Cloudflare Developers•2mo ago

Is there a way to register an unhandledrejection event handler in Durable Objects?

SSH Is there a way to register an unhandledrejection event handler in Durable Object...

Larry•10/24/25, 7:22 PM

What do you mean by "rejection"?

LLarry What do you mean by "rejection"?

SHOP•10/24/25, 7:43 PM

https://developers.cloudflare.com/workers/runtime-apis/web-standards/#unhandled-promise-rejections

Cloudflare Docs

Web standards

Standardized APIs for use by Workers running on Cloudflare's global network.

Larry•10/24/25, 11:08 PM

When I return a DO stub over Workers RPC, in vitest environment, the connection breaks unless I use setTimeout. Is this a known limitation of vitest, also what happens in prod, or am I just doing something wrong? I can share code if you like?

LLarry When I return a DO stub over Workers RPC, in vitest environment, the connection ...

1984 Ford Laser•10/24/25, 11:57 PM

Are you returning an

RpcTarget

RpcTarget

LLarry When I return a DO stub over Workers RPC, in vitest environment, the connection ...

1984 Ford Laser•10/25/25, 12:02 AM

Also for testing, is the DO class being returned in the same Worker? If not, you might need to run both Workers concurrently but I don't have much experience there

JJohn Spurlock now that DOs are on sqlite 3.47, any reason why the jsonb functions (https://sql...

John Spurlock•10/25/25, 9:43 PM

looks like JSONB support is now available in sqlite DOs, thanks so much to whoever made this change!

1984 Ford Laser•10/26/25, 11:32 PM

There needs to be a better way to track logs on a DO, especially when working with WebSockets. I have a DO that manages inbound (hibernated) sockets as well as multiple outgoing socket connections, as well as alarms and HTTP requests. Every WS message I receive I log, but those logs can be split between the different events that the DO manages. I can see the full list of logs for the current IOContext() of the outgoing sockets within the event invocation of the alarms, which feels very unintuitive. Should I be pushing the logs to observability or elsewhere instead of relying on the built-in logic?

Larry•10/27/25, 2:23 AM

I had a chance over the last week to do a deep dive on Cap'n Web. Here is my multi-page writeup as a comparison to my own Lumenize RPC. Please let me know what you think. I'm particularly interested in hearing if I've misconfigured anything on the Cap'n Web side which would explain some of the troubles I had: https://lumenize.com/docs/rpc/capn-web-comparison

vs Cap'n Web (summary) | Lumenize

Comparing Lumenize RPC to Cloudflare Cap'n Web

Larry•10/27/25, 1:57 PM

Is there a way for a DO instance to know what binding name was used to connect to it without explicitly passing that in? I know it's tricky with service bindings to it's not consistent so I'm guessing the answer is "no" but thought I'd ask.

LLarry Is there a way for a DO instance to know what binding name was used to connect t...

Hello, I’m Allie!•10/27/25, 2:16 PM

Not yet. The tricky part is that names aren’t bounded by size, so theoretically you could have a 50 MB name, which is not great to be shipping around the world. Though iirc the team is looking into supporting it somehow

ALECKS•10/27/25, 3:35 PM

I'm seeing some strange behavior after destroying a durable object.

I have this destory method():

async destroy() {
    // drop all tables
    this.sql`DROP TABLE IF EXISTS state`;
    this.sql`DROP TABLE IF EXISTS alarms`;
    this.sql`DROP TABLE IF EXISTS jobs`;

    // delete all alarms
    try {
      await this.ctx.storage.deleteAlarm();
      await this.ctx.storage.deleteAll();
      this.logger.info(`Destroying Durable Object ${this.ctx.id.toString()}`);
      this.logger.info(`Alarm: ${await this.ctx.storage.getAlarm()}`);
      this.ctx.abort("destroyed");
    } catch (_) {}
  }

async destroy() {
    // drop all tables
    this.sql`DROP TABLE IF EXISTS state`;
    this.sql`DROP TABLE IF EXISTS alarms`;
    this.sql`DROP TABLE IF EXISTS jobs`;

    // delete all alarms
    try {
      await this.ctx.storage.deleteAlarm();
      await this.ctx.storage.deleteAll();
      this.logger.info(`Destroying Durable Object ${this.ctx.id.toString()}`);
      this.logger.info(`Alarm: ${await this.ctx.storage.getAlarm()}`);
      this.ctx.abort("destroyed");
    } catch (_) {}
  }

When it executes, I see normal logs:

Destroying Durable Object 130f15d64c383661002b1c10796016628280fda1f20c1557eb8ff89543479444
Alarm: null 
✘ [ERROR] Uncaught Error: destroyed

