add --direct-mounts option to spin up
#967
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This option tells `spin up` to directly mount any asset directories specified in the manifest file instead of copying the contents to a temporary directory and mounting that. This is useful when iteratively developing the static assets in the app, since any modifications to assets are immediately visible to subsequent invocations -- no restart required. Closes fermyon#964. Signed-off-by: Joel Dice <joel.dice@fermyon.com>
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Manually tested this using tests/build/assets-test. I removed the excluded files line from the spin.toml, used the new flag, and then changed the text in the assets to see the change and it worked!!! 🎉
I did see an initial lag the first few times I updated the text but that might have been a vscode thing. Not sure. It'd be nice to have a separate test with assets and no exclusions already set up somewhere so we can manually (or with a testing framework) test this scenario more easily.
crates/loader/src/local/assets.rs
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| tracing::info!("directly mounting local asset directories into guest"); | ||
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| if !exclude_files.is_empty() { | ||
| bail!("exclusions not permitted when mounting directories directly") |
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Does this mean that hidden files will also be mounted?
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Separately, should we allow exclusions for this feature in the future?
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This line means that if you ask for direct mounts for an app that specifies on or more files to be excluded, we'll raise an error and exit without running the app.
Per Ivan's comment, we'll need a more general "hot reload" solution to handle exclusions correctly. It will probably involve using a temporary directory and simultaneously monitoring the original directories and files, copying the non-excluded items over to the temporary directory as they change.
crates/loader/src/local/assets.rs
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| host: source.clone(), | ||
| }), | ||
| RawFileMount::Pattern(_) => Err(anyhow!( | ||
| "patterns not permitted when mounting directories directly" |
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Should we permit patterns in the future for this feature?
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Yes, I think that's doable using WASI preopens -- not sure how much work would be required, though. As I mentioned above, a general-purpose "hot reload" feature could handle this using a dynamically-updated temporary directory.
Personally, I prefer the tidiness of directory mounts anyway: you designate a directory for assets, put the ones you need in it (possibly as part of spin build) and omit the ones you don't. You don't need to fuss with patterns or exclusions that way.
Signed-off-by: Joel Dice <joel.dice@fermyon.com>
Signed-off-by: Joel Dice <joel.dice@fermyon.com>
This option tells
spin upto directly mount any asset directories specified in the manifest file instead of copying the contents to a temporary directory and mounting that. This is useful when iteratively developing the static assets in the app, since any modifications to assets are immediately visible to subsequent invocations -- no restart required.Closes #964.
Signed-off-by: Joel Dice joel.dice@fermyon.com