Make sure we finish sending the HTML payload before we exit the process (#38)
I encountered a page which responded successfully but all of the Hydrogen HTML was missing. It just had the boilerplate around it.
What I am guessing happened is that since `process.send` is async, with a sufficiently large
payload and race condition, `process.exit(0)` was being called before it finished sending.
Related:
- https://stackoverflow.com/questions/34627546/process-send-is-sync-async-on-nix-windows
- 56d9584a0e
- https://github.com/nodejs/node/issues/6767
This commit is contained in:
parent
7eaa103a28
commit
13eb92b067
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@ -6,6 +6,7 @@
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const fork = require('child_process').fork;
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const assert = require('assert');
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const RethrownError = require('../lib/rethrown-error');
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// The render should be fast. If it's taking more than 5 seconds, something has
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@ -60,12 +61,16 @@ async function renderHydrogenToString(options) {
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} else {
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let extraErrorsMessage = '';
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if (childErrors.length > 1) {
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extraErrorsMessage = ` (somehow we saw ${childErrors.length} errors but we really always expect 1 error)`;
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extraErrorsMessage = ` (somehow we saw ${
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childErrors.length
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} errors but we really always expect 1 error)\n${childErrors
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.map((childError, index) => ` ${index}. ${childError.message} ${childError.stack}`)
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.join('\n')}`;
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}
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const error = new RethrownError(
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`Child process failed with exit code ${exitCode}${extraErrorsMessage}`,
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childErrors[0]
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childErrors[0] || new Error('No child errors')
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);
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reject(error);
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}
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@ -84,6 +89,11 @@ async function renderHydrogenToString(options) {
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});
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});
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assert(
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data,
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`No HTML sent from child process to render Hydrogen. Any child errors? (${childErrors.length})`
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);
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return data;
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} catch (err) {
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throw new RethrownError(
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@ -4,6 +4,8 @@
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// get the data and exit the process cleanly. We don't want Hydrogen to keep
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// running after we get our initial rendered HTML.
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const assert = require('assert');
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const _renderHydrogenToStringUnsafe = require('./3-render-hydrogen-to-string-unsafe');
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// Only kick everything off once we receive the options. We pass in the options
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@ -13,12 +15,31 @@ process.on('message', async (options) => {
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try {
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const resultantHtml = await _renderHydrogenToStringUnsafe(options);
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// Send back the data we need
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process.send({
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assert(resultantHtml, `No HTML returned from _renderHydrogenToStringUnsafe.`);
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// Send back the data we need to the parent.
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await new Promise((resolve, reject) => {
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process.send(
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{
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data: resultantHtml,
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});
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// End the process gracefully. We got all the data we need.
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},
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(err) => {
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if (err) {
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return reject(err);
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}
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// Exit once we know the data was sent out. We can't gurantee the
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// message was received but this should work pretty well.
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//
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// Related:
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// - https://stackoverflow.com/questions/34627546/process-send-is-sync-async-on-nix-windows
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// - https://github.com/nodejs/node/commit/56d9584a0ead78874ca9d4de2e55b41c4056e502
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// - https://github.com/nodejs/node/issues/6767
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process.exit(0);
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resolve();
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}
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);
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});
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} catch (err) {
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// Serialize the error and send it back up to the parent process so we can
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// interact with it and know what happened when the process exits.
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@ -94,6 +94,7 @@ async function _renderHydrogenToStringUnsafe({ fromTimestamp, roomData, events,
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await vmResult;
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const documentString = dom.document.body.toString();
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assert(documentString, 'Document body should not be empty after we rendered Hydrogen');
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return documentString;
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}
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