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[bugfix] move SQLite pragmas into connection string (#2171)
* move SQLite pragmas into connection string Signed-off-by: kim <grufwub@gmail.com> * use url.Values type for SQLite connection preferences Signed-off-by: kim <grufwub@gmail.com> * set SQLite URI prefs properly using _pragma query key Signed-off-by: kim <grufwub@gmail.com> * add notes on SQLite connection preferences Signed-off-by: kim <grufwub@gmail.com> * fix typo Signed-off-by: kim <grufwub@gmail.com> * add one extra line regarding connection pooling Signed-off-by: kim <grufwub@gmail.com> --------- Signed-off-by: kim <grufwub@gmail.com>
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kim
GitHub
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1ee99fc165
commit
4eb77ff5d7
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@ -25,9 +25,9 @@
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"encoding/pem"
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"errors"
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"fmt"
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"net/url"
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"os"
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"runtime"
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"strconv"
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"strings"
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"time"
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@ -140,14 +140,6 @@ func NewBunDBService(ctx context.Context, state *state.State) (db.DB, error) {
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db.AddQueryHook(tracing.InstrumentBun())
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}
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// execute sqlite pragmas *after* adding database hook;
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// this allows the pragma queries to be logged
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if t == "sqlite" {
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if err := sqlitePragmas(ctx, db); err != nil {
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return nil, err
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}
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}
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// table registration is needed for many-to-many, see:
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// https://bun.uptrace.dev/orm/many-to-many-relation/
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for _, t := range registerTables {
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@ -296,42 +288,8 @@ func sqliteConn(ctx context.Context) (*DB, error) {
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return nil, fmt.Errorf("'%s' was not set when attempting to start sqlite", config.DbAddressFlag())
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}
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// Drop anything fancy from DB address
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address = strings.Split(address, "?")[0] // drop any provided query strings
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address = strings.TrimPrefix(address, "file:") // we'll prepend this later ourselves
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// build our own SQLite preferences
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prefs := []string{
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// use immediate transaction lock mode to fail quickly if tx can't lock
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// see https://pkg.go.dev/modernc.org/sqlite#Driver.Open
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"_txlock=immediate",
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}
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if address == ":memory:" {
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log.Warn(ctx, "using sqlite in-memory mode; all data will be deleted when gts shuts down; this mode should only be used for debugging or running tests")
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// Use random name for in-memory instead of ':memory:', so
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// multiple in-mem databases can be created without conflict.
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address = uuid.NewString()
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// in-mem-specific preferences
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prefs = append(prefs, []string{
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"mode=memory", // indicate in-memory mode using query
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"cache=shared", // shared cache so that tests don't fail
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}...)
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}
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// rebuild address string with our derived preferences
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address = "file:" + address
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for i, q := range prefs {
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var prefix string
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if i == 0 {
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prefix = "?"
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} else {
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prefix = "&"
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}
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address += prefix + q
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}
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// Build SQLite connection address with prefs.
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address = buildSQLiteAddress(address)
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// Open new DB instance
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sqldb, err := sql.Open("sqlite", address)
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@ -462,49 +420,107 @@ func deriveBunDBPGOptions() (*pgx.ConnConfig, error) {
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return cfg, nil
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}
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// sqlitePragmas sets desired sqlite pragmas based on configured values, and
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// logs the results of the pragma queries. Errors if something goes wrong.
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func sqlitePragmas(ctx context.Context, db *DB) error {
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var pragmas [][]string
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// buildSQLiteAddress will build an SQLite address string from given config input,
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// appending user defined SQLite connection preferences (e.g. cache_size, journal_mode etc).
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func buildSQLiteAddress(addr string) string {
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// Notes on SQLite preferences:
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//
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// - SQLite by itself supports setting a subset of its configuration options
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// via URI query arguments in the connection. Namely `mode` and `cache`.
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// This is the same situation for the directly transpiled C->Go code in
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// modernc.org/sqlite, i.e. modernc.org/sqlite/lib, NOT the Go SQL driver.
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//
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// - `modernc.org/sqlite` has a "shim" around it to allow the directly
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// transpiled C code to be usable with a more native Go API. This is in
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// the form of a `database/sql/driver.Driver{}` implementation that calls
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// through to the transpiled C code.
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//
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// - The SQLite shim we interface with adds support for setting ANY of the
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// configuration options via query arguments, through using a special `_pragma`
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// query key that specifies SQLite PRAGMAs to set upon opening each connection.
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// As such you will see below that most config is set with the `_pragma` key.
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//
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// - As for why we're setting these PRAGMAs by connection string instead of
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// directly executing the PRAGMAs ourselves? That's to ensure that all of
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// configuration options are set across _all_ of our SQLite connections, given
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// that we are a multi-threaded (not directly in a C way) application and that
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// each connection is a separate SQLite instance opening the same database.
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// And the `database/sql` package provides transparent connection pooling.
