[libvirt] [PATCHv2 2/4] API: Add api to set and get domain metadata
Eric Blake
eblake at redhat.com
Tue Jan 31 00:20:01 UTC 2012
On 01/30/2012 08:09 AM, Peter Krempa wrote:
> This patch adds API to modify domain metadata for running and stopped
> domains. The api supports changing description, title as well as the
> newly added <metadata> element. The API has support for storing data in
> the metadata element using xml namespaces.
>
> * include/libvirt/libvirt.h.in
> * src/libvirt_public.syms
> - add function headers
> - add enum to select metadata to operate on
> - export functions
> * src/libvirt.c
> - add public api implementation
> * src/driver.h
> - add driver support
> * src/remote/remote_driver.c
> * src/remote/remote_protocol.x
> - wire up the remote protocol
> * include/libvirt/virterror.h
> * src/util/virterror.c
> - add a new error message note that metadata for domain are
> missing
> ---
> Diff to v1:
> - lifted the length restriction and tweaked commands according to that
> - moved argument checks from driver to main library implementation
> - sorted entries in symbol list
>
> include/libvirt/libvirt.h.in | 24 ++++++
> include/libvirt/virterror.h | 1 +
> src/driver.h | 16 ++++
> src/libvirt.c | 181 ++++++++++++++++++++++++++++++++++++++++++
> src/libvirt_public.syms | 2 +
> src/remote/remote_driver.c | 2 +
> src/remote/remote_protocol.x | 24 ++++++-
'yum install dwarves' then 'make check' fails, because you didn't update
src/remote_protocol-structs.
> /**
> + * virDomainSetMetadata:
> + * @domain: a domain object
> + * @type: type of description, from virDomainMetadataType
> + * @metadata: new metadata text
> + * @key: XML namespace key, or NULL
> + * @uri: XML namespace URI, or NULL
> + * @flags: bitwise-OR of virDomainModificationImpact
> + *
> + * Sets the appropriate domain element given by @type to the
> + * value of @description. A @type of VIR_DOMAIN_METADATA_DESCRIPTION
> + * is free-form text; VIR_DOMAIN_METADATA_TITLE is free-form, but no
> + * newlines are permitted, and should be short (although the length is
> + * not enforced). For these two options @key and @uri are irrelevant and
> + * can be set to NULL.
s/can be/must be/ (since you error out if they are non-NULL)
> + *
> + * For type VIR_DOMAIN_METADATA_ELEMENT @metadata must be well-formed
> + * XML belonging to namespace defined by @uri with local name @key.
> + *
> + * Passing NULL for @metadata says to remove that element from the
> + * domain XML (passing the empty string leaves the element present).
> + *
> + * The resulting metadata will be present in virDomainGetXMLDesc(),
> + * as well as quick access through virDomainGetMetadata().
> + *
> + * @flags controls whether the live domain, persistent configuration,
> + * or both will be modified.
> + *
> + * Returns 0 on success, -1 in case of failure.
> + */
> +int
> +virDomainSetMetadata(virDomainPtr domain,
> + int type,
> + const char *metadata,
> + const char *key,
> + const char *uri,
> + unsigned int flags)
I think we've settled on a good API.
> +
> + switch (type) {
> + case VIR_DOMAIN_METADATA_TITLE:
> + if (metadata && strchr(metadata, '\n')) {
> + virLibDomainError(VIR_ERR_INVALID_ARG, "%s",
> + _("Domain title can't contain newlines"));
> + goto error;
> + }
> + /* fallthrough */
> + case VIR_DOMAIN_METADATA_DESCRIPTION:
> + if (uri || key) {
> + virLibDomainError(VIR_ERR_INVALID_ARG, __FUNCTION__);
> + goto error;
> + }
> + break;
> + case VIR_DOMAIN_METADATA_ELEMENT:
> + if (!uri || !key) {
> + virLibDomainError(VIR_ERR_INVALID_ARG, __FUNCTION__);
> + goto error;
> + }
> + break;
These are okay,
> + default:
> + virLibDomainError(VIR_ERR_INVALID_ARG, "%s",
> + _("Invalid metadata type"));
> + goto error;
> + break;
but I don't like this one. If you have an older client trying to talk
to a newer server, where the newer server understands a fourth type of
metadata, then we should not be getting in the way of the client passing
that data over RPC.
> +/**
> + * virDomainGetMetadata:
> + * @domain: a domain object
> + * @type: type of description, from virDomainMetadataType
> + * @uri: XML namespace identifier
> + * @flags: bitwise-OR of virDomainModificationImpact
> + *
> + * Retrieves the appropriate domain element given by @type.
