If you're stuck with Cloudflare, this makes sense. I've tried CF workers and don't like them because they are not developer friendly.
I prefer https://fly.io - their dev experience is 10x better.
Miniflare – Local simulator for developing and testing Cloudflare Workers
11–20 of 30 posts
Re: Miniflare – Local simulator for developing and testing Cloudflare Workers
#12Oh awesome. Cloudflare Workers dev environment leaves something to be desired. Does this run in the same JS engine Cloudflare uses (V8 Chrome)? The particular subset of web standards that Cloudflare supports can be tricky to work around. Is there any support for emulating the CPU runtime limitations that Cloudflare imposes (10ms or 50ms for paid plans)?
Miniflare author here. Miniflare uses the Node VM module ( https://nodejs.org/api/vm.html#vm_class_vm_script ) which is slightly higher level than V8 isolates used by Cloudflare Workers, but the same underlying engine. Without low level isolate support in Node, it would be difficult to emulate CPU time limitations. Miniflare will report how long requests take, but this includes I/O time.
I think the hard limit CF imposes is of wall-clock time, not CPU time specifically. The CPU-time limit is a soft limit (i.e. not something that kills your Worker; only something used after-the-fact to determine whether your Worker “gets to succeed”.)
From their docs:
> Cloudflare will bill for Duration charges based on the higher of your wall time or CPU time, with a multiple applied to the CPU time to account for the processing power allotted to your script. We will not bill for wall time Duration charges beyond the execution limit given.
I think what this means in practice (as someone who has tried to implement similar “user workload total-resource-spend limiting” before) is that CloudFlare
1. Start a wall-clock timer, and a CPU-accounting sampler, when the task begins;
2. let the workload run until either it completes, or the timer goes off (and if the timer goes off, the task is hard-killed);
3. If the task was hard-killed, the load-balancing layer is then responsible for responding with a 503 (or whatever error CF uses for this case);
4. If the task wasn’t hard-killed, CF calculate CPU-seconds spent as the area under the curve of CPU-usage * wall-clock-time, and check whether the workload exceeded its CPU budget;
5. If the workload did exceed its budget, then — even though the request was calculated successfully — they nevertheless toss the result away, and reply with a 503 (or whatever) from the Workers control-plane layer;
6. If it didn’t, then they actually forward the result of your request back to the user.
(Meanwhile, handling memory limits is a lot easier — they can just ride the coattails of V8’s own per-ExecutionContext memory accounting, to trigger an OOM event on allocation when area-under-the-curve of GB-secs goes over-limit. But, as a workload might do all its allocations at the beginning and then exceed the memory GB-seconds limit due to the time component increasing, you need to do one final calculation of this at the same time you’re doing the final CPU-accounting check.)
Re: Miniflare – Local simulator for developing and testing Cloudflare Workers
#13Earlier quoted context omitted.
Miniflare author here. Miniflare uses the Node VM module ( https://nodejs.org/api/vm.html#vm_class_vm_script ) which is slightly higher level than V8 isolates used by Cloudflare Workers, but the same underlying engine. Without low level isolate support in Node, it would be difficult to emulate CPU time limitations. Miniflare will report how long requests take, but this includes I/O time.
I think the hard limit CF imposes is of wall-clock time, not CPU time specifically. The CPU-time limit is a soft limit (i.e. not something that kills your Worker; only something used after-the-fact to determine whether your Worker “gets to succeed”.) From their docs: > Cloudflare will bill for Duration charges based on the higher of your wall time or CPU time, with a multiple applied to the CPU time to account for th…
[deleted]
Re: Miniflare – Local simulator for developing and testing Cloudflare Workers
#14Earlier quoted context omitted.
Miniflare author here. Miniflare uses the Node VM module ( https://nodejs.org/api/vm.html#vm_class_vm_script ) which is slightly higher level than V8 isolates used by Cloudflare Workers, but the same underlying engine. Without low level isolate support in Node, it would be difficult to emulate CPU time limitations. Miniflare will report how long requests take, but this includes I/O time.
I think the hard limit CF imposes is of wall-clock time, not CPU time specifically. The CPU-time limit is a soft limit (i.e. not something that kills your Worker; only something used after-the-fact to determine whether your Worker “gets to succeed”.) From their docs: > Cloudflare will bill for Duration charges based on the higher of your wall time or CPU time, with a multiple applied to the CPU time to account for th…
That could be the case. I ran in to this trying to rescale PNGs in pure JS and hit CPU time limits immediately with lots of wall-clock time to spare. In practice it doesn't matter too much if the CPU limit kills the task or not, we're talking 50ms at most.
Re: Miniflare – Local simulator for developing and testing Cloudflare Workers
#15Oh awesome. Cloudflare Workers dev environment leaves something to be desired. Does this run in the same JS engine Cloudflare uses (V8 Chrome)? The particular subset of web standards that Cloudflare supports can be tricky to work around. Is there any support for emulating the CPU runtime limitations that Cloudflare imposes (10ms or 50ms for paid plans)?
