github.com/vescale/zgraph@v0.0.0-20230410094002-959c02d50f95/storage/storage.go (about)

     1  // Copyright 2022 zGraph Authors. All rights reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package storage
    16  
    17  import (
    18  	"time"
    19  
    20  	"github.com/cockroachdb/pebble"
    21  	"github.com/vescale/zgraph/storage/gc"
    22  	"github.com/vescale/zgraph/storage/kv"
    23  	"github.com/vescale/zgraph/storage/latch"
    24  	"github.com/vescale/zgraph/storage/resolver"
    25  )
    26  
    27  type mvccStorage struct {
    28  	db        *pebble.DB
    29  	latches   *latch.LatchesScheduler
    30  	resolver  *resolver.Scheduler
    31  	gcManager *gc.Manager
    32  }
    33  
    34  // Open returns a new storage instance.
    35  func Open(dirname string, options ...Option) (kv.Storage, error) {
    36  	opt := &pebble.Options{}
    37  	for _, op := range options {
    38  		op(opt)
    39  	}
    40  	db, err := pebble.Open(dirname, opt)
    41  	if err != nil {
    42  		return nil, err
    43  	}
    44  
    45  	s := &mvccStorage{
    46  		db:        db,
    47  		latches:   latch.NewScheduler(8),
    48  		resolver:  resolver.NewScheduler(4),
    49  		gcManager: gc.NewManager(2),
    50  	}
    51  	s.resolver.SetDB(db)
    52  	s.gcManager.SetDB(db)
    53  	s.gcManager.SetResolver(s.resolver)
    54  
    55  	// Run all background services.
    56  	s.latches.Run()
    57  	s.resolver.Run()
    58  	s.gcManager.Run()
    59  
    60  	return s, nil
    61  }
    62  
    63  // Begin implements the Storage interface
    64  func (s *mvccStorage) Begin() (kv.Transaction, error) {
    65  	curVer := s.CurrentVersion()
    66  	snap, err := s.Snapshot(curVer)
    67  	if err != nil {
    68  		return nil, err
    69  	}
    70  	txn := &Txn{
    71  		vp:        s,
    72  		db:        s.db,
    73  		us:        NewUnionStore(snap),
    74  		latches:   s.latches,
    75  		resolver:  s.resolver,
    76  		valid:     true,
    77  		startTime: time.Now(),
    78  		startVer:  curVer,
    79  		snapshot:  snap,
    80  	}
    81  	return txn, nil
    82  }
    83  
    84  // Snapshot implements the Storage interface.
    85  func (s *mvccStorage) Snapshot(ver kv.Version) (kv.Snapshot, error) {
    86  	snap := &KVSnapshot{
    87  		db:       s.db,
    88  		vp:       s,
    89  		ver:      ver,
    90  		resolver: s.resolver,
    91  	}
    92  	return snap, nil
    93  }
    94  
    95  // CurrentVersion implements the VersionProvider interface.
    96  // Currently, we use the system time as our startVer, and the system time
    97  // rewind cannot be tolerant.
    98  func (s *mvccStorage) CurrentVersion() kv.Version {
    99  	return kv.Version(time.Now().UnixNano())
   100  }
   101  
   102  // Close implements the Storage interface.
   103  func (s *mvccStorage) Close() error {
   104  	s.latches.Close()
   105  	s.resolver.Close()
   106  	s.gcManager.Close()
   107  	if s.db != nil {
   108  		return s.db.Close()
   109  	}
   110  	return nil
   111  }