ingest: Add support for ledger entry change type "restore"

Author: urvisavla

ingest/change.go

@@ -42,6 +42,8 @@ type Change struct {
 	// The type of the ledger entry being changed.
 	Type xdr.LedgerEntryType
 
+	ChangeType xdr.LedgerEntryChangeType
+
 	// The state of the LedgerEntry before the change. This will be nil if the entry was created.
 	Pre *xdr.LedgerEntry
 
@@ -144,25 +146,49 @@ func GetChangesFromLedgerEntryChanges(ledgerEntryChanges xdr.LedgerEntryChanges)
 		case xdr.LedgerEntryChangeTypeLedgerEntryCreated:
 			created := entryChange.MustCreated()
 			changes = append(changes, Change{
-				Type: created.Data.Type,
-				Pre:  nil,
-				Post: &created,
+				Type:       created.Data.Type,
+				Pre:        nil,
+				Post:       &created,
+				ChangeType: xdr.LedgerEntryChangeTypeLedgerEntryCreated,
 			})
 		case xdr.LedgerEntryChangeTypeLedgerEntryUpdated:
 			state := ledgerEntryChanges[i-1].MustState()
 			updated := entryChange.MustUpdated()
 			changes = append(changes, Change{
-				Type: state.Data.Type,
-				Pre:  &state,
-				Post: &updated,
+				Type:       state.Data.Type,
+				Pre:        &state,
+				Post:       &updated,
+				ChangeType: xdr.LedgerEntryChangeTypeLedgerEntryUpdated,
 			})
 		case xdr.LedgerEntryChangeTypeLedgerEntryRemoved:
 			state := ledgerEntryChanges[i-1].MustState()
 			changes = append(changes, Change{
-				Type: state.Data.Type,
-				Pre:  &state,
-				Post: nil,
+				Type:       state.Data.Type,
+				Pre:        &state,
+				Post:       nil,
+				ChangeType: xdr.LedgerEntryChangeTypeLedgerEntryRemoved,
+			})
+		case xdr.LedgerEntryChangeTypeLedgerEntryRestored:
+			restored := entryChange.MustRestored()
+			if i > 0 {
+				if state, ok := ledgerEntryChanges[i-1].GetState(); ok {
+					changes = append(changes, Change{
+						Type:       restored.Data.Type,
+						Pre:        &state,
+						Post:       &restored,
+						ChangeType: xdr.LedgerEntryChangeTypeLedgerEntryRestored,
+					})
+					continue
+				}
+			}
+
+			changes = append(changes, Change{
+				Type:       restored.Data.Type,
+				Pre:        nil,
+				Post:       &restored,
+				ChangeType: xdr.LedgerEntryChangeTypeLedgerEntryRestored,
 			})
+
 		case xdr.LedgerEntryChangeTypeLedgerEntryState:
 			continue
 		default:
@@ -223,16 +249,7 @@ func sortChanges(changes []Change) {
 
 // LedgerEntryChangeType returns type in terms of LedgerEntryChangeType.
 func (c Change) LedgerEntryChangeType() xdr.LedgerEntryChangeType {
-	switch {
-	case c.Pre == nil && c.Post != nil:
-		return xdr.LedgerEntryChangeTypeLedgerEntryCreated
-	case c.Pre != nil && c.Post == nil:
-		return xdr.LedgerEntryChangeTypeLedgerEntryRemoved
-	case c.Pre != nil && c.Post != nil:
-		return xdr.LedgerEntryChangeTypeLedgerEntryUpdated
-	default:
-		panic("Invalid state of Change (Pre == nil && Post == nil)")
-	}
+	return c.ChangeType
 }
 
 // getLiquidityPool gets the most recent state of the LiquidityPool that exists or existed.

