gtsocial-umbx

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util.go (2739B)

      1 // GoToSocial
      2 // Copyright (C) GoToSocial Authors admin@gotosocial.org
      3 // SPDX-License-Identifier: AGPL-3.0-or-later
      4 //
      5 // This program is free software: you can redistribute it and/or modify
      6 // it under the terms of the GNU Affero General Public License as published by
      7 // the Free Software Foundation, either version 3 of the License, or
      8 // (at your option) any later version.
      9 //
     10 // This program is distributed in the hope that it will be useful,
     11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
     12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     13 // GNU Affero General Public License for more details.
     14 //
     15 // You should have received a copy of the GNU Affero General Public License
     16 // along with this program.  If not, see <http://www.gnu.org/licenses/>.
     17 
     18 package cache
     19 
     20 import (
     21 	"context"
     22 	"errors"
     23 	"fmt"
     24 	"time"
     25 
     26 	"codeberg.org/gruf/go-cache/v3/result"
     27 	errorsv2 "codeberg.org/gruf/go-errors/v2"
     28 	"github.com/superseriousbusiness/gotosocial/internal/log"
     29 )
     30 
     31 // SentinelError is returned to indicate a non-permanent error return,
     32 // i.e. a situation in which we do not want a cache a negative result.
     33 var SentinelError = errors.New("BUG: error should not be returned") //nolint:revive
     34 
     35 // ignoreErrors is an error ignoring function capable of being passed to
     36 // caches, which specifically catches and ignores our sentinel error type.
     37 func ignoreErrors(err error) bool {
     38 	return errorsv2.Comparable(
     39 		err,
     40 		SentinelError,
     41 		context.DeadlineExceeded,
     42 		context.Canceled,
     43 	)
     44 }
     45 
     46 // nocopy when embedded will signal linter to
     47 // error on pass-by-value of parent struct.
     48 type nocopy struct{}
     49 
     50 func (*nocopy) Lock() {}
     51 
     52 func (*nocopy) Unlock() {}
     53 
     54 // tryStart will attempt to start the given cache only if sweep duration > 0 (sweeping is enabled).
     55 func tryStart[ValueType any](cache *result.Cache[ValueType], sweep time.Duration) {
     56 	if sweep > 0 {
     57 		var z ValueType
     58 		msg := fmt.Sprintf("starting %T cache", z)
     59 		tryUntil(msg, 5, func() bool {
     60 			return cache.Start(sweep)
     61 		})
     62 	}
     63 }
     64 
     65 // tryStop will attempt to stop the given cache only if sweep duration > 0 (sweeping is enabled).
     66 func tryStop[ValueType any](cache *result.Cache[ValueType], sweep time.Duration) {
     67 	if sweep > 0 {
     68 		var z ValueType
     69 		msg := fmt.Sprintf("stopping %T cache", z)
     70 		tryUntil(msg, 5, cache.Stop)
     71 	}
     72 }
     73 
     74 // tryUntil will attempt to call 'do' for 'count' attempts, before panicking with 'msg'.
     75 func tryUntil(msg string, count int, do func() bool) {
     76 	for i := 0; i < count; i++ {
     77 		if do() {
     78 			// success.
     79 			return
     80 		}
     81 
     82 		// Sleep for a little before retry (a bcakoff).
     83 		time.Sleep(time.Millisecond * 1 << (i + 1))
     84 	}
     85 
     86 	// panic on total failure as this shouldn't happen.
     87 	log.Panicf(nil, "failed %s after %d tries", msg, count)
     88 }