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// Some data is shared between connections, for example the `journal_mode`
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// as that is set in a bit of the file header, but to be sure with the other
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// settings we just add them all to the connection URI string.
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//
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// - We specifically set the `busy_timeout` PRAGMA before the `journal_mode`.
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// When Write-Ahead-Logging (WAL) is enabled, in order to handle the issues
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// that may arise between separate concurrent read/write threads racing for
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// the same database file (and write-ahead log), SQLite will sometimes return
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// an `SQLITE_BUSY` error code, which indicates that the query was aborted
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// due to a data race and must be retried. The `busy_timeout` PRAGMA configures
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// a function handler that SQLite can use internally to handle these data races,
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// in that it will attempt to retry the query until the `busy_timeout` time is
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// reached. And for whatever reason (:shrug:) SQLite is very particular about
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// setting this BEFORE the `journal_mode` is set, otherwise you can end up
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// running into more of these `SQLITE_BUSY` return codes than you might expect.
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//
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// - One final thing (I promise!): `SQLITE_BUSY` is only handled by the internal
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// `busy_timeout` handler in the case that a data race occurs contending for
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// table locks. THERE ARE STILL OTHER SITUATIONS IN WHICH THIS MAY BE RETURNED!
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// As such, we use our wrapping DB{} and Tx{} types (in "db.go") which make use
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// of our own retry-busy handler.
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// Drop anything fancy from DB address
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addr = strings.Split(addr, "?")[0] // drop any provided query strings
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addr = strings.TrimPrefix(addr, "file:") // we'll prepend this later ourselves
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// build our own SQLite preferences
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// as a series of URL encoded values
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prefs := make(url.Values)
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// use immediate transaction lock mode to fail quickly if tx can't lock
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// see https://pkg.go.dev/modernc.org/sqlite#Driver.Open
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prefs.Add("_txlock", "immediate")
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if addr == ":memory:" {
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log.Warn(nil, "using sqlite in-memory mode; all data will be deleted when gts shuts down; this mode should only be used for debugging or running tests")
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// Use random name for in-memory instead of ':memory:', so
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// multiple in-mem databases can be created without conflict.
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addr = uuid.NewString()
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// in-mem-specific preferences
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// (shared cache so that tests don't fail)
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prefs.Add("mode", "memory")
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prefs.Add("cache", "shared")
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}
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if dur := config.GetDbSqliteBusyTimeout(); dur > 0 {
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// Set the user provided SQLite busy timeout
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// NOTE: MUST BE SET BEFORE THE JOURNAL MODE.
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prefs.Add("_pragma", fmt.Sprintf("busy_timeout(%d)", dur.Milliseconds()))
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}
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if mode := config.GetDbSqliteJournalMode(); mode != "" {
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// Set the user provided SQLite journal mode
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pragmas = append(pragmas, []string{"journal_mode", mode})
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// Set the user provided SQLite journal mode.
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prefs.Add("_pragma", fmt.Sprintf("journal_mode(%s)", mode))
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}
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if mode := config.GetDbSqliteSynchronous(); mode != "" {
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// Set the user provided SQLite synchronous mode
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pragmas = append(pragmas, []string{"synchronous", mode})
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// Set the user provided SQLite synchronous mode.
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prefs.Add("_pragma", fmt.Sprintf("synchronous(%s)", mode))
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}
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if size := config.GetDbSqliteCacheSize(); size > 0 {
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if sz := config.GetDbSqliteCacheSize(); sz > 0 {
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// Set the user provided SQLite cache size (in kibibytes)
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// Prepend a '-' character to this to indicate to sqlite
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// that we're giving kibibytes rather than num pages.
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// https://www.sqlite.org/pragma.html#pragma_cache_size
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s := "-" + strconv.FormatUint(uint64(size/bytesize.KiB), 10)
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pragmas = append(pragmas, []string{"cache_size", s})
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prefs.Add("_pragma", fmt.Sprintf("cache_size(-%d)", uint64(sz/bytesize.KiB)))
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}
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if timeout := config.GetDbSqliteBusyTimeout(); timeout > 0 {
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t := strconv.FormatInt(timeout.Milliseconds(), 10)
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pragmas = append(pragmas, []string{"busy_timeout", t})
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}
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for _, p := range pragmas {
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pk := p[0]
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pv := p[1]
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if _, err := db.ExecContext(ctx, "PRAGMA ?=?", bun.Ident(pk), bun.Safe(pv)); err != nil {
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return fmt.Errorf("error executing sqlite pragma %s: %w", pk, err)
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}
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var res string
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if err := db.NewRaw("PRAGMA ?", bun.Ident(pk)).Scan(ctx, &res); err != nil {
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return fmt.Errorf("error scanning sqlite pragma %s: %w", pv, err)
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}
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log.Infof(ctx, "sqlite pragma %s set to %s", pk, res)
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}
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return nil
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var b strings.Builder
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b.WriteString("file:")
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b.WriteString(addr)
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b.WriteString("?")
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b.WriteString(prefs.Encode())
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return b.String()
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}
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