ingest/change_compactor.go

@@ -25,34 +25,58 @@ import (
 //
 //  1. If the change is CREATED it checks if any change connected to given entry
 //     is already in the cache. If not, it adds CREATED change. Otherwise, if
-//     existing change is:
-//     a. CREATED it returns error because we can't add an entry that already
+//     existing change is
+//     a. CREATED: return an error because we can't add an entry that already exists.
+//     b. UPDATED: return an error because we can't add an entry that already exists.
+//     c. REMOVED: entry exists in the DB but was marked for removal; change the type
+//     to UPDATED and update the new value.
+//     d. RESTORED: return an error as the RESTORED change indicates the entry already
 //     exists.
-//     b. UPDATED it returns error because we can't add an entry that already
-//     exists.
-//     c. REMOVED it means that due to previous transitions we want to remove
-//     this from a DB what means that it already exists in a DB so we need to
-//     update the type of change to UPDATED.
+//
 //  2. If the change is UPDATE it checks if any change connected to given entry
 //     is already in the cache. If not, it adds UPDATE change. Otherwise, if
-//     existing change is:
-//     a. CREATED it means that due to previous transitions we want to create
-//     this in a DB what means that it doesn't exist in a DB so we need to
-//     update the entry but stay with CREATED type.
-//     b. UPDATED we simply update it with the new value.
+//     existing change is
+//     a. CREATED: We want to create this in a DB which means that it doesn't exist
+//     in a DB so we need to update the entry but stay with CREATED type.
+//     b. UPDATED: update it with the new value.
 //     c. REMOVED it means that at this point in the ledger the entry is removed
 //     so updating it returns an error.
-//  3. If the change is REMOVE it checks if any change connected to given entry
-//     is already in the cache. If not, it adds REMOVE change. Otherwise, if
-//     existing change is:
-//     a. CREATED it means that due to previous transitions we want to create
-//     this in a DB what means that it doesn't exist in a DB. If it was
-//     created and removed in the same ledger it's a noop so we remove entry
-//     from the cache.
-//     b. UPDATED we simply update it to be a REMOVE change because the UPDATE
-//     change means the entry exists in a DB.
-//     c. REMOVED it returns error because we can't remove an entry that was
-//     already removed.
+//     d. RESTORED: update it with the new value but keep the type as RESTORED.
+//
+//  3. If the change is REMOVED, it checks if any change related to the given entry
+//     already exists in the cache. If not, it adds the `REMOVED` change. Otherwise,
+//     if existing change is
+//     a. CREATED: due to previous transitions we want to create
+//     this in a DB which means that it doesn't exist in a DB. If it was created and
+//     removed in the same ledger it's a noop so we remove the entry from the cache.
+//     b. UPDATED: update it to be a REMOVE change because the UPDATE change means
+//     the entry exists in a DB.
+//     c. REMOVED: return an error because we can't remove an entry that was already
+//     removed.
+//     d. RESTORED: if the item was previously restored from an archived state, it means
+//     it already exists in the DB, so change it to REMOVED type. If the restored item
+//     was evicted, it doesn't exist in the DB, so it's a noop so remove the entry from
+//     the cache.
+//
+//  4. If the change is RESTORED for an evicted entry (pre is nil), it checks if any
+//     change related to the given entry already exists in the cache. If not, it adds
+//     the RESTORED change. Otherwise, if existing change is
+//     a. CREATED: return an error because we can't restore and entry that already exists.
+//     b. UPDATED: return an error because we can't restore an entry that already exists.
+//     c. REMOVED: entry exists in the DB but was marked for removal; change the
+//     type to RESTORED and update the new value.
+//     d. RESTORED: return an error as the RESTORED change indicates the entry
+//     already exists.
+//
+//  5. If the change is RESTORED for an archived entry (pre and post not nil), it checks
+//     if any change related to the given entry already exists in the cache. If not,
+//     it adds the RESTORED change. Otherwise, if existing change is
+//     a. CREATED: it means that it doesn't exist in the DB so we need to update the
+//     entry but stay with CREATED type.
+//     b. UPDATED: update it with the new value and change the type to RESTORED.
+//     c. REMOVED: return an error because we can not RESTORE an entry that was already
+//     removed.
+//     d. RESTORED: update it with the new value.
 type ChangeCompactor struct {
 	// ledger key => Change
 	cache          map[string]Change
@@ -75,13 +99,15 @@ func NewChangeCompactor() *ChangeCompactor {
 // cache takes too much memory, you apply changes returned by GetChanges and
 // create a new ChangeCompactor object to continue ingestion.
 func (c *ChangeCompactor) AddChange(change Change) error {
-	switch {
-	case change.Pre == nil && change.Post != nil:
+	switch change.ChangeType {
+	case xdr.LedgerEntryChangeTypeLedgerEntryCreated:
 		return c.addCreatedChange(change)
-	case change.Pre != nil && change.Post != nil:
+	case xdr.LedgerEntryChangeTypeLedgerEntryUpdated:
 		return c.addUpdatedChange(change)
-	case change.Pre != nil && change.Post == nil:
+	case xdr.LedgerEntryChangeTypeLedgerEntryRemoved:
 		return c.addRemovedChange(change)
+	case xdr.LedgerEntryChangeTypeLedgerEntryRestored:
+		return c.addRestoredChange(change)
 	default:
 		return errors.New("Unknown entry change state")
 	}
@@ -110,11 +136,10 @@ func (c *ChangeCompactor) addCreatedChange(change Change) error {
 
