Fatal error: concurrent map iteration and map write

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1

I’m building locally. No problems. I’m building on netlify - it is causing a panic 50% of the time. Same code. Same variables. Any ideas?

10:14:03 AM: [09:14:03] Finished ‘build-prod’ after 37 s

10:14:04 AM: Building sites …

10:14:04 AM: fatal error: concurrent map iteration and map write

10:14:04 AM: goroutine 543 [running]:

10:14:04 AM: runtime.throw(0xea0a11, 0x26)

10:14:04 AM: /usr/local/go/src/runtime/panic.go:616 +0x81 fp=0xc420f165d0 sp=0xc420f165b0 pc=0x429f01

10:14:04 AM: runtime.mapiternext(0xc420d6d860)

10:14:04 AM: /usr/local/go/src/runtime/hashmap.go:747 +0x55c fp=0xc420f16660 sp=0xc420f165d0 pc=0x40877c

10:14:04 AM: reflect.mapiternext(0xc420d6d860)

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Do you use a netlify.toml file? If so, post it here

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Reason I ask is to confirm that the hugo version in your netlify.toml is the same version that you’re using locally. See:

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I’m not using a netlify.toml - I am however setting the HUGO_VERSION in the env vars to 0.42. Interestingly the same error occurred when I went up to 0.49.2 - its really random. Kind of good to know I’m the only one… I’m thinking its something other than hugo doing this. I’ll keep digging.

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Interesting. Are you setting any other env vars in Netlify? (Such as an env var for what command to run to build your site)

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I’ll be honest… It’s not your standard site. A working version is here: https://servicefinder.acecentre.net I’m really not thinking this is a standard bug - more something we have created!

This is the build command

git submodule update --init --recursive && cd res/scripts && npm install && node ./fetch-ccg-geodata.js && cd ../../themes/hugo-acecentre-theme/ && npm install && npm install bower && ./node_modules/.bin/bower install && ./node_modules/.bin/gulp build-prod && cd ../../ && hugo

This the code… https://github.com/acecentre/nhs-service-finder

I’m sure its something rather stupid… Oh - and the env vars are in the screenshot attached

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Screenshot 2018-10-14 at 19.52.30.png1446×478 36.7 KB

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The above is by definition a bug in Hugo (or somewhere in Go). But it can be hard to identify/fix. As I have not seen this in a live site for years, and you say this happens with the latest Hugo, I suspect you must do “something special”. But it’s still a bug.

Can you post the full stack trace? I.e. is it more after “10:14:04 AM: reflect.mapiternext(0xc420d6d860)”?

"

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Ahh… I always think its me!

Here is the full log https://gist.githubusercontent.com/willwade/bf1b3b445f887e1161ac775805fd1319/raw/67b729db9f57a20b64fa68a6b2dda0ff8afd2ce5/error-log.txt

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I take back the “bug in Hugo” …

I’m pretty sure that it’s the .Scratch.Get "rawdata" that is the problem. Pulling in data from other pages via Scratch just does not work in a concurrent context.

1 Like
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For once in my life I’m right! (Thanks @bep ! - I feel bad I made you look at that now… But its appreciated… )

1 Like
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@bep Thanks for looking into the issue. Do you have any suggestion on how can one form an array of json like that?

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Use append (Scratch.Add will also work) and jsonify. There are working examples floating around.

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I did post a PR for this issue within nhs-service-finder hugo site. The problem was writing in the same key of a specific Scratch instance within loop of Pages. And the solution was to use a different name for each Page.
This issue may not be resolved with this change. Though i didn’t see it after the change.

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@bep, would you mind explaining “concurrent context” further? I’m getting the same fatal error (a lot) and trying to debug.

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Hi @AlanBreck
This topic is three years old and many things have changed since. Please have a read about Requesting Help and then start a new topic describing your issue.