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We clone a running VM in 2 seconds (2022)

(codesandbox.io)
169 points hunvreus | 7 comments | 08 Apr 25 14:55 UTC | HN request time: 1.028s | source | bottom
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londons_explore ◴[11 Apr 25 14:08 UTC] No.43653973[source]▶
Unmentioned: there are serious security issues with memory cloning code not designed for it.

For example, an SSL library might have pre-calculated the random nonce for the next incoming SSL connection.

If you clone the VM containing a process using that library, now both child VM's will use the same nonce. Some crypto is 100% broken open if a nonce is reused.

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1. sunshinekitty ◴[11 Apr 25 14:56 UTC] No.43654513[source]▶
GCP’s ‘live migrations’ have been doing this for close to a decade or more. Must not be that big of a problem.
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2. londons_explore ◴[11 Apr 25 14:57 UTC] No.43654524[source]▶
It isn't a problem if you guarantee only one child of the clone lives on - which GCP does.
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3. matt-p ◴[11 Apr 25 15:20 UTC] No.43654845[source]▶
How do we know that isn't enforced here too?
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4. jsnell ◴[11 Apr 25 16:15 UTC] No.43655491{3}[source]▶
Because their main selling point is to run the copies concurrently with the original.
5. oceanplexian ◴[11 Apr 25 19:03 UTC] No.43657289[source]▶
Live Migration on VMWare has been a thing before Google even had a cloud service.
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6. tanelpoder ◴[11 Apr 25 19:34 UTC] No.43657602[source]▶
VMware even has a vSphere Fault Tolerance product that creates a "live shadow instance" of a VM that mirrors the primary virtual machine (with up to 4 vCPUs). So you can do a quick failover in case of an "immediate planned" failover case, but apparently even when the primary DB goes down. I guess this might work when some external system (like a storage array) goes down in the primary, you can just switch to the other VM (with latest memory/CPU state) and replay that I/O there and keep going... But if there's a hard crash of the primary, if it actually does work, then they must be doing lots of reasoning about internal state change ordering & external device side-effect (somewhat like Antithesis, but for a different purpose). Back in the day, they supported only uniprocessor VMs (with something called vLockstep) and later up to 4 vCPUs with something called Fast Checkpointing.

I've always wanted to test this out for fun, by now 15 years have gone by and I've never got to it...

https://www.vmware.com/products/cloud-infrastructure/vsphere...

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7. umachin ◴[11 Apr 25 20:01 UTC] No.43657915{3}[source]▶
VMware has also had a patent on live VM cloning (called it VMfork) for quite a few years now. I worked on the team that built related features. Feature itself was in the desktop product. https://blogs.vmware.com/euc/2016/02/horizon-7-view-instant-...

Live migration had some very cool demos. They would have an intensive workload such as a game playing and cause a crash and the VM would resume with 0 buffering.