Destroying Durable Object 130f15d64c383661002b1c10796016628280fda1f20c1557eb8ff89543479444
Alarm: null 
✘ [ERROR] Uncaught Error: destroyed

Then strangely, a few seconds later I see this:

Creating DO tables (alarms, jobs, state)   // this is logged from my DO's constructor
NOSENTRY SQLite alarm handler canceled with requestScheduledAlarm.; scheduledTime = 1761578532s; localAlarmState.orDefault(kj::UNIX_EPOCH) = 0ns; actorId = 130f15d64c383661002b1c10796016628280fda1f20c1557eb8ff89543479444

Creating DO tables (alarms, jobs, state)   // this is logged from my DO's constructor
NOSENTRY SQLite alarm handler canceled with requestScheduledAlarm.; scheduledTime = 1761578532s; localAlarmState.orDefault(kj::UNIX_EPOCH) = 0ns; actorId = 130f15d64c383661002b1c10796016628280fda1f20c1557eb8ff89543479444

After it's destroyed, something else wakes up the DO only to warn me that an alarm was replaced. Why is this happening?

ALECKS•10/27/25, 5:01 PM

Yes, the destroy() is called from within an alarm.. it's a sort of TTL where I tell the DO to destroy itself sometime in teh future. I do catch the exception thrown by abort() tho...

ALECKS•10/27/25, 5:02 PM

and the destory is working, i can see everything wiped in the sqlite file

ALECKS•10/27/25, 5:04 PM

that I don't know, just following code i saw in some examples

HHello, I’m Allie!Not yet. The tricky part is that names aren’t bounded by size, so theoretically ...

Larry•10/27/25, 5:11 PM

Thanks, while we're on the subject, is

ctx.id

ctx.id

always valid even when you got to the DO via

getByName()

getByName()

, meaning I can use it as a "return address" for in-Cloudflare communication even if my client-side application always uses the name?

LLarry Thanks, while we're on the subject, is `ctx.id` always valid even when you got t...

Hard@Work•10/27/25, 5:27 PM

It should be, since

getByName

getByName

is just a convenience utility mapping to

.get(DO.idFromName()

.get(DO.idFromName()

I think

LLarry Thanks, while we're on the subject, is `ctx.id` always valid even when you got t...

lambrospetrou•10/27/25, 5:45 PM

Yes, the ID is always populated and correct. And you can route to a DO by the ID even if other callers route by name.

Larry•10/27/25, 5:51 PM

I don't see a channel for Cloudflare Queues but please excuse me if this is the wrong channgel to ask on, but what's the expected latency for Cloudflare Queues between the time you push a message in and the time your Queue consumer is called?

LLarry I don't see a channel for Cloudflare Queues but please excuse me if this is the ...

Chaika•10/27/25, 6:00 PM

#queues

Chaika•10/27/25, 6:01 PM

it can def take a few seconds though How to make queues pick up messages

Larry•10/27/25, 6:28 PM

I am never sure I get the unit conversions correct. I've seen folks say it costs about $4/month to run a DO 24/7, but I've also seen $0.34/day which works out to about $10/month. Can someone show me the math?

LLarry I am never sure I get the unit conversions correct. I've seen folks say it costs...

lambrospetrou•10/27/25, 6:37 PM

1 DO running 24/7 needs:

0.128 GB-s * 3600 seconds_per_hour * 744 hours_in_month = 342_835 GB-s/month

0.128 GB-s * 3600 seconds_per_hour * 744 hours_in_month = 342_835 GB-s/month

and at the price

$12.50/million GB-s

$12.50/million GB-s

that's 4.285 USD/month (

342_835/1_000_000*12.50

342_835/1_000_000*12.50

).
You get 400,000 GB-s for free.

The above is duration only charges.

edit: using the correct

0.128 GB-s

0.128 GB-s

0.125GB-s

0.125GB-s

Larry•10/27/25, 6:38 PM

Thanks! I only need duration charge help. I can count requests, just not unit convert.

PhoenixSpace•10/27/25, 6:53 PM

Is there any way to get a hook to run code before a DO is evicted from memory? Would love to use it to flush in memory stuff to sql storage rather than needing to write a value that will be modified often in short bursts.

PPhoenixSpace Is there any way to get a hook to run code before a DO is evicted from memory? W...

Larry•10/27/25, 6:56 PM

There is no such hook and even if there were, it wouldn't always work because it can evicted for crazy reasons. The saving grace is that reading from and writing to storage is very fast due to caching and locality. I have switched to a coding style where I don't have instance variables unless the in-memory representation is an expensive transformation from the in-storage representation. It's counter-intuitive but think of storage like you used to think of instance variables.

