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http_client.go
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http_client.go
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// SPDX-License-Identifier: Apache-2.0
// Copyright Authors of Cilium
package statedb
import (
"bytes"
"context"
"encoding/base64"
"encoding/json"
"errors"
"io"
"net/http"
"net/url"
)
// NewRemoteTable creates a new handle for querying a remote StateDB table over the HTTP.
// Example usage:
//
// devices := statedb.NewRemoteTable[*tables.Device](url.Parse("http://localhost:8080/db"), "devices")
//
// // Get all devices ordered by name.
// iter, errs := devices.LowerBound(ctx, tables.DeviceByName(""))
// for device, revision, ok := iter.Next(); ok; device, revision, ok = iter.Next() { ... }
//
// // Get device by name.
// iter, errs := devices.Get(ctx, tables.DeviceByName("eth0"))
// if dev, revision, ok := iter.Next(); ok { ... }
//
// // Get devices in revision order, e.g. oldest changed devices first.
// iter, errs = devices.LowerBound(ctx, statedb.ByRevision(0))
func NewRemoteTable[Obj any](base *url.URL, table TableName) *RemoteTable[Obj] {
return &RemoteTable[Obj]{base: base, tableName: table}
}
type RemoteTable[Obj any] struct {
client http.Client
base *url.URL
tableName TableName
}
func (t *RemoteTable[Obj]) SetTransport(tr *http.Transport) {
t.client.Transport = tr
}
func (t *RemoteTable[Obj]) query(ctx context.Context, lowerBound bool, q Query[Obj]) (iter Iterator[Obj], errChan <-chan error) {
// Use a channel to return errors so we can use the same Iterator[Obj] interface as StateDB does.
errChanSend := make(chan error, 1)
errChan = errChanSend
key := base64.StdEncoding.EncodeToString(q.key)
queryReq := QueryRequest{
Key: key,
Table: t.tableName,
Index: q.index,
LowerBound: lowerBound,
}
bs, err := json.Marshal(&queryReq)
if err != nil {
errChanSend <- err
return
}
url := t.base.JoinPath("/query")
req, err := http.NewRequestWithContext(ctx, http.MethodGet, url.String(), bytes.NewBuffer(bs))
if err != nil {
errChanSend <- err
return
}
req.Header.Add("Content-Type", "application/json")
req.Header.Add("Accept", "application/json")
resp, err := t.client.Do(req)
if err != nil {
errChanSend <- err
return
}
return &remoteGetIterator[Obj]{json.NewDecoder(resp.Body), errChanSend}, errChan
}
func (t *RemoteTable[Obj]) Get(ctx context.Context, q Query[Obj]) (Iterator[Obj], <-chan error) {
return t.query(ctx, false, q)
}
func (t *RemoteTable[Obj]) LowerBound(ctx context.Context, q Query[Obj]) (Iterator[Obj], <-chan error) {
return t.query(ctx, true, q)
}
type remoteGetIterator[Obj any] struct {
decoder *json.Decoder
errChan chan error
}
// responseObject is a typed counterpart of [queryResponseObject]
type responseObject[Obj any] struct {
Rev uint64 `json:"rev"`
Obj Obj `json:"obj"`
Err string `json:"err,omitempty"`
}
func (it *remoteGetIterator[Obj]) Next() (obj Obj, revision Revision, ok bool) {
if it.decoder == nil {
return
}
var resp responseObject[Obj]
err := it.decoder.Decode(&resp)
errString := ""
if err != nil {
if errors.Is(err, io.EOF) {
close(it.errChan)
return
}
errString = "Decode error: " + err.Error()
} else {
errString = resp.Err
}
if errString != "" {
it.decoder = nil
it.errChan <- errors.New(errString)
return
}
obj = resp.Obj
revision = resp.Rev
ok = true
return
}