 	switch existingChange.LedgerEntryChangeType() {
 	case xdr.LedgerEntryChangeTypeLedgerEntryCreated:
-		return NewStateError(errors.Errorf(
-			"can't create an entry that already exists (ledger key = %s)",
-			base64.StdEncoding.EncodeToString(ledgerKey),
-		))
+		fallthrough
 	case xdr.LedgerEntryChangeTypeLedgerEntryUpdated:
+		fallthrough
+	case xdr.LedgerEntryChangeTypeLedgerEntryRestored:
 		return NewStateError(errors.Errorf(
 			"can't create an entry that already exists (ledger key = %s)",
 			base64.StdEncoding.EncodeToString(ledgerKey),
@@ -123,9 +148,10 @@ func (c *ChangeCompactor) addCreatedChange(change Change) error {
 		// If existing type is removed it means that this entry does exist
 		// in a DB so we update entry change.
 		c.cache[ledgerKeyString] = Change{
-			Type: key.Type,
-			Pre:  existingChange.Pre,
-			Post: change.Post,
+			Type:       key.Type,
+			Pre:        existingChange.Pre,
+			Post:       change.Post,
+			ChangeType: xdr.LedgerEntryChangeTypeLedgerEntryUpdated,
 		}
 	default:
 		return errors.Errorf("Unknown LedgerEntryChangeType: %d", existingChange.LedgerEntryChangeType())
@@ -157,26 +183,25 @@ func (c *ChangeCompactor) addUpdatedChange(change Change) error {
 
 	switch existingChange.LedgerEntryChangeType() {
 	case xdr.LedgerEntryChangeTypeLedgerEntryCreated:
+		fallthrough
+	case xdr.LedgerEntryChangeTypeLedgerEntryUpdated:
+		fallthrough
+	case xdr.LedgerEntryChangeTypeLedgerEntryRestored:
 		// If existing type is created it means that this entry does not
 		// exist in a DB so we update entry change.
 		c.cache[ledgerKeyString] = Change{
-			Type: key.Type,
-			Pre:  existingChange.Pre, // = nil
-			Post: change.Post,
-		}
-	case xdr.LedgerEntryChangeTypeLedgerEntryUpdated:
-		c.cache[ledgerKeyString] = Change{
-			Type: key.Type,
-			Pre:  existingChange.Pre,
-			Post: change.Post,
+			Type:       key.Type,
+			Pre:        existingChange.Pre, // = nil for created type
+			Post:       change.Post,
+			ChangeType: existingChange.ChangeType,
 		}
 	case xdr.LedgerEntryChangeTypeLedgerEntryRemoved:
 		return NewStateError(errors.Errorf(
 			"can't update an entry that was previously removed (ledger key = %s)",
 			base64.StdEncoding.EncodeToString(ledgerKey),
 		))
 	default:
-		return errors.Errorf("Unknown LedgerEntryChangeType: %d", existingChange.Type)
+		return errors.Errorf("Unknown LedgerEntryChangeType: %d", existingChange.LedgerEntryChangeType())
 	}
 
