Add `--runtime_info_file` flag for ephemeral port discovery by pwojcikdev · Pull Request #5013 · nanocurrency/nano-node

pwojcikdev · 2026-01-26T18:34:46Z

New CLI Options

--runtime_info_file [path]

Writes a JSON file containing runtime information after the node starts. This is particularly useful when running with ephemeral ports (peering_port=0, rpc.port=0) where the actual bound ports are assigned by the OS.

Usage:

nano_node --daemon --runtime_info_file                     # Uses default: runtime_info.json                                                                                                                                                                                                                                                                                                                                            
nano_node --daemon --runtime_info_file /path/to/info.json  # Custom path

JSON output:

{                                                                                                                                                                                                                                                                                                                                                                                                                                       
  "peering_port": 54321,                                                                                                                                                                                                                                                                                                                                                                                                                
  "rpc_port": 54322,                                                                                                                                                                                                                                                                                                                                                                                                                    
  "node_id": "node_1abc..."                                                                                                                                                                                                                                                                                                                                                                                                             
}

Notes:

rpc_port is only included when RPC is enabled
File is automatically deleted on clean process exit (SIGINT/SIGTERM or RPC stop)

--pid_file [path] (improved)

Now uses the same automatic cleanup infrastructure. File is automatically deleted on process exit.

nano_node --daemon --pid_file                    # Uses default: nano_node.pid                                                                                                                                                                                                                                                                                                                                                          
nano_node --daemon --pid_file /path/to/node.pid  # Custom path

This should fix system test flakiness.

gr0vity-dev-bot · 2026-01-26T19:35:01Z

Test Results for Commit `1fe6305`

Pull Request 5013: Results
Overall Status: ❌

Test Case Results

✅ 5n4pr_conf_10k_bintree: PASS (Duration: 110s)
✅ 5n4pr_conf_10k_change: PASS (Duration: 123s)
✅ 5n4pr_conf_change_dependant: PASS (Duration: 140s)
✅ 5n4pr_conf_change_independant: PASS (Duration: 133s)
✅ 5n4pr_conf_send_dependant: PASS (Duration: 131s)
✅ 5n4pr_conf_send_independant: PASS (Duration: 114s)
✅ 5n4pr_rocks_10k_bintree: PASS (Duration: 109s)
❌ 5n4pr_rocks_10k_change: FAIL (Duration: 271s)
Log

Last updated: 2026-01-27 04:32:06 UTC

Copilot

Pull request overview

This pull request adds support for discovering ephemeral ports through a new --runtime_info_file flag and improves the existing --pid_file flag by implementing automatic cleanup on process exit.

Changes:

Introduces a runtime file management system that registers files for automatic cleanup on process exit using std::atexit()
Adds --runtime_info_file CLI flag that writes a JSON file containing the node's actual bound ports (peering_port, rpc_port) and node_id, particularly useful when using ephemeral ports (port=0)
Updates system tests to use ephemeral ports and the new runtime_info_file for discovering actual bound ports, eliminating hardcoded ports that caused test flakiness

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
nano/lib/runtime_files.hpp	New header defining runtime file management API for automatic cleanup of PID and runtime info files
nano/lib/runtime_files.cpp	Implementation of runtime file management with thread-safe registration and atexit-based cleanup
nano/lib/CMakeLists.txt	Added new runtime_files source files to build
nano/node/nodeconfig.hpp	Added runtime_info_file optional field to node_flags
nano/node/cli.cpp	Added --runtime_info_file CLI option with implicit value support
nano/node/network.cpp	Minor style change to use brace initialization for endpoint
nano/nano_node/daemon.hpp	Updated parameter name for clarity
nano/nano_node/daemon.cpp	Integrated runtime_info_file creation after node and RPC startup
nano/nano_node/entry.cpp	Refactored PID file handling to use new runtime_files infrastructure
systest/runtime_files.sh	New comprehensive test for PID file and runtime info file creation and cleanup
systest/rpc_stop.sh	Updated to use ephemeral ports and runtime_info_file for port discovery
systest/daemon_interrupt.sh	Updated to use ephemeral ports and runtime_info_file for readiness detection
systest/bind_failure.sh	Updated to use ephemeral ports and runtime_info_file instead of hardcoded ports

