Merge bitcoin/bitcoin#23289: test: add stress tests for initialization

d9803f7a0a33688f7429cf10384244f4770851ca test: add stress tests for initialization (James O'Beirne)
23f85616a8d9c9a1b054e492eca4d199028f34dc test: add node.chain_path and node.debug_log_path (James O'Beirne)

Pull request description:

  In the course of coming up with a test plan for #23280, I thought it would be neat to include a Python snippet showing how I tested the initialization process. I quickly realized I was reinventing the functional test framework... so here's a new test.

  This change bangs init around like the Fonz hitting a jukebox. It adds some interesting (read: lazy and random) coverage for the initialization process by
  - interrupting init with SIGTERM after certain log statements,
  - interrupting init at random points, and
  - starting init with some essential data missing (block files, block indices, etc.) to test init error paths.

  As far as I can tell, some of these code paths are uncovered otherwise (namely the startup errors).

  ---

  Incidentally, I think I may have uncovered some kind of a bug or race condition with indexing initialization based on an intermittent failure in this testcase. This test sometimes fails after shutting down immediately after `loadblk` thread start:
  ```
  2021-10-15T21:14:51.295000Z TestFramework (INFO): Starting node and will exit after line 'loadblk thread start'
    36   │ 2021-10-15T21:14:51.296000Z TestFramework.node0 (DEBUG): bitcoind started, waiting for RPC to come up
    37   │ 2021-10-15T21:14:51.493000Z TestFramework (INFO): terminating node after 110 log lines seen
    38   │ 2021-10-15T21:14:51.625000Z TestFramework (INFO): Starting node and will exit after line 'txindex thread start'
    39   │ 2021-10-15T21:14:51.625000Z TestFramework.node0 (DEBUG): bitcoind started, waiting for RPC to come up
    ------> [[ FAILURE HERE ]] 2021-10-15T21:15:21.626000Z TestFramework (WARNING): missed line {bail_line}; bailing now after {num_lines} lines
  ```
  and then fails to start up afterwards. Combined logs showing `Error: txindex best block of the index goes beyond pruned data`, when the node under test is not pruned:

  ```
    node0 2021-10-15T21:16:51.848439Z [shutoff] [validationinterface.cpp:244] [ChainStateFlushed] Enqueuing ChainStateFlushed: block hash=1014bc4ff4917602ae53d10e9dfe230af4b7d52a6cdaa8a47798b9c288180907
     node0 2021-10-15T21:16:51.848954Z [shutoff] [init.cpp:302] [Shutdown] Shutdown: done
     test  2021-10-15T21:16:51.882000Z TestFramework (ERROR): Unexpected exception caught during testing
       Traceback (most recent call last):
         File "/home/james/src/bitcoin/test/functional/test_framework/test_framework.py", line 132, in main
   self.run_test()
         File "/home/james/src/bitcoin/./test/functional/stress_init.py", line 87, in run_test
   check_clean_start()
         File "/home/james/src/bitcoin/./test/functional/stress_init.py", line 60, in check_clean_start
   node.wait_for_rpc_connection()
         File "/home/james/src/bitcoin/test/functional/test_framework/test_node.py", line 224, in wait_for_rpc_connection
   raise FailedToStartError(self._node_msg(
       test_framework.test_node.FailedToStartError: [node 0] bitcoind exited with status 1 during initialization
     test  2021-10-15T21:16:51.882000Z TestFramework (DEBUG): Closing down network thread
     test  2021-10-15T21:16:51.933000Z TestFramework (INFO): Stopping nodes
     test  2021-10-15T21:16:51.933000Z TestFramework.node0 (DEBUG): Stopping node

     node0 stderr Error: txindex best block of the index goes beyond pruned data. Please disable the index or reindex (which will download the whole blockchain again)
     node0 stderr Error: txindex best block of the index goes beyond pruned data. Please disable the index or reindex (which will download the whole blockchain again)
     node0 stderr Error: txindex best block of the index goes beyond pruned data. Please disable the index or reindex (which will download the whole blockchain again)
     node0 stderr Error: txindex best block of the index goes beyond pruned data. Please disable the index or reindex (which will download the whole blockchain again)
     node0 stderr Error: txindex best block of the index goes beyond pruned data. Please disable the index or reindex (which will download the whole blockchain again)
  ```

ACKs for top commit:
  laanwj:
    Code review ACK d9803f7a0a33688f7429cf10384244f4770851ca

