channel_db.load_data() is slow, slowing down startup time (when trampoline is disabled).
util.list_enabled_bits() is one of the main contributors to the slowness, called by validate_features().
One could argue that we could even simply *not* call validate_features for gossip messages as part of load_data,
as they have already been validated before storing them in the db. However re-validating them there is a good
clean-up/sanity check IMO. Note that what is considered "valid" can change over time, so just because validate_features
passed when we originally received and stored a gossip message, it might no longer be valid a year later if the bolts change.
This caching decreases the time needed for load_data on two different machines / gossip dbs as below:
47 sec -> 10 sec
18 sec -> 6 sec
If instead of caching, I just rm the validate_features() calls, the benchmarks are almost identical, within noise.
That is, the cache looks really effective.
(the rest of the slowness is mostly due to lnmsg.decode_msg)
```
>>> lnutil.validate_features.cache_info()
CacheInfo(hits=172674, misses=287, maxsize=1000, currsize=277)
```
-----
We could alternatively directly cache util.list_enabled_bits (instead of validate_features).
That would be a bit slower and might end up using a lot more memory in some cases I think, but maybe conceptually would be cleaner.
Also note that if validate_features() raises an exception, that is not cached.
```
$ export ELECTRUM_LINTERS=E9,E101,E129,E273,E274,E703,E71,E722,F5,F6,F7,F8,W191,W29,B
$ export ELECTRUM_LINTERS_IGNORE=B007,B009,B010,B019,B036,F541,F841
$ flake8 . --count --select="$ELECTRUM_LINTERS" --ignore="$ELECTRUM_LINTERS_IGNORE" --show-source --statistics --exclude "*_pb2.py,electrum/_vendor/"
./electrum/commands.py:98:1: F811 redefinition of unused 'format_satoshis' from line 48
def format_satoshis(x):
^
./electrum/commands.py:437:9: F811 redefinition of unused 'Mnemonic' from line 62
from .mnemonic import Mnemonic
^
./electrum/gui/qt/wizard/wallet.py:37:5: F811 redefinition of unused 'Daemon' from line 14
from electrum.daemon import Daemon
^
./electrum/lntransport.py:14:1: F811 redefinition of unused 'Optional' from line 12
from typing import NamedTuple, List, Tuple, Mapping, Optional, TYPE_CHECKING, Union, Dict, Set, Sequence
^
./electrum/lntransport.py:14:1: F811 redefinition of unused 'TYPE_CHECKING' from line 12
from typing import NamedTuple, List, Tuple, Mapping, Optional, TYPE_CHECKING, Union, Dict, Set, Sequence
^
./electrum/plugin.py:966:13: F811 redefinition of unused 'hid' from line 593
import hid
^
./electrum/plugin.py:1040:13: F811 redefinition of unused 'hid' from line 593
import hid
^
./electrum/util.py:44:1: F811 redefinition of unused 'json' from line 26
import json
^
./electrum/util.py:46:1: F811 redefinition of unused 'NamedTuple' from line 29
from typing import NamedTuple, Optional
^
./electrum/util.py:46:1: F811 redefinition of unused 'Optional' from line 29
from typing import NamedTuple, Optional
^
./electrum/util.py:1456:56: F811 redefinition of unused 'traceback' from line 34
async def __aexit__(self, exc_type, exc_value, traceback):
^
./electrum/wallet_db.py:536:9: F811 redefinition of unused 'LOCAL' from line 46
LOCAL = 1
^
./electrum/wallet_db.py:537:9: F811 redefinition of unused 'REMOTE' from line 46
REMOTE = -1
^
./tests/test_bitcoin.py:28:1: F811 redefinition of unused 'bitcoin' from line 9
from electrum import crypto, constants, bitcoin
^
./tests/test_txbatcher.py:11:1: F811 redefinition of unused 'Transaction' from line 7
from electrum.transaction import Transaction, PartialTxInput, PartialTxOutput, TxOutpoint
^
./tests/test_wallet_vertical.py:20:1: F811 redefinition of unused 'Transaction' from line 10
from electrum.transaction import Transaction, PartialTxOutput, tx_from_any, Sighash
^
16 F811 redefinition of unused 'format_satoshis' from line 48
16
```
```
./electrum/commands.py:144:9: F824 `global known_commands` is unused: name is never assigned in scope
global known_commands
^
./electrum/commands.py:1916:9: F824 `global known_commands` is unused: name is never assigned in scope
global known_commands
^
./electrum/gui/qt/main_window.py:2405:13: F824 `nonlocal done` is unused: name is never assigned in scope
nonlocal done
^
./electrum/i18n.py:52:5: F824 `global language` is unused: name is never assigned in scope
global language
^
./electrum/plugin.py:189:9: F824 `global _root_permission_cache` is unused: name is never assigned in scope
global _root_permission_cache
^
5 F824 `global known_commands` is unused: name is never assigned in scope
5
```
With `txbatcher.SLEEP_INTERVAL = 0.01`, on my laptop, the batcher called try_broadcasting() even before next_tx() effectively awaited _tx_event.
This resulted in the test failing due to timeout.
Basically, if the txbatcher.SLEEP_INTERVAL was too low, the 2-4 event loop iterations needed to await _tx_event.wait() took too long.
(note that the exact number of event loop iterations needed depends on the python version and the OS)