Miniflare author here. Miniflare uses the Node VM module ( https://nodejs.org/api/vm.html#vm_class_vm_script ) which is slightly higher level than V8 isolates used by Cloudflare Workers, but the same underlying engine. Without low level isolate support in Node, it would be difficult to emulate CPU time limitations. Miniflare will report how long requests take, but this includes I/O time.
Isolated VM is a decent way to use lower level v8, but replicating "fetch" and the other CF workers primitives is a big chunk of work: https://github.com/laverdet/isolated-vm
Deno is the best OSS out there for "faking" edge workers: https://deno.land/manual@v1.4.6/runtime/workers
Re: Miniflare – Local simulator for developing and testing Cloudflare Workers
#16Question: how are people using Workers today?
I'd love a service where I can push my {INSERT_YOUR_FAVORITE_WEBAPP_FRAMEWORK} to the edge and not have to manage the OS and Database. Is that what fly.io is building?
Re: Miniflare – Local simulator for developing and testing Cloudflare Workers
#17Oh awesome. Cloudflare Workers dev environment leaves something to be desired. Does this run in the same JS engine Cloudflare uses (V8 Chrome)? The particular subset of web standards that Cloudflare supports can be tricky to work around. Is there any support for emulating the CPU runtime limitations that Cloudflare imposes (10ms or 50ms for paid plans)?
Miniflare author here. Miniflare uses the Node VM module ( https://nodejs.org/api/vm.html#vm_class_vm_script ) which is slightly higher level than V8 isolates used by Cloudflare Workers, but the same underlying engine. Without low level isolate support in Node, it would be difficult to emulate CPU time limitations. Miniflare will report how long requests take, but this includes I/O time.
vm2 does what you're looking for IIRC. Do a dynamic import check with an optionalDependency and write some glue over vm2 with a fallback to the built-in.
Just a thought.
Re: Miniflare – Local simulator for developing and testing Cloudflare Workers
#18Earlier quoted context omitted.
Miniflare author here. Miniflare uses the Node VM module ( https://nodejs.org/api/vm.html#vm_class_vm_script ) which is slightly higher level than V8 isolates used by Cloudflare Workers, but the same underlying engine. Without low level isolate support in Node, it would be difficult to emulate CPU time limitations. Miniflare will report how long requests take, but this includes I/O time.
I think the hard limit CF imposes is of wall-clock time, not CPU time specifically. The CPU-time limit is a soft limit (i.e. not something that kills your Worker; only something used after-the-fact to determine whether your Worker “gets to succeed”.) From their docs: > Cloudflare will bill for Duration charges based on the higher of your wall time or CPU time, with a multiple applied to the CPU time to account for th…
> I think the hard limit CF imposes is of wall-clock time, not CPU time specifically.
No, it's the other way around. The enforced limit is strictly on CPU time, not wall time. We use Linux's timer_create() with CLOCK_THREAD_CPUTIME_ID to set a timer that delivers a signal when a CPU time threshold is reached. The signal handler immediately terminates execution of JavaScript using V8's TerminateExecution() (which only terminates the specific isolate).
It sounds like your experience is from a system where each guest runs in their own process. Cloudflare Workers runs many guest isolates in a single process, therefore we cannot simply kill the process when one guest misbehaves. So, we have to do everything very differently from what a container host would do.
The line you quoted from the docs is about billing. The enforcement of limits, and the calculation of billing, are completely unrelated.
Here are some reference links if you want to understand more about how our platform is implemented:
https://www.infoq.com/presentations/cloudflare-v8/
https://blog.cloudflare.com/mitigating-spectre-and-other-sec...
Re: Miniflare – Local simulator for developing and testing Cloudflare Workers
#19If you're stuck with Cloudflare, this makes sense. I've tried CF workers and don't like them because they are not developer friendly. I prefer https://fly.io - their dev experience is 10x better.
Would you mind expanding on how fly.io dev experience is better.
See my similarly related question in this thread below.
Re: Miniflare – Local simulator for developing and testing Cloudflare Workers
#20Earlier quoted context omitted.
I think the hard limit CF imposes is of wall-clock time, not CPU time specifically. The CPU-time limit is a soft limit (i.e. not something that kills your Worker; only something used after-the-fact to determine whether your Worker “gets to succeed”.) From their docs: > Cloudflare will bill for Duration charges based on the higher of your wall time or CPU time, with a multiple applied to the CPU time to account for th…
> I think the hard limit CF imposes is of wall-clock time, not CPU time specifically. No, it's the other way around. The enforced limit is strictly on CPU time, not wall time. We use Linux's timer_create() with CLOCK_THREAD_CPUTIME_ID to set a timer that delivers a signal when a CPU time threshold is reached. The signal handler immediately terminates execution of JavaScript using V8's TerminateExecution() (which only…
> "Cloudflare Workers runs many guest isolates in a single process, therefore we cannot simply kill the process when one guest misbehaves. So, we have to do everything very differently from what a container host would do."
Does this imply that another guest Worker can impact/takedown my Worker due to their tasks misbehaving?