github.com/cockroachdb/pebble@v1.1.1-0.20240513155919-3622ade60459/log_recycler.go (about)

     1  // Copyright 2019 The LevelDB-Go and Pebble Authors. All rights reserved. Use
     2  // of this source code is governed by a BSD-style license that can be found in
     3  // the LICENSE file.
     4  
     5  package pebble
     6  
     7  import (
     8  	"sync"
     9  
    10  	"github.com/cockroachdb/errors"
    11  )
    12  
    13  type logRecycler struct {
    14  	// The maximum number of log files to maintain for recycling.
    15  	limit int
    16  
    17  	// The minimum log number that is allowed to be recycled. Log numbers smaller
    18  	// than this will be subject to immediate deletion. This is used to prevent
    19  	// recycling a log written by a previous instance of the DB which may not
    20  	// have had log recycling enabled. If that previous instance of the DB was
    21  	// RocksDB, the old non-recyclable log record headers will be present.
    22  	minRecycleLogNum FileNum
    23  
    24  	mu struct {
    25  		sync.Mutex
    26  		logs      []fileInfo
    27  		maxLogNum FileNum
    28  	}
    29  }
    30  
    31  // add attempts to recycle the log file specified by logInfo. Returns true if
    32  // the log file should not be deleted (i.e. the log is being recycled), and
    33  // false otherwise.
    34  func (r *logRecycler) add(logInfo fileInfo) bool {
    35  	if logInfo.fileNum.FileNum() < r.minRecycleLogNum {
    36  		return false
    37  	}
    38  
    39  	r.mu.Lock()
    40  	defer r.mu.Unlock()
    41  
    42  	if logInfo.fileNum.FileNum() <= r.mu.maxLogNum {
    43  		// The log file number was already considered for recycling. Don't consider
    44  		// it again. This avoids a race between adding the same log file for
    45  		// recycling multiple times, and removing the log file for actual
    46  		// reuse. Note that we return true because the log was already considered
    47  		// for recycling and either it was deleted on the previous attempt (which
    48  		// means we shouldn't get here) or it was recycled and thus the file
    49  		// shouldn't be deleted.
    50  		return true
    51  	}
    52  	r.mu.maxLogNum = logInfo.fileNum.FileNum()
    53  	if len(r.mu.logs) >= r.limit {
    54  		return false
    55  	}
    56  	r.mu.logs = append(r.mu.logs, logInfo)
    57  	return true
    58  }
    59  
    60  // peek returns the log at the head of the recycling queue, or the zero value
    61  // fileInfo and false if the queue is empty.
    62  func (r *logRecycler) peek() (fileInfo, bool) {
    63  	r.mu.Lock()
    64  	defer r.mu.Unlock()
    65  
    66  	if len(r.mu.logs) == 0 {
    67  		return fileInfo{}, false
    68  	}
    69  	return r.mu.logs[0], true
    70  }
    71  
    72  func (r *logRecycler) stats() (count int, size uint64) {
    73  	r.mu.Lock()
    74  	defer r.mu.Unlock()
    75  	count = len(r.mu.logs)
    76  	for i := 0; i < count; i++ {
    77  		size += r.mu.logs[i].fileSize
    78  	}
    79  	return count, size
    80  }
    81  
    82  // pop removes the log number at the head of the recycling queue, enforcing
    83  // that it matches the specified logNum. An error is returned of the recycling
    84  // queue is empty or the head log number does not match the specified one.
    85  func (r *logRecycler) pop(logNum FileNum) error {
    86  	r.mu.Lock()
    87  	defer r.mu.Unlock()
    88  
    89  	if len(r.mu.logs) == 0 {
    90  		return errors.New("pebble: log recycler empty")
    91  	}
    92  	if r.mu.logs[0].fileNum.FileNum() != logNum {
    93  		return errors.Errorf("pebble: log recycler invalid %d vs %d", errors.Safe(logNum), errors.Safe(fileInfoNums(r.mu.logs)))
    94  	}
    95  	r.mu.logs = r.mu.logs[1:]
    96  	return nil
    97  }
    98  
    99  func fileInfoNums(finfos []fileInfo) []FileNum {
   100  	if len(finfos) == 0 {
   101  		return nil
   102  	}
   103  	nums := make([]FileNum, len(finfos))
   104  	for i := range finfos {
   105  		nums[i] = finfos[i].fileNum.FileNum()
   106  	}
   107  	return nums
   108  }