/
redka.go
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/
redka.go
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// Package Redka implements Redis-like database backed by SQLite.
// It provides an API to interact with data structures like keys,
// strings and hashes.
//
// Typically, you open a database with [Open] and use the returned
// [DB] instance methods like [DB.Key] or [DB.Str] to access the
// data structures. You should only use one instance of DB throughout
// your program and close it with [DB.Close] when the program exits.
package redka
import (
"context"
"database/sql"
"io"
"log/slog"
"time"
"github.com/nalgeon/redka/internal/core"
"github.com/nalgeon/redka/internal/rhash"
"github.com/nalgeon/redka/internal/rkey"
"github.com/nalgeon/redka/internal/rlist"
"github.com/nalgeon/redka/internal/rset"
"github.com/nalgeon/redka/internal/rstring"
"github.com/nalgeon/redka/internal/rzset"
"github.com/nalgeon/redka/internal/sqlx"
)
const driverName = "sqlite3"
// Common errors returned by data structure methods.
var (
ErrKeyType = core.ErrKeyType // key type mismatch
ErrNotFound = core.ErrNotFound // key or element not found
ErrValueType = core.ErrValueType // invalid value type
)
// Key represents a key data structure.
// Each key uniquely identifies a data structure stored in the
// database (e.g. a string, a list, or a hash). There can be only one
// data structure with a given key, regardless of type. For example,
// you can't have a string and a hash map with the same key.
type Key = core.Key
// Value represents a value stored in a database (a byte slice).
// It can be converted to other scalar types.
type Value = core.Value
// Options is the configuration for the database.
type Options struct {
// Logger is the logger for the database.
// If nil, a silent logger is used.
Logger *slog.Logger
}
var defaultOptions = Options{
Logger: slog.New(slog.NewTextHandler(io.Discard, nil)),
}
// DB is a Redis-like database backed by SQLite.
// Provides access to data structures like keys, strings, and hashes.
//
// DB is safe for concurrent use by multiple goroutines as long as you use
// a single instance of DB throughout your program.
type DB struct {
*sqlx.DB[*Tx]
hashDB *rhash.DB
keyDB *rkey.DB
listDB *rlist.DB
setDB *rset.DB
stringDB *rstring.DB
zsetDB *rzset.DB
bg *time.Ticker
log *slog.Logger
}
// Open opens a new or existing database at the given path.
// Creates the database schema if necessary.
//
// Expects the database driver to be already imported with the name "sqlite3".
// See the [simple] and [modernc] examples for details.
//
// The returned [DB] is safe for concurrent use by multiple goroutines
// as long as you use a single instance throughout your program.
// Typically, you only close the DB when the program exits.
//
// The opts parameter is optional. If nil, uses default options.
//
// [simple]: https://github.com/nalgeon/redka/blob/main/example/simple/main.go
// [modernc]: https://github.com/nalgeon/redka/blob/main/example/modernc/main.go
func Open(path string, opts *Options) (*DB, error) {
// Open the read-write database handle.
dataSource := sqlx.DataSource(path, true)
rw, err := sql.Open(driverName, dataSource)
if err != nil {
return nil, err
}
// Open the read-only database handle.
dataSource = sqlx.DataSource(path, false)
ro, err := sql.Open(driverName, dataSource)
if err != nil {
return nil, err
}
// Create the database-backed repository.
sdb, err := sqlx.Open(rw, ro, newTx)
if err != nil {
return nil, err
}
// Create the database instance.
opts = applyOptions(defaultOptions, opts)
rdb := &DB{
DB: sdb,
hashDB: rhash.New(rw, ro),
keyDB: rkey.New(rw, ro),
listDB: rlist.New(rw, ro),
setDB: rset.New(rw, ro),
stringDB: rstring.New(rw, ro),
zsetDB: rzset.New(rw, ro),
log: opts.Logger,
}
rdb.bg = rdb.startBgManager()
return rdb, nil
}
// Hash returns the hash repository.
// A hash (hashmap) is a field-value map associated with a key.
// Use the hash repository to work with individual hashmaps
// and their fields.
func (db *DB) Hash() *rhash.DB {
return db.hashDB
}
// Key returns the key repository.
// A key is a unique identifier for a data structure
// (string, list, hash, etc.). Use the key repository
// to manage all keys regardless of their type.
func (db *DB) Key() *rkey.DB {
return db.keyDB
}
// List returns the list repository.
// A list is a sequence of strings ordered by insertion order.
// Use the list repository to work with lists and their elements.
func (db *DB) List() *rlist.DB {
return db.listDB
}
// Set returns the set repository.
// A set is an unordered collection of unique strings.
// Use the set repository to work with individual sets
// and their elements, and to perform set operations.
func (db *DB) Set() *rset.DB {
return db.setDB
}
// Str returns the string repository.
