Re: [pbs-devel] [PATCH proxmox-backup] tools/daemon: improve reload behaviour

[Fabian Ebner <f.ebner@proxmox.com>]

This fixes the postinst problem for me. I let dpkg -i run in a loop 50 
times and it never got stuck anymore.

Tested-By: Fabian Ebner <f.ebner@proxmox.com>

Am 16.12.20 um 09:12 schrieb Dominik Csapak:
> it seems that sometimes, the child process signal gets handled
> before the parent process signal. Systemd then ignores the
> childs signal (finished reloading) and only after going into
> reloading state because of the parent. this will never finish.
> 
> Instead, wait for the state to change to 'reloading' after sending
> that signal in the parent, an only fork afterwards. This way
> we ensure that systemd knows about the reloading before actually trying
> to do it.
> 
> Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
> ---
> this all goes away with systemds notify barrier hopefully....
> 
>   src/tools/daemon.rs | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/src/tools/daemon.rs b/src/tools/daemon.rs
> index 6bb4a41b..2aa52772 100644
> --- a/src/tools/daemon.rs
> +++ b/src/tools/daemon.rs
> @@ -291,6 +291,7 @@ where
>           if let Err(e) = systemd_notify(SystemdNotify::Reloading) {
>               log::error!("failed to notify systemd about the state change: {}", e);
>           }
> +        wait_service_is_active_or_reloading(service_name, true).await?;
>           if let Err(e) = reloader.take().unwrap().fork_restart() {
>               log::error!("error during reload: {}", e);
>               let _ = systemd_notify(SystemdNotify::Status("error during reload".to_string()));
> @@ -305,7 +306,7 @@ where
>   
>       // FIXME: this is a hack, replace with sd_notify_barrier when available
>       if server::is_reload_request() {
> -        wait_service_is_active(service_name).await?;
> +        wait_service_is_active_or_reloading(service_name, false).await?;
>       }
>   
>       log::info!("daemon shut down...");
> @@ -313,7 +314,7 @@ where
>   }
>   
>   // hack, do not use if unsure!
> -async fn wait_service_is_active(service: &str) -> Result<(), Error> {
> +async fn wait_service_is_active_or_reloading(service: &str, wait_for_reload: bool) -> Result<(), Error> {
>       tokio::time::delay_for(std::time::Duration::new(1, 0)).await;
>       loop {
>           let text = match tokio::process::Command::new("systemctl")
> @@ -328,7 +329,8 @@ async fn wait_service_is_active(service: &str) -> Result<(), Error> {
>               Err(err) => bail!("executing 'systemctl is-active' failed - {}", err),
>           };
>   
> -        if text.trim().trim_start() != "reloading" {
> +        let is_reload = text.trim().trim_start() == "reloading";
> +        if is_reload == wait_for_reload {
>               return Ok(());
>           }
>           tokio::time::delay_for(std::time::Duration::new(5, 0)).await;
>