[libvirt] [PATCH] Make error reporting for QEMU JSON mode more friendly

[Daniel P. Berrange]

Current error reporting for JSON mode returns the full JSON
command string and full JSON error string. This is not very
user friendly, so this change makes the error report only
contain the basic command name, and friendly error message
description string. The full JSON data is logged instead.

* src/qemu/qemu_monitor_json.c: Always return the 'desc' field from
  the JSON error message to users.
---
 src/qemu/qemu_monitor_json.c |   58 ++++++++++++++++++++++++++++-------------
 1 files changed, 39 insertions(+), 19 deletions(-)

diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c
index f0dcf81..9875f38 100644
--- a/src/qemu/qemu_monitor_json.c
+++ b/src/qemu/qemu_monitor_json.c
@@ -246,15 +246,33 @@ qemuMonitorJSONCommand(qemuMonitorPtr mon,
  *
  * XXX see qerror.h for different klasses & fill out useful params
  */
-static char *qemuMonitorJSONStringifyError(virJSONValuePtr error)
+static const char *
+qemuMonitorJSONStringifyError(virJSONValuePtr error)
 {
     const char *klass = virJSONValueObjectGetString(error, "class");
+    const char *detail = NULL;
 
-    if (klass) {
-        return strdup(klass);
-    } else {
-        return strdup(_("Missing QEMU error klass"));
-    }
+    /* The QMP 'desc' field is usually sufficient for our generic
+     * error reporting needs.
+     */
+    if (klass)
+        detail = virJSONValueObjectGetString(error, "desc");
+
+
+    if (!detail)
+        detail = "unknown QEMU command error";
+
+    return detail;
+}
+
+static const char *
+qemuMonitorJSONCommandName(virJSONValuePtr cmd)
+{
+    const char *name = virJSONValueObjectGetString(cmd, "execute");
+    if (name)
+        return name;
+    else
+        return "<unknown>";
 }
 
 static int
@@ -266,20 +284,21 @@ qemuMonitorJSONCheckError(virJSONValuePtr cmd,
         char *cmdstr = virJSONValueToString(cmd);
         char *replystr = virJSONValueToString(reply);
 
-        if (!error) {
-            VIR_DEBUG("Saw a JSON error, but value is null for %s: %s",
-                      cmdstr, replystr);
+        /* Log the full JSON formatted command & error */
+        VIR_DEBUG("unable to execute QEMU command %s: %s",
+                  cmdstr, replystr);
+
+        /* Only send the user the command name + friendly error */
+        if (!error)
             qemuReportError(VIR_ERR_INTERNAL_ERROR,
-                            _("error running QEMU command '%s': '%s'"),
-                            cmdstr, replystr);
-        } else {
-            VIR_DEBUG("Got a JSON error set for %s", cmdstr);
-            char *detail = qemuMonitorJSONStringifyError(error);
+                            _("unable to execute QEMU command '%s'"),
+                            qemuMonitorJSONCommandName(cmd));
+        else
             qemuReportError(VIR_ERR_INTERNAL_ERROR,
-                            _("error running QEMU command '%s': %s ('%s')"),
-                            cmdstr, detail, replystr);
-            VIR_FREE(detail);
-        }
+                            _("unable to execute QEMU command '%s': %s"),
+                            qemuMonitorJSONCommandName(cmd),
+                            qemuMonitorJSONStringifyError(error));
+
         VIR_FREE(cmdstr);
         VIR_FREE(replystr);
         return -1;
@@ -290,7 +309,8 @@ qemuMonitorJSONCheckError(virJSONValuePtr cmd,
         VIR_DEBUG("Neither 'return' nor 'error' is set in the JSON reply %s: %s",
                   cmdstr, replystr);
         qemuReportError(VIR_ERR_INTERNAL_ERROR,
-                        _("error running QEMU command '%s': '%s'"), cmdstr, replystr);
+                        _("unable to execute QEMU command '%s'"),
+                        qemuMonitorJSONCommandName(cmd));
         VIR_FREE(cmdstr);
         VIR_FREE(replystr);
         return -1;
-- 
1.6.6