Files
pixa/internal/config/cachesize.go
sneak ca47bb096c style: mechanical lint conformance for #55's code under the canonical config
No behavior changes. Covers the purely mechanical findings the canonical
v2.12.2 config raises on the cache-size/eviction work:

- nolintlint: deleted 7 dead //nolint:gosec directives (cachesize.go x2,
  config.go, eviction.go x2, storage.go x2). gosec never raises G115/G703
  on those lines under the pinned toolchain, exactly the defect class
  that failed round 2 of this PR. The 6 live gosec suppressions are
  untouched.
- funcorder: moved writeIfAbsent after Exists (storage.go) and
  touchVariant/touchSourceContent after IncrementStats (cache.go).
- lll: wrapped over-length signatures, calls and messages at 88 columns.
- paralleltest: t.Parallel() on the new eviction, contentlock and
  cache_max_bytes tests and their subtests. configFromYAML uses only
  t.TempDir, so the config cases are parallel-safe.
- noctx: test helper DB calls now use ExecContext/QueryContext/
  QueryRowContext with t.Context().
- goconst: extracted testHeaderContentType into the shared test constant
  block and testVariantKeyOne into the eviction tests; reused the
  existing testContentTypeJPEG and keyCacheMaxBytes constants.
- modernize: interface{} to any, atomic.Int32 for the contentlock
  counters, min/max in ComputeDefaultCacheMaxBytes.
- intrange: integer range loops in the contentlock tests.
- wsl_v5: whitespace before the contentlock rendezvous statements.
- sloglint: slog.DiscardHandler in the config test logger.
- cyclop/funlen: split TestZeroMaxBytesDisablesDiskCache into four
  assertion helpers and extracted the concurrent store goroutine from
  TestEvictSourceBlobExcludesConcurrentStoreOfIdenticalContent. Every
  assertion is preserved verbatim; only their grouping changed.
2026-08-09 13:28:12 +00:00

110 lines
3.4 KiB
Go

package config
import (
"fmt"
"log/slog"
"math"
"os"
"path/filepath"
"syscall"
)
// DefaultCacheMaxBytesFloor is the minimum computed default for the
// cache_max_bytes setting: 500 MiB. The floor applies only to the
// computed default (when the key is omitted from the configuration),
// never to explicitly configured values.
const DefaultCacheMaxBytesFloor int64 = 524288000
// cacheDirPerms is the permission mode for the cache directory created
// before probing free space, matching the state directory permissions.
const cacheDirPerms = 0o750
// freeSpaceFractionNumerator and freeSpaceFractionDenominator express
// the 75% share of free space used for the computed default limit as
// integer arithmetic (dividing before multiplying avoids overflow).
const (
freeSpaceFractionNumerator uint64 = 3
freeSpaceFractionDenominator uint64 = 4
)
// FreeSpaceProbeFunc reports the number of free bytes available on the
// filesystem containing path. It is a function type so tests can
// inject a fake probe instead of depending on the host disk.
type FreeSpaceProbeFunc func(path string) (uint64, error)
// defaultFreeSpaceProbe reports free filesystem bytes via statfs on
// the given path, as available to unprivileged processes.
func defaultFreeSpaceProbe(path string) (uint64, error) {
var stat syscall.Statfs_t
if err := syscall.Statfs(path, &stat); err != nil {
return 0, err
}
if stat.Bsize < 0 {
return 0, fmt.Errorf("statfs reported negative block size %d for %q", stat.Bsize, path)
}
blockSize := uint64(stat.Bsize)
return stat.Bavail * blockSize, nil
}
// ComputeDefaultCacheMaxBytes returns the default cache size limit for
// the filesystem containing cacheDir: 75% of the free bytes reported
// by probe, with a floor of DefaultCacheMaxBytesFloor.
func ComputeDefaultCacheMaxBytes(
cacheDir string, probe FreeSpaceProbeFunc,
) (int64, error) {
freeBytes, err := probe(cacheDir)
if err != nil {
return 0, fmt.Errorf("config key %q: cannot determine free space for %q: %w",
"cache_max_bytes", cacheDir, err)
}
computed := freeBytes / freeSpaceFractionDenominator * freeSpaceFractionNumerator
computed = min(computed, math.MaxInt64)
limit := int64(computed)
limit = max(limit, DefaultCacheMaxBytesFloor)
return limit, nil
}
// resolveCacheMaxBytes finalizes CacheMaxBytes after state_dir
// validation: an explicitly configured value is kept as-is (no floor
// applies), while an omitted key receives the computed default based
// on free space in <state_dir>/cache/. The cache directory is created
// first so statfs measures the filesystem that will actually hold the
// cache. The effective limit is logged either way.
func (c *Config) resolveCacheMaxBytes(
log *slog.Logger, probe FreeSpaceProbeFunc,
) error {
if !c.cacheMaxBytesExplicit {
cacheDir := filepath.Join(c.StateDir, "cache")
if err := os.MkdirAll(cacheDir, cacheDirPerms); err != nil {
return fmt.Errorf("config key %q: cannot create cache directory %q: %w",
"cache_max_bytes", cacheDir, err)
}
limit, err := ComputeDefaultCacheMaxBytes(cacheDir, probe)
if err != nil {
return err
}
c.CacheMaxBytes = limit
log.Info("computed default cache size limit from free space",
"cache_max_bytes", limit,
"cache_dir", cacheDir,
)
}
log.Info("effective cache size limit",
"cache_max_bytes", c.CacheMaxBytes,
"cache_disabled", c.CacheMaxBytes == 0,
)
return nil
}