Files
zapdb/errors.go
Manish R JainandGitHub 4ed8fbdc02 [BREAKING]: Change how Badger handles WAL (#1555)
This PR significantly improves Badger's disk usage behavior.

Breaking: This PR increases the magic version from 7 to 8. So, no older Badger directories would work with this change.

With this PR, we no longer use value log as write-ahead log. Instead, each MemTable has its own WAL. Value logs now only write values which are greater than ValueThreshold, while MemTable WAL only writes smaller values and value pointers.

On a crash and restart, the MemTable WALs are replayed to apply updates to Skiplist. When MemTables are flushed to L0, the corresponding WALs are deleted.

This PR makes big changes to how value log GC works:
- Discard stats are now stored in a separate file, instead of within the LSM tree.
- GC only picks up value logs based off discard stats.
- GC no longer does sampling, it uses discard stats to inform when a value log needs to be GCed.
- Value log would now no longer grow indefinitely, because of the shift to MemTable WAL.
- Removed the `badger gc` tool.
- Value Log Head pointer tracking is removed.
- Only the last value log file is replayed on every start, and truncated as necessary.

This PR also makes a bunch of other changes:
- Removes ValueLogLoadingMode (always uses mmap now).
- Removes TableLoadingMode (always uses mmap now).
- Removes Truncate option.
- Removes KeepL0InMemory option.
2020-10-06 18:41:41 -07:00

123 lines
5.3 KiB
Go

/*
* Copyright 2017 Dgraph Labs, Inc. and Contributors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package badger
import (
"math"
"github.com/pkg/errors"
)
const (
// ValueThresholdLimit is the maximum permissible value of opt.ValueThreshold.
ValueThresholdLimit = math.MaxUint16 - 16 + 1
)
var (
// ErrValueLogSize is returned when opt.ValueLogFileSize option is not within the valid
// range.
ErrValueLogSize = errors.New("Invalid ValueLogFileSize, must be in range [1MB, 2GB)")
// ErrKeyNotFound is returned when key isn't found on a txn.Get.
ErrKeyNotFound = errors.New("Key not found")
// ErrTxnTooBig is returned if too many writes are fit into a single transaction.
ErrTxnTooBig = errors.New("Txn is too big to fit into one request")
// ErrConflict is returned when a transaction conflicts with another transaction. This can
// happen if the read rows had been updated concurrently by another transaction.
ErrConflict = errors.New("Transaction Conflict. Please retry")
// ErrReadOnlyTxn is returned if an update function is called on a read-only transaction.
ErrReadOnlyTxn = errors.New("No sets or deletes are allowed in a read-only transaction")
// ErrDiscardedTxn is returned if a previously discarded transaction is re-used.
ErrDiscardedTxn = errors.New("This transaction has been discarded. Create a new one")
// ErrEmptyKey is returned if an empty key is passed on an update function.
ErrEmptyKey = errors.New("Key cannot be empty")
// ErrInvalidKey is returned if the key has a special !badger! prefix,
// reserved for internal usage.
ErrInvalidKey = errors.New("Key is using a reserved !badger! prefix")
// ErrThresholdZero is returned if threshold is set to zero, and value log GC is called.
// In such a case, GC can't be run.
ErrThresholdZero = errors.New(
"Value log GC can't run because threshold is set to zero")
// ErrNoRewrite is returned if a call for value log GC doesn't result in a log file rewrite.
ErrNoRewrite = errors.New(
"Value log GC attempt didn't result in any cleanup")
// ErrRejected is returned if a value log GC is called either while another GC is running, or
// after DB::Close has been called.
ErrRejected = errors.New("Value log GC request rejected")
// ErrInvalidRequest is returned if the user request is invalid.
ErrInvalidRequest = errors.New("Invalid request")
// ErrManagedTxn is returned if the user tries to use an API which isn't
// allowed due to external management of transactions, when using ManagedDB.
ErrManagedTxn = errors.New(
"Invalid API request. Not allowed to perform this action using ManagedDB")
// ErrInvalidDump if a data dump made previously cannot be loaded into the database.
ErrInvalidDump = errors.New("Data dump cannot be read")
// ErrZeroBandwidth is returned if the user passes in zero bandwidth for sequence.
ErrZeroBandwidth = errors.New("Bandwidth must be greater than zero")
// ErrInvalidLoadingMode is returned when opt.ValueLogLoadingMode option is not
// within the valid range
ErrInvalidLoadingMode = errors.New("Invalid ValueLogLoadingMode, must be FileIO or MemoryMap")
// ErrWindowsNotSupported is returned when opt.ReadOnly is used on Windows
ErrWindowsNotSupported = errors.New("Read-only mode is not supported on Windows")
// ErrPlan9NotSupported is returned when opt.ReadOnly is used on Plan 9
ErrPlan9NotSupported = errors.New("Read-only mode is not supported on Plan 9")
// ErrTruncateNeeded is returned when the value log gets corrupt, and requires truncation of
// corrupt data to allow Badger to run properly.
ErrTruncateNeeded = errors.New(
"Log truncate required to run DB. This might result in data loss")
// ErrBlockedWrites is returned if the user called DropAll. During the process of dropping all
// data from Badger, we stop accepting new writes, by returning this error.
ErrBlockedWrites = errors.New("Writes are blocked, possibly due to DropAll or Close")
// ErrNilCallback is returned when subscriber's callback is nil.
ErrNilCallback = errors.New("Callback cannot be nil")
// ErrEncryptionKeyMismatch is returned when the storage key is not
// matched with the key previously given.
ErrEncryptionKeyMismatch = errors.New("Encryption key mismatch")
// ErrInvalidDataKeyID is returned if the datakey id is invalid.
ErrInvalidDataKeyID = errors.New("Invalid datakey id")
// ErrInvalidEncryptionKey is returned if length of encryption keys is invalid.
ErrInvalidEncryptionKey = errors.New("Encryption key's length should be" +
"either 16, 24, or 32 bytes")
// ErrGCInMemoryMode is returned when db.RunValueLogGC is called in in-memory mode.
ErrGCInMemoryMode = errors.New("Cannot run value log GC when DB is opened in InMemory mode")
// ErrDBClosed is returned when a get operation is performed after closing the DB.
ErrDBClosed = errors.New("DB Closed")
)