fix another order by id instead of balanceDate.

Have the now calculation for contribution links within the semaphore lock

backend/src/graphql/resolver/TransactionLinkResolver.ts

@@ -166,13 +166,13 @@ export class TransactionLinkResolver {
   ): Promise<boolean> {
     const clientTimezoneOffset = getClientTimezoneOffset(context)
     const user = getUser(context)
-    const now = new Date()
 
     if (code.match(/^CL-/)) {
       // acquire lock
       const releaseLock = await TRANSACTIONS_LOCK.acquire()
       console.log(`locked for redeemTransactionLink ${code}`)
       logger.info('redeem contribution link...')
+      const now = new Date()
       const queryRunner = getConnection().createQueryRunner()
       await queryRunner.connect()
       await queryRunner.startTransaction('REPEATABLE READ')
@@ -277,7 +277,7 @@ export class TransactionLinkResolver {
           .select('transaction')
           .from(DbTransaction, 'transaction')
           .where('transaction.userId = :id', { id: user.id })
-          .orderBy('transaction.balanceDate', 'DESC')
+          .orderBy('transaction.id', 'DESC')
           .getOne()
         let newBalance = new Decimal(0)
 
@@ -318,6 +318,7 @@ export class TransactionLinkResolver {
       }
       return true
     } else {
+      const now = new Date()
       const transactionLink = await DbTransactionLink.findOneOrFail({ code })
       const linkedUser = await DbUser.findOneOrFail(
         { id: transactionLink.userId },
@@ -328,6 +329,9 @@ export class TransactionLinkResolver {
         throw new Error('Cannot redeem own transaction link.')
       }
 
+      // TODO: The now check should be done within the semaphore lock,
+      // since the program might wait a while till it is ready to proceed
+      // writing the transaction.
       if (transactionLink.validUntil.getTime() < now.getTime()) {
         throw new Error('Transaction Link is not valid anymore.')
       }