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Re: [libvirt] [PATCHv4 06/10] Widening API change - accept empty path for virDomainBlockStats



On 14.02.2014 18:49, Thorsten Behrens wrote:
And provide domain summary stat in that case, for lxc backend.
Use case is a container inheriting all devices from the host,
e.g. when doing application containerization.
---
  src/libvirt.c                |  8 ++++++--
  tools/virsh-domain-monitor.c | 11 ++++++++---
  tools/virsh.pod              |  5 +++--
  3 files changed, 17 insertions(+), 7 deletions(-)

Very wise! We unfortunately can't allow NULL here as it would require RPC change (and thus a new API - we have no upstream experience with introducing a new version on RPC :))


diff --git a/src/libvirt.c b/src/libvirt.c
index 666ab1e..b0051bb 100644
--- a/src/libvirt.c
+++ b/src/libvirt.c
@@ -7747,7 +7747,9 @@ error:
   * an unambiguous source name of the block device (the <source
   * file='...'/> sub-element, such as "/path/to/image").  Valid names
   * can be found by calling virDomainGetXMLDesc() and inspecting
- * elements within //domain/devices/disk.
+ * elements within //domain/devices/disk. Some drivers might also
+ * accept the empty string for the @disk parameter, and then yield
+ * summary stats for the entire domain.
   *
   * Domains may have more than one block device.  To get stats for
   * each you should make multiple calls to this function.
@@ -7813,7 +7815,9 @@ error:
   * an unambiguous source name of the block device (the <source
   * file='...'/> sub-element, such as "/path/to/image").  Valid names
   * can be found by calling virDomainGetXMLDesc() and inspecting
- * elements within //domain/devices/disk.
+ * elements within //domain/devices/disk. Some drivers might also
+ * accept the empty string for the @disk parameter, and then yield
+ * summary stats for the entire domain.
   *
   * Domains may have more than one block device.  To get stats for
   * each you should make multiple calls to this function.
diff --git a/tools/virsh-domain-monitor.c b/tools/virsh-domain-monitor.c
index de4afbb..105f841 100644
--- a/tools/virsh-domain-monitor.c
+++ b/tools/virsh-domain-monitor.c
@@ -888,7 +888,7 @@ static const vshCmdOptDef opts_domblkstat[] = {
      },
      {.name = "device",
       .type = VSH_OT_DATA,
-     .flags = VSH_OFLAG_REQ,
+     .flags = VSH_OFLAG_EMPTY_OK,
       .help = N_("block device")
      },
      {.name = "human",
@@ -954,8 +954,13 @@ cmdDomblkstat(vshControl *ctl, const vshCmd *cmd)
      if (!(dom = vshCommandOptDomain(ctl, cmd, &name)))
          return false;

-    if (vshCommandOptStringReq(ctl, cmd, "device", &device) < 0)
-        goto cleanup;
+    /* device argument is optional now. if it's missing, supply empty
+       string to denote 'all devices'. A NULL device arg would violate
+       API contract.
+     */
+    rc = vshCommandOptStringReq(ctl, cmd, "device", &device); /* and ignore rc */
+    if (!device)
+        device = "";

Well, we rather check the return value in a different manner. Although this should never return an error.


      rc = virDomainBlockStatsFlags(dom, device, NULL, &nparams, 0);

diff --git a/tools/virsh.pod b/tools/virsh.pod
index f221475..a13a1c7 100644
--- a/tools/virsh.pod
+++ b/tools/virsh.pod
@@ -623,12 +623,13 @@ If I<--graceful> is specified, don't resort to extreme measures
  (e.g. SIGKILL) when the guest doesn't stop after a reasonable timeout;
  return an error instead.

-=item B<domblkstat> I<domain> I<block-device> [I<--human>]
+=item B<domblkstat> I<domain> [I<block-device>] [I<--human>]

  Get device block stats for a running domain.  A I<block-device> corresponds
  to a unique target name (<target dev='name'/>) or source file (<source
  file='name'/>) for one of the disk devices attached to I<domain> (see
-also B<domblklist> for listing these names).
+also B<domblklist> for listing these names). On a lxc domain, omitting the
+I<block-device> yields device block stats summarily for the entire domain.

  Use I<--human> for a more human readable output.



Michal


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