Documentation

Overview

    Package db defines common database interface.

    Index

    Constants

    This section is empty.

    Variables

    This section is empty.

    Functions

    func Kinds

    func Kinds() []string

      Kinds returns IDs of registered database implementations.

      func Register

      func Register(db Impl)

        Register registers a database implementation.

        Must be called during init() time.

        func VisitImpls

        func VisitImpls(cb func(db *Impl))

          VisitImpls calls the callback for all registered implementation.

          Types

          type DB

          type DB interface {
          	// Kind identifies this particular database implementation.
          	//
          	// Among other things it is used in Cloud Tasks messages involved in the
          	// implementation of the distributed sweeping.
          	Kind() string
          
          	// Defer defers the execution of the callback until the transaction lands.
          	//
          	// Panics if called outside of a transaction.
          	//
          	// The callback will receive the original non-transactional context.
          	Defer(context.Context, func(context.Context))
          
          	// SaveReminder persists reminder in a transaction context.
          	//
          	// Tags retriable errors as transient.
          	SaveReminder(context.Context, *reminder.Reminder) error
          
          	// DeleteReminder deletes reminder in a non-transaction context.
          	DeleteReminder(context.Context, *reminder.Reminder) error
          
          	// FetchRemindersMeta fetches Reminders with Ids in [low..high) range.
          	//
          	// RawPayload of Reminders should not be fetched.
          	// Both fresh & stale reminders should be fetched.
          	// The reminders should be returned in order of ascending Id.
          	//
          	// In case of error, partial result of fetched Reminders so far should be
          	// returned alongside the error. The caller will later call this method again
          	// to fetch the remaining of Reminders in range of [<lastReturned.Id+1> .. high).
          	FetchRemindersMeta(ctx context.Context, low, high string, limit int) ([]*reminder.Reminder, error)
          
          	// FetchReminderRawPayloads fetches raw payloads of a batch of Reminders.
          	//
          	// The Reminder objects are re-used in the returned batch.
          	// If any Reminder is no longer found, it is silently omitted in the returned
          	// batch.
          	// In case of any other error, partial result of fetched Reminders so far
          	// should be returned alongside the error.
          	FetchReminderRawPayloads(context.Context, []*reminder.Reminder) ([]*reminder.Reminder, error)
          }

            DB abstracts out specific storage implementation.

            func NonTxnDB

            func NonTxnDB(ctx context.Context, id string) DB

              NonTxnDB returns a database with given ID or nil if not registered.

              func TxnDB

              func TxnDB(ctx context.Context) (db DB)

                TxnDB returns a Database that matches the context or nil.

                The process has a list of database engines registered via Register. Given a context, TxnDB examines if it carries a transaction with any of the registered DBs.

                Panics if more than one database matches the context.

                type Impl

                type Impl struct {
                	// Kind identifies this particular DB implementation.
                	//
                	// Must match Kind() of the produced DB instance.
                	Kind string
                
                	// Module is name of the server module with DB implementation.
                	Module module.Name
                
                	// ProbeForTxn "probes" a context for an active transaction, returning a DB
                	// that can be used to transactionally submit reminders or nil if this is not
                	// a transactional context.
                	ProbeForTxn func(context.Context) DB
                
                	// NonTxn returns an instance of DB that can be used outside of
                	// transactions.
                	//
                	// This is used by the sweeper to enumerate reminders.
                	NonTxn func(context.Context) DB
                }

                  Impl knows how to instantiate DB instances.

                  Source Files