Feature: Log to file for GraphServer CLI

src/ezmsg/core/commands/common.py

@@ -1,4 +1,8 @@
 import argparse
+import logging
+import os
+from datetime import datetime
+from pathlib import Path
 
 from ..graphserver import GraphService
 from ..netprotocol import Address
@@ -8,6 +12,14 @@ def add_address_argument(parser: argparse.ArgumentParser) -> None:
     parser.add_argument("--address", help="Address for GraphServer", default=None)
 
 
+def add_log_file_argument(parser: argparse.ArgumentParser) -> None:
+    parser.add_argument(
+        "--log-file",
+        help="Path to the ezmsg service log file",
+        default=None,
+    )
+
+
 def add_compact_argument(parser: argparse.ArgumentParser) -> None:
     parser.add_argument(
         "-c",
@@ -24,3 +36,51 @@ def graph_address_from_args(args: argparse.Namespace) -> Address:
     if args.address is None:
         return GraphService.default_address()
     return Address.from_string(args.address)
+
+
+def resolve_log_file(args: argparse.Namespace, address: Address) -> Path:
+    if args.log_file is not None:
+        return Path(args.log_file).expanduser()
+
+    env_log_file = os.environ.get("EZMSG_LOG_FILE")
+    if env_log_file is not None:
+        return Path(env_log_file).expanduser()
+
+    if os.name == "nt":
+        data_home = Path(
+            os.environ.get("LOCALAPPDATA", Path.home() / "AppData" / "Local")
+        )
+    else:
+        data_home = Path(
+            os.environ.get("XDG_DATA_HOME", Path.home() / ".local" / "share")
+        )
+
+    log_dir = data_home / "ezmsg" / "logs" / f"GraphServer-{address.port}"
+    timestamp = datetime.now().strftime("%Y-%m-%dT%H-%M-%S")
+    return log_dir / f"{timestamp}.log"
+
+
+def configure_log_file(log_file: Path) -> Path:
+    log_path = log_file.expanduser().resolve()
+    log_path.parent.mkdir(parents=True, exist_ok=True)
+
+    logger = logging.getLogger("ezmsg")
+    if not any(
+        isinstance(handler, logging.FileHandler)
+        and getattr(handler, "baseFilename", None) == str(log_path)
+        for handler in logger.handlers
+    ):
+        formatter = next(
+            (
+                handler.formatter
+                for handler in logger.handlers
+                if handler.formatter is not None
+            ),
+            None,
+        )
+        handler = logging.FileHandler(log_path, encoding="utf-8")
+        if formatter is not None:
+            handler.setFormatter(formatter)
+        logger.addHandler(handler)
+
+    return log_path

src/ezmsg/core/commands/serve.py

@@ -3,7 +3,13 @@
 import logging
 
 from ..graphserver import GraphService
-from .common import add_address_argument, graph_address_from_args
+from .common import (
+    add_address_argument,
+    add_log_file_argument,
+    configure_log_file,
+    graph_address_from_args,
+    resolve_log_file,
+)
 from .dashboard import (
     DashboardDependencyError,
     add_dashboard_argument,
@@ -15,9 +21,11 @@
 
 async def handle_serve(args: argparse.Namespace) -> None:
     graph_address = graph_address_from_args(args)
+    log_path = configure_log_file(resolve_log_file(args, graph_address))
     graph_service = GraphService(graph_address)
 
     logger.info(f"GraphServer Address: {graph_address}")
+    logger.info(f"GraphServer Log File: {log_path}")
     graph_server = graph_service.create_server()
     dashboard_server = None
 
@@ -43,5 +51,6 @@ async def handle_serve(args: argparse.Namespace) -> None:
 def setup_serve_cmdline(subparsers: argparse._SubParsersAction) -> None:
     parser = subparsers.add_parser("serve")
     add_address_argument(parser)
+    add_log_file_argument(parser)
     add_dashboard_argument(parser)
     parser.set_defaults(_handler=handle_serve)

src/ezmsg/core/commands/start.py

@@ -6,7 +6,7 @@
 
 from ..graphserver import GraphService
 from ..netprotocol import close_stream_writer
-from .common import add_address_argument, graph_address_from_args
+from .common import add_address_argument, add_log_file_argument, graph_address_from_args
 from .dashboard import (
     DashboardDependencyError,
     add_dashboard_argument,
@@ -20,6 +20,8 @@ async def handle_start(args: argparse.Namespace) -> None:
     graph_address = graph_address_from_args(args)
     graph_service = GraphService(graph_address)
     cmd = [sys.executable, "-m", "ezmsg.core", "serve", f"--address={graph_address}"]
+    if args.log_file is not None:
+        cmd.append(f"--log-file={args.log_file}")
     if args.dashboard is not None:
         try:
             require_dashboard_dependency()
@@ -46,5 +48,6 @@ async def handle_start(args: argparse.Namespace) -> None:
 def setup_start_cmdline(subparsers: argparse._SubParsersAction) -> None:
     parser = subparsers.add_parser("start")
     add_address_argument(parser)
+    add_log_file_argument(parser)
     add_dashboard_argument(parser)
     parser.set_defaults(_handler=handle_start)

tests/test_command.py

@@ -1,8 +1,11 @@
 import pytest
 import argparse
+import asyncio
+import sys
 from pathlib import Path
 
 from ezmsg.core.command import build_parser, cmdline
+from ezmsg.core.commands.start import handle_start
 
 
 def test_mermaid_subparser_accepts_mermaid_specific_args():
@@ -140,6 +143,15 @@ def test_start_subparser_accepts_dashboard_flag():
     assert args.dashboard is True
 
 
+def test_serve_subparser_accepts_log_file():
+    parser = build_parser()
+
+    args = parser.parse_args(["serve", "--log-file", "/tmp/ezmsg.log"])
+
+    assert args.command == "serve"
+    assert args.log_file == "/tmp/ezmsg.log"
+
+
 def test_serve_subparser_accepts_dashboard_port():
     parser = build_parser()
 
@@ -222,3 +234,54 @@ def fake_import(name, globals=None, locals=None, fromlist=(), level=0):
         args._handler(args)
 
     assert "pip install ezmsg-dashboard" in caplog.text
+
+
+def test_start_passes_log_file_to_serve(monkeypatch):
+    commands = []
+
+    class DummyPopen:
+        pid = 123
+
+        def __init__(self, cmd):
+            commands.append(cmd)
+
+    class DummyWriter:
+        def close(self):
+            pass
+
+        async def wait_closed(self):
+            pass
+
+    class DummyGraphService:
+        async def open_connection(self):
+            return object(), DummyWriter()
+
+    async def noop_close_stream_writer(writer):
+        return None
+
+    monkeypatch.setattr("ezmsg.core.commands.start.subprocess.Popen", DummyPopen)
+    monkeypatch.setattr(
+        "ezmsg.core.commands.start.GraphService", lambda address: DummyGraphService()
+    )
+    monkeypatch.setattr(
+        "ezmsg.core.commands.start.close_stream_writer", noop_close_stream_writer
+    )
+
+    args = argparse.Namespace(
+        address="127.0.0.1:25978",
+        dashboard=None,
+        log_file="/tmp/ezmsg.log",
+    )
+
+    asyncio.run(handle_start(args))
+
+    assert commands == [
+        [
+            sys.executable,
+            "-m",
+            "ezmsg.core",
+            "serve",
+            "--address=127.0.0.1:25978",
+            "--log-file=/tmp/ezmsg.log",
+        ]
+    ]