gotosocial/internal/cache/util.go

94 lines
2.9 KiB
Go

// GoToSocial
// Copyright (C) GoToSocial Authors admin@gotosocial.org
// SPDX-License-Identifier: AGPL-3.0-or-later
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package cache
import (
"database/sql"
"errors"
"fmt"
"time"
"codeberg.org/gruf/go-cache/v3/result"
errorsv2 "codeberg.org/gruf/go-errors/v2"
"github.com/superseriousbusiness/gotosocial/internal/db"
"github.com/superseriousbusiness/gotosocial/internal/log"
)
// SentinelError is an error that can be returned and checked against to indicate a non-permanent
// error return from a cache loader callback, e.g. a temporary situation that will soon be fixed.
var SentinelError = errors.New("BUG: error should not be returned") //nolint:revive
// ignoreErrors is an error matching function used to signal which errors
// the result caches should NOT hold onto. these amount to anything non-permanent.
func ignoreErrors(err error) bool {
return !errorsv2.Comparable(
err,
// the only cacheable errs,
// i.e anything permanent
// (until invalidation).
db.ErrNoEntries,
db.ErrAlreadyExists,
sql.ErrNoRows,
)
}
// nocopy when embedded will signal linter to
// error on pass-by-value of parent struct.
type nocopy struct{}
func (*nocopy) Lock() {}
func (*nocopy) Unlock() {}
// tryStart will attempt to start the given cache only if sweep duration > 0 (sweeping is enabled).
func tryStart[ValueType any](cache *result.Cache[ValueType], sweep time.Duration) {
if sweep > 0 {
var z ValueType
msg := fmt.Sprintf("starting %T cache", z)
tryUntil(msg, 5, func() bool {
return cache.Start(sweep)
})
}
}
// tryStop will attempt to stop the given cache only if sweep duration > 0 (sweeping is enabled).
func tryStop[ValueType any](cache *result.Cache[ValueType], sweep time.Duration) {
if sweep > 0 {
var z ValueType
msg := fmt.Sprintf("stopping %T cache", z)
tryUntil(msg, 5, cache.Stop)
}
}
// tryUntil will attempt to call 'do' for 'count' attempts, before panicking with 'msg'.
func tryUntil(msg string, count int, do func() bool) {
for i := 0; i < count; i++ {
if do() {
// success.
return
}
// Sleep for a little before retry (a bcakoff).
time.Sleep(time.Millisecond * 1 << (i + 1))
}
// panic on total failure as this shouldn't happen.
log.Panicf(nil, "failed %s after %d tries", msg, count)
}