What's the error you'll get if you exceed the pending outgoing fetch limit? I know the current in fl

What's the error you'll get if you exceed the pending outgoing fetch limit? I know the current in flight limit is 6, but I've tried getting 200 in flight at the same time and I haven't exceeded that limit or gotten an error. This is in vitest-pool-workers so maybe I need to experiment in prod?

LLarry What's the error you'll get if you exceed the pending outgoing fetch limit? I kn...

1984 Ford Laser•10/28/25, 1:20 PM

Definitely wanna test in prod first

LLarry What's the error you'll get if you exceed the pending outgoing fetch limit? I kn...

lambrospetrou•10/28/25, 1:21 PM

You don't get an error when you have more than 6, they just get queued and once one completes another one runs. The error is when you are more than 1000 by default I think.

Llambrospetrou You don't get an error when you have more than 6, they just get queued and once ...

LarryOP•10/28/25, 1:25 PM

Thanks. What are the details of the error so I can catch it specifically? Or should I just send 2000 and see?

Chris•10/28/25, 6:45 PM

2 [ sse / durable object ] questions please. 1) There is a lovely blog about hibernating ws's, is this something we should also do for sse's? 2) How does pricing for sse's work please?

ty!!!

CChris 2 [ sse / durable object ] questions please. 1) There is a lovely blog about hib...

Hard@Work•10/28/25, 6:48 PM

Hibernation is only available for WebSockets at the moment

HHard@Work Hibernation is only available for WebSockets at the moment

Chris•10/28/25, 7:50 PM

Thanks for the info! Do we get charged for like amount of time writers exist in do's, here's the simple prototype that I'd like to build up, unless it'll we are charged for each moment the do exists!

worker:

import { DurableObject } from "cloudflare:workers"

export default {
  async fetch(request, env, ctx): Promise<Response> {
    const stub = env.MY_DURABLE_OBJECT.getByName("foo");

    if (request.url.includes('/subscribe')) return stub.subscribe(request)
    else if (request.url.includes('/message')) return await stub.message(request) 
    else return new Response(html, {headers: {'content-type': 'text/html'}})
  },
} satisfies ExportedHandler<Env>

import { DurableObject } from "cloudflare:workers"

export default {
  async fetch(request, env, ctx): Promise<Response> {
    const stub = env.MY_DURABLE_OBJECT.getByName("foo");

    if (request.url.includes('/subscribe')) return stub.subscribe(request)
    else if (request.url.includes('/message')) return await stub.message(request) 
    else return new Response(html, {headers: {'content-type': 'text/html'}})
  },
} satisfies ExportedHandler<Env>

html:

const html = `
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <title>Durable Object SSE Test</title>
</head>
<body>
  <h1>New Durable Object SSE Test</h1>
  <button id="send">Send Message</button>
  <div id="log" style="margin-top: 1em; white-space: pre;"></div>

  <script>
    const log = (msg) => {
      const el = document.getElementById('log');
      el.textContent += msg + "\\n";
    };

    // Subscribe to the stream
    const es = new EventSource('/subscribe');
    es.onopen = () => log('[connected]');
    es.onerror = (err) => log('[error] ' + JSON.stringify(err));
    es.onmessage = (e) => log('[message] ' + e.data);

    // Send a message to broadcast
    document.getElementById('send').addEventListener('click', async () => {
      const res = await fetch('/message', {
        method: 'POST',
        body: JSON.stringify({ time: new Date().toISOString() }),
        headers: { 'Content-Type': 'application/json' }
      });
      log('[sent] ' + (await res.text()));
    });
  </script>
</body>
</html>
`

const html = `
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <title>Durable Object SSE Test</title>
</head>
<body>
  <h1>New Durable Object SSE Test</h1>
  <button id="send">Send Message</button>
  <div id="log" style="margin-top: 1em; white-space: pre;"></div>

  <script>
    const log = (msg) => {
      const el = document.getElementById('log');
      el.textContent += msg + "\\n";
    };

    // Subscribe to the stream
    const es = new EventSource('/subscribe');
    es.onopen = () => log('[connected]');
    es.onerror = (err) => log('[error] ' + JSON.stringify(err));
    es.onmessage = (e) => log('[message] ' + e.data);

    // Send a message to broadcast
    document.getElementById('send').addEventListener('click', async () => {
      const res = await fetch('/message', {
        method: 'POST',
        body: JSON.stringify({ time: new Date().toISOString() }),
        headers: { 'Content-Type': 'application/json' }
      });
      log('[sent] ' + (await res.text()));
    });
  </script>
</body>
</html>
`

