This package provides helper code for automatic retries of database transactions. It is primarily intended to be used against sqlc-generated code.
While not strictly necessary, this README assumes you have a pkg/database
directory containing your slqc.yaml, schema and queries; the sqlc.yaml
is configured such that your generated Go files are at pkg/database/gendb
within package gendb. If you have a different structure, modify your import
paths below as appropriate.
To get started, create a pkg/database/db.go. First, define a func Init()
which creates your database pool and then calls trxwrap.Init(), passing your
database handle and a function that wraps a transaction handle within your
sqlc-generated Queries object:
package database
import (
// ...
"github.com/Jille/trxwrap"
"github.com/you/yourproject/pkg/database/gendb"
)
var (
db trxwrap.TrxWrap[gendb.Queries]
)
func Init() {
// ...
pgx, err := pgxpool.ConnectConfig(context.Background(), pgxConfig)
if err != nil {
log.Fatal(err)
}
db = trxwrap.New(pgx, func(tx trxwrap.PGDBTX) *gendb.Queries {
return gendb.New(tx)
}
}Then, after this, you can wrap the transaction functions e.g. as:
func RunRWTransaction(ctx context.Context, isolationLevel pgx.TxIsoLevel, runner func(*gendb.Queries) error) error {
return db.RunRWTransaction(ctx, isolationLevel, runner)
}
func RunROTransaction(ctx context.Context, isolationLevel pgx.TxIsoLevel, runner func(*gendb.Queries) error) error {
return db.RunROTransaction(ctx, isolationLevel, runner)
}Now, you can write your transactions like this:
func GetStudents(ctx context.Context, enrolled bool) ([]Student, error) {
var res []Student
err := database.RunRWTransaction(ctx, pgx.RepeatableRead, func(q *gendb.Queries) error {
// Remember that the transaction can be re-run, so we need to start over
res = nil
students, err := q.GetStudents(ctx, gendb.GetStudentsParams{
Enrolled: enrolled,
})
if err != nil {
return err
}
for _, student := range students {
res = append(res, Student{
Name: student.Name,
Birthdate: student.Birthdate,
})
}
return nil
})
return res, err
}If your transaction fails because of a transient error, e.g. a database instance restarting or a TCP connection drop, the transaction will be retried after a while, performing at most 3 attempts. The error of the last attempt will be returned.