8/26/2023 0 Comments Puppeteer github download![]() # Pick and land one fileĪt this point we had our migration ready to go and a robust CI server full of tests to watch our backs. This work isn't glamorous, and it's frustrating watching endless CI runs, but it was vital to have our test suite running reliably given the number of pull requests that the migration was throwing at it. This happened so often that we'd gotten into the habit of ignoring our CI and merging the pull requests anyway, assuming that the failure was a one-off issue on CI rather than a problem in Puppeteer.Īfter some general maintenance and dedicated time to fix some regular test flakes, we got it into a much more consistently passing state, enabling us to listen to CI and know that a failure was indicating an actual problem. We noticed that CI runs against pull requests were flaky and often failed. One thing we did invest time in upfront was our Continuous Integration (CI) setup. When making mechanical changes, it's easy to miss a step, and on multiple occasions the tests caught a problem that had slipped past both the implementer and the reviewer. Performing any code change without tests is risky, but changes where you're touching entire files or the entirety of the codebase are especially risky. If we hadn't had good test coverage, we would have added that before continuing with the migration. The goal of the migration was to complete it without any Puppeteer users even realising that we'd migrated, and the tests were a vital part of that strategy. This meant we could be confident that we weren't breaking code as we migrated, but also that we weren't introducing changes to our API. ![]() We were also fortunate that Puppeteer has a robust set of unit tests in place covering all of its functionality. Puppeteer has a lot of users and a broken release would cause problems for lots of them, so it was vital that we kept the risk of breaking changes to a minimum. If anything goes wrong with one of the steps you can easily revert it. This keeps the overhead of the migration down-you're working only on a small part of the code at anyone time-and keeps the risk down, too. When planning how to migrate we wanted to be able to make progress in small steps. ![]() It therefore made perfect sense to look at migrating Puppeteer's codebase to TypeScript, too. You can find out more about that migration in our talk at Chrome Dev Summit 2020. We're big fans of TypeScript on the DevTools team-so much so that new code in DevTools is being authored in it and we're in the middle of a big migration of the entire codebase to being type-checked by TypeScript. log( "CHILD: url received from parent process", url) Ĭonst browser = await puppeteer.Interested in helping improve DevTools? Sign up to participate in Google User Research here. The code snippet below is a simple example of running parallel downloads with Puppeteer.Ĭonst downloadPath = path. □ If you are not familiar with how child process work in Node I highly encourage you to give this article a read. We can combine the child process module with our Puppeteer script and download files in parallel. Child process is how Node.js handles parallel programming. We can fork multiple child_proces in Node. Our CPU cores can run multiple processes at the same time. □ Learn more about the single threaded architecture of node here Therefore if we have to download 10 files each 1 gigabyte in size and each requiring about 3 mins to download then with a single process we will have to wait for 10 x 3 = 30 minutes for the task to finish. It can only execute one process at a time. You see Node.js in its core is a single-threaded system. However, if you have to download multiple large files things start to get complicated. In this next part, we will dive deep into some of the advanced concepts.
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