Chris•10/28/25, 7:51 PM

durable object:

export class MyDurableObject extends DurableObject<Env> {
  encoder = new TextEncoder()
  writers: Map<string, WritableStreamDefaultWriter<Uint8Array>> = new Map()


  constructor(ctx: DurableObjectState, env: Env) {
    super(ctx, env);
  }

  subscribe(request: Request): Response {
    const stream = new IdentityTransformStream()
    const writer = stream.writable.getWriter()
    const id = crypto.randomUUID()
    this.writers.set(id, writer)

    const headers = {
      'Connection': 'keep-alive',
      'Cache-Control': 'no-cache',
      'Content-Type': 'text/event-stream',
      'Access-Control-Allow-Origin': request.headers.get('Origin')!, // secured @ worker (outside world portal)
    }

    // initial comment
    writer.write(this.encoder.encode(`: connected\n\n`))

    // clean up on abort
    request.signal.addEventListener('abort', () => {
      writer.close()
      this.writers.delete(id)
    })

    return new Response(stream.readable, { headers })
  }


  async message(request: Request): Promise<Response> {
    const data = await request.text()

    for (const [_, writer] of this.writers) {
      writer.write(this.encoder.encode(`data: ${data}\n\n`))
    }

    return new Response('good', {
      status: 200,
      headers: {
        'Access-Control-Allow-Headers': 'Content-Type',
        'Access-Control-Allow-Methods': 'GET, POST, OPTIONS',
        'Access-Control-Allow-Origin': request.headers.get('Origin')!,
      },
    })
  }
}

export class MyDurableObject extends DurableObject<Env> {
  encoder = new TextEncoder()
  writers: Map<string, WritableStreamDefaultWriter<Uint8Array>> = new Map()


  constructor(ctx: DurableObjectState, env: Env) {
    super(ctx, env);
  }

  subscribe(request: Request): Response {
    const stream = new IdentityTransformStream()
    const writer = stream.writable.getWriter()
    const id = crypto.randomUUID()
    this.writers.set(id, writer)

    const headers = {
      'Connection': 'keep-alive',
      'Cache-Control': 'no-cache',
      'Content-Type': 'text/event-stream',
      'Access-Control-Allow-Origin': request.headers.get('Origin')!, // secured @ worker (outside world portal)
    }

    // initial comment
    writer.write(this.encoder.encode(`: connected\n\n`))

    // clean up on abort
    request.signal.addEventListener('abort', () => {
      writer.close()
      this.writers.delete(id)
    })

    return new Response(stream.readable, { headers })
  }


  async message(request: Request): Promise<Response> {
    const data = await request.text()

    for (const [_, writer] of this.writers) {
      writer.write(this.encoder.encode(`data: ${data}\n\n`))
    }

    return new Response('good', {
      status: 200,
      headers: {
        'Access-Control-Allow-Headers': 'Content-Type',
        'Access-Control-Allow-Methods': 'GET, POST, OPTIONS',
        'Access-Control-Allow-Origin': request.headers.get('Origin')!,
      },
    })
  }
}

CChris 2 [ sse / durable object ] questions please. 1) There is a lovely blog about hib...

LarryOP•10/28/25, 8:16 PM

I have been pestering the agents team about this since I become a member of Anthropic's MCP Transports Working Group. We either need hibernating SSE's or we need to get my WebSocket SEP approved.

LarryOP•10/28/25, 8:18 PM

For now, I'm working on productionalizing my proxyFetch. I have the Queue based one out. The SSE one is coming soon. https://lumenize.com/docs/proxy-fetch/

Introduction | Lumenize

Cost-effective external API calls from Durable Objects using Cloudflare Queues

Aalgads Ive been having some weird performance issues during testing a new app. The lat...

1984 Ford Laser•10/28/25, 8:23 PM

I had this issue just last week, the ID will always spawn in WEUR regardless of deletion of storage or anything. Best suggestion has been to use a different ID I guess (which might not work depending on use case)

1984 Ford Laser•10/28/25, 8:24 PM

I was getting DOs spawning in Perth Australia instead of Melbourne where I live or Sydney, so I was getting hit with 100s of ms extra request time

11984 Ford Laser I had this issue just last week, the ID will always spawn in WEUR regardless of ...

Chaika•10/28/25, 8:31 PM

well the DO won't move once it's created, and even deleting the storage it still sticks around for a while, at least a few hours last I knew, not sure if there's any better docs/knowledge on that but afaik it's all heavily cached once created.

I think here some location hints might be more helpful if your users are from a specific area, to force it consistently

Chaika•10/28/25, 8:32 PM

fwiw there was a decent bit of request rerouting from north america -> europe earlier today (requests being sent in North America being handled in Europe usually due to capacity reasons), like over 50% going to Europe for 3 hours or so peak US time (for free plan, slightly less for pro/biz/etc, going up the plans). It's calmed down now, but if your request gets bounced over there, Worker runs over there, placement of the DO will be near there

Aalgads It's still happening - I am in NY and about an hour ago I was making calls to EW...

