locache

A very simple in-memory cache for time.Locations, written in pure Go.

Why?

It is known that time.LoadLocation is reading the locations information from disk. Furthermore, previously retrieved locations are not being cached: the same location is looked up as many times as time.LoadLocation is called. If your application needs to open a bunch of locations very limited number of times, this behaviour would be desirable. On the other hand, when it is constantly looking up the same locations, this may seem wasteful. locache allows to perform disk lookups only once per location, and then reuse the results.

The mitigation becomes more noticeable as the number of repeated lookups grows:

goos: darwin
goarch: arm64
pkg: github.com/esimonov/locache
PASS
benchmark                                                 iter         time/iter    bytes alloc            allocs
---------                                                 ----         ---------    -----------            ------
Benchmark_LoadLocation/time_10_RepeatedLookups-10         6994      181.24 μs/op     51136 B/op     220 allocs/op
Benchmark_LoadLocation/time_100_RepeatedLookups-10         705     1638.50 μs/op    511217 B/op    2200 allocs/op
Benchmark_LoadLocation/time_1000_RepeatedLookups-10         75    16422.01 μs/op   5112026 B/op   22000 allocs/op
Benchmark_LoadLocation/locache_10_RepeatedLookups-10     58425       20.53 μs/op      5328 B/op      23 allocs/op
Benchmark_LoadLocation/locache_100_RepeatedLookups-10    54592       23.36 μs/op      5328 B/op      23 allocs/op
Benchmark_LoadLocation/locache_1000_RepeatedLookups-10   31910       35.70 μs/op      5328 B/op      23 allocs/op
ok      github.com/esimonov/locache     16.247s

Usage

locache.LoadLocation has the same signature as time.LoadLocation, so they can be used interchangeably.

package main

import (
	"fmt"
	"github.com/esimonov/locache"
)

func main() {
	location, err := locache.LoadLocation("America/Los_Angeles")
	if err != nil {
		panic(err)
	}

	fmt.Println(time.Date(2018, 8, 30, 12, 0, 0, 0, time.UTC).In(location))
}

would produce the same result as:

package main

import (
	"fmt"
	"time"
)

func main() {
	location, err := time.LoadLocation("America/Los_Angeles")
	if err != nil {
		panic(err)
	}

	fmt.Println(time.Date(2018, 8, 30, 12, 0, 0, 0, time.UTC).In(location))
}