add mempool.get_info, update relayfee comments

Adds the `mempool.get_info` rpc to fetch mempoolminfee, minrelaytxfee
and incrementalrelayfee from the daemons getmempoolinfo rpc.
Updates the relayfee comments as the fee returned by
`blockchain.relayfee` doesn't guarantee to get into the mempool as
previously stated in the docstrings.

Author: f321x

docs/rpc-interface.rst

@@ -98,6 +98,7 @@ A typical result is as follows (with annotated comments)::
           "getinfo": 3,
           "groups": 1,
           "mempool.get_fee_histogram": 3194,
+          "mempool.get_info": 121,
           "server.add_peer": 9,
           "server.banner": 740,
           "server.donation_address": 754,

src/electrumx/server/daemon.py

@@ -79,6 +79,9 @@ def __init__(
         self._networkinfo_cache = (None, 0)
         self._networkinfo_lock = asyncio.Lock()
 
+        self._mempoolinfo_cache = (None, 0)
+        self._mempoolinfo_lock = asyncio.Lock()
+
     async def __aenter__(self):
         self.session = aiohttp.ClientSession(connector=self.connector())
         return self
@@ -284,12 +287,38 @@ async def getnetworkinfo(self):
             self._networkinfo_cache = (val, time.time())
             return val
 
+    async def getmempoolinfo(self):
+        """Return the result of the 'getmempoolinfo' RPC call."""
+        async with self._mempoolinfo_lock:
+            cache_val, cache_time = self._mempoolinfo_cache
+            if time.time() - cache_time < 60:  # seconds
+                return cache_val
+            val = await self._send_single('getmempoolinfo')
+            self._mempoolinfo_cache = (val, time.time())
+            return val
+
     async def relayfee(self):
-        '''The minimum fee a low-priority tx must pay in order to be accepted
-        to the daemon's memory pool.'''
+        """Same as getmempoolinfo['minrelaytxfee'].
+        The minimum fee required for a transaction to be relayed on by the daemon to the
+        bitcoin network. Doesn't guarantee mempool acceptance."""
         network_info = await self.getnetworkinfo()
         return network_info['relayfee']
 
+    async def mempool_info(self) -> dict[str, float]:
+        """
+        returns: {
+            "mempoolminfee": Minimum fee rate in BTC/kvB for tx to be accepted. Is the maximum of minrelaytxfee and minimum mempool fee
+            "minrelaytxfee": Minimum relay fee for transactions in BTC/kvB, configured, static.
+            "incrementalrelayfee": Minimum fee rate increment for mempool limiting or replacement in BTC/kvB, static, configured.
+        }
+        """
+        mempool_info = await self.getmempoolinfo()
+        return {
+            'mempoolminfee': mempool_info['mempoolminfee'],
+            'minrelaytxfee': mempool_info['minrelaytxfee'],
+            'incrementalrelayfee': mempool_info['incrementalrelayfee'],
+        }
+
     async def getrawtransaction(self, hex_hash, verbose=False):
         '''Return the serialized raw transaction with the given hash.'''
         # Cast to int because some coin daemons are old and require it
@@ -350,8 +379,8 @@ async def estimatefee(self, block_count):
         return self.coin.ESTIMATE_FEE
 
     async def relayfee(self):
-        '''The minimum fee a low-priority tx must pay in order to be accepted
-        to the daemon's memory pool.'''
+        """The minimum fee required for a transaction to be relayed on by the server to the
+        bitcoin network. Doesn't guarantee mempool acceptance."""
         return self.coin.RELAY_FEE
 
 

src/electrumx/server/session.py

@@ -1396,11 +1396,22 @@ async def banner(self):
         return banner
 
     async def relayfee(self):
-        '''The minimum fee a low-priority tx must pay in order to be accepted
-        to the daemon's memory pool.'''
+        """The minimum fee required for a transaction to be relayed on by the daemon to the
+        bitcoin network. Doesn't guarantee mempool acceptance."""
         self.bump_cost(1.0)
         return await self.daemon_request('relayfee')
 
+    async def mempool_info(self):
+        """
+        returns: {
+            "mempoolminfee": Minimum fee rate in BTC/kvB for tx to be accepted. Is the maximum of minrelaytxfee and minimum mempool fee
+            "minrelaytxfee": Minimum relay fee for transactions in BTC/kvB, configured, static.
+            "incrementalrelayfee": Minimum fee rate increment for mempool limiting or replacement in BTC/kvB, static, configured.
+        }
+        """
+        self.bump_cost(1.0)
+        return await self.daemon_request('mempool_info')
+
     async def estimatefee(self, number, mode=None):
         '''The estimated transaction fee per kilobyte to be paid for a
         transaction to be included within a certain number of blocks.
@@ -1647,6 +1658,7 @@ def set_request_handlers(self, ptuple):
             'blockchain.transaction.get_merkle': self.transaction_merkle,
             'blockchain.transaction.id_from_pos': self.transaction_id_from_pos,
             'mempool.get_fee_histogram': self.compact_fee_histogram,
+            'mempool.get_info': self.mempool_info,
             'server.add_peer': self.add_peer,
             'server.banner': self.banner,
             'server.donation_address': self.donation_address,

tests/server/test_daemon.py

@@ -255,6 +255,21 @@ async def test_relayfee(daemon):
     assert await daemon.relayfee() == sats
 
 
+@pytest.mark.asyncio
+async def test_mempool_info(daemon):
+    bitcoin_per_kvb = 0.00002123
+    response = {
+        'mempoolminfee': bitcoin_per_kvb,
+        'minrelaytxfee': bitcoin_per_kvb,
+        'incrementalrelayfee': bitcoin_per_kvb,
+        'other': 'cruft',
+    }
+    daemon.session = ClientSessionGood(('getmempoolinfo', [], response))
+    expected_result = dict(response)
+    del expected_result['other']
+    assert await daemon.mempool_info() == expected_result
+
+
 @pytest.mark.asyncio
 async def test_mempool_hashes(daemon):
     hashes = ['hex_hash1', 'hex_hash2']