Chaika•10/28/25, 8:55 PM

yea it's still happening but has just gone down, if the primary concern of yours is this rerouting it's not very often it's done, only recently there's been some of it. It's pretty transient but yea annoying to work around for still. Ultimately during the rerouting the placing of the object in Europe is good placement, since going back to NA would be further, it's just after it gets messy

Chaika•10/28/25, 8:56 PM

last major time it was happening was August (for North America), and then nothing for the months before, going to vary depending on the exact location you're hitting though

Aalgads Ive been having some weird performance issues during testing a new app. The lat...

Chaika•10/28/25, 9:10 PM

I was trying to find a good reference and as far as I know and can find, the ID and the location exists forever even if you delete all storage, won't be re-placed
durable-objects

Storage gone, the object lives forever though

I have some DOs at least a month old which say they have no storage that still are "around" in CF's Durable Objects Objects list api.

There's some downstream constraints from this like re-creating R2 buckets with the same name (which use DOs) never change regions, I imagine from the same reason...

LarryOP•10/29/25, 12:56 AM

We release the Queues based variant of proxy-fetch yesterday. Today we release the Durable Objects based one. latency of 50-100ms compared to 200ms to 3 seconds for the Queue based one. Stay tuned for the SSE one next. See: https://lumenize.com/docs/proxy-fetch/durable-object

Durable Object | Lumenize

Use a dedicated proxy DO to handle external fetches

LarryOP•10/29/25, 1:42 AM

Sstickman wouldn't this hit the simultaneous open connection limit of 6 pretty quickly? Or...

1984 Ford Laser•10/29/25, 8:48 AM

The idea is that it would be dealing with only so many requests at once so that the 6 outgoing limit isn't an issue. If you needed more concurrency you could spin up more ProxyFetchDO instances

LLarry We release the Queues based variant of proxy-fetch yesterday. Today we release t...

1984 Ford Laser•10/29/25, 8:51 AM

This is great. I have a bunch of use cases for this already. I had planned on implementing Queues in some way but the variable delay for consuming was making me weary. ProxyFetch should be a great solution, now you just need to port the Schedule API from Agents so we can easily add delays to the proxy-fetch/callback firing

tobystr•10/29/25, 8:59 AM

When a Frontend Worker calls a DO which is in a different datacenter, does the request go over public internet or across CFs own fiber?

Ttobystr When a Frontend Worker calls a DO which is in a different datacenter, does the r...

lambrospetrou•10/29/25, 9:03 AM

Our own internal networking.

Llambrospetrou Our own internal networking.

1984 Ford Laser•10/29/25, 9:06 AM

Is that the case for all requests from Cloudflare assets/resources to other Cloudflare assets/resources? Like if a DO requests a file from R2 is that also internal networking?

11984 Ford Laser Is that the case for all requests from Cloudflare assets/resources to other Clou...

lambrospetrou•10/29/25, 9:08 AM

In theory it should, yes. I cannot answer for "all" Cloudflare products with certainty though! If it's an internal dev platform product though, it usually stays within our network as much as possible.

Llambrospetrou Our own internal networking.

tobystr•10/29/25, 9:10 AM

thanks

Llambrospetrou In theory it should, yes. I cannot answer for "all" Cloudflare products with cer...

1984 Ford Laser•10/29/25, 9:20 AM

That's cool thank you, always like getting more info about the inner workings. Helps me to be able to appropriately build stuff to take advantage of the platform where possible

CChaika I was trying to find a good reference and as far as I know and can find, the ID ...

lambrospetrou•10/29/25, 9:20 AM

As said, the DO will move towards the original location/colo if that is healthy for it to run. See durable-objects

11984 Ford Laser That's cool thank you, always like getting more info about the inner workings. H...

lambrospetrou•10/29/25, 9:22 AM

Network routing has MANY complexities and edge cases, colos going down, peers going down, cables being bitten by sharks or cut by people, so my suggestion is to benchmark first and not base your assumptions on theoritical statements.

Sstickman wouldn't this hit the simultaneous open connection limit of 6 pretty quickly? Or...

LarryOP•10/29/25, 11:46 AM

Stay tuned. The next variant will have ProxyFetchDO spin up Workers to do the fetches. That might be next week though, because I have to do a deep dive on the differences between inheriting from RpcTarget and DurableObject. That may result in optimization of proxy-fetch.

When I'm done with all the variants, I'll upgrade my measurment framework (current 3x more effort than the implementations themselves) and do a big writeup of what I learned.

