don't deserialize mempool in a thread

lbry/wallet/server/mempool.py

@@ -6,13 +6,11 @@
 # and warranty status of this software.
 
 """Mempool handling."""
-import os
 import asyncio
 import itertools
 import time
 from abc import ABC, abstractmethod
 from collections import defaultdict
-from concurrent.futures.thread import ThreadPoolExecutor
 from prometheus_client import Histogram
 
 import attr
@@ -117,7 +115,6 @@ class MemPool:
         # Prevents mempool refreshes during fee histogram calculation
         self.lock = asyncio.Lock()
         self.wakeup = asyncio.Event()
-        self.executor = ThreadPoolExecutor(max(os.cpu_count() - 1, 1))
         self.mempool_process_time_metric = mempool_process_time_metric
 
     async def _logging(self, synchronized_event):
@@ -135,15 +132,11 @@ class MemPool:
             await synchronized_event.wait()
 
     async def _refresh_histogram(self, synchronized_event):
-        try:
         while True:
             await synchronized_event.wait()
             async with self.lock:
-                    # Threaded as can be expensive
-                    await asyncio.get_event_loop().run_in_executor(self.executor, self._update_histogram, 100_000)
+                self._update_histogram(100_000)
             await asyncio.sleep(self.coin.MEMPOOL_HISTOGRAM_REFRESH_SECS)
-        finally:
-            self.executor.shutdown(wait=True)
 
     def _update_histogram(self, bin_size):
         # Build a histogram by fee rate
@@ -286,11 +279,10 @@ class MemPool:
         hex_hashes_iter = (hash_to_hex_str(hash) for hash in hashes)
         raw_txs = await self.api.raw_transactions(hex_hashes_iter)
 
-        def deserialize_txs():    # This function is pure
         to_hashX = self.coin.hashX_from_script
         deserializer = self.coin.DESERIALIZER
 
-            txs = {}
+        tx_map = {}
         for hash, raw_tx in zip(hashes, raw_txs):
             # The daemon may have evicted the tx from its
             # mempool or it may have gotten in a block
@@ -304,12 +296,8 @@ class MemPool:
                                if not txin.is_generation())
             txout_pairs = tuple((to_hashX(txout.pk_script), txout.value)
                                 for txout in tx.outputs)
-                txs[hash] = MemPoolTx(txin_pairs, None, txout_pairs,
+            tx_map[hash] = MemPoolTx(txin_pairs, None, txout_pairs,
                                      0, tx_size)
-            return txs
-
-        # Thread this potentially slow operation so as not to block
-        tx_map = await asyncio.get_event_loop().run_in_executor(self.executor, deserialize_txs)
 
         # Determine all prevouts not in the mempool, and fetch the
         # UTXO information from the database.  Failed prevout lookups