Tree-SHA512: 4d80dc399daf199a6222e81e47d12d830dc7af07355eddbb7f52479a676a645b8d3d45093ff54a9295f01a163b2f4fe0e038e83fc269969e03d4cfda69eaf111

3 files changed, 194 insertions, 3 deletions

diff --git a/test/functional/feature_init.py b/test/functional/feature_init.py
new file mode 100755
index 0000000000..cffbd40271
--- /dev/null
+++ b/test/functional/feature_init.py
@@ -0,0 +1,182 @@
+#!/usr/bin/env python3
+# Copyright (c) 2021 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Stress tests related to node initialization."""
+import random
+import time
+import os
+from pathlib import Path
+
+from test_framework.test_framework import BitcoinTestFramework, SkipTest
+from test_framework.test_node import ErrorMatch
+from test_framework.util import assert_equal
+
+
+class InitStressTest(BitcoinTestFramework):
+    """
+    Ensure that initialization can be interrupted at a number of points and not impair
+    subsequent starts.
+    """
+
+    def set_test_params(self):
+        self.setup_clean_chain = False
+        self.num_nodes = 1
+
+    def run_test(self):
+        """
+        - test terminating initialization after seeing a certain log line.
+        - test terminating init after seeing a random number of log lines.
+        - test removing certain essential files to test startup error paths.
+        """
+        # TODO: skip Windows for now since it isn't clear how to SIGTERM.
+        #
+        # Windows doesn't support `process.terminate()`.
+        # and other approaches (like below) don't work:
+        #
+        #   os.kill(node.process.pid, signal.CTRL_C_EVENT)
+        if os.name == 'nt':
+            raise SkipTest("can't SIGTERM on Windows")
+
+        self.stop_node(0)
+        node = self.nodes[0]
+
+        def sigterm_node():
+            node.process.terminate()
+            node.process.wait()
+            node.debug_log_path.unlink()
+            node.debug_log_path.touch()
+
+        def check_clean_start():
+            """Ensure that node restarts successfully after various interrupts."""
+            # TODO: add -txindex=1 to fully test index initiatlization.
+            # See https://github.com/bitcoin/bitcoin/pull/23289#discussion_r735159180 for
+            # a discussion of the related bug.
+            node.start()
+            node.wait_for_rpc_connection()
+            assert_equal(200, node.getblockcount())
+
+        lines_to_terminate_after = [
+            'scheduler thread start',
+            'Loading P2P addresses',
+            'Loading banlist',
+            'Loading block index',
+            'Switching active chainstate',
+            'Loaded best chain:',
+            'init message: Verifying blocks',
+            'loadblk thread start',
+            # TODO: reenable - see above TODO
+            # 'txindex thread start',
+            'net thread start',
+            'addcon thread start',
+            'msghand thread start',
+        ]
+        if self.is_wallet_compiled():
+            lines_to_terminate_after.append('Verifying wallet')
+
+        for terminate_line in lines_to_terminate_after:
+            self.log.info(f"Starting node and will exit after line '{terminate_line}'")
+            node.start(
+                # TODO: add -txindex=1 to fully test index initiatlization.
+                # extra_args=['-txindex=1'],
+            )
+            logfile = open(node.debug_log_path, 'r', encoding='utf8')
+
+            MAX_SECS_TO_WAIT = 30
+            start = time.time()
+            num_lines = 0
+
+            while True:
+                line = logfile.readline()
+                if line:
+                    num_lines += 1
+
+                if line and terminate_line.lower() in line.lower():
+                    self.log.debug(f"Terminating node after {num_lines} log lines seen")
+                    sigterm_node()
+                    break
+
+                if (time.time() - start) > MAX_SECS_TO_WAIT:
+                    raise AssertionError(
+                        f"missed line {terminate_line}; terminating now after {num_lines} lines")
+
+                if node.process.poll() is not None:
+                    raise AssertionError(f"node failed to start (line: '{terminate_line}')")
+
+        check_clean_start()
+        num_total_logs = len(node.debug_log_path.read_text().splitlines())
+        self.stop_node(0)
+
+        self.log.info(
+            f"Terminate at some random point in the init process (max logs: {num_total_logs})")
+
+        for _ in range(40):
+            terminate_after = random.randint(1, num_total_logs)
+            self.log.debug(f"Starting node and will exit after {terminate_after} lines")
+            node.start(
+                # TODO: add -txindex=1 to fully test index initiatlization.
+                # extra_args=['-txindex=1'],
+            )
+            logfile = open(node.debug_log_path, 'r', encoding='utf8')
+
+            MAX_SECS_TO_WAIT = 10
+            start = time.time()
+            num_lines = 0
+
+            while True:
+                line = logfile.readline()
+                if line:
+                    num_lines += 1
+
+                if num_lines >= terminate_after or (time.time() - start) > MAX_SECS_TO_WAIT:
+                    self.log.debug(f"Terminating node after {num_lines} log lines seen")
+                    sigterm_node()
+                    break
+
+                if node.process.poll() is not None:
+                    raise AssertionError("node failed to start")
+
+        check_clean_start()
+        self.stop_node(0)
+
+        self.log.info("Test startup errors after removing certain essential files")
+
+        files_to_disturb = {
+            'blocks/index/*.ldb': 'Error opening block database.',
+            'chainstate/*.ldb': 'Error opening block database.',
+            'blocks/blk*.dat': 'Error loading block database.',
+        }
+
+        for file_patt, err_fragment in files_to_disturb.items():
+            target_file = list(node.chain_path.glob(file_patt))[0]
+
+            self.log.info(f"Tweaking file to ensure failure {target_file}")
+            bak_path = str(target_file) + ".bak"
+            target_file.rename(bak_path)
+
+            # TODO: at some point, we should test perturbing the files instead of removing
+            # them, e.g.
+            #
+            # contents = target_file.read_bytes()
+            # tweaked_contents = bytearray(contents)
+            # tweaked_contents[50:250] = b'1' * 200
+            # target_file.write_bytes(bytes(tweaked_contents))
+            #
+            # At the moment I can't get this to work (bitcoind loads successfully?) so
+            # investigate doing this later.
+
+            node.assert_start_raises_init_error(
+                # TODO: add -txindex=1 to fully test index initiatlization.
+                # extra_args=['-txindex=1'],
+                expected_msg=err_fragment,
+                match=ErrorMatch.PARTIAL_REGEX,
+            )
+
+            self.log.info(f"Restoring file from {bak_path} and restarting")
+            Path(bak_path).rename(target_file)
+            check_clean_start()
+            self.stop_node(0)
+
+
+if __name__ == '__main__':
+    InitStressTest().main()
diff --git a/test/functional/test_framework/test_node.py b/test/functional/test_framework/test_node.py
index 269f2442a9..b3279666b2 100755
--- a/test/functional/test_framework/test_node.py
+++ b/test/functional/test_framework/test_node.py
@@ -20,6 +20,7 @@ import urllib.parse
 import collections
 import shlex
 import sys
+from pathlib import Path
 
