Recuperar cambios de las entradas del ledger dentro de un rango

Este código invoca el binario stellar-core (según lo configurado en ledgerbackend.CaptiveCoreConfig) para reproducir ledgers desde un rango de ledger dado. Utiliza el ingest.LedgerChangeReader para leer cambios de cada ledger (xdr.LedgerCloseMeta) y categoriza los cambios según si representan entradas de ledger creadas, actualizadas o eliminadas. La estructura ingest.Change se utiliza para capturar cambios individuales, y el código rastrea varios tipos de cambios, como los relacionados con tarifas, transacciones u operaciones.

Go

// Filename: change_entries.go

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"github.com/stellar/go/ingest"
	"github.com/stellar/go/ingest/ledgerbackend"
	"github.com/stellar/go/network"
	"github.com/stellar/go/xdr"
	"io"
)

func panicIf(err error) {
	if err != nil {
		panic(fmt.Errorf("An error occurred, panicking: %s\n", err))
	}
}

func getChangesFromLedger(passphrase string, ledger xdr.LedgerCloseMeta) []ingest.Change {
	changeReader, err := ingest.NewLedgerChangeReaderFromLedgerCloseMeta(passphrase, ledger)
	panicIf(err)
	defer changeReader.Close()

	changes := make([]ingest.Change, 0)
	for {
		change, err := changeReader.Read()
		if err == io.EOF {
			break
		}
		panicIf(err)
		changes = append(changes, change)
	}
	return changes
}

func getLedgers(config ledgerbackend.CaptiveCoreConfig, startingLedger uint32, endLedger uint32) []xdr.LedgerCloseMeta {
	captiveCore, err := ledgerbackend.NewCaptive(config)
	panicIf(err)

	ctx := context.Background()
	err = captiveCore.PrepareRange(ctx, ledgerbackend.BoundedRange(startingLedger, endLedger))
	panicIf(err)
	defer captiveCore.Close()

	var ledgers []xdr.LedgerCloseMeta
	for ledgerSeq := startingLedger; ledgerSeq <= endLedger; ledgerSeq++ {
		ledger, err := captiveCore.GetLedger(ctx, ledgerSeq)
		panicIf(err)
		ledgers = append(ledgers, ledger)
	}
	return ledgers
}

type ChangesInfo struct {
	LedgerEntriesCreated    int32
	LedgerEntriesUpdated    int32
	LedgerEntriesDeleted    int32
	FeeRelatedChanges       int32
	TxRelatedChanges        int32
	OperationRelatedChanges int32
}

func changeCausedBy(change ingest.Change) xdr.LedgerEntryChangeType {
	if change.Pre == nil && change.Post != nil {
		return xdr.LedgerEntryChangeTypeLedgerEntryCreated
	} else if change.Pre != nil && change.Post == nil {
		return xdr.LedgerEntryChangeTypeLedgerEntryRemoved
	} else if change.Pre != nil && change.Post != nil {
		return xdr.LedgerEntryChangeTypeLedgerEntryUpdated
	}
	// this should not happen
	panic(fmt.Errorf("unable to dertermine LedgerEntryChangeType from change"))
}

func main() {
	archiveURLs := network.PublicNetworkhistoryArchiveURLs
	networkPassphrase := network.PublicNetworkPassphrase
	captiveCoreToml, err := ledgerbackend.NewCaptiveCoreToml(ledgerbackend.CaptiveCoreTomlParams{
		NetworkPassphrase:  networkPassphrase,
		HistoryArchiveURLs: archiveURLs,
	})
	panicIf(err)

	config := ledgerbackend.CaptiveCoreConfig{
		// Change these based on your environment:
		BinaryPath:         "/usr/local/bin/stellar-core",
		NetworkPassphrase:  networkPassphrase,
		HistoryArchiveURLs: archiveURLs,
		Toml:               captiveCoreToml,
	}

	startingLedger := uint32(28921599) // Replace with your desired ledger number
	endLedger := startingLedger + 5

	// NOTE: connecting to pubnet and getting ledgers might take a while.
	ledgers := getLedgers(config, startingLedger, endLedger)

	for seq, ledgerMeta := range ledgers {
		fmt.Printf("Processing ledger: %d\n", startingLedger+uint32(seq))
		changes := getChangesFromLedger(config.NetworkPassphrase, ledgerMeta)
		info := ChangesInfo{}
		for _, change := range changes {

			/* Uncomment this code to print the change struct
			jsonData, err := json.MarshalIndent(change, "", "  ")
			panicIf(err)
			fmt.Println(string(jsonData))
			*/

			switch changeCausedBy(change) {
			case xdr.LedgerEntryChangeTypeLedgerEntryCreated:
				info.LedgerEntriesCreated++
			case xdr.LedgerEntryChangeTypeLedgerEntryRemoved:
				info.LedgerEntriesDeleted++
			case xdr.LedgerEntryChangeTypeLedgerEntryUpdated:
				info.LedgerEntriesUpdated++
			}

			switch change.Reason {
			case ingest.LedgerEntryChangeReasonFee:
				info.FeeRelatedChanges++
			case ingest.LedgerEntryChangeReasonTransaction:
				info.TxRelatedChanges++
			case ingest.LedgerEntryChangeReasonOperation:
				info.OperationRelatedChanges++
			default:
			}

		}
		jsonData, err := json.MarshalIndent(info, "", "  ")
		panicIf(err)
		fmt.Println(string(jsonData))
	}
}

Respuesta de Ejemplo:

>> go run ./change_entries.go

// Log lines truncated for clarity

Processing ledger: 28921599
{
  "LedgerEntriesCreated": 59,
  "LedgerEntriesUpdated": 907,
  "LedgerEntriesDeleted": 62,
  "FeeRelatedChanges": 227,
  "TxRelatedChanges": 227,
  "OperationRelatedChanges": 574
}
Processing ledger: 28921600
{
  "LedgerEntriesCreated": 58,
  "LedgerEntriesUpdated": 679,
  "LedgerEntriesDeleted": 58,
  "FeeRelatedChanges": 120,
  "TxRelatedChanges": 120,
  "OperationRelatedChanges": 555
}
Processing ledger: 28921601
{
  "LedgerEntriesCreated": 61,
  "LedgerEntriesUpdated": 885,
  "LedgerEntriesDeleted": 63,
  "FeeRelatedChanges": 224,
  "TxRelatedChanges": 224,
  "OperationRelatedChanges": 561
}
Processing ledger: 28921602
{
  "LedgerEntriesCreated": 57,
  "LedgerEntriesUpdated": 609,
  "LedgerEntriesDeleted": 56,
  "FeeRelatedChanges": 106,
  "TxRelatedChanges": 106,
  "OperationRelatedChanges": 510
}
Processing ledger: 28921603
{
  "LedgerEntriesCreated": 62,
  "LedgerEntriesUpdated": 922,
  "LedgerEntriesDeleted": 59,
  "FeeRelatedChanges": 230,
  "TxRelatedChanges": 230,
  "OperationRelatedChanges": 583
}
Processing ledger: 28921604
{
  "LedgerEntriesCreated": 61,
  "LedgerEntriesUpdated": 670,
  "LedgerEntriesDeleted": 58,
  "FeeRelatedChanges": 119,
  "TxRelatedChanges": 119,
  "OperationRelatedChanges": 551
}