plugin/cache: Reword serve_stale docs for clarity (#5394)

* reword for clarity; use consistent terminology

Signed-off-by: Chris O'Haver <cohaver@infoblox.com>
This commit is contained in:
Chris O'Haver
2022-06-07 09:43:03 -04:00
committed by GitHub
parent 3f07c2397a
commit 4690d10f87

View File

@@ -54,12 +54,12 @@ cache [TTL] [ZONES...] {
**DURATION** defaults to 1m. Prefetching will happen when the TTL drops below **PERCENTAGE**, **DURATION** defaults to 1m. Prefetching will happen when the TTL drops below **PERCENTAGE**,
which defaults to `10%`, or latest 1 second before TTL expiration. Values should be in the range `[10%, 90%]`. which defaults to `10%`, or latest 1 second before TTL expiration. Values should be in the range `[10%, 90%]`.
Note the percent sign is mandatory. **PERCENTAGE** is treated as an `int`. Note the percent sign is mandatory. **PERCENTAGE** is treated as an `int`.
* `serve_stale`, when serve\_stale is set, cache always will serve an expired entry to a client if there is one * `serve_stale`, when serve\_stale is set, cache will always serve an expired entry to a client if there is one
available. When this happens, cache will attempt to refresh the cache entry after sending the expired cache available as long as it has not been expired for longer than **DURATION** (default 1 hour). By default, the _cache_ plugin will
entry to the client. The responses have a TTL of 0. **DURATION** is how far back to consider attempt to refresh the cache entry after sending the expired cache entry to the client. The
stale responses as fresh. The default duration is 1h. **REFRESH_MODE** controls when the attempt to refresh responses have a TTL of 0. **REFRESH_MODE** controls the timing of the expired cache entry refresh.
the cache happens. `verified` will first verify that an entry is still unavailable from the source before sending `verified` will first verify that an entry is still unavailable from the source before sending the expired entry to the client.
the stale response to the client. `immediate` will immediately send the expired response to the client before `immediate` will immediately send the expired entry to the client before
checking to see if the entry is available from the source. **REFRESH_MODE** defaults to `immediate`. Setting this checking to see if the entry is available from the source. **REFRESH_MODE** defaults to `immediate`. Setting this
value to `verified` can lead to increased latency when serving stale responses, but will prevent stale entries value to `verified` can lead to increased latency when serving stale responses, but will prevent stale entries
from ever being served if an updated response can be retrieved from the source. from ever being served if an updated response can be retrieved from the source.