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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,95 @@ | ||
| import sbp from '@sbp/sbp' | ||
|
|
||
| let wallBase = Date.now() | ||
| let monotonicBase = performance.now() | ||
| // `undefined` means the sync process has been stopped, `null` that the current | ||
| // request has finished | ||
| let resyncTimeout | ||
| let watchdog | ||
|
|
||
| const syncServerTime = async function () { | ||
| // Get our current monotonic time | ||
| const newMonotonicBase = performance.now() | ||
| // Now, ask the server for the time | ||
| const time = await fetch(`${this.config.connectionURL}/time`, { signal: this.abortController.signal }) | ||
| const requestTimeElapsed = performance.now() | ||
| if (requestTimeElapsed - newMonotonicBase > 1000) { | ||
| throw new Error('Error fetching server time: request took too long') | ||
| } | ||
| // If the request didn't succeed, report it | ||
| if (!time.ok) throw new Error('Error fetching server time') | ||
| const serverTime = (new Date(await time.text())).valueOf() | ||
| // If the value could not be parsed, report that as well | ||
| if (Number.isNaN(serverTime)) throw new Error('Unable to parse server time') | ||
| wallBase = serverTime | ||
| monotonicBase = newMonotonicBase | ||
| } | ||
|
|
||
| export default (sbp('sbp/selectors/register', { | ||
| 'chelonia/private/startClockSync': function () { | ||
| // Default re-sync every 5 minutes | ||
| const resync = (delay: number = 300000) => { | ||
| // If there's another time sync process in progress, don't do anything | ||
| if (resyncTimeout !== null) return | ||
| const timeout = setTimeout(() => { | ||
| // Get the server time | ||
| syncServerTime.call(this).then(() => { | ||
| // Mark the process as finished | ||
| if (resyncTimeout === timeout) resyncTimeout = null | ||
| // And then restart the listener | ||
| resync() | ||
| }).catch(e => { | ||
| // If there was an error, log it and possibly attempt again | ||
| if (resyncTimeout === timeout) { | ||
| // In this case, it was the current task that failed | ||
| resyncTimeout = null | ||
| console.error('Error re-syncing server time; will re-attempt in 5s', e) | ||
| // Call resync again, with a shorter delay | ||
| setTimeout(() => resync(0), 5000) | ||
| } else { | ||
| // If there is already another attempt, just log it | ||
| console.error('Error re-syncing server time; another attempt is in progress', e) | ||
| } | ||
| }) | ||
| }, delay) | ||
| resyncTimeout = timeout | ||
| } | ||
|
|
||
| let wallLast = Date.now() | ||
| let monotonicLast = performance.now() | ||
|
|
||
| // Watchdog to ensure our time doesn't drift. Periodically check for | ||
| // differences between the elapsed wall time and the elapsed monotonic | ||
| // time | ||
| watchdog = setInterval(() => { | ||
| const wallNow = Date.now() | ||
| const monotonicNow = performance.now() | ||
| const difference = Math.abs(Math.abs((wallNow - wallLast)) - Math.abs((monotonicNow - monotonicLast))) | ||
| // Tolerate up to a 10ms difference | ||
| if (difference > 10) { | ||
| clearTimeout(resyncTimeout) | ||
| resyncTimeout = null | ||
| resync(0) | ||
| } | ||
| wallLast = wallNow | ||
| monotonicLast = monotonicNow | ||
| }, 10000) | ||
|
|
||
| // Start the sync process | ||
| resyncTimeout = null | ||
| resync(0) | ||
| }, | ||
| 'chelonia/private/stopClockSync': () => { | ||
| if (resyncTimeout !== undefined) { | ||
| clearInterval(watchdog) | ||
| clearTimeout(resyncTimeout) | ||
| watchdog = undefined | ||
| resyncTimeout = undefined | ||
| } | ||
| }, | ||
| 'chelonia/time': function () { | ||
| const monotonicNow = performance.now() | ||
| const wallNow = wallBase - monotonicBase + monotonicNow | ||
| return (wallNow / 1e3 | 0) | ||
| } | ||
| }): string[]) |
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