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New cache implementation and prefetch handing in mw/cache (#731)

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* cache: add sharded cache implementation

Add Cache impl and a few tests. This cache is 256-way sharded, mainly
so each shard has it's own lock. The main cache structure is a readonly
jump plane into the right shard.

This should remove the single lock contention on the main lock and
provide more concurrent throughput - Obviously this hasn't been tested
or measured.

The key into the cache was made a uint32 (hash.fnv) and the hashing op
is not using strings.ToLower anymore remove any GC in that code path.

* here too

* Minimum shard size

* typos

* blurp

* small cleanups no defer

* typo

* Add freq based on Johns idea

* cherry-pick conflict resolv

* typo

* update from early code review from john

* add prefetch to the cache

* mw/cache: add prefetch

* remove println

* remove comment

* Fix tests

* Test prefetch in setup

* Add start of cache

* try add diff cache options

* Add hacky testcase

* not needed

* allow the use of a percentage for prefetch

If the TTL falls below xx% do a prefetch, if the record was popular.
Some other fixes and correctly prefetch only popular records.
This commit is contained in:
Miek Gieben
2017-06-13 12:39:10 -07:00
committed by GitHub
parent b1efd3736e
commit e9eda7e7c8
23 changed files with 595 additions and 142 deletions
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16
middleware/cache/README.md vendored
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@@ -10,13 +10,12 @@ cache [TTL] [ZONES...]
* **TTL** max TTL in seconds. If not specified, the maximum TTL will be used which is 3600 for
noerror responses and 1800 for denial of existence ones.
A set TTL of 300 *cache 300* would cache the record up to 300 seconds.
Smaller record provided TTLs will take precedence.
Setting a TTL of 300 *cache 300* would cache the record up to 300 seconds.
* **ZONES** zones it should cache for. If empty, the zones from the configuration block are used.
Each element in the cache is cached according to its TTL (with **TTL** as the max).
For the negative cache, the SOA's MinTTL value is used. A cache can contain up to 10,000 items by
default. A TTL of zero is not allowed. No cache invalidation triggered by other middlewares is available. Therefore even reloaded items might still be cached for the duration of the TTL.
default. A TTL of zero is not allowed.
If you want more control:
@@ -24,16 +23,21 @@ If you want more control:
cache [TTL] [ZONES...] {
success CAPACITY [TTL]
denial CAPACITY [TTL]
prefetch AMOUNT [[DURATION] [PERCENTAGE%]]
}
~~~
* **TTL** and **ZONES** as above.
* `success`, override the settings for caching successful responses, **CAPACITY** indicates the maximum
number of packets we cache before we start evicting (LRU). **TTL** overrides the cache maximum TTL.
number of packets we cache before we start evicting (*randomly*). **TTL** overrides the cache maximum TTL.
* `denial`, override the settings for caching denial of existence responses, **CAPACITY** indicates the maximum
number of packets we cache before we start evicting (LRU). **TTL** overrides the cache maximum TTL.
There is a third category (`error`) but those responses are never cached.
There is a third category (`error`) but those responses are never cached.
* `prefetch`, will prefetch popular items when they are about to be expunged from the cache.
Popular means **AMOUNT** queries have been seen no gaps of **DURATION** or more between them.
**DURATION** defaults to 1m. Prefetching will happen when the TTL drops below **PERCENTAGE**,
which defaults to `10%`. Values should be in the range `[10%, 90%]`. Note the percent sign is
mandatory. **PERCENTAGE** is treated as an `int`.
The minimum TTL allowed on resource records is 5 seconds.