Merge #12479: RPC: Add child transactions to getrawmempool verbose output

1dfb4e7d7 [Tests] Check output of parent/child tx list from getrawmempool, getmempooldescendants, getmempoolancestors, and REST interface (Conor Scott)
fc44cb108 [RPC] Add list of child transactions to verbose output of getrawmempool (Conor Scott)

Pull request description:

  `bitcoin-cli getrawmempool true` only lists a transaction's parents in the `depends` field. This change adds a `spentby` field to the json response, which lists the transaction's children in the mempool.

  Currently the only way to find child transactions is to use `getrawmempool` or make another call to `getmempooldescendants` and search the response for transactions that list the parent_txid in the `depends` list, which is inefficient.

  This change allows direct lookup of children.

  Example Output
  ```
    "9a9b5733c0d89f207908cfa3fe17809bee71f629aa095c9f8754524e29e98ba4": {
      ...other geterawmempool data...
      "wtxid": "9a9b5733c0d89f207908cfa3fe17809bee71f629aa095c9f8754524e29e98ba4",
      "depends": [
        "bdd92851d5766a42aeb62af667bb422a116cab4e032bba5e3dd6efe5b4b40aa0"
      ],
      "spentby": [
        "dc5d3ec388a9121421208738a041ac30a22163bc2e17758f2275b6c51a15ba7b"
      ]
    },
  ```

Tree-SHA512: 83da7d421c9799a40ef65af3b7fdb586d6d87385f3f2ede3afd2c311725444b858f9d91cc110422a0fa31905779934fee07211ca6fe6b746792b83692c94b3ce

src/rpc/blockchain.cpp

@@ -372,6 +372,9 @@ std::string EntryDescriptionString()
            "    \"wtxid\" : hash,         (string) hash of serialized transaction, including witness data\n"
            "    \"depends\" : [           (array) unconfirmed transactions used as inputs for this transaction\n"
            "        \"transactionid\",    (string) parent transaction id\n"
+           "       ... ]\n"
+           "    \"spentby\" : [           (array) unconfirmed transactions spending outputs from this transaction\n"
+           "        \"transactionid\",    (string) child transaction id\n"
            "       ... ]\n";
 }
 
@@ -406,6 +409,15 @@ void entryToJSON(UniValue &info, const CTxMemPoolEntry &e)
     }
 
     info.pushKV("depends", depends);
+
+    UniValue spent(UniValue::VARR);
+    const CTxMemPool::txiter &it = mempool.mapTx.find(tx.GetHash());
+    const CTxMemPool::setEntries &setChildren = mempool.GetMemPoolChildren(it);
+    for (const CTxMemPool::txiter &childiter : setChildren) {
+        spent.push_back(childiter->GetTx().GetHash().ToString());
+    }
+
+    info.pushKV("spentby", spent);
 }
 
 UniValue mempoolToJSON(bool fVerbose)

test/functional/interface_rest.py

@@ -296,8 +296,10 @@ class RESTTest (BitcoinTestFramework):
         # check that there are our submitted transactions in the TX memory pool
         json_string = http_get_call(url.hostname, url.port, '/rest/mempool/contents'+self.FORMAT_SEPARATOR+'json')
         json_obj = json.loads(json_string)
-        for tx in txs:
+        for i, tx in enumerate(txs):
             assert_equal(tx in json_obj, True)
+            assert_equal(json_obj[tx]['spentby'], txs[i+1:i+2])
+            assert_equal(json_obj[tx]['depends'], txs[i-1:i])
 
         # now mine the transactions
         newblockhash = self.nodes[1].generate(1)

test/functional/mempool_packages.py

@@ -47,7 +47,7 @@ class MempoolPackagesTest(BitcoinTestFramework):
             value = sent_value
             chain.append(txid)
 
-        # Check mempool has MAX_ANCESTORS transactions in it, and descendant
+        # Check mempool has MAX_ANCESTORS transactions in it, and descendant and ancestor
         # count and fees should look correct
         mempool = self.nodes[0].getrawmempool(True)
         assert_equal(len(mempool), MAX_ANCESTORS)
@@ -55,6 +55,10 @@ class MempoolPackagesTest(BitcoinTestFramework):
         descendant_fees = 0
         descendant_size = 0
 
+        ancestor_size = sum([mempool[tx]['size'] for tx in mempool])
+        ancestor_count = MAX_ANCESTORS
+        ancestor_fees = sum([mempool[tx]['fee'] for tx in mempool])
+
         descendants = []
         ancestors = list(chain)
         for x in reversed(chain):
@@ -71,14 +75,43 @@ class MempoolPackagesTest(BitcoinTestFramework):
             assert_equal(mempool[x]['descendantsize'], descendant_size)
             descendant_count += 1
 
