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Fix bug which caused startup to hang if the clock was wound back since a previous session (#29558)

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* SessionLock: reduce the stale time

30 seconds staring at a spinner while we wait for a stale lock to expire is
rather painful. Pretty sure 15 seconds will be fine.

* SessionLock: deal with the clock having been wound back

If a previous session terminated uncleanly, and then the clock is wound back,
we could be waiting a very long time for the previous session's claim to
expire.

We can fix this by simply treating a future claim the same as "now", and
waiting for the normal stale timeout.

* fixup! SessionLock: deal with the clock having been wound back
This commit is contained in:
Richard van der Hoff
2025-03-24 16:43:53 +00:00
committed by GitHub
parent a6e8d512d0
commit f3653abe92
2 changed files with 53 additions and 6 deletions
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19
src/utils/SessionLock.ts
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@@ -57,7 +57,7 @@ export const SESSION_LOCK_CONSTANTS = {
/**
* The number of milliseconds after which we consider a lock claim stale
*/
LOCK_EXPIRY_TIME_MS: 30000,
LOCK_EXPIRY_TIME_MS: 15000,
};
/**
@@ -140,7 +140,10 @@ export async function getSessionLock(onNewInstance: () => Promise<void>): Promis
}
const timeAgo = Date.now() - parseInt(lastPingTime);
const remaining = SESSION_LOCK_CONSTANTS.LOCK_EXPIRY_TIME_MS - timeAgo;
// If the last ping time is in the future (i.e., timeAgo is negative), the chances are that the system clock has
// been wound back since the ping. Rather than waiting hours/days/millenia for us to get there, treat a future
// ping as "just now" by clipping to 0.
const remaining = SESSION_LOCK_CONSTANTS.LOCK_EXPIRY_TIME_MS - Math.max(timeAgo, 0);
if (remaining <= 0) {
// another session claimed the lock, but it is stale.
prefixedLogger.info(`Last ping (from ${lockHolder}) was ${timeAgo}ms ago: proceeding with startup`);
@@ -242,13 +245,23 @@ export async function getSessionLock(onNewInstance: () => Promise<void>): Promis
};
});
// We construct our own promise here rather than using the `sleep` utility, to make it easier to test the
// SessionLock in a separate Window.
const sleepPromise = new Promise((resolve) => {
setTimeout(resolve, remaining, undefined);
});
window.addEventListener("storage", onStorageUpdate!);
await Promise.race([sleepPromise, storageUpdatePromise]);
const winner = await Promise.race([sleepPromise, storageUpdatePromise]);
window.removeEventListener("storage", onStorageUpdate!);
// If we got through the whole of the sleep without any writes to the store, we know that the
// ping is now stale. There's no point in going round and calling `checkLock` again: we know that
// nothing has changed since last time.
if (!(winner instanceof StorageEvent)) {
prefixedLogger.info("Existing claim went stale: proceeding with startup");
break;
}
}
// If we get here, we know the lock is ours for the taking.