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Prevent races by blocking on SDK builds

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If we don't block on SDK builds, then the riot-web build fails due to half-built dependencies. This needs to be done at two levels: the js-sdk because it is used by both the react-sdk and riot-web, and at the react-sdk because riot-web needs it. This means our build process is synchronous for js -> react -> riot, at least for the initial build. 

This does increase the startup time, particularly because the file watch timer is at 5 seconds. The timer is used to detect a storm of file changes in the underlying SDKs and give the build process some room to compile larger files if needed. 

The file watcher is accompanied by a "canary signal file" to prevent the build-blocking script from unblocking too early. Both the js and react SDKs build when `npm install` is run, so we ensure that we only listen for the `npm start` build for each SDK.

This is all done at the riot level instead of at the individual SDK levels (where we could use a canary file to signal up the stack) because:
* babel (used by the js-sdk) doesn't really provide an "end up build" signal
* webpack is a bit of a nightmare to get it to behave at times
* this blocking approach is really only applicable to riot-web, although may be useful to some other projects.

Hopefully that all makes sense.
This commit is contained in:
Travis Ralston 2018-09-24 17:12:42 -06:00
parent c6da122e41
commit 2b037ee146
5 changed files with 97 additions and 8 deletions
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25
scripts/build-watch-sdk.js
View file

@ -36,9 +36,34 @@ if (fs.existsSync(path.join(sdkPath, '.git'))) {
});
}
console.log("Sending signal that other processes may unblock");
triggerCanarySignal(sdkName);
console.log("Performing task: " + task);
child_process.execSync(`npm ${task === "build" ? "run build" : "start"}`, {
env: process.env,
cwd: sdkPath,
});
}
function triggerCanarySignal(sdkName) {
const tmpPath = path.resolve(".tmp");
try {
fs.mkdirSync(tmpPath);
} catch (e) {
if (e.code !== 'EEXIST') {
console.error(e);
throw "Failed to create temporary directory";
}
}
// Note: we intentionally create then delete the file to work around
// a file watching problem where if the file exists on startup it may
// fire a "created" event for the file. By having the behaviour be "do
// something on delete" we avoid accidentally firing the signal too
// early.
const canaryPath = path.join(tmpPath, sdkName);
fs.closeSync(fs.openSync(canaryPath, 'w'));
fs.unlinkSync(canaryPath);
}