Re: [PATCH proxmox-backup 4/6] task tracking: count WriteNonExpanding datastore operations

[Christian Ebner <c.ebner@proxmox.com>]

Code wise this looks good to me, but I was pondering a bit if we should 
take the occasion here and define a `format-version` field in order to 
have some way of checking this in case of future extension. The older 
process might then only update values it knows about, but write out all 
the contents known to the newer versions.

Other opinions on that?

On 6/2/26 3:00 PM, Robert Obkircher wrote:
> Count WriteNonExpanding as writes to ensure that switching over from
> Write does not break forward compatibility when older versions read
> the counters.
> 
> Also add a new counter to display the GarbageCollection maintenance
> mode conflicts. It may not be accurate while older processes are
> running but it should be good enough for the UI.
> 
> Signed-off-by: Robert Obkircher <r.obkircher@proxmox.com>

Reviewed-by: Christian Ebner <c.ebner@proxmox.com>

> ---
>   pbs-datastore/src/task_tracking.rs | 12 ++++++++++++
>   src/api2/admin/datastore.rs        |  1 +
>   2 files changed, 13 insertions(+)
> 
> diff --git a/pbs-datastore/src/task_tracking.rs b/pbs-datastore/src/task_tracking.rs
> index a67b77221..87ce4f5de 100644
> --- a/pbs-datastore/src/task_tracking.rs
> +++ b/pbs-datastore/src/task_tracking.rs
> @@ -13,6 +13,12 @@ use serde::{Deserialize, Serialize};
>   pub struct ActiveOperationStats {
>       pub read: i64,
>       pub write: i64,
> +    /// The number of writers that do not significantly increase disk usage.
> +    ///
> +    /// The count is unreliable because older processes without this field
> +    /// will delete it on every update!
> +    #[serde(default)]
> +    pub write_non_expanding: i64,
>   }
>   
>   impl ActiveOperationStats {
> @@ -20,6 +26,11 @@ impl ActiveOperationStats {
>           match operation {
>               Operation::Read => self.read += count,
>               Operation::Write => self.write += count,
> +            Operation::WriteNonExpanding => {
> +                self.write += count;
> +                // prevent underflow if an older process deleted the field
> +                self.write_non_expanding = (self.write_non_expanding + count).max(0);
> +            }
>               Operation::Lookup => (), // no IO must happen there
>           }
>       }
> @@ -33,6 +44,7 @@ impl Sum<Self> for ActiveOperationStats {
>           iter.fold(Self::default(), |a, b| Self {
>               read: a.read + b.read,
>               write: a.write + b.write,
> +            write_non_expanding: a.write_non_expanding + b.write_non_expanding,
>           })
>       }
>   }
> diff --git a/src/api2/admin/datastore.rs b/src/api2/admin/datastore.rs
> index 94272c32d..3cbdd8922 100644
> --- a/src/api2/admin/datastore.rs
> +++ b/src/api2/admin/datastore.rs
> @@ -2024,6 +2024,7 @@ pub fn get_active_operations(store: String, _param: Value) -> Result<Value, Erro
>       Ok(json!({
>           "read": active_operations.read,
>           "write": active_operations.write,
> +        "writeNonExpanding": active_operations.write_non_expanding,
>       }))
>   }
>