Inspired by https://www.npmjs.com/package/dataloader, this is a generic utility to be used as part of your application's data fetching layer to allow naive calls to databases and other services without sacrificing performance via caching and batching.
func getUsers(userIds []string) (map[string]User, map[string]error) {
...
}
const maxConcurrentBatches = 3
const maxBatchSize = 9999
batcher := NewQueryBatcher(getUsers, maxConcurrentBatches, maxBatchSize)
user, err := batcher.Load("user-id-0001")QueryBatcher's name says it all: it represents a pool that limits the number and size of simultaneous requests a service can make to a resource like a database. When more requests come in at once than are allowed by maxConcurrentBatches, these excess requests will be added to a batch (with a size capped at maxBatchSize) which will all be queried at once as soon as a current request finishes.
DataLoader is functionally the same as QueryBatcher, but with an added cache to prevent repeating calls after they've already been made.
For convenience, there are also the GormGetter and GormListGetter functions, which simplify lookups in databases managed by gorm.io/gorm
type User struct {
ID string `gorm:"primaryKey"`
Name string // not unique
...
}
userLoader := dataloader.NewDataLoader(
GormGetter(db, "id", func (usr User) string { return usr.ID }),
maxConcurrentBatches,
maxBatchSize,
)
user, err := batcher.Load("user-id-0001")
usersByNameLoader := dataloader.NewDataLoader(
GormListGetter(db, "name", func (tst User) string { return usr.Name }),
maxConcurrentBatches,
maxBatchSize,
)
users, err := batcher.Load("bob")