Instead it might be better to have the Runtime manage both, the Component instances as well as the RuntimeServer insteances and glue them together?

Another thing we need to think about is the deprecation path for the host mode (which is not supported anymore with the new runtime server).
Unfortunately, a quick and dirty GitHub search shows that there are quite a lot of usages out there in the wild which we need to phase out.
Maybe we could already include a deprecation notice for the usage of the host mode in the CLI in this PR?

Again, truly a great step forward! I'm really looking forward to separating the code into proper namespace packages! 🥳 🚀 🦸🏽

localstack-core/localstack/runtime/hooks.py

alexrashed · 2024-06-11T08:17:46Z

localstack-core/localstack/runtime/legacy.py

+# event flag indicating the infrastructure has been started and that the ready marker has been printed
+# TODO: deprecated, use events.infra_ready
+INFRA_READY = events.infra_ready
+
+# event flag indicating that the infrastructure has been shut down
+SHUTDOWN_INFRA = threading.Event()


nit: I don't think this is used anywhere (yet), could this maybe be removed?
Actually, I don't think there's even a usage across all repos in this org:
https://github.com/search?q=org%3Alocalstack+%22INFRA_READY%22&type=code
https://github.com/search?q=org%3Alocalstack+%22SHUTDOWN_INFRA%22&type=code

Fair, I'll remove it as part of the cleanup I'm a second PR.

localstack-core/localstack/runtime/server/core.py

alexrashed · 2024-06-12T15:43:06Z

FYI: I pushed a small commit with a small adjustment to localstack.testing.pytest.in_memory_localstack

This module contains a pytest hook which starts LocalStack if the startup has not explicitly been disabled.

This hook has also been executed in "collect only" phases of LocalStack used in a preflight check.

This means that it unnecessarily started LocalStack in this check which should just collect tests.

We can see this for example in this run on master: https://app.circleci.com/pipelines/github/localstack/localstack/25701/workflows/b45d7ddd-e561-4c13-9501-61e8615d75e7/jobs/216512

2024-06-12T12:00:26.374  WARN --- [  MainThread] localstack.dns.server      : DNS server did not come up within 5 seconds.
Ready.
2024-06-12T12:00:26.693  INFO --- [-functhread4] l.t.p.in_memory_localstack : stopping infra
2024-06-12T12:00:26.693  INFO --- [  MainThread] l.t.p.in_memory_localstack : waiting for infra to stop
2024-06-12T12:00:27.069  INFO --- [-functhread4] l.runtime.shutdown         : [shutdown] Stopping all services

Unfortunately, this hook is also executed in some preflight checks (in downstream dependencies using this module), which might not have the proper entrypoints available at that time.
With the new changes in this PR, this step then fails (because with this change LocalStack wouldn't even start without entrypoints because the components are discovered via the plugin mechanism).

All my change does is that it fixes the hook to avoid starting LocalStack if we are in a "collect only" session.

dominikschubert

Awesome progress and I love the much cleaner way of "how to bootstrap an e2e emulator instance".
Great attention to deprecations and I like that even the in memory client has been considered from the start 🚀

There are some lower hanging fruits for follow-ups that we should get in sooner rather than later, especially starting the deprecation warnings and communication around that, so that we can phase them out with 4.0.

The config also seems to become more critical again. Maybe we could do a first step where we split the config into "global" and component config, so that we can then use dynamic component loading based on plugin name as mentioned in one of the comments.

I had a few nits but nothing that would block a merge and couldn't be handled in a follow-up PR, if at all.

dominikschubert · 2024-06-12T18:22:52Z

localstack-core/localstack/runtime/main.py

+            image_sha = inspect_result["Image"]
+            print("LocalStack Docker image sha: %s" % image_sha)


This needs to be adapted for #10951 but it's not critical and can be done in a follow-up, just shouldn't forget about it 👍

dominikschubert · 2024-06-12T18:37:04Z

localstack-core/localstack/runtime/hooks.py

+"""Hooks that are executed right before the LocalstackRuntime is created. These can be used to apply
+patches or otherwise configure the interpreter before any other code is imported."""
+
+on_runtime_start = on_infra_start


let's start deprecating this asap so that we can remove it with 4.0 at least

dominikschubert · 2024-06-12T18:39:58Z

localstack-core/localstack/testing/pytest/in_memory_localstack.py

+    # avoid starting up localstack if we only collect the tests (-co / --collect-only)
+    if session.config.option.collectonly:
+        return


Awesome, thanks for adding this. I think I had this in at least one local branch somewhere already when playing around more with filtering tests. 😅

dominikschubert · 2024-06-12T18:46:19Z

localstack-core/localstack/runtime/server/core.py

+        ssl_creds: tuple[str, str] | None = None,
+    ):
+        """
+        Registers the Gateway and the port configuration into the server. Some servers like ``twisted`` or


Might it not make sense to word this a bit differently then: Attempts to... to signal that this could also not work depending on the used RuntimeServer plugin?

