add detailed scanInterval description #397
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Ethan-Arrowood
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Ethan-Arrowood
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I'm not sure I really understand the description here. It could use clearer examples I think.
| - `eviction` - The amount of time after expiration before a record can be evicted (defaults to zero). | ||
| - `scanInterval` - The interval for scanning for expired records (defaults to one quarter of the total of expiration and eviction). | ||
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| How often records are evicted is based on the `scanInterval` setting. Using Javascript's `setHours` method, we divide days and years by the interval in the local timezone of the Harper server to find the specific times to run at, regardless of the start time of the Harper server. For example, if the Harper server started at 1205 and the table `expiration` was set to 1 hour, with the default `scanInterval` (here being 15 minutes, one quarter of the TTL) eviction would run at 1215, 1230, 1245, 1300 etc. If the Harper server started at 1205pm and the `expiration` was set to 1 day, with the default `scanInterval` (now of 6 hours) the eviction would run at 1800 the same day, 0000 and 0600 the next day, etc. |
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What is "JavaScript's setHours method"? This: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/setHours ?
Furthermore, I feel like this description is missing something. I understand the start time doesn't have any impact, so then what does? Would a server that started at any time and an expiration of 1 day also have an eviction at 1800 the same day? What if my server started after 1800?
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Something more like this (easier to scan and remove impl detail)?
- `scanInterval` - The interval for scanning for expired records, in seconds (defaults to 1/4 of the total of expiration and eviction).
**Scan Alignment Examples**:
- 1-hour expiration, default interval (15 min): :00, :15, :30, :45 each hour
- 6-hour expiration, default interval (90 min): 00:00, 01:30, 03:00, 04:30, 06:00, 07:30...
- 1-day expiration, default interval (6 hours): 00:00, 06:00, 12:00, 18:00 daily
- 1-day expiration, custom 8-hour interval: 00:00, 08:00, 16:00 daily
Scans occur at these clock times in the server's local timezone, regardless of when the server started.
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Provided a detailed description of how to determine when the eviction cycle will run based on the scanInterval setting.