Re: [libvirt] [PATCH v2] lib: Add note that bulk stats API queries may overrun RPC buffers

On 05/23/2017 04:35 PM, Martin Kletzander wrote: > On Tue, May 23, 2017 at 04:23:30PM +0200, Peter Krempa wrote: >> Hint that the users should limit the number of VMs queried in the bulk >> stats API. >> --- >> v2: >> - added a suggestion of the number of queried VMs (valid after bump to >> 32M message) >> >> src/libvirt-domain.c | 8 ++++++++ >> 1 file changed, 8 insertions(+) >> >> diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c >> index 310b91b37..aef061943 100644 >> --- a/src/libvirt-domain.c >> +++ b/src/libvirt-domain.c >> @@ -11315,6 +11315,10 @@ virConnectGetDomainCapabilities(virConnectPtr >> conn, >> * VIR_CONNECT_GET_ALL_DOMAINS_STATS_SHUTOFF and/or >> * VIR_CONNECT_GET_ALL_DOMAINS_STATS_OTHER for all other states. >> * >> + * Note that this API is prone to exceeding maximum RPC message size >> on hosts >> + * with lots of VMs so it's suggested to use virDomainListGetStats >> with a >> + * reasonable list of VMs as the argument. >> + * >> * Returns the count of returned statistics structures on success, -1 >> on error. >> * The requested data are returned in the @retStats parameter. The >> returned >> * array should be freed by the caller. See virDomainStatsRecordListFree. >> @@ -11386,6 +11390,10 @@ virConnectGetAllDomainStats(virConnectPtr conn, >> * Note that any of the domain list filtering flags in @flags may be >> rejected >> * by this function. >> * >> + * Note that this API is prone to exceeding maximum RPC if querying >> too many VMs >> + * with lots of statistics. It's suggested to query in batches of >> 10VMs, which >> + * should be good enough for VMs with 3000 disks + networks. >> + * > > Coming to think about it... Why don't we just batch this ourselves under > the hood and just return the merged result? Because: https://www.redhat.com/archives/libvir-list/2017-May/msg00088.html

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