What causes "RAF err: ${ioe.getMessage()}" in Tencent/matrix?

Catch ParseException around parse calls and skip/ignore that pid (transient process-exit is expected).

Tencent/matrix · warning · ProcStatUtil.ParseException

RAF err

Error message

RAF err: ${ioe.getMessage()}

What it means

ProcStatReader.reset() lazily opens /proc/<pid>/stat as a RandomAccessFile; if the open throws IOException the reader marks itself invalid, closes, and rethrows as ParseException("RAF err: <message>"). It signals that the proc stat file could not be opened for reading at all, before any parsing starts.

Solutions

Catch ParseException around parse calls and skip/ignore that pid (transient process-exit is expected).
Verify the target pid is still alive (e.g. check /proc/<pid> exists or Process.isThreadRunning) before parsing.
Retry on the next sampling tick; if it fails persistently for the app's own pid, log the device/SELinux context.
Ensure the reader path points to the app's own process stats when lacking permission to read others.

Example fix

// before
StatModel stat = ProcStatUtil.instance.parse(pid);
// after
try {
    StatModel stat = ProcStatUtil.instance.parse(pid);
} catch (ProcStatUtil.ParseException e) {
    // process died or file unreadable; skip this tick
    return;
}

Defensive patterns

Strategy: try-catch

Validate before calling

java.io.File f = new File("/proc/" + pid + "/stat");
if (!f.exists() || !f.canRead()) { /* skip pid */ }

Try / catch

try { StatModel s = ProcStatUtil.instance.parse(pid); } catch (ProcStatUtil.ParseException e) { Log.w(TAG, "stat open failed: " + e.getMessage()); }

Prevention

Check pid liveness before each sample
Only read the app's own /proc stats unless root privileges are available
Treat each parse as best-effort; never let one pid failure break the sampling loop
Log device/SELinux context for persistent failures

When it happens

Trigger: Calling ProcStatUtil.parse/parseWithBufferForPath for a pid whose /proc/<pid>/stat cannot be opened: the process exited between listing and reading, the path does not exist, or the kernel/security module denies open.

Common situations: Short-lived child processes dying before the battery canary polls them; restricted SELinux policies on some Android vendors; reading stats of other users' processes on non-rooted devices.

Understand the failure class

Background: "open() failed", "failed to open file", "cannot create file" — what a file open error means and how to fix it — this error's family across 42 libraries.

Related errors

AI-assisted analysis of Tencent/matrix@3b8293bd65 (2026-09-08). Data as JSON: /api/errors/1d215e01bb1a2778. Report an issue: GitHub.

Appendix: source

Thrown at matrix/matrix-android/matrix-battery-canary/src/main/java/com/tencent/matrix/batterycanary/utils/ProcStatReader.java:60

        mIsValid = true;

        // First, try to move the pointer if a file exists
        if (mFile != null) {
            try {
                mFile.seek(0);
            } catch (IOException ioe) {
                close();
            }
        }

        // Otherwise try to open/reopen the file and fail
        if (mFile == null) {
            try {
                mFile = new RandomAccessFile(mPath, "r");
            } catch (IOException ioe) {
                mIsValid = false;
                close();
                throw new ProcStatUtil.ParseException("RAF err: " + ioe.getMessage());
            }
        }

        if (mIsValid) {
            mPosition = -1;
            mBufferSize = 0;

            mChar = 0;
            mPrev = 0;

            mRewound = false;
        }

        return this;
    }

    public boolean isValid() {
        return mIsValid;

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