[PATCH 3/4] virDomainCheckpointCreateXML: Add disclaimer about creating checkpoints

Jonathon Jongsma jjongsma at redhat.com
Tue Aug 23 14:04:04 UTC 2022


On 8/23/22 6:32 AM, Peter Krempa wrote:
> Checkpoints created via virDomainCheckpointCreateXML are generally not
> very useful as they need to be coupled with a backup.
> 
> Add a disclaimer to the docs explaining why users should use
> virDomainBackupBegin instead.
> 
> Signed-off-by: Peter Krempa <pkrempa at redhat.com>
> ---
>   src/libvirt-domain-checkpoint.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
> 
> diff --git a/src/libvirt-domain-checkpoint.c b/src/libvirt-domain-checkpoint.c
> index de747aff01..078e999bf3 100644
> --- a/src/libvirt-domain-checkpoint.c
> +++ b/src/libvirt-domain-checkpoint.c
> @@ -142,6 +142,16 @@ virDomainCheckpointGetConnect(virDomainCheckpointPtr checkpoint)
>    * present, an error is thrown. This flag is incompatible with
>    * VIR_DOMAIN_CHECKPOINT_CREATE_REDEFINE.
>    *
> + * Note: A checkpoint represent s point in time since which blocks changed by
> + * the hypervisor are tracked. 

extra space in "represent s"

Also, I think it would be more clearly understood if we changed "since" 
to "after".

"Note: a checkpoint represents a point in time after which blocks 
changed..."


> This means that
> + * for a checkpoint to be generally usable for doing an incremental backup it's
> + * required to perform a backup at the same time as taking the checkpoint.

I might suggest something like:

"The main purpose of checkpoints is to enable incremental backups. But 
for a checkpoint to be useful for this purpose, a backup should be 
performed at the same time as the checkpoint is created."

> + * This is done via the virDomainBackupBegin API, which also allows to create
> + * a checkpoint at the same time. virDomainCheckpointCreateXML is generally not
> + * useful for creating checkpoints but rather only for re-creating the libvirt
> + * metadata.

my suggestion here:

"This is done via the virDomainBackupBegin API, which also allows to 
create a checkpoint at the same time. Creating checkpoints with 
virDomainCheckpointCreateXML is generally only useful for re-creating 
the libvirt metadata"


Reviewed-by: Jonathon Jongsma <jjongsma at redhat.com>



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