Retrieve ledger entry changes within a range

This code invokes the stellar-core binary (as configured in ledgerbackend.CaptiveCoreConfig) to replay ledgers from a given ledger range. It uses the ingest.LedgerChangeReader to read changes from each ledger (xdr.LedgerCloseMeta) and categorizes the changes based on whether they represent created, updated, or deleted ledger entries. The ingest.Change structure is used to capture individual changes, and the code tracks various types of changes such as those related to fees, transactions, or operations.

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))
	}
}

Sample Response:

>> 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
}