[Feature] Container creation and execution

[vicb]

Starting of the container

We do start container using a start command

I believe this will re-start an existing container if it already exists. That's not the same as starting a new container when the container is stateful.

Does that match what we do in prod?

Creation of the container

If a container of the same name already exists (error 409) we will re-use that.

That could be a problem when the existing container had a different environment/entrypoint as it will not be updated.

One way to overcome that would be to hash {environment, entrypoint} and attach that to the container (via the name or a label). And re-create the container if something changed.

/cc @mikenomitch @gabivlj @emily-shen @anonrig

[anonrig]

I believe this will re-start an existing container if it already exists. That's not the same as starting a new container when the container is stateful.

@vicb If the container is already started, we throw an error:

workerd/src/workerd/server/container-client.c++

Line 299 in 6a10e29

JSG_REQUIRE(response.statusCode != 304, Error, "Container already started");

[vicb]

@vicb If the container is already started, we throw an error:

Oh sorry I should have been clearer by "re-start" I do not mean "start" -> "start" but "stop" -> "start" (i.e. start a stopped container).

[gabivlj]

In production, when we stop a container, we start all-over with a brand new rootfs. The new configuration from start() always has precedence. In summary, there is nothing stateful across restarts.

[emily-shen]

so it looks like we want to destroy and recreate here if we get a 409? https://github.com/cloudflare/workerd/blob/6a10e29237a9824051a142bfcd8dab1a1138f01e/src/workerd/server/container-client.c%2B%2B#L284C53-L284C54