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perf: skip the per-flush stat and mkdir in the event log writer #14828

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Merged
teamleaderleo merged 1 commit into from
Sep 26, 2026
Merged

perf: skip the per-flush stat and mkdir in the event log writer #14828

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30 changes: 20 additions & 10 deletions Sources/CmuxEventLogWriter.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -137,18 +137,14 @@ final class CmuxEventLogWriter: @unchecked Sendable {
private func append(_ lines: [String]) {
guard !lines.isEmpty else { return }
do {
try FileManager.default.createDirectory(
at: eventLogURL.deletingLastPathComponent(),
withIntermediateDirectories: true
)
let fileManager = FileManager.default
if !fileManager.fileExists(atPath: eventLogURL.path) {
_ = fileManager.createFile(atPath: eventLogURL.path, contents: nil)
}
var handle = try FileHandle(forWritingTo: eventLogURL)
// Every agent hook event flushes here, so the steady state is one
// open + seek + write. Directory and file creation run only when the
// open fails, and the end-of-file offset doubles as the current size
// instead of a separate attributesOfItem stat per flush.
var handle = try openForAppending(fileManager: fileManager)
defer { try? handle.close() }
try handle.seekToEnd()
var currentSize = Self.fileSize(at: eventLogURL, fileManager: fileManager)
var currentSize = try handle.seekToEnd()
// One file segment at a time bounds the extra buffer to the rotation limit,
// except for an indivisible oversized record (the existing write-whole policy).
var batchData = Data()
Expand Down Expand Up @@ -178,6 +174,20 @@ final class CmuxEventLogWriter: @unchecked Sendable {
}
}

private func openForAppending(fileManager: FileManager) throws -> FileHandle {
if let handle = try? FileHandle(forWritingTo: eventLogURL) {
return handle
}
try fileManager.createDirectory(
at: eventLogURL.deletingLastPathComponent(),
withIntermediateDirectories: true
)
if !fileManager.fileExists(atPath: eventLogURL.path) {
_ = fileManager.createFile(atPath: eventLogURL.path, contents: nil)
}
return try FileHandle(forWritingTo: eventLogURL)
}

private func rotate(fileManager: FileManager) throws {
let currentSize = Self.fileSize(at: eventLogURL, fileManager: fileManager)
let rotatedURL = eventLogURL.appendingPathExtension("1")
Expand Down
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