31 lines
1.7 KiB
Markdown
31 lines
1.7 KiB
Markdown
# Configuration watcher
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- Relevant schema: [[syndicate-rs]/syndicate-server/protocols/schemas/internalServices.prs](https://git.syndicate-lang.org/syndicate-lang/syndicate-rs/src/branch/main/syndicate-server/protocols/schemas/internalServices.prs)
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Assertions [requiring](../service.md#require-service) a service with name matching
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`ConfigWatcher` cause the server to start a configuration watcher service monitoring files in
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and subdirectories of the given `path` for changes:
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```preserves-schema
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ConfigWatcher = <config-watcher @path string @env ConfigEnv>.
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ConfigEnv = { symbol: any ...:... }.
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```
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The `path` may name either a file or directory. Any time the configuration watcher finds a file
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matching the glob `*.pr` within the tree rooted at `path`, it loads the file. Each time a
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`*.pr` file is loaded, it is interpreted as a [configuration scripting
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language](../scripting.md) program, with a copy of `env` as the "initial environment" for the
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script.
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Whenever a change to a `*.pr` file is detected, the configuration watcher reloads the file,
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discarding previous internal state related to the file.
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Note that a quirk of the config language requires that there exist an entry in `env` with key
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the symbol `config` and value an [entity reference](../../glossary.md#reference) (usually
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denoting a [dataspace entity](../../glossary.md#dataspace)). However, the `config` entry need
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not be the same as the surrounding `$config`! A useful pattern is to set up a new
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`ConfigWatcher` with `env` containing a `config` binding pointing to an
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[attenuated](../../glossary.md#attenuation) reference to the current `config` dataspace, or
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even [an entirely fresh dataspace](../scripting.md#expr:dataspace) created specifically for the
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task.
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