Adds a dict of sent receipts to act as a cache and avoid sending the same data more than once

The dict is supposed to be reset periodically so it does not grow unbounded

pisa/carrier.py

@@ -38,8 +38,16 @@ class Carrier:
     """
     The :class:`Carrier` is the class in charge of interacting with ``bitcoind`` to send/get transactions. It uses
     :obj:`Receipt` objects to report about the sending outcome.
+
+    Attributes:
+        issued_receipts (:obj:`dict`): a dictionary of issued receipts to prevent resending the same transaction over
+            and over. It should periodically be reset to prevent it from growing unbounded.
+
     """
 
+    def __init__(self):
+        self.issued_receipts = {}
+
     # NOTCOVERED
     def send_transaction(self, rawtx, txid):
         """
@@ -53,6 +61,12 @@ class Carrier:
             :obj:`Receipt`: A receipt reporting whether the transaction was successfully delivered or not and why.
         """
 
+        if txid in self.issued_receipts:
+            logger.info("Transaction already sent", txid=txid)
+            receipt = self.issued_receipts[txid]
+
+            return receipt
+
         try:
             logger.info("Pushing transaction to the network", txid=txid, rawtx=rawtx)
             bitcoin_cli().sendrawtransaction(rawtx)
@@ -101,6 +115,8 @@ class Carrier:
                 logger.error("JSONRPCException", method="Carrier.send_transaction", error=e.error)
                 receipt = Receipt(delivered=False, reason=UNKNOWN_JSON_RPC_EXCEPTION)
 
+        self.issued_receipts[txid] = receipt
+
         return receipt
 
     @staticmethod