[pbs-devel] [PATCH proxmox-backup v2] api2/node/termproxy: fix zombies on worker abort

[pbs-devel] [PATCH proxmox-backup v2] api2/node/termproxy: fix zombies on worker abort

[Dominik Csapak]

tokios kill_on_drop sometimes leaves zombies around, especially
when there is not another tokio::process::Command spawned after

so instead of relying on the 'kill_on_drop' feature, we explicitly
kill the child on a worker abort. to be able to do this
we have to use 'tokio::select' instead of 'futures::select' since
the latter requires the future to be fused, which consumes the
child handle, leaving us no possibility to kill it after fusing.
(tokio::select does not need the futures to be fused, so we
can reuse the child future after the select again)

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
changes from v1:
* if the worker future is ok, bubble errors up from child kill/await
  if the worker future is err, log errors from kill/await and return
  the error from the abort
 src/api2/node.rs | 36 ++++++++++++++++++++++++++----------
 1 file changed, 26 insertions(+), 10 deletions(-)

diff --git a/src/api2/node.rs b/src/api2/node.rs
index 9be5fe6d..5a3ea0ff 100644
--- a/src/api2/node.rs
+++ b/src/api2/node.rs
@@ -2,10 +2,7 @@ use std::net::TcpListener;
 use std::os::unix::io::AsRawFd;
 
 use anyhow::{bail, format_err, Error};
-use futures::{
-    future::{FutureExt, TryFutureExt},
-    select,
-};
+use futures::future::{FutureExt, TryFutureExt};
 use hyper::body::Body;
 use hyper::http::request::Parts;
 use hyper::upgrade::Upgraded;
@@ -172,7 +169,6 @@ async fn termproxy(
             let mut cmd = tokio::process::Command::new("/usr/bin/termproxy");
 
             cmd.args(&arguments)
-                .kill_on_drop(true)
                 .stdout(std::process::Stdio::piped())
                 .stderr(std::process::Stdio::piped());
 
@@ -199,8 +195,9 @@ async fn termproxy(
                 Ok::<(), Error>(())
             };
 
-            select!{
-                res = child.fuse() => {
+            let mut needs_kill = false;
+            let res = tokio::select!{
+                res = &mut child => {
                     let exit_code = res?;
                     if !exit_code.success() {
                         match exit_code.code() {
@@ -210,10 +207,29 @@ async fn termproxy(
                     }
                     Ok(())
                 },
-                res = stdout_fut.fuse() => res,
-                res = stderr_fut.fuse() => res,
-                res = worker.abort_future().fuse() => res.map_err(Error::from),
+                res = stdout_fut => res,
+                res = stderr_fut => res,
+                res = worker.abort_future() => {
+                    needs_kill = true;
+                    res.map_err(Error::from)
+                }
+            };
+
+            if needs_kill {
+                if res.is_ok() {
+                    child.kill()?;
+                    child.await?;
+                    return Ok(());
+                }
+
+                if let Err(err) = child.kill() {
+                    worker.warn(format!("error killing termproxy: {}", err));
+                } else if let Err(err) = child.await {
+                    worker.warn(format!("error awaiting termproxy: {}", err));
+                }
             }
+
+            res
         },
     )?;
 
-- 
2.20.1

[pbs-devel] applied: [PATCH proxmox-backup v2] api2/node/termproxy: fix zombies on worker abort

[Wolfgang Bumiller]

applied

On Wed, Jul 29, 2020 at 01:50:27PM +0200, Dominik Csapak wrote:
> tokios kill_on_drop sometimes leaves zombies around, especially
> when there is not another tokio::process::Command spawned after
> 
> so instead of relying on the 'kill_on_drop' feature, we explicitly
> kill the child on a worker abort. to be able to do this
> we have to use 'tokio::select' instead of 'futures::select' since
> the latter requires the future to be fused, which consumes the
> child handle, leaving us no possibility to kill it after fusing.
> (tokio::select does not need the futures to be fused, so we
> can reuse the child future after the select again)
> 
> Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
> ---
> changes from v1:
> * if the worker future is ok, bubble errors up from child kill/await
>   if the worker future is err, log errors from kill/await and return
>   the error from the abort
>  src/api2/node.rs | 36 ++++++++++++++++++++++++++----------
>  1 file changed, 26 insertions(+), 10 deletions(-)
> 
> diff --git a/src/api2/node.rs b/src/api2/node.rs
> index 9be5fe6d..5a3ea0ff 100644
> --- a/src/api2/node.rs
> +++ b/src/api2/node.rs
> @@ -2,10 +2,7 @@ use std::net::TcpListener;
>  use std::os::unix::io::AsRawFd;
>  
>  use anyhow::{bail, format_err, Error};
> -use futures::{
> -    future::{FutureExt, TryFutureExt},
> -    select,
> -};
> +use futures::future::{FutureExt, TryFutureExt};
>  use hyper::body::Body;
>  use hyper::http::request::Parts;
>  use hyper::upgrade::Upgraded;
> @@ -172,7 +169,6 @@ async fn termproxy(
>              let mut cmd = tokio::process::Command::new("/usr/bin/termproxy");
>  
>              cmd.args(&arguments)
> -                .kill_on_drop(true)
>                  .stdout(std::process::Stdio::piped())
>                  .stderr(std::process::Stdio::piped());
>  
> @@ -199,8 +195,9 @@ async fn termproxy(
>                  Ok::<(), Error>(())
>              };
>  
> -            select!{
> -                res = child.fuse() => {
> +            let mut needs_kill = false;
> +            let res = tokio::select!{
> +                res = &mut child => {
>                      let exit_code = res?;
>                      if !exit_code.success() {
>                          match exit_code.code() {
> @@ -210,10 +207,29 @@ async fn termproxy(
>                      }
>                      Ok(())
>                  },
> -                res = stdout_fut.fuse() => res,
> -                res = stderr_fut.fuse() => res,
> -                res = worker.abort_future().fuse() => res.map_err(Error::from),
> +                res = stdout_fut => res,
> +                res = stderr_fut => res,
> +                res = worker.abort_future() => {
> +                    needs_kill = true;
> +                    res.map_err(Error::from)
> +                }
> +            };
> +
> +            if needs_kill {
> +                if res.is_ok() {
> +                    child.kill()?;
> +                    child.await?;
> +                    return Ok(());
> +                }
> +
> +                if let Err(err) = child.kill() {
> +                    worker.warn(format!("error killing termproxy: {}", err));
> +                } else if let Err(err) = child.await {
> +                    worker.warn(format!("error awaiting termproxy: {}", err));
> +                }
>              }
> +
> +            res
>          },
>      )?;
>  
> -- 
> 2.20.1