Add Argument validation, report interval must be >= sample interval

README.md

@@ -48,9 +48,10 @@ options:
                         False)
   --sample-interval SAMPLE_INTERVAL, --s-i SAMPLE_INTERVAL
                         Interval in seconds between status checks of the
-                        running process. Sample interval should be larger than
-                        the runtime of the process or `duct` may underreport
-                        the number of processes started. (default: 1.0)
+                        running process. Sample interval must be less than or
+                        equal to Report interval, and achieves the best
+                        results when sample is significantly less than the
+                        runtime of the process. (default: 1.0)
   --report-interval REPORT_INTERVAL, --r-i REPORT_INTERVAL
                         Interval in seconds at which to report aggregated
                         data. (default: 60.0)

src/duct/__main__.py

@@ -332,6 +332,13 @@ class Arguments:
     outputs: Outputs
     record_types: RecordTypes
 
+    def __post_init__(self) -> None:
+        if self.report_interval < self.sample_interval:
+            raise argparse.ArgumentError(
+                None,
+                "--report-interval must be greater than or equal to --sample-interval.",
+            )
+
     @classmethod
     def from_argv(cls) -> Arguments:  # pragma: no cover
         parser = argparse.ArgumentParser(
@@ -373,8 +380,8 @@ def from_argv(cls) -> Arguments:  # pragma: no cover
             type=float,
             default=float(os.getenv("DUCT_SAMPLE_INTERVAL", "1.0")),
             help="Interval in seconds between status checks of the running process. "
-            "Sample interval should be larger than the runtime of the process or `duct` may "
-            "underreport the number of processes started.",
+            "Sample interval must be less than or equal to Report interval, and achieves the "
+            "best results when sample is significantly less than the runtime of the process.",
         )
         parser.add_argument(
             "--report-interval",

test/test_validation.py

@@ -0,0 +1,48 @@
+import argparse
+import pytest
+from duct.__main__ import Arguments, Outputs, RecordTypes
+
+
+def test_sample_less_than_report_interval() -> None:
+    args = Arguments(
+        command="fake",
+        command_args=[],
+        output_prefix="fake",
+        sample_interval=0.01,
+        report_interval=0.1,
+        capture_outputs=Outputs.NONE,
+        outputs=Outputs.ALL,
+        record_types=RecordTypes.SYSTEM_SUMMARY,
+        clobber=False,
+    )
+    assert args.sample_interval <= args.report_interval
+
+
+def test_sample_equal_to_report_interval() -> None:
+    args = Arguments(
+        command="fake",
+        command_args=[],
+        output_prefix="fake",
+        sample_interval=0.1,
+        report_interval=0.1,
+        capture_outputs=Outputs.NONE,
+        outputs=Outputs.ALL,
+        record_types=RecordTypes.SYSTEM_SUMMARY,
+        clobber=False,
+    )
+    assert args.sample_interval == args.report_interval
+
+
+def test_sample_equal_greater_than_report_interval() -> None:
+    with pytest.raises(argparse.ArgumentError):
+        Arguments(
+            command="fake",
+            command_args=[],
+            output_prefix="fake",
+            sample_interval=1.0,
+            report_interval=0.1,
+            capture_outputs=Outputs.NONE,
+            outputs=Outputs.ALL,
+            record_types=RecordTypes.SYSTEM_SUMMARY,
+            clobber=False,
+        )