> + * If VIR_DOMAIN_METADATA_ELEMENT is requested parameter @uri
> + * must be set to the name of the namespace the requested elements
> + * belong to.
Also mention:
Otherwise, uri must be NULL.
> + *
> + * If an element of the domain XML is not present, the resulting
> + * error will be VIR_ERR_NO_DOMAIN_METADATA. This method forms
> + * a shortcut for seeing information from virDomainSetMetadata()
> + * without having to go through virDomainGetXMLDesc().
> + *
> + * @flags controls whether the live domain or persistent
> + * configuration will be queried.
> + *
> + * Returns the metadata string on success (caller must free),
> + * or NULL in case of failure.
> + */
> +char *
> +virDomainGetMetadata(virDomainPtr domain,
> + int type,
> + const char *uri,
> + unsigned int flags)
> +{
> + virConnectPtr conn;
> +
> + VIR_DOMAIN_DEBUG(domain, "type=%d, uri=%p, flags=%x",
> + type, uri, flags);
Here (and in the setter), I'd use "uri=%s"/NULLSTR(uri), rather
"uri=%p"/uri, as that makes debugging a bit nicer when we know we have a
validly-null string.
> +
> + if (!VIR_IS_CONNECTED_DOMAIN(domain)) {
> + virLibDomainError(VIR_ERR_INVALID_DOMAIN, __FUNCTION__);
> + goto error;
> + }
> +
> + if ((flags & VIR_DOMAIN_AFFECT_LIVE) &&
> + (flags & VIR_DOMAIN_AFFECT_CONFIG)) {
> + virLibDomainError(VIR_ERR_INVALID_ARG, "%s",
> + _("Can't specify both LIVE and CONFIG flags"));
> + goto error;
Elsewhere, we just used the terser:
if ((flags & VIR_DOMAIN_AFFECT_LIVE) &&
(flags & VIR_DOMAIN_AFFECT_CONFIG)) {
virLibDomainError(VIR_ERR_INVALID_ARG, __FUNCTION__);
goto error;
}
> + }
> +
> + switch (type) {
> + case VIR_DOMAIN_METADATA_TITLE:
> + case VIR_DOMAIN_METADATA_DESCRIPTION:
> + if (uri) {
> + virLibDomainError(VIR_ERR_INVALID_ARG, __FUNCTION__);
> + goto error;
> + }
> + break;
> + case VIR_DOMAIN_METADATA_ELEMENT:
> + if (!uri) {
> + virLibDomainError(VIR_ERR_INVALID_ARG, __FUNCTION__);
> + goto error;
> + }
> + break;
Again, fine with these, (we have a defined semantic for these flags)
> + default:
> + virLibDomainError(VIR_ERR_INVALID_ARG, "%s",
> + _("Invalid metadata type"));
> + goto error;
> + break;
but not this (this prevents expansion).
> --- a/src/remote/remote_protocol.x
> +++ b/src/remote/remote_protocol.x
> @@ -1114,6 +1114,26 @@ struct remote_domain_set_autostart_args {
> int autostart;
> };
>
> +struct remote_domain_set_metadata_args {
> + remote_nonnull_domain dom;
> + int type;
> + remote_string metadata;
> + remote_string key;
> + remote_string uri;
> + unsigned int flags;
> +};
> +
> +struct remote_domain_get_metadata_args {
> + remote_nonnull_domain dom;
> + int type;
> + remote_string uri;
> + unsigned int flags;
> +};
> +
> +struct remote_domain_get_metadata_ret {
> + remote_string metadata;
This should be remote_nonnull_string (errors are returned automatically;
the _ret struct is only used on success, which means it will never be
used for NULL).
> @@ -2708,7 +2728,9 @@ enum remote_procedure {
> REMOTE_PROC_STORAGE_VOL_RESIZE = 260, /* autogen autogen */
>
> REMOTE_PROC_DOMAIN_PM_SUSPEND_FOR_DURATION = 261, /* autogen autogen */
> - REMOTE_PROC_DOMAIN_GET_CPU_STATS = 262 /* skipgen skipgen */
> + REMOTE_PROC_DOMAIN_GET_CPU_STATS = 262, /* skipgen skipgen */
> + REMOTE_PROC_DOMAIN_SET_METADATA = 263, /* autogen autogen */
> + REMOTE_PROC_DOMAIN_GET_METADATA = 264 /* autogen autogen */
I'm surprised our generator didn't complain about things - it should be
requiring nonnull_string in *_ret (but that can be a patch for a
different day).
I'm interested in this API making it into 0.9.10, and I think you're
close enough that you could push this after fixing the issues I pointed
out above. ACK with above issues fixed.
--
Eric Blake eblake at redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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