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Copilot · 2026-01-26T20:16:48Z

nano/nano_node/entry.cpp

+		nano::runtime_files::create_pid_file (pid_filepath);
+		std::cerr << "PID file created: " << pid_filepath << std::endl;


Similar to the runtime_info_file handling in daemon.cpp, if create_pid_file() throws an exception, there's no specific error handling. The exception will propagate and may not provide a clear error message to the user about what went wrong with PID file creation. Consider adding a try-catch block to provide a more informative error message.

Suggested change

nano::runtime_files::create_pid_file (pid_filepath);

std::cerr << "PID file created: " << pid_filepath << std::endl;

try

{

nano::runtime_files::create_pid_file (pid_filepath);

std::cerr << "PID file created: " << pid_filepath << std::endl;

}

catch (std::exception const & e)

{

std::cerr << "Failed to create PID file '" << pid_filepath << "': " << e.what () << std::endl;

return 1;

}

Copilot · 2026-01-26T20:16:48Z

nano/lib/runtime_files.cpp

+	{
+		std::lock_guard<std::mutex> lock (mutex);
+		registered_files.erase (path);
+	}
+
+	std::error_code ec;
+	std::filesystem::remove (path, ec);
+	// Ignore errors - file may not exist


The lock is released before the file is removed from the filesystem at line 66. This means another thread could re-insert the same path into registered_files between the erase and the actual file removal. While this is unlikely to cause issues in practice (since the file removal is best-effort anyway), it creates a small window where the state is inconsistent. Consider moving the filesystem removal inside the locked section, or document this behavior if it's intentional for performance reasons.

Suggested change

{

std::lock_guard<std::mutex> lock (mutex);

registered_files.erase (path);

}

std::error_code ec;

std::filesystem::remove (path, ec);

// Ignore errors - file may not exist

std::error_code ec;

{

std::lock_guard<std::mutex> lock (mutex);

registered_files.erase (path);

std::filesystem::remove (path, ec);

// Ignore errors - file may not exist

}

Copilot · 2026-01-26T20:16:49Z

nano/lib/runtime_files.cpp

+std::mutex mutex;
+std::set<std::filesystem::path> registered_files;
+bool atexit_registered = false;


The atexit_registered flag should be std::atomic<bool> to ensure thread safety. Currently, it's a plain bool that's accessed under a mutex lock, but the mutex is only held during the registration check and insert operation. If multiple threads call create() concurrently, there's a potential race condition where the mutex is released after checking atexit_registered but before std::atexit() completes, allowing another thread to register the handler multiple times. Using std::atomic<bool> would provide proper memory ordering guarantees.

Copilot · 2026-01-26T20:16:49Z

nano/lib/runtime_files.cpp

+	out << contents;
+	out.close ();


The file write operation should verify that the write succeeded before closing. Currently, out << contents may fail silently (e.g., disk full, permissions issue after opening). Consider checking the stream state after writing and before closing to ensure data was actually written successfully.

Suggested change

out << contents;

out.close ();

out << contents;

if (!out)

{

throw std::runtime_error ("Unable to write to runtime file: " + path.string ());

}

out.close ();

if (!out)

{

throw std::runtime_error ("Unable to close runtime file: " + path.string ());

}

Copilot · 2026-01-26T20:16:49Z

nano/lib/runtime_files.cpp

+void nano::runtime_files::create_pid_file (std::filesystem::path const & path)
+{
+	auto pid = boost::this_process::get_id ();
+	nano::runtime_files::create (path, std::to_string (pid));


The PID file content is written without a trailing newline, but when it's read in the test at systest/runtime_files.sh:38, the newline is explicitly stripped with tr -d '\n'. However, this is inconsistent with typical PID file conventions which usually include a trailing newline. Consider adding a newline after the PID for consistency with standard PID file format (i.e., change to std::to_string (pid) + "\n").

