Improve memory performance

[martinmr]

• Use an int64 instead of a time.Time struct to represent the time.
• By default, include the cost of the storeItem in the cost calculation.

Related to DGRAPH-1378

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This change is 

[CLAassistant]

All committers have signed the CLA.

[manishrjain]

Reviewed 3 of 3 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @anurags92 and @karlmcguire)

[manishrjain]

This is good to go.

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @anurags92 and @karlmcguire)

[varun06]

@martinmr I have a test where I add a value to cache with TTL and then check for that value after TTL passed(say one second), that test is failing after this change(works fine with v0.0.3 ofc). I had to increase my wait time to make that test pass. I don't see any change that would do that in quick pass over code, but it would be a good idea to check SetWithTTL tests after this change.

[varun06]

Alright, so did some testing with couple sha's around this change, and this change definitely has some kind of regression with TTL.

[jarifibrahim]

hey @varun06 , can you share your test? Maybe send a PR to add it to ristretto? We can look at the failing test if this change has caused it.

[varun06]

sure @jarifibrahim
going to replicate it this weekend and if it fails again, will send you the test...

[varun06]

@jarifibrahim This is the test that's failing

func TestRisPutGetOnExpiredItem(t *testing.T) {
	c, err := NewCache(10, 100, 1, false)
	if err != nil {
		t.Fatalf("cache creation error: %v", err)
	}

	value := []byte("my cache value")
	key := getCacheKey(t)
	keyStr := key.String()
	defer key.Close()

	// put
	err = c.Put(&key, bytes.NewBuffer(value), time.Now().Add(1*time.Second))
	if err != nil {
		t.Fatalf("key %s was not put", keyStr)
	}

	//wait for values to settle
	time.Sleep(10 * time.Millisecond)

	// get
	_, _, stat, err := c.Get(&key)
	if err != nil {
		t.Fatalf("key %s was not get", keyStr)
	}

	if stat != cutl.StatusPresent {
		t.Errorf("key %s expected to be 'present': got %q.", keyStr, stat)
	}

	// Wait for 1 second, item will expire
	time.Sleep(1 * time.Second)

	// verify item is missing
	_, _, stat, err = c.Get(&key)
	if err != nil {
		t.Fatalf("key %s was not get", keyStr)
	}

	if stat != cutl.StatusMissing {
		t.Errorf("key %s expected to be 'missing': got %s", keyStr, stat)
	}
}

=== RUN   TestRisPutGetOnExpiredItem
    ristretto_test.go:179: key 0#0#0#example.com/ expected to be 'missing': got PRESENT
--- FAIL: TestRisPutGetOnExpiredItem (1.01s)

[varun06]

so it seems that there is a regression when we use SetWithTTL.

[jarifibrahim]

Looks like I missed the replies. @varun06 the issue has been resolved now via #277 .
Apologies for the late reply.