i just built R2 support into our container last night. i have the access key id and secret key in th

i just built R2 support into our container last night. i have the access key id and secret key in the env of the worker, and i set the environment variables when i invoke the container itself.

this.container.start({
  // Need egress
  enableInternet: true,
  // Set env vars for R2 access in the container
  env: {
    R2_ENDPOINT_URL: `https://${this.env.CLOUDFLARE_ACCOUNT_ID}.r2.cloudflarestorage.com`,
    R2_ACCESS_KEY_ID: this.env.R2_ACCESS_KEY_ID,
    R2_SECRET_ACCESS_KEY: this.env.R2_SECRET_ACCESS_KEY,
    R2_BUCKET_NAME: this.env.BUNDLE_R2_BUCKET_NAME,
  },
});

this.container.start({
  // Need egress
  enableInternet: true,
  // Set env vars for R2 access in the container
  env: {
    R2_ENDPOINT_URL: `https://${this.env.CLOUDFLARE_ACCOUNT_ID}.r2.cloudflarestorage.com`,
    R2_ACCESS_KEY_ID: this.env.R2_ACCESS_KEY_ID,
    R2_SECRET_ACCESS_KEY: this.env.R2_SECRET_ACCESS_KEY,
    R2_BUCKET_NAME: this.env.BUNDLE_R2_BUCKET_NAME,
  },
});

this.container.start({
  // Need egress
  enableInternet: true,
  // Set env vars for R2 access in the container
  env: {
    R2_ENDPOINT_URL: `https://${this.env.CLOUDFLARE_ACCOUNT_ID}.r2.cloudflarestorage.com`,
    R2_ACCESS_KEY_ID: this.env.R2_ACCESS_KEY_ID,
    R2_SECRET_ACCESS_KEY: this.env.R2_SECRET_ACCESS_KEY,
    R2_BUCKET_NAME: this.env.BUNDLE_R2_BUCKET_NAME,
  },
});

this.container.start({
  // Need egress
  enableInternet: true,
  // Set env vars for R2 access in the container
  env: {
    R2_ENDPOINT_URL: `https://${this.env.CLOUDFLARE_ACCOUNT_ID}.r2.cloudflarestorage.com`,
    R2_ACCESS_KEY_ID: this.env.R2_ACCESS_KEY_ID,
    R2_SECRET_ACCESS_KEY: this.env.R2_SECRET_ACCESS_KEY,
    R2_BUCKET_NAME: this.env.BUNDLE_R2_BUCKET_NAME,
  },
});

no need to use ENV commands in the Dockerfile!

Brett (Fiberplane)OP•7/22/25, 7:40 PM

******

btw for the containers team: i have a small feature request for the dashboard!

if there is any way to provide metrics on when containers are killed for exceeding memory, that'd be awesome to surface in the dashboard. right now you have to cross-reference the P99 of memory usage with the instance sizee

BBrett (Fiberplane)i just built R2 support into our container last night. i have the access key id ...

Manuel Ogomigo•7/22/25, 7:53 PM

Thank you for this, this worked, how do you send the reqeusts, you use it's api right?

Brett (Fiberplane)OP•7/22/25, 7:56 PM

yeah so i'm using a bun/hono api and just load in the aws s3 sdk to upload the file

also btw, where did you find the r2 access key id? i resorted to looking up the id of my api key in my browser inspector network tab from inside the dashboard

Manuel Ogomigo•7/22/25, 8:00 PM

I got it from the API.

I'm using rust to run ffmpeg, I think that's the problem, it's not working proeprly. I'll check again.
Thank you for the tip!

Ricardo Gonçalves•7/22/25, 8:02 PM

Just for confirmation, is it possible to run docker-in-docker with Cloudflare Worker Containers? (I guess the answer is "no")

Bbrainstorm Do you have your code publicly available? I'd love to take a peek at how you str...

Brett (Fiberplane)OP•7/23/25, 10:34 PM

So the code is on a private repo but we just finally got around to refactoring to use the new Container class so we’re setting the env vars on the class itself per the docs — so it looks slightly different than what I posted (though that was working)

Brett (Fiberplane)OP•7/23/25, 10:34 PM

Pretty sure cf bindings in the container are an inevitability though

ralphjsmit•7/24/25, 11:01 AM

Hey guys, I am getting the following error all the time when making requests from local:

There is no Container instance available at this time.  This is likely because you have reached your max concurrent instance count (set in wrangler config) or are you currently provisioning the Container. If you are deploying your Container for the first time, check your dashboard to see provisioning status, this may take a few minutes.

There is no Container instance available at this time.  This is likely because you have reached your max concurrent instance count (set in wrangler config) or are you currently provisioning the Container. If you are deploying your Container for the first time, check your dashboard to see provisioning status, this may take a few minutes.