 	return nil
@@ -210,22 +235,108 @@ func (c *ChangeCompactor) addRemovedChange(change Change) error {
 		delete(c.cache, ledgerKeyString)
 	case xdr.LedgerEntryChangeTypeLedgerEntryUpdated:
 		c.cache[ledgerKeyString] = Change{
-			Type: key.Type,
-			Pre:  existingChange.Pre,
-			Post: nil,
+			Type:       key.Type,
+			Pre:        existingChange.Pre,
+			Post:       nil,
+			ChangeType: change.ChangeType,
 		}
 	case xdr.LedgerEntryChangeTypeLedgerEntryRemoved:
 		return NewStateError(errors.Errorf(
 			"can't remove an entry that was previously removed (ledger key = %s)",
 			base64.StdEncoding.EncodeToString(ledgerKey),
 		))
+	case xdr.LedgerEntryChangeTypeLedgerEntryRestored:
+		if existingChange.Pre == nil {
+			// Entry was created and removed in the same ledger; deleting it is effectively a noop.
+			delete(c.cache, ledgerKeyString)
+		} else {
+			// If the entry exists, we mark it as removed by setting Post to nil.
+			c.cache[ledgerKeyString] = Change{
+				Type:       existingChange.Type,
+				Pre:        existingChange.Pre,
+				Post:       nil,
+				ChangeType: change.ChangeType,
+			}
+		}
 	default:
-		return errors.Errorf("Unknown LedgerEntryChangeType: %d", existingChange.Type)
+		return errors.Errorf("Unknown LedgerEntryChangeType: %d", existingChange.LedgerEntryChangeType())
 	}
 
 	return nil
 }
 
+// addRestoredChange adds a change to the cache, but returns an error if the restore
+// change is unexpected.
+func (c *ChangeCompactor) addRestoredChange(change Change) error {
+	// safe, since we later cast to string (causing a copy)
+	key, err := change.Post.LedgerKey()
+	if err != nil {
+		return errors.Wrap(err, "error getting ledger key for updated entry")
+	}
+	ledgerKey, err := c.encodingBuffer.UnsafeMarshalBinary(key)
+	if err != nil {
+		return errors.Wrap(err, "error marshaling ledger key for updated entry")
+	}
+
+	ledgerKeyString := string(ledgerKey)
+
+	existingChange, exist := c.cache[ledgerKeyString]
+	if !exist {
+		c.cache[ledgerKeyString] = change
+		return nil
+	}
+	// If 'Pre' is nil, it indicates that an item previously *evicted* is being restored.
+	if change.Pre == nil {
+		switch existingChange.ChangeType {
+		case xdr.LedgerEntryChangeTypeLedgerEntryCreated:
+			fallthrough
+		case xdr.LedgerEntryChangeTypeLedgerEntryUpdated:
+			fallthrough
+		case xdr.LedgerEntryChangeTypeLedgerEntryRestored:
+			return NewStateError(errors.Errorf(
+				"can't restore an entry that already exists (ledger key = %s)",
+				base64.StdEncoding.EncodeToString(ledgerKey),
+			))
+		case xdr.LedgerEntryChangeTypeLedgerEntryRemoved:
+			c.cache[ledgerKeyString] = Change{
+				Type:       key.Type,
+				Pre:        existingChange.Pre,
+				Post:       change.Post,
+				ChangeType: change.ChangeType,
+			}
+		default:
+			return errors.Errorf("Unknown LedgerEntryChangeType: %d", existingChange.LedgerEntryChangeType())
+		}
+	} else {
+		// If 'Pre' is not nil, it indicates that an item previously *archived* is being restored.
+		switch existingChange.ChangeType {
+		case xdr.LedgerEntryChangeTypeLedgerEntryCreated:
+			c.cache[ledgerKeyString] = Change{
+				Type:       key.Type,
+				Pre:        nil,
+				Post:       change.Post,
+				ChangeType: existingChange.ChangeType,
+			}
+		case xdr.LedgerEntryChangeTypeLedgerEntryUpdated:
+			fallthrough
+		case xdr.LedgerEntryChangeTypeLedgerEntryRestored:
+			c.cache[ledgerKeyString] = Change{
+				Type:       key.Type,
+				Pre:        existingChange.Pre,
+				Post:       change.Post,
+				ChangeType: change.ChangeType,
+			}
+		case xdr.LedgerEntryChangeTypeLedgerEntryRemoved:
+			return NewStateError(errors.Errorf(
+				"can't restore an entry that was previously removed (ledger key = %s)", ledgerKey,
+			))
+		default:
+			return errors.Errorf("Unknown LedgerEntryChangeType: %d", existingChange.LedgerEntryChangeType())
+		}
+	}
+	return nil
+}
+
 // GetChanges returns a slice of Changes in the cache. The order of changes is
 // random but each change is connected to a separate entry.
 func (c *ChangeCompactor) GetChanges() []Change {