Same cache dir between multiple projects errors with parallel usage

[bluetech]

My build system creates 3 bundles with rollup. If I build each bundle serially, it succeeds. However, if I build them concurrently (e.g. with make -j4, gulp, ...), it fails like this:

[19:54:40] Using gulpfile client/gulpfile.js
[19:54:40] Starting 'scripts.foo'...
[19:54:42] Starting 'scripts.bar'...
[19:54:44] Starting 'scripts.baz'...
Error: ENOENT: no such file or directory, open 'client/.rpt2_cache/c96394021b516827cdd67f325bc8e31a9c85a68e/code/cache_/c25c849c2122f988238ef5fb3159bccdcf3167ca'
    at error (client/node_modules/rollup/dist/rollup.js:170:12)
    at client/node_modules/rollup/dist/rollup.js:8926:6
    at process._tickCallback (internal/process/next_tick.js:109:7)
    at Module.runMain (module.js:607:11)
    at run (bootstrap_node.js:423:7)
    at startup (bootstrap_node.js:147:9)
    at bootstrap_node.js:538:3
Error: ENOENT: no such file or directory, open 'client/.rpt2_cache/c96394021b516827cdd67f325bc8e31a9c85a68e/code/cache_/fe9b01c7ea2aa0c98e1433b824f39491fdead469'
    at error (client/node_modules/rollup/dist/rollup.js:170:12)
    at client/node_modules/rollup/dist/rollup.js:8926:6
    at process._tickCallback (internal/process/next_tick.js:109:7)
    at Module.runMain (module.js:607:11)
    at run (bootstrap_node.js:423:7)
    at startup (bootstrap_node.js:147:9)
    at bootstrap_node.js:538:3
[19:54:49] Finished 'scripts.bar' after 6.27 s
[19:54:49] Finished 'scripts.foo' after 8.97 s
[19:54:49] Finished 'scripts.baz' after 5.65 s
[19:54:49] Starting 'scripts'...
[19:54:49] Finished 'scripts' after 67 μs

I can try to provide a reproducer, if needed.

These are the relevant package versions:

$ npm ls --depth=0
├── resolve@1.3.2
├── rollup@0.41.6
├── rollup-plugin-typescript2@0.4.0
├── tslib@1.6.0
└── typescript@2.2.2

Thanks.

[ezolenko]

A workaround would be to give each process its own cache, for example with process.pid:

typescript({ cacheRoot: `.cache_${process.pid}` })

This will create new cache for every run, so not a long term workaround, unless you also add a step to clean those up.

I'll look into using target names in cache path later.

[ezolenko]

BTW, if you manage to make it work with separate caches, check if your parallel execution makes a difference -- seems like rollup does one transpiling and then makes bundles for different targets from its own memory cache.

So depending on which plugins you are using (transpile work heavy or bundle work heavy) you might not gain much speed up, because you would force rollup to retranspile for each target.

[bluetech]

Thanks for your comments!

seems like rollup does one transpiling and then makes bundles for different targets from its own memory cache.

I am not sure what you mean by different targets - as far as I can tell, rollup can only create one bundle at a time (here is an issue: rollup/rollup#863). So if I want multiple bundles, I must run it multiple times?

[bluetech]

BTW, there is something strange in RollingCache.write:

	public write(name: string, data: DataType): void
	{
		if (this.rolled)
			return;

		if (data === undefined)
			return;

		if (this.rolled)
			fs.writeJsonSync(`${this.oldCacheRoot}/${name}`, data);
		else
			fs.writeJsonSync(`${this.newCacheRoot}/${name}`, data);
	}

The second if (this.rolled) is dead because the first if (this.rolled) already returns if true. So there may be a bug here?

[ezolenko]

Yep, looks like left overs after watch fix, thanks!

I assumed you were building different targets in parallel from the same code somehow... (for example this plugin builds 2 bundles in cjs and es formats).

Are you saying you have multiple whole rollup configs and they conflict when getting built at the same time? Could you post how you have it setup in guilp? Might be able to simply hardcode different cache roots, and then they shouldn't conflict.

[bluetech]

Yes, that's what I meant - entirely different bundles, not multiple targets (I never noticed this functionality in rollup at all - sorry for the confusion).

Following your suggestion, I used the following:

cacheRoot: process.cwd() + `/.rpt2_cache/${app.name}`,

(where app.name is the name I give to the bundle being built), and now it finished without conflicts.

So I think the issue is clear - a single cache directory cannot be used concurrently - and the solution is to use different cache directories. So we can close this issue, unless you want to make it work transparently in some fashion.

Thanks!

[ezolenko]

Cool, I'll add hash of rollup config itself to the cache path, should handle a number of possible conflicts.

[ezolenko]

Ok, 0.4.1 should behave better in this case out of the box (if contents of your rollup configs actually differ).

[lobsterkatie]

I am running into this on v 0.31.2. My use case is applying the same rollup config to a number of different files via use of an environment variable, as can be seen in the PR linked just above. Interestingly, I only see these error messages if I pass the --silent option to rollup; otherwise, I'd have no idea anything was wrong.