However, live usage appears pretty normal with just 4 live instances and all way below the concurrency limits.

laurynas•7/24/25, 3:35 PM

Heya, ran into this error when deploying a new worker (with containers) from CI:

 {"error":"SURPASSED_TOTAL_LIMITS","details":{"reason":"This application requires more than the allocated quota of disk in this account to run its requested instances of count 5.","used_disk_mb":90000,"requested_disk_mb":20000,"remaining_disk_mb":10000}}

 {"error":"SURPASSED_TOTAL_LIMITS","details":{"reason":"This application requires more than the allocated quota of disk in this account to run its requested instances of count 5.","used_disk_mb":90000,"requested_disk_mb":20000,"remaining_disk_mb":10000}}

I am not sure where these limits come from as the numbers are different than what's on https://developers.cloudflare.com/containers/platform-details/ ? What's the best course of action here - our deploys are blocked.

Llaurynas Heya, ran into this error when deploying a new worker (with containers) from CI:...

Chaika•7/24/25, 3:41 PM

Are they different? It says the max GB Disk for all instances combined is 100 GB. That error message is saying you're using 90 GB, asking for 20 GB more for this app but you only have 10 GB available. If you could use less/less max instances, should be able to get around it, otherwise there's the feedback link for higher limits

laurynas•7/24/25, 3:45 PM

the thing that's confusing is that we don't currently have live running instances. There are containers deployed but they're not live and running so until I hit this error I don't have a good intuition of how much my things are really taking up where is my limit etc.

Chaika•7/24/25, 3:49 PM

hmm yea, seems like it's just based on peak possible, (disk size for instance type * max instances)

spike•7/24/25, 8:45 PM

is it possible to set wranglers to use arm64 for local dev

Sspike is it possible to set wranglers to use arm64 for local dev

Hard@Work•7/24/25, 8:45 PM

It should by default?

HHard@Work It should by default?

spike•7/24/25, 8:46 PM

interesting, okay gotta dig deeper

FrozenFire•7/24/25, 10:48 PM

How do I ensure that a request is routed to the lowest latency zone, even if it means spinning up a new container? My application is extremely latency sensitive.

I set the max instances to 10, and then hit the workers.dev endpoint for my container deployment.

I had someone from the UK hit that same endpoint, and it didn't spin up a nearer instance.

FFrozenFire How do I ensure that a request is routed to the lowest latency zone, even if it ...

Chaika•7/24/25, 10:53 PM

Right now the routing just isn't very latency/geographic aware (Edit: well, your Durable Objects it spins up with random IDs for the getRandom/load balancing don't move with sort of pre-determine your location pools and mess with overall routing). Something they're working on: https://developers.cloudflare.com/containers/scaling-and-routing/#autoscaling-and-routing-unreleased
As for right now, "load balancing" is done via getRandom/just grabbing a random container id, which will create an object near the requester and container hopefully close as well. They never move though and sometimes the placement of the container instance themselves isn't great

FrozenFire•7/24/25, 10:56 PM

Huh. That's rough. Are there any strategies for dealing with this? I'm primarily interested in CloudFlare because I need low-latency placement.

FrozenFire•7/24/25, 11:01 PM

https://developers.cloudflare.com/containers/scaling-and-routing/#scaling-container-instances-with-get

I wonder if using env.container.get(<region>) would be effective-ish.

Cloudflare Docs

Scaling and Routing

Currently, Containers are only scaled manually by calling BINDING.get() with a unique ID, then
starting the container. Unless manualStart is set to true on the Container class, each
instance will start when get() is called.

FrozenFire•7/24/25, 11:40 PM

This sort of seems to work

export default {
  async fetch(request, env) {
    let container_id = request.cf?.colo || request.cf?.region || "default";
    return getContainer(env.MY_CONTAINER, container_id).fetch(request);
  },
};

export default {
  async fetch(request, env) {
    let container_id = request.cf?.colo || request.cf?.region || "default";
    return getContainer(env.MY_CONTAINER, container_id).fetch(request);
  },
};

spike•7/25/25, 6:34 AM

onStart()

onStart()

and the other lifecycle hooks only fire when you use

startAndWaitForPorts()

startAndWaitForPorts()

and onStart fires when the container is started or the container and the port is ready?

Sspike so `onStart()` and the other lifecycle hooks only fire when you use `startAndWai...

John Spurlock•7/25/25, 3:40 PM

the Container helper class is open source here: https://github.com/cloudflare/containers/blob/main/src/lib/container.ts

GitHub

containers/src/lib/container.ts at main · cloudflare/containers

Contribute to cloudflare/containers development by creating an account on GitHub.

FrozenFire•7/25/25, 11:06 PM

https://developers.cloudflare.com/containers/examples/env-vars-and-secrets/#using-envvars-on-the-container-class

I get

env is not defined

env is not defined

in the worker logs when I use this

Cloudflare Docs

Env Vars and Secrets

Pass in environment variables and secrets to your container

FrozenFire•7/25/25, 11:09 PM

I am needing to map a secret defined in the default(?) secret store to a specific environment variable name.

itisyev•7/26/25, 1:27 AM

Is there a way to do TCP communication with a container or would it have to be wrapped with a websocket and following the pattern described here https://developers.cloudflare.com/containers/examples/websocket/

itisyev•7/26/25, 1:29 AM

Last resort would be wrapping the functionalities of interest with an HTTP API but tryna do little as possible lol

itisyev•7/26/25, 1:34 AM

According to this, it looks like websockets are generally not friendly with workers/containers https://github.com/cloudflare/workerd/issues/2319

GitHub

WebSocket Serialization Error in Durable Objects RPC · Issue #2319...

