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After the recent changes to limit the dev-cli watcher to relevant packages, the watcher started logging tons of unnecessary changes, and in some cases breaking based on the state of the repo. I have seen this happen with Chokidar before, and I'm not convinced we'll be able to fix it, so instead I decided to swap it out with `@parcel/watcher`, which is a conceptually simpler implementation that automatically batches changes and watches an entire directory, rather than tons of unique directories/files. This new implementation is conceptually simpler, and because of the design of the `@parcel/watcher` module I was pushed to reuse the `RepoSourceClassifier` to determine if we should restart the server based on a specific change. This means we now have a single source of truth for test files and the like (the classifier will tell us if a file is a test file, regardless of where it exists in the repo). Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>
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2.7 KiB
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57 lines
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2.7 KiB
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---
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id: kibDevDocsOpsCliDevMode
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slug: /kibana-dev-docs/ops/cli-dev-mode
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title: "@kbn/cli-dev-mode"
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description: A package to manage the Kibana cli behavior when in development
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date: 2022-05-24
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tags: ['kibana', 'dev', 'contributor', 'operations', 'cli', 'dev', 'mode']
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---
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This package exposes a function that manages the alternate behavior of the Kibana cli when using
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the `--dev` flag. This mode provides several useful features in a single CLI for a nice developer
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experience:
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- automatic server restarts when code changes
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- runs the `@kbn/optimizer` to build browser bundles
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- runs a base path proxy which helps developers test that they are writing code which is
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compatible with custom basePath settings while they work
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- pauses requests when the server or optimizer are not ready to handle requests so that when
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users load Kibana in the browser it's always using the code as it exists on disk
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To accomplish this, and to make it easier to test, the `CliDevMode` class manages the following
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objects.
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## `Watcher`
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The `Watcher` manages a [@parcel/watcher](https://github.com/parcel-bundler/watcher) instance to watch the
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server files, logs about file changes observed and provides an observable to the `DevServer` via
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its `serverShouldRestart$()` method.
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## `DevServer`
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The `DevServer` object is responsible for everything related to running and restarting the Kibana
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server process:
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- listens to restart notifications from the `Watcher` object, sending `SIGKILL` to the existing
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server and launching a new instance with the current code
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- writes the stdout/stderr logs from the Kibana server to the parent process
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- gracefully kills the process if the SIGINT signal is sent
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- kills the server if the SIGTERM signal is sent, process.exit() is used, a second SIGINT is
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sent, or the graceful shutdown times out
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- proxies SIGHUP notifications to the child process, though the core team is working on
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migrating this functionality to the KP and making this unnecessary
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## `Optimizer`
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The `Optimizer` object manages a `@kbn/optimizer` instance, adapting its configuration and
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logging to the data available to the CLI.
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## `BasePathProxyServer`
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This proxy injects a random three character base path in the URL that Kibana is served from to
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help ensure that Kibana features are written to adapt to custom base path configurations from users.
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The basePathProxy also has another important job, ensuring that requests don't fail because the
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server is restarting and that the browser receives front-end assets containing all saved
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changes. We accomplish this by observing the ready state of the `Optimizer` and `DevServer`
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objects and pausing all requests through the proxy until both objects report that they
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aren't building/restarting based on recently saved changes. |