+            # Check that ancestor calculations are correct
+            assert_equal(mempool[x]['ancestorcount'], ancestor_count)
+            assert_equal(mempool[x]['ancestorfees'], ancestor_fees * COIN)
+            assert_equal(mempool[x]['ancestorsize'], ancestor_size)
+            ancestor_size -= mempool[x]['size']
+            ancestor_fees -= mempool[x]['fee']
+            ancestor_count -= 1
+
+            # Check that parent/child list is correct
+            assert_equal(mempool[x]['spentby'], descendants[-1:])
+            assert_equal(mempool[x]['depends'], ancestors[-2:-1])
+
             # Check that getmempooldescendants is correct
             assert_equal(sorted(descendants), sorted(self.nodes[0].getmempooldescendants(x)))
+
+            # Check getmempooldescendants verbose output is correct
+            for descendant, dinfo in self.nodes[0].getmempooldescendants(x, True).items():
+                assert_equal(dinfo['depends'], [chain[chain.index(descendant)-1]])
+                if dinfo['descendantcount'] > 1:
+                    assert_equal(dinfo['spentby'], [chain[chain.index(descendant)+1]])
+                else:
+                    assert_equal(dinfo['spentby'], [])
             descendants.append(x)
 
             # Check that getmempoolancestors is correct
             ancestors.remove(x)
             assert_equal(sorted(ancestors), sorted(self.nodes[0].getmempoolancestors(x)))
 
+            # Check that getmempoolancestors verbose output is correct
+            for ancestor, ainfo in self.nodes[0].getmempoolancestors(x, True).items():
+                assert_equal(ainfo['spentby'], [chain[chain.index(ancestor)+1]])
+                if ainfo['ancestorcount'] > 1:
+                    assert_equal(ainfo['depends'], [chain[chain.index(ancestor)-1]])
+                else:
+                    assert_equal(ainfo['depends'], [])
+
+
         # Check that getmempoolancestors/getmempooldescendants correctly handle verbose=true
         v_ancestors = self.nodes[0].getmempoolancestors(chain[-1], True)
         assert_equal(len(v_ancestors), len(chain)-1)
@@ -100,7 +133,7 @@ class MempoolPackagesTest(BitcoinTestFramework):
         for x in chain:
             ancestor_fees += mempool[x]['fee']
             assert_equal(mempool[x]['ancestorfees'], ancestor_fees * COIN + 1000)
-        
+
         # Undo the prioritisetransaction for later tests
         self.nodes[0].prioritisetransaction(txid=chain[0], fee_delta=-1000)
 
@@ -149,6 +182,7 @@ class MempoolPackagesTest(BitcoinTestFramework):
         vout = utxo[1]['vout']
 
         transaction_package = []
+        tx_children = []
         # First create one parent tx with 10 children
         (txid, sent_value) = self.chain_transaction(self.nodes[0], txid, vout, value, fee, 10)
         parent_transaction = txid
@@ -159,11 +193,17 @@ class MempoolPackagesTest(BitcoinTestFramework):
         for i in range(MAX_DESCENDANTS - 1):
             utxo = transaction_package.pop(0)
             (txid, sent_value) = self.chain_transaction(self.nodes[0], utxo['txid'], utxo['vout'], utxo['amount'], fee, 10)
+            if utxo['txid'] is parent_transaction:
+                tx_children.append(txid)
             for j in range(10):
                 transaction_package.append({'txid': txid, 'vout': j, 'amount': sent_value})
 
         mempool = self.nodes[0].getrawmempool(True)
         assert_equal(mempool[parent_transaction]['descendantcount'], MAX_DESCENDANTS)
+        assert_equal(sorted(mempool[parent_transaction]['spentby']), sorted(tx_children))
+
+        for child in tx_children:
+            assert_equal(mempool[child]['depends'], [parent_transaction])
 
         # Sending one more chained transaction will fail
         utxo = transaction_package.pop(0)
@@ -232,7 +272,7 @@ class MempoolPackagesTest(BitcoinTestFramework):
         signedtx = self.nodes[0].signrawtransactionwithwallet(rawtx)
         txid = self.nodes[0].sendrawtransaction(signedtx['hex'])
         sync_mempools(self.nodes)
-        
+
         # Now try to disconnect the tip on each node...
         self.nodes[1].invalidateblock(self.nodes[1].getbestblockhash())
         self.nodes[0].invalidateblock(self.nodes[0].getbestblockhash())