[libvirt PATCH v2] src: warn if client hits the max requests limit

Since they are simply normal RPC messages, the keep alive packets are subject to the "max_client_requests" limit just like any API calls. Thus, if a client hits the 'max_client_requests' limit and all the pending API calls take a long time to complete, it may result in keep-alives firing and dropping the client connection. This has been seen by a number of users with the default value of max_client_requests=5, by issuing 5 concurrent live migration operations. By printing a warning message when this happens, admins will be alerted to the fact that their active clients are exceeding the default client requests limit. Signed-off-by: Daniel P. Berrangé <berrange(a)redhat.com&gt; --- In v2: - now only warn once per client to avoid log spam src/rpc/virnetserverclient.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/src/rpc/virnetserverclient.c b/src/rpc/virnetserverclient.c index 30f6af7be5..c9a4eb521e 100644 --- a/src/rpc/virnetserverclient.c +++ b/src/rpc/virnetserverclient.c @@ -93,6 +93,9 @@ struct _virNetServerClient * throttling calculations */ size_t nrequests; size_t nrequests_max; + /* True if we've warned about nrequests hittin + * the server limit already */ + bool nrequests_warning; /* Zero or one messages being received. Zero if * nrequests >= max_clients and throttling */ virNetMessage *rx; @@ -1261,6 +1264,11 @@ static virNetMessage *virNetServerClientDispatchRead(virNetServerClient *client) client->rx->buffer = g_new0(char, client->rx->bufferLength); client->nrequests++; } + } else if (!client->nrequests_warning) { + client->nrequests_warning = true; + VIR_WARN("Client hit max requests limit %zd. This may result " + "in keep-alive timeouts. Consider tuning the " + "max_client_requests server parameter", client->nrequests); } virNetServerClientUpdateEvent(client); -- 2.37.3