Larry•10/27/25, 7:04 PM

For the cases where the in-memory transformation is expensive, I have also adopted a coding style where I save and retrieve that largish structure in one whole shot using the fact that the KV API let's you store just about everything (objects with cycles or aliases, Date, Map, Set, Infinity, NaN, etc.). See the complete list in the second column here

LLarry There is no such hook and even if there were, it wouldn't always work because it...

PhoenixSpace•10/27/25, 7:05 PM

That's pretty fair, wishful thinking I guess. Wanted to avoid the $1/million write charges because it's an extremely bursty workflow (counting a rapid stream of events), but honestly not that bad

PhoenixSpace•10/27/25, 7:05 PM

the storage backend KV-like API for sqlite is OP though

Larry•10/27/25, 7:08 PM

Reads are so inexpensive I ignore the cost. Write costs can add up.

PhoenixSpace•10/27/25, 7:08 PM

Yup, that's why I was wondering if I could just flush it with a handle

PhoenixSpace•10/27/25, 7:09 PM

Guess this might be a better task for a container

Larry•10/27/25, 7:10 PM

I don't know the costs for containers but I find it hard to image it would be less under the vast majority of circumstances.

PhoenixSpace•10/27/25, 7:56 PM

On average it will undergo ~250,000 events in a 8 minute span, and then go silent for up to a month, so about $0.25 in writes vs probably a couple cents for the container

PhoenixSpace•10/27/25, 7:56 PM

very niche/weird usecase lol

PPhoenixSpace On average it will undergo ~250,000 events in a 8 minute span, and then go silen...

1984 Ford Laser•10/27/25, 8:24 PM

Could the events be grouped in some way? Store groups of events per write request

Larry•10/27/25, 8:27 PM

For $0.25, I wouldn't bother optimizing. Not even for $25. Maybe at $250 if it was simple to implement and manage but containers are generally harder to manage in my experience.

11984 Ford Laser Could the events be grouped in some way? Store groups of events per write reques...

PhoenixSpace•10/27/25, 8:39 PM

Unfortunately I don’t control that side. Been asking for that, but they don’t want to do it

LLarry For $0.25, I wouldn't bother optimizing. Not even for $25. Maybe at $250 if it w...

PhoenixSpace•10/27/25, 8:41 PM

I totally agree, but I’m basically donating the cost to manage this out of pocket currently. I was originally going to just spin up a VPS but figured scale to zero could save a bit (and scale horizontally since I don’t know how many events per month will be happening initially)

PhoenixSpace•10/27/25, 8:42 PM

It’s for managing some stuff for a highschool competition being spun up. Infra is a bit of a mess but until it goes public and gets sponsored basically just doing it for free.

PPhoenixSpace It’s for managing some stuff for a highschool competition being spun up. Infra i...

1984 Ford Laser•10/27/25, 8:44 PM

If it is actually only once a month then you'll stay within the included limits with workers paid anyway

1984 Ford Laser•10/27/25, 8:45 PM

Doing lots of writes sucks but I wouldnt worry unless your use case would easily push you over included limits

11984 Ford Laser If it is actually only once a month then you'll stay within the included limits ...

PhoenixSpace•10/27/25, 8:45 PM

It’s once a month per team per event

1984 Ford Laser•10/27/25, 8:45 PM

ahhh

PhoenixSpace•10/27/25, 8:45 PM

And I have no clue what the number of teams or events will be

1984 Ford Laser•10/27/25, 8:45 PM

THat might be an issue lol

PhoenixSpace•10/27/25, 8:46 PM

Yeah

1984 Ford Laser•10/27/25, 8:46 PM

What are you doing with the data afterwards?

PhoenixSpace•10/27/25, 8:46 PM

It gets processed into a leaderboard, basically

PhoenixSpace•10/27/25, 8:46 PM

Hmm. It just occurred to me this could totally be done with WAE

PhoenixSpace•10/27/25, 8:47 PM

Probably much simpler

async destroy() { // drop all tables this.sql`DROP TABLE IF EXISTS state`; this.sql`DROP TABLE IF EXISTS alarms`; this.sql`DROP TABLE IF EXISTS jobs`; // delete all alarms try { await this.ctx.storage.deleteAlarm(); await this.ctx.storage.deleteAll(); this.logger.info(`Destroying Durable Object ${this.ctx.id.toString()}`); this.logger.info(`Alarm: ${await this.ctx.storage.getAlarm()}`); this.ctx.abort("destroyed"); } catch (_) {} }

Creating DO tables (alarms, jobs, state) // this is logged from my DO's constructor NOSENTRY SQLite alarm handler canceled with requestScheduledAlarm.; scheduledTime = 1761578532s; localAlarmState.orDefault(kj::UNIX_EPOCH) = 0ns; actorId = 130f15d64c383661002b1c10796016628280fda1f20c1557eb8ff89543479444