refactor(macrobenchmark): Collect log chunks per file

Chunks were merged across every *.log found, so two devices each emitting the
same number of chunks would overwrite each other's indices and reassemble into
one bogus document. Collect per file and report when more than one log carries
results, which also drops the cross-file total comparison that was standing in
for this check.

Build the summary table and per-iteration details in one pass while here.

Author: runningcode

scripts/parse-macrobenchmark-log.py

@@ -39,23 +39,14 @@ def log_messages(log_file):
         yield line
 
 
-def collect_chunks(log_files):
-    """Returns the chunk texts keyed by index, plus the expected total."""
-    chunks = {}
-    total = None
-    for log_file in log_files:
-        for message in log_messages(log_file):
-            match = CHUNK_RE.search(message)
-            if not match:
-                continue
-            index, chunk_total, text = int(match.group(1)), int(match.group(2)), match.group(3)
-            if total is not None and chunk_total != total:
-                sys.exit(
-                    f"Found chunks from more than one benchmark run "
-                    f"(totals {total} and {chunk_total}) in {log_file}"
-                )
-            total = chunk_total
-            chunks[index] = text
+def collect_chunks(log_file):
+    """Returns one log's chunk texts keyed by index, plus the expected total."""
+    chunks, total = {}, None
+    for message in log_messages(log_file):
+        match = CHUNK_RE.search(message)
+        if match:
+            index, total = int(match.group(1)), int(match.group(2))
+            chunks[index] = match.group(3)
     return chunks, total
 
 
@@ -86,25 +77,30 @@ def format_summary(data):
             "",
         ]
 
-    lines += ["| Benchmark | Metric | min | median | max | CoV | iterations |", "|---|---|--:|--:|--:|--:|--:|"]
+    table = [
+        "| Benchmark | Metric | min | median | max | CoV | iterations |",
+        "|---|---|--:|--:|--:|--:|--:|",
+    ]
+    details = []
     for benchmark in data["benchmarks"]:
+        name = f"{benchmark['className'].rsplit('.', 1)[-1]}.{benchmark['name']}"
         for metric, result in sorted(benchmark["metrics"].items()):
-            lines.append(
-                f"| `{benchmark['className'].rsplit('.', 1)[-1]}.{benchmark['name']}` "
-                f"| {metric} "
-                f"| {result['minimum']:.1f} "
-                f"| {result['median']:.1f} "
-                f"| {result['maximum']:.1f} "
-                f"| {result['coefficientOfVariation'] * 100:.1f}% "
-                f"| {len(result['runs'])} |"
+            table.append(
+                f"| `{name}` | {metric} "
+                f"| {result['minimum']:.1f} | {result['median']:.1f} | {result['maximum']:.1f} "
+                f"| {result['coefficientOfVariation'] * 100:.1f}% | {len(result['runs'])} |"
             )
-
-    for benchmark in data["benchmarks"]:
-        for metric, result in sorted(benchmark["metrics"].items()):
             runs = ", ".join(f"{run:.1f}" for run in result["runs"])
-            lines += ["", f"<details><summary>{metric} per iteration</summary>", "", runs, "", "</details>"]
+            details += [
+                "",
+                f"<details><summary>{metric} per iteration</summary>",
+                "",
+                runs,
+                "",
+                "</details>",
+            ]
 
-    return "\n".join(lines)
+    return "\n".join(lines + table + details)
 
 
 def main():
@@ -117,12 +113,22 @@ def main():
     if not log_files:
         sys.exit(f"No *.log files under {args.artifacts_dir}")
 
-    chunks, total = collect_chunks(log_files)
-    if total is None:
+    # Keyed by file so chunks from two devices can never be merged into one bogus document.
+    per_log = {log: collect_chunks(log) for log in log_files}
+    with_chunks = {log: result for log, (result, total) in per_log.items() if total}
+    if not with_chunks:
         sys.exit(
             "No SentryBenchmarkData chunks in the device log. The benchmark most likely "
             "failed before reporting — check junit.xml and the log for Macrobenchmark errors."
         )
+    if len(with_chunks) > 1:
+        sys.exit(
+            "Chunks from more than one run: "
+            + ", ".join(str(log) for log in with_chunks)
+            + ". This parser reports a single device."
+        )
+    log_file = next(iter(with_chunks))
+    chunks, total = per_log[log_file]
 
     data = json.loads(reassemble(chunks, total))