That said, the theoretical cost savings of this variant is 6x, so not bad for 10s of ms latency add. Think of a chat use case. 95% of the time a post doesn't require an external round trip, but what if your policy was to check links against a pornography or scam listing server before you allow links to go into the thread. Say you have 1000 rooms, you'll have 10s of these per second happen and it won't be all that bursty.

11984 Ford Laser This is great. I have a bunch of use cases for this already. I had planned on im...

LarryOP•10/29/25, 11:48 AM

port the Schedule API from Agents so we can easily add delays to the proxy-fetch/callback firing

Can you elaborate?

Sstickman wouldn't this hit the simultaneous open connection limit of 6 pretty quickly? Or...

LarryOP•10/29/25, 11:51 AM

BTW, it handles spikes shockingly well. The DO lets you queue 1000 or so outgoing fetches. Sure, they take a while to all resolve because there are only 6 in flight at a time, but it doesn't crash.

tiw•10/29/25, 2:20 PM

Hi, I'm new here and from Malaysia. My timing will be off from you guys but I do have some questions in mind that may sound dumb (i'm only learning BE this year), but I've been trying to understand and use Agent SDK.

I'm trying to build a websocket connection using the Agent SDK framework. I was concern on how is the lifecycle of the agent is going to be? because when reading through the documentation there are 2 types of Websockets connection and was suggesting to use the Hibernation Websocket.

With the Agent SDK basically handling everything even on the frontend with useAgent() and backend handling all the routing to the unique agent I will be creating, does the durable object goes into hibernation / sleep when the the agent websocket is onClose() ? Or it will be a default durable object behavior where it still wait for the 10s before hibernation?

Ttiw Hi, I'm new here and from Malaysia. My timing will be off from you guys but I do...

LarryOP•10/29/25, 2:46 PM

While it is an option in PartyKit, upon which Agents is built, Agents always sets up a hibernating WebSocket.

Paul•10/29/25, 7:01 PM

Just updated

wrangler

wrangler

to v4.45.2 but still not seeing "do" or "durable-objects" in there, is it somewhere else in the CLI?

Paul•10/29/25, 7:29 PM

How can I DELETE a durable object instance?

PPaul Just updated `wrangler` to v4.45.2 but still not seeing "do" or "durable-objects...

lambrospetrou•10/29/25, 7:34 PM

What do you expect to see? You cannot interact with individual Durable Objects outside of a worker (in addition to the just launched Studio in the dashboard).

PPaul How can I DELETE a durable object instance?

lambrospetrou•10/29/25, 7:35 PM

You don't delete DOs. You can clear their storage by calling the

storage.deleteAll()

storage.deleteAll()

method, and

deleteAlarm()

deleteAlarm()

to clear any alarms, but you cannot delete an object itself.

Llambrospetrou You don't delete DOs. You can clear their storage by calling the `storage.delete...

Paul•10/29/25, 7:37 PM

Hmm, trying to see if I can use Cloudflare containers for single use jobs, but their are tied to DOs, so I want to delete the container instance after use. Maybe I need to use the storage.deleteAll() and deleteAlam() to clear the DO context then I can reuse that slot?

Llambrospetrou What do you expect to see? You cannot interact with individual Durable Objects o...

Paul•10/29/25, 7:41 PM

I was trying to figure out how to delete a durable object instance, because I have container images that are just piling up taking tons of space (probably), I actaully don't know, cant see that information.

PPaul I was trying to figure out how to delete a durable object instance, because I ha...

lambrospetrou•10/29/25, 7:42 PM

Asking in #containers-beta will give you better answers on how to clean up resources created for containers.

Llambrospetrou Asking in #containers-beta will give you better answers on how to clean up resou...

Paul•10/29/25, 7:43 PM

actually no one from Cloudflare answers anything there, I've been trying for a few days now. This is how I've started venturing into these other places

PPaul actually no one from Cloudflare answers anything there, I've been trying for a f...

lambrospetrou•10/29/25, 7:44 PM

I doubt the DOs hold any image space. Check out the wrangler commands if you want to delete images: https://developers.cloudflare.com/workers/wrangler/commands/#containers

Llambrospetrou I doubt the DOs hold any image space. Check out the wrangler commands if you wan...

Paul•10/29/25, 7:47 PM

Sorry I meant to say "instance", not "image"... every container execution loads an image into an instance. When the instance is finished, it just sits around. That is the thing I'm trying to clean up and I think it's the thing associated with a DO.

PPaul Sorry I meant to say "instance", not "image"... every container execution loads ...

lambrospetrou•10/29/25, 7:48 PM

I still don't understand why you want to clean it up? If you don't use it, it will disappear, isn't it? I haven't followed much on containers but it seems weird to me that you want to delete a DO to cleanup some container image space.

Paul•10/29/25, 7:49 PM

In this particular use case, it's kind of a security best practice, these are ephermal github runners, so they run once and they should be completeley deleted after