Suggested change

nano::runtime_files::create (path, std::to_string (pid));

nano::runtime_files::create (path, std::to_string (pid) + "\n");

systest/runtime_files.sh

systest/daemon_interrupt.sh

Copilot · 2026-01-26T20:16:50Z

nano/nano_node/daemon.cpp

+			nano::runtime_files::create_runtime_info (*flags.runtime_info_file, info);
+			std::cerr << "Runtime info file created: " << *flags.runtime_info_file << std::endl;


If create_runtime_info() throws an exception (e.g., due to disk full, permission issues, or invalid path), the node will terminate via the catch block at line 225. However, the node will have already started and bound to ports. Consider wrapping this in a try-catch block to provide a more specific error message, or documenting that runtime_info_file creation failures are fatal and will terminate the node during startup.

Suggested change

nano::runtime_files::create_runtime_info (*flags.runtime_info_file, info);

std::cerr << "Runtime info file created: " << *flags.runtime_info_file << std::endl;

try

{

nano::runtime_files::create_runtime_info (*flags.runtime_info_file, info);

std::cerr << "Runtime info file created: " << *flags.runtime_info_file << std::endl;

}

catch (std::exception const & ex)

{

logger.critical (

nano::log::type::daemon,

"Failed to create runtime info file '{}': {}",

*flags.runtime_info_file,

ex.what ());

// Rethrow so that startup still fails as before

throw;

}

pwojcikdev added documentation This item indicates the need for or supplies updated or expanded documentation cli Changes related to the Command Line Interface labels Jan 26, 2026

pwojcikdev requested a review from Copilot January 26, 2026 20:09

Copilot started reviewing on behalf of pwojcikdev January 26, 2026 20:09 View session

Copilot AI reviewed Jan 26, 2026

View reviewed changes

Introduce runtime_files helper for automatic cleanup on process exit

2989d46

pwojcikdev force-pushed the system-test-port-conflicts branch from 9b83e98 to b708b54 Compare January 26, 2026 20:38

pwojcikdev added 2 commits January 27, 2026 01:24

Add --runtime_info_file flag to write bound ports to JSON file

2706662

Use ephemeral ports in system tests to avoid port conflicts

1fe6305

pwojcikdev force-pushed the system-test-port-conflicts branch from b708b54 to 1fe6305 Compare January 27, 2026 00:24

pwojcikdev merged commit a952ae2 into nanocurrency:develop Jan 27, 2026
25 of 26 checks passed

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Add `--runtime_info_file` flag for ephemeral port discovery#5013

Add `--runtime_info_file` flag for ephemeral port discovery#5013
pwojcikdev merged 3 commits intonanocurrency:developfrom
pwojcikdev:system-test-port-conflicts

pwojcikdev commented Jan 26, 2026

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		nano::runtime_files::create_pid_file (pid_filepath);
		std::cerr << "PID file created: " << pid_filepath << std::endl;

	nano::runtime_files::create (path, std::to_string (pid));
	nano::runtime_files::create (path, std::to_string (pid) + "\n");

		nano::runtime_files::create_runtime_info (*flags.runtime_info_file, info);
		std::cerr << "Runtime info file created: " << *flags.runtime_info_file << std::endl;

-			nano::runtime_files::create_runtime_info (*flags.runtime_info_file, info);
-			std::cerr << "Runtime info file created: " << *flags.runtime_info_file << std::endl;
+			try
+			{
+				nano::runtime_files::create_runtime_info (*flags.runtime_info_file, info);
+				std::cerr << "Runtime info file created: " << *flags.runtime_info_file << std::endl;
+			}
+			catch (std::exception const & ex)
+			{
+				logger.critical (
+			        nano::log::type::daemon,
+			        "Failed to create runtime info file '{}': {}",
+			        *flags.runtime_info_file,
+			        ex.what ());
+				// Rethrow so that startup still fails as before
+				throw;
+			}

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gr0vity-dev-bot commented Jan 26, 2026 •

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Test Results for Commit `1fe6305`