From d4d6d0a686e208c5f1eee9f6d07ecde66b20fae7 Mon Sep 17 00:00:00 2001
From: Yuyi-Oak <1722157266@qq.com>
Date: Fri, 17 Jul 2026 07:30:20 -0700
Subject: [PATCH] =?UTF-8?q?fix(curl):=20=E5=B0=86=20ETXTBSY=20=E5=BD=92?=
 =?UTF-8?q?=E4=B8=BA=E5=8F=AF=E9=87=8D=E8=AF=95=E7=9A=84=E7=9E=AC=E6=97=B6?=
 =?UTF-8?q?=E5=90=AF=E5=8A=A8=E5=A4=B1=E8=B4=A5?=
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启动 curl 子进程时命中的 ETXTBSY（可执行文件忙）是多线程程序里
fork/exec 与"刚写出的可执行文件"之间的瞬时竞态：另一线程 fork 出的
子进程在 fork 与 execve 之间短暂持有目标文件的可写句柄，导致本次
exec 被内核判为忙。此前它被并入 ProcessFailed 且 retryable=false，
per-URL 层直接放弃。

新增 CurlFailureKind::ProcessBusy（retryable=true），在 process_failed
中按 io::ErrorKind::ExecutableFileBusy 精确识别，并在 busy 重试前做
极短退避让兄弟进程完成 execve。生产中 curl 是固定系统二进制、从不
被并发改写，故此变更对真实下载无影响，仅消除集成测试在高并发下偶发的
"Text file busy" flake（fetch_bootstrap unwrap 失败）。

验证：以 8-10 并发 worker × 8 线程 / 4 核（≈64-80 线程超载）复现，
修复前首轮即挂；修复后 200+ 次超压运行零 ETXTBSY、零失败。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 infrastructure/src/curl_transfer.rs | 49 +++++++++++++++++++++++++++--
 1 file changed, 47 insertions(+), 2 deletions(-)

diff --git a/infrastructure/src/curl_transfer.rs b/infrastructure/src/curl_transfer.rs
index 318bb5f..927e6aa 100644
--- a/infrastructure/src/curl_transfer.rs
+++ b/infrastructure/src/curl_transfer.rs
@@ -205,6 +205,11 @@ pub(crate) enum CurlFailureKind {
     /// 代理自身故障：无法解析/连接代理，或代理返回 407 认证失败等。
     Proxy,
     ProcessFailed,
+    /// 启动 curl 进程时命中 `ETXTBSY`（可执行文件忙）。这是多线程程序里
+    /// fork/exec 与"刚写出的可执行文件"之间的瞬时竞态：另一线程 fork 出的
+    /// 子进程在 fork 与 execve 之间短暂持有该文件的可写句柄，导致本次 exec
+    /// 被内核判为忙。属瞬时错误，可重试。
+    ProcessBusy,
     Unknown,
 }
 
@@ -225,6 +230,7 @@ impl CurlFailureKind {
             Self::Network => "network",
             Self::Proxy => "proxy",
             Self::ProcessFailed => "process_failed",
+            Self::ProcessBusy => "process_busy",
             Self::Unknown => "unknown",
         }
     }
@@ -245,7 +251,7 @@ impl CurlFailureKind {
             Self::Interrupted => ErrorCode::NETWORK_INTERRUPTED,
             Self::Proxy => ErrorCode::PROXY_FAILURE,
             Self::HttpUnknown | Self::Network | Self::Unknown => ErrorCode::NETWORK_OTHER,
-            Self::ProcessFailed => ErrorCode::INTERNAL,
+            Self::ProcessFailed | Self::ProcessBusy => ErrorCode::INTERNAL,
         }
     }
 
@@ -268,6 +274,7 @@ impl CurlFailureKind {
             | Self::Tls
             | Self::Interrupted
             | Self::Network
+            | Self::ProcessBusy
             | Self::Unknown => true,
         }
     }
@@ -305,13 +312,20 @@ impl CurlFailure {
         curl_command: &Path,
         error: std::io::Error,
     ) -> Self {
+        // ETXTBSY（可执行文件忙）是 fork/exec 的瞬时竞态，可重试；其余启动失败
+        // （如命令不存在、权限不足）是确定性错误，不重试。
+        let kind = if error.kind() == std::io::ErrorKind::ExecutableFileBusy {
+            CurlFailureKind::ProcessBusy
+        } else {
+            CurlFailureKind::ProcessFailed
+        };
         Self {
             url: url.to_string(),
             destination: destination.map(Path::to_path_buf),
             exit_code: None,
             stderr: format!("启动 curl 命令失败 {}：{error}", curl_command.display()),
             http_status: None,
-            kind: CurlFailureKind::ProcessFailed,
+            kind,
         }
     }
 
@@ -434,6 +448,9 @@ pub(crate) fn run_curl_with_retry_with_proxy(
             Err(error) => CurlFailure::process_failed(url, destination, curl_command, error),
         };
         let retryable = failure.retryable();
+        // ETXTBSY 是 fork/exec 竞态窗口造成的瞬时忙，立刻重试往往仍落在同一窗口内。
+        // 让出 CPU 并做一次极短退避，使持有可写句柄的兄弟进程完成其 execve。
+        let busy = failure.kind == CurlFailureKind::ProcessBusy;
         failures.push(CurlAttemptFailure {
             attempt,
             attempts,
@@ -442,6 +459,9 @@ pub(crate) fn run_curl_with_retry_with_proxy(
         if !retryable {
             break;
         }
+        if busy && attempt < attempts {
+            std::thread::sleep(std::time::Duration::from_millis(5 * attempt as u64));
+        }
     }
 
     Err(CurlRetryError { attempts: failures })
@@ -588,6 +608,31 @@ mod tests {
         assert_eq!(CurlFailureKind::Network.error_code().id(), "BAT-ERR-300015");
     }
 
+    #[test]
+    fn etxtbsy_spawn_failure_is_retryable() {
+        // ETXTBSY（可执行文件忙）来自 fork/exec 竞态，应归为可重试的 ProcessBusy；
+        // 其余启动失败（如命令不存在）保持不可重试的 ProcessFailed。
+        let busy = std::io::Error::from(std::io::ErrorKind::ExecutableFileBusy);
+        let failure = CurlFailure::process_failed(
+            "https://example.test/a",
+            None,
+            Path::new("/tmp/fake-curl"),
+            busy,
+        );
+        assert_eq!(failure.kind, CurlFailureKind::ProcessBusy);
+        assert!(failure.retryable());
+
+        let missing = std::io::Error::from(std::io::ErrorKind::NotFound);
+        let failure = CurlFailure::process_failed(
+            "https://example.test/a",
+            None,
+            Path::new("/tmp/fake-curl"),
+            missing,
+        );
+        assert_eq!(failure.kind, CurlFailureKind::ProcessFailed);
+        assert!(!failure.retryable());
+    }
+
     #[test]
     fn parse_http_status_anchors_on_curl_error_context() {
         // 状态码前出现无关三位数字（如端口 443）时，仍从 "error" 之后取真正的状态码。