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Use a task queue to ensure code blocks are executed sequentially (#510)
* Only `await` on the last code block This ensures that all of the blocks are sent over in a single sequential batch, with no way for anyone else to execute their own block between two of ours, which would cause ordering issues * Introduce a task queue for running `blocks` * Abstract out a `callback` * Move the queue to its own file * Simplify API and add ability to have multiple queues * `await` calls to `run()` * Switch to more official PQueue Lmao at the fact that I implemented this from scratch * Rename to `ExecuteQueue` * Tweak docs * Delete `queue.ts`
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,69 @@ | ||
| /* | ||
| * execute-queue.ts | ||
| * | ||
| * Copyright (C) 2024 by Posit Software, PBC | ||
| * | ||
| * Unless you have received this program directly from Posit Software pursuant | ||
| * to the terms of a commercial license agreement with Posit Software, then | ||
| * this program is licensed to you under the terms of version 3 of the | ||
| * GNU Affero General Public License. This program is distributed WITHOUT | ||
| * ANY EXPRESS OR IMPLIED WARRANTY, INCLUDING THOSE OF NON-INFRINGEMENT, | ||
| * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Please refer to the | ||
| * AGPL (http://www.gnu.org/licenses/agpl-3.0.txt) for more details. | ||
| * | ||
| */ | ||
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| import PQueue from 'p-queue'; | ||
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| /** | ||
| * Language specific execution queue | ||
| * | ||
| * A singleton class that constructs and manages multiple execution queues, identified by | ||
| * their `key` (typically the language name). | ||
| */ | ||
| export class ExecuteQueue { | ||
| /// Singleton instance | ||
| private static _instance: ExecuteQueue; | ||
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| /// Maps a `key` to its `queue` | ||
| private _queues = new Map<string, PQueue>(); | ||
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| /** | ||
| * Constructor | ||
| * | ||
| * Private since we only want one of these. Access using `instance()` instead. | ||
| */ | ||
| private constructor() { } | ||
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| /** | ||
| * Accessor for the singleton instance | ||
| * | ||
| * Creates it if it doesn't exist. | ||
| */ | ||
| static get instance(): ExecuteQueue { | ||
| if (!ExecuteQueue._instance) { | ||
| // Initialize if we've never accessed it | ||
| ExecuteQueue._instance = new ExecuteQueue(); | ||
| } | ||
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| return ExecuteQueue._instance; | ||
| } | ||
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| /** | ||
| * Add a `callback` for execution on `key`'s task queue | ||
| * | ||
| * Returns a promise that resolves when the task finishes | ||
| */ | ||
| async add(key: string, callback: () => Promise<void>): Promise<void> { | ||
| let queue = this._queues.get(key); | ||
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| if (queue === undefined) { | ||
| // If we've never initialized this key's queue, do so now. | ||
| // Limit `concurrency` to 1, because we don't want tasks run out of order. | ||
| queue = new PQueue({ concurrency: 1 }); | ||
| this._queues.set(key, queue); | ||
| } | ||
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| return queue.add(callback); | ||
| } | ||
| } |
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