sgl-project/sglang · error · ValueError

No trace files found for profile_id: {self.profile_id}

Error message

No trace files found for profile_id: {self.profile_id}

What it means

ProfileTraceMerger.merge_chrome_traces discovers trace files by profile_id under the output directory and found none, so it cannot merge. Raised before any merging work starts.

Source

Thrown at python/sglang/srt/utils/profile_merger.py:50

            "pp_rank": 10_000,
            "tp_rank": 100,
        }

        # PID threshold for sort_index updates (only update for system PIDs < 1000)
        self.pid_sort_index_threshold = 1000

    def merge_chrome_traces(self) -> str:
        """Merge Chrome traces from all ranks into a single trace.

        Returns:
            Path to merged trace file.

        Raises:
            ValueError: If no trace files found.
        """
        trace_files = self._discover_trace_files()
        if not trace_files:
            raise ValueError(f"No trace files found for profile_id: {self.profile_id}")

        logger.info(f"Found {len(trace_files)} trace files to merge")

        merged_trace = {"traceEvents": []}
        all_device_properties = []

        for trace_file in sorted(trace_files, key=self._get_rank_sort_key):
            rank_info = self._extract_rank_info(trace_file)
            logger.info(f"Processing {trace_file} with rank info: {rank_info}")

            output = self._handle_file(trace_file, rank_info)

            merged_trace["traceEvents"].extend(output["traceEvents"])

            if "deviceProperties" in output:
                all_device_properties.extend(output["deviceProperties"])
                del output["deviceProperties"]

View on GitHub (pinned to 0132848349)

Solutions

1. Verify the trace directory exists and contains *.json/.gz trace files for the profile_id
2. Ensure output_dir and profile_id passed to the merger match those used when starting profiling
3. Confirm the profiling session actually started (check logs for 'Profiling starts') and workers flushed traces before merging

Example fix

# before
merger = ProfileTraceMerger(output_dir='/tmp/wrong', profile_id='p1').merge_chrome_traces()
# after
merger = ProfileTraceMerger(output_dir=real_output_dir, profile_id='p1').merge_chrome_traces()

from pathlib import Path
traces = list(Path(output_dir).rglob(f'*{profile_id}*trace*'))
assert traces, f'no traces for {profile_id}, not starting merge'

null

try:
    merger.merge_chrome_traces()
except ValueError as e:
    if 'No trace files' in str(e):
        logger.error('profiling produced no output; rerun with wider window')

When it happens

Trigger: Calling merge_chrome_traces with a profile_id whose directory is empty/missing, traces written to a different output_dir, or profiling never actually produced a trace (failed start, wrong worker).

Common situations: Merging after a profiler run where workers crashed, output_dir misconfigured between start and merge, or profile_id typo'd/mismatched with the folder name.

Related errors

• Trace file is empty.
• Module instance {} is not unique
• manually start is only supported yet
• manually stop is only supported yet
• unsupported profile stage: {forward_mode=}

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/765a490006d9488c. Report an issue: GitHub.