Did you have a particular potential RuntimeServer implementation in mind that would not allow this? Otherwise I guess let's just leave it as is and assume we can always add multiple gateways

dominikschubert · 2024-06-12T18:53:44Z

localstack-core/localstack/runtime/components.py

+        # TODO: rename to RUNTIME_SERVER
+        server_type = config.GATEWAY_SERVER


nit: That comment should probably go into config.py

dominikschubert · 2024-06-12T18:58:12Z

localstack-core/localstack/runtime/current.py

+def get_current_runtime() -> "LocalstackRuntime":
+    with _runtime_lock:
+        if not _runtime:
+            raise ValueError("LocalStack runtime has not yet been set")


Not sure a ValueError is necessarily the clearest Exception here.

What's the reason for not just returning an optional/None here? Downstream typing having to handle the None?

dominikschubert · 2024-06-12T19:01:57Z

localstack-core/localstack/runtime/runtime.py

+      - Manage localstack filesystem directories
+      - Execute runtime lifecycle hook plugins from ``localstack.runtime.hooks``.
+      - Manage the localstack SSL certificate
+      - Serve the gateway (It uses a ``RuntimeServer`` to serve a ``Gateway`` instance coming from the


Q: What's the reason by the way why we don't just keep calling it the GatewayServer, like in the (now deprecated) config variable?

dominikschubert · 2024-06-12T19:14:43Z

localstack-core/localstack/runtime/runtime.py

+    Creates a new runtime instance from the current environment. It uses a plugin manager to resolve the
+    necessary components from the ``localstack.runtime.components`` plugin namespace to start the runtime.
+
+    TODO: perhaps we could control which components should be instantiated with a config variable/constant


We should just directly map the environment variable to the name of the components plugin.
There's a few other implications there though that have been addressed in other code comments here like the need for a scoped config per component for example. (i.e. the config being part of the components plugin and thus only instantiated with them).

dominikschubert · 2024-06-12T19:15:25Z

localstack-core/localstack/runtime/runtime.py

+    if len(components) > 1:
+        LOG.warning(
+            "There are more than one component plugins, using the first one which is %s",
+            components[0].name,
+        )


nit: Feels a bit too lenient for me. I'd personally prefer it to raise in that case. 🤷‍♂️

thrau requested a review from alexrashed June 3, 2024 10:35

thrau added the semver: minor Non-breaking changes which can be included in minor releases, but not in patch releases label Jun 3, 2024

thrau changed the title ~~implement new runtime framework to bootstrap localstack~~ implement new runtime framework for bootstrapping localstack Jun 3, 2024

thrau force-pushed the runtime-experiments branch from 7cea57e to 1d9b1e1 Compare June 4, 2024 15:04

This was referenced Jun 4, 2024

add code to debug monkey patches applied through localstack.utils.patch #10957

Merged

move aws-specific patches into localstack.aws.patches #10958

Merged

add DaemonAwareThreadPool for thread pools to block shutdown #10959

Merged

thrau force-pushed the runtime-experiments branch from 1d9b1e1 to c91a896 Compare June 6, 2024 12:45

thrau force-pushed the runtime-experiments branch 2 times, most recently from 149a3b9 to 5104264 Compare June 9, 2024 13:08

thrau marked this pull request as ready for review June 9, 2024 13:28

thrau requested a review from dominikschubert as a code owner June 9, 2024 13:28

thrau mentioned this pull request Jun 9, 2024

Reduce coupling between generic and AWS specific code #10946

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alexrashed added this to the 3.5 milestone Jun 10, 2024

alexrashed approved these changes Jun 11, 2024

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thrau added 4 commits June 11, 2024 22:33

implement new runtime framework to bootstrap localstack

8407697

fix duplex socket patch

6375701

decouple new runtime from localstack.services.infra

a432874

fix tests and pr comments

00bccf3

thrau force-pushed the runtime-experiments branch from 5104264 to 00bccf3 Compare June 11, 2024 21:25

avoid starting LocalStack in pytest collect-only

7639225

dominikschubert approved these changes Jun 12, 2024

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thrau merged commit 614dc96 into master Jun 12, 2024
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thrau deleted the runtime-experiments branch June 12, 2024 22:19

dominikschubert mentioned this pull request Jun 13, 2024

Fix runtime shutdown when triggered via signal handlers #11018

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alexrashed mentioned this pull request Jun 13, 2024

extend bootstrap lifecycle test to include restarts #11021

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dfangl mentioned this pull request Jun 20, 2024

Print LocalStackExitErrors in the new runtime #11066

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thrau mentioned this pull request Jun 21, 2024

enhancement request: Native support for Kubernetes livenessProbe, readinessProbe #10398

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dominikschubert mentioned this pull request Jun 27, 2024

Fix docker image digest in startup runtime information for new runtime #11100

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thrau mentioned this pull request Jul 11, 2024

use new runtime procedure for starting localstack in host mode #11181

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whummer mentioned this pull request Jul 12, 2024

Handle analytics publishing errors more gracefully #10185

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thrau mentioned this pull request Jul 14, 2024

remove legacy runtime in localstack/service/infra.py #11202

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simonrw mentioned this pull request Jul 30, 2024

fix: replace DEVELOP mode #11285

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		image_sha = inspect_result["Image"]
		print("LocalStack Docker image sha: %s" % image_sha)

		# TODO: rename to RUNTIME_SERVER
		server_type = config.GATEWAY_SERVER

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RuntimeServer

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Bootstrapping

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