# FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory
**URL:** https://meta.discourse.org/t/fatal-error-reached-heap-limit-allocation-failed-javascript-heap-out-of-memory/288543
**Category:** Self-hosting
**Created:** [December 12, 2023, 7:29am UTC](https://meta.discourse.org/t/fatal-error-reached-heap-limit-allocation-failed-javascript-heap-out-of-memory/288543 "2023-12-12T07:29:17Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@mholt](https://meta.discourse.org/u/mholt)
#### Post date: [December 12, 2023, 7:29am UTC](https://meta.discourse.org/t/fatal-error-reached-heap-limit-allocation-failed-javascript-heap-out-of-memory/288543/1 "2023-12-12T07:29:17Z")
[Rebuild failure: "extconf failed, exit code 1" -- due to old Docker?](https://meta.discourse.org/t/rebuild-failure-extconf-failed-exit-code-1-due-to-old-docker/287756)
I’m getting this too, and now our forum is offline 🤔
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### Author:  [@pfaffman](https://meta.discourse.org/u/pfaffman)
#### Post date: [December 12, 2023, 7:50am UTC](https://meta.discourse.org/t/fatal-error-reached-heap-limit-allocation-failed-javascript-heap-out-of-memory/288543/2 "2023-12-12T07:50:48Z")
Do you have a very old Docker version?
Can you run `./launcher start app `
To restart?
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### Author:  [@mholt](https://meta.discourse.org/u/mholt)
#### Post date: [December 13, 2023, 3:48am UTC](https://meta.discourse.org/t/fatal-error-reached-heap-limit-allocation-failed-javascript-heap-out-of-memory/288543/3 "2023-12-13T03:48:34Z")
Ok, we’re back online now. Our Ubuntu system was fully up-to-date but for some reason the Docker version was years old still.
Runnning `./launcher start app` didn’t help. The only thing that fixed it was `/var/discourse/discourse_doctor` but when I ran it my SSH session froze. Another maintainer ran it and it succeeded and solved the problem. 🤷♂️
Apparently it ran out of memory:
> FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory
I’m not sure why it should take more than 2 GB of RAM to run/compile (?) JS…? Any chance it could be made leaner?
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### Author:  [@itsbhanusharma](https://meta.discourse.org/u/itsbhanusharma)
#### Post date: [December 13, 2023, 5:21am UTC](https://meta.discourse.org/t/fatal-error-reached-heap-limit-allocation-failed-javascript-heap-out-of-memory/288543/4 "2023-12-13T05:21:17Z")
I’ve seen a fair bit of rebuilds failing even on 8GB RAM where a SWAP was not configured. If this server doesn’t have swap, it might be worth setting up a 2GB swap then rebuilding again.
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### Author:  [@mholt](https://meta.discourse.org/u/mholt)
#### Post date: [December 13, 2023, 2:40pm UTC](https://meta.discourse.org/t/fatal-error-reached-heap-limit-allocation-failed-javascript-heap-out-of-memory/288543/5 "2023-12-13T14:40:24Z")
We already had swap space configured.
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### Author:  [@JammyDodger](https://meta.discourse.org/u/JammyDodger)
#### Post date: [December 13, 2023, 4:27pm UTC](https://meta.discourse.org/t/fatal-error-reached-heap-limit-allocation-failed-javascript-heap-out-of-memory/288543/6 "2023-12-13T16:27:41Z")
There have been a few reports of `JavaScript heap out of memory` recently, and a change has been made to account for it (all being well 🤞 🙂)
[https://github.com/discourse/discourse/pull/24850](https://github.com/discourse/discourse/pull/24850)
I don’t think your issue is the same as the one in the OP so I’ll split this off into a new topic. 👍