// A string is a slice of bytes associated with a key.
// Use the string repository to work with individual strings.
func (db *DB) Str() *rstring.DB {
return db.stringDB
}
// ZSet returns the sorted set repository.
// A sorted set (zset) is a like a set, but each element has a score,
// and elements are ordered by score from low to high.
// Use the sorted set repository to work with individual sets
// and their elements, and to perform set operations.
func (db *DB) ZSet() *rzset.DB {
return db.zsetDB
}
// Update executes a function within a writable transaction.
// See the [tx] example for details.
//
// [tx]: https://github.com/nalgeon/redka/blob/main/example/tx/main.go
func (db *DB) Update(f func(tx *Tx) error) error {
return db.DB.Update(f)
}
// UpdateContext executes a function within a writable transaction.
// See the [tx] example for details.
//
// [tx]: https://github.com/nalgeon/redka/blob/main/example/tx/main.go
func (db *DB) UpdateContext(ctx context.Context, f func(tx *Tx) error) error {
return db.DB.UpdateContext(ctx, f)
}
// View executes a function within a read-only transaction.
// See the [tx] example for details.
//
// [tx]: https://github.com/nalgeon/redka/blob/main/example/tx/main.go
func (db *DB) View(f func(tx *Tx) error) error {
return db.DB.View(f)
}
// ViewContext executes a function within a read-only transaction.
// See the [tx] example for details.
//
// [tx]: https://github.com/nalgeon/redka/blob/main/example/tx/main.go
func (db *DB) ViewContext(ctx context.Context, f func(tx *Tx) error) error {
return db.DB.ViewContext(ctx, f)
}
// Close closes the database.
// It's safe for concurrent use by multiple goroutines.
func (db *DB) Close() error {
db.bg.Stop()
var allErr error
if err := db.RW.Close(); err != nil {
allErr = err
}
if err := db.RO.Close(); allErr == nil {
allErr = err
}
return allErr
}
// startBgManager starts the goroutine than runs
// in the background and deletes expired keys.
// Triggers every 60 seconds, deletes up all expired keys.
func (db *DB) startBgManager() *time.Ticker {
// TODO: needs further investigation. Deleting all keys may be expensive
// and lead to timeouts for concurrent write operations.
// Adaptive limits based on the number of changed keys may be a solution.
// (see https://redis.io/docs/management/config-file/ > SNAPSHOTTING)
// And it doesn't help that SQLite's drivers do not support DELETE LIMIT,
// so we have to use DELETE IN (SELECT ...), which is more expensive.
const interval = 60 * time.Second
const nKeys = 0
ticker := time.NewTicker(interval)
go func() {
for range ticker.C {
count, err := db.keyDB.DeleteExpired(nKeys)
if err != nil {
db.log.Error("bg: delete expired keys", "error", err)
} else {
db.log.Info("bg: delete expired keys", "count", count)
}
}
}()
return ticker
}
// Tx is a Redis-like database transaction.
// Same as [DB], Tx provides access to data structures like keys,
// strings, and hashes. The difference is that you call Tx methods
// within a transaction managed by [DB.Update] or [DB.View].
//
// See the [tx] example for details.
//
// [tx]: https://github.com/nalgeon/redka/blob/main/example/tx/main.go
type Tx struct {
tx sqlx.Tx
hashTx *rhash.Tx
keyTx *rkey.Tx
listTx *rlist.Tx
setTx *rset.Tx
strTx *rstring.Tx
zsetTx *rzset.Tx
}
// newTx creates a new database transaction.
func newTx(tx sqlx.Tx) *Tx {
return &Tx{tx: tx,
hashTx: rhash.NewTx(tx),
keyTx: rkey.NewTx(tx),
listTx: rlist.NewTx(tx),
setTx: rset.NewTx(tx),
strTx: rstring.NewTx(tx),
zsetTx: rzset.NewTx(tx),
}
}
// Hash returns the hash transaction.
func (tx *Tx) Hash() *rhash.Tx {
return tx.hashTx
}
// Keys returns the key transaction.
func (tx *Tx) Key() *rkey.Tx {
return tx.keyTx
}
// List returns the list transaction.
func (tx *Tx) List() *rlist.Tx {
return tx.listTx
}
// Set returns the set transaction.
func (tx *Tx) Set() *rset.Tx {
return tx.setTx
}
// Str returns the string transaction.
func (tx *Tx) Str() *rstring.Tx {
return tx.strTx
}
// ZSet returns the sorted set transaction.
func (tx *Tx) ZSet() *rzset.Tx {
return tx.zsetTx
}
// applyOptions applies custom options to the
// default options and returns the result.
func applyOptions(opts Options, custom *Options) *Options {
if custom == nil {
return &opts
}
if custom.Logger != nil {
opts.Logger = custom.Logger
}
return &opts
}