 from .authproxy import JSONRPCException
 from .descriptors import descsum_create
@@ -380,13 +381,20 @@ class TestNode():
     def wait_until_stopped(self, timeout=BITCOIND_PROC_WAIT_TIMEOUT):
         wait_until_helper(self.is_node_stopped, timeout=timeout, timeout_factor=self.timeout_factor)
 
+    @property
+    def chain_path(self) -> Path:
+        return Path(self.datadir) / self.chain
+
+    @property
+    def debug_log_path(self) -> Path:
+        return self.chain_path / 'debug.log'
+
     @contextlib.contextmanager
     def assert_debug_log(self, expected_msgs, unexpected_msgs=None, timeout=2):
         if unexpected_msgs is None:
             unexpected_msgs = []
         time_end = time.time() + timeout * self.timeout_factor
-        debug_log = os.path.join(self.datadir, self.chain, 'debug.log')
-        with open(debug_log, encoding='utf-8') as dl:
+        with open(self.debug_log_path, encoding='utf-8') as dl:
             dl.seek(0, 2)
             prev_size = dl.tell()
 
@@ -394,7 +402,7 @@ class TestNode():
 
         while True:
             found = True
-            with open(debug_log, encoding='utf-8') as dl:
+            with open(self.debug_log_path, encoding='utf-8') as dl:
                 dl.seek(prev_size)
                 log = dl.read()
             print_log = " - " + "\n - ".join(log.splitlines())
diff --git a/test/functional/test_runner.py b/test/functional/test_runner.py
index b9b4edf0ba..35cab8f6ec 100755
--- a/test/functional/test_runner.py
+++ b/test/functional/test_runner.py
@@ -278,6 +278,7 @@ BASE_SCRIPTS = [
     'wallet_taproot.py',
     'p2p_fingerprint.py',
     'feature_uacomment.py',
+    'feature_init.py',
     'wallet_coinbase_category.py --legacy-wallet',
     'wallet_coinbase_category.py --descriptors',
     'feature_filelock.py',