When attempting to use DurableObjects RPC with a WebSocket, an error is encountered during serialization. The error message indicates that objects of type WebSocket cannot be serialized. This issue...

Iitisyev According to this, it looks like websockets are generally not friendly with work...

Chaika•7/26/25, 1:36 AM

use fetch not containerFetch, as per: https://developers.cloudflare.com/containers/examples/websocket/

Cloudflare Docs

Websocket to Container

Forwarding a Websocket request to a Container

Chaika•7/26/25, 1:37 AM

containerFetch uses RPC which would hit that. Fetch passes it without RPC which should be fine. Ignore the bottom bit of that doc...

CChaika use fetch not containerFetch, as per: https://developers.cloudflare.com/containe...

itisyev•7/26/25, 1:38 AM

So if I have a TCP endpoint listening on a container (with defaultPort set to the one to be listening at) and wrap in a Worker with

container.fetch

container.fetch

that should do the trick?

Iitisyev So if I have a TCP endpoint listening on a container (with defaultPort set to th...

Chaika•7/26/25, 1:40 AM

In theory. I haven't tried websockets before w/ containers, all I know for sure is avoid rpc/containerFetch to avoid the seralization issues you linked

CChaika In theory. I haven't tried websockets before w/ containers, all I know for sure ...

itisyev•7/26/25, 1:44 AM

I've tried a few instances of switchPort and container.fetch with little success but will see if doing defaultPort helps. Thanks!

Iitisyev I've tried a few instances of switchPort and container.fetch with little success...

Chaika•7/26/25, 1:47 AM

My understanding is you should only have to use switchPort if the default port isn't set

defaultPort?: Optional default port to use when communicating with the container. If not set, you must specify port in containerFetch calls, or use switchPort.

So if not using containerFetch (and not using default port), use normal fetch like:

container.fetch(switchPort(request, port))

As per README.md of the containers lib

**Do not use 'containerFetch' when trying to send a Request object with a websocket, until this issue is addressed. You can overcome this limitation by doing: container.fetch(switchPort(request, port))

https://github.com/cloudflare/containers/tree/main

Alexander•7/26/25, 4:15 PM

Anyone else hitting

AssertionError: Build ID should be set if containers are defined and enabled

AssertionError: Build ID should be set if containers are defined and enabled

when running integration tests with containers enabled?

�

😈 Donkey 💫•7/27/25, 11:14 AM

My container cannot complete any request, but gets stuck at the middle of request and returns error: Container suddenly disconnected. Try again. Any one encountered the same?

�

😈 Donkey 💫•7/27/25, 11:15 AM

metrics show that it never reach the limit of memory/cpu

Ghost Furry•7/27/25, 5:25 PM

Does uploading to R2 count as egress?

GGhost Furry Does uploading to R2 count as egress?

Hello, I’m Allie!•7/27/25, 5:30 PM

If you are doing so from a cloud that charges egress, yes

Hello, I’m Allie!•7/27/25, 5:30 PM

We won’t bill you for it, but they might

HHello, I’m Allie!If you are doing so from a cloud that charges egress, yes

Ghost Furry•7/27/25, 5:32 PM

From where i will bet object is different things

Take a example

I got the object file in container

Then upload that to R2 like we do using workers by binding

Then it will charge for uploading to R2 ?

GGhost Furry From where i will bet object is different things Take a example I got the ob...

Hello, I’m Allie!•7/27/25, 5:37 PM

You will be charged a single Class A operation(assuming you don’t use a Mulitpart Upload). R2 doesn’t bill by the gigabyte for uploads, just for storage and Infrequent Access Retrieval

HHello, I’m Allie!You will be charged a single Class A operation(assuming you don’t use a Mulitpar...

Ghost Furry•7/27/25, 5:38 PM

Yeah that i get but talking about egress charges in Cloudflare container

So putting file in r2 doesn't count as leaving out the network

GGhost Furry Yeah that i get but talking about egress charges in Cloudflare container So pu...

Hello, I’m Allie!•7/27/25, 5:39 PM

Sorry about that, I completely missed which channel we are in. R2 does not bill for Ingress, but Containers does bill requests to R2 for egress

1•7/28/25, 6:52 AM

Would containerFetch be the reason why my container takes a long time between requests to many routes? Making many containers - one for each pathname - makes things fast but every weird, that’s one container per pathname

Marcell•7/29/25, 7:44 PM

Is it possible to route request to a container without javascript fetch?

i just built R2 support into our container last night. i have the access key id and secret key in th

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