[libvirt] [PATCH 2/3] Improve error reporting with LXC controller

[Daniel P. Berrange]

From: "Daniel P. Berrange" <berrange at redhat.com>

The LXC code would read the log file if an LXC guest failed to
startup. There were a number of failure cases where the guest
will not start and libvirtd never gets as far as looking at the
log file.

Fix this by replacing some earlier generic errors with messages
from the log.

Signed-off-by: Daniel P. Berrange <berrange at redhat.com>
---
 src/lxc/lxc_process.c | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/src/lxc/lxc_process.c b/src/lxc/lxc_process.c
index d07ff13..840e138 100644
--- a/src/lxc/lxc_process.c
+++ b/src/lxc/lxc_process.c
@@ -980,6 +980,7 @@ int virLXCProcessStart(virConnectPtr conn,
     virErrorPtr err = NULL;
     virLXCDriverConfigPtr cfg = virLXCDriverGetConfig(driver);
     virCgroupPtr selfcgroup;
+    int status;
 
     if (virCgroupNewSelf(&selfcgroup) < 0)
         return -1;
@@ -1182,9 +1183,18 @@ int virLXCProcessStart(virConnectPtr conn,
         VIR_WARN("Unable to seek to end of logfile: %s",
                  virStrerror(errno, ebuf, sizeof(ebuf)));
 
-    if (virCommandRun(cmd, NULL) < 0)
+    if (virCommandRun(cmd, &status) < 0)
         goto cleanup;
 
+    if (status != 0) {
+        if (virLXCProcessReadLogOutput(vm, logfile, pos, ebuf, sizeof(ebuf)) <= 0)
+            snprintf(ebuf, sizeof(ebuf), "unexpected exit status %d", status);
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("guest failed to start: %s"), ebuf);
+        goto cleanup;
+    }
+
+
     if (VIR_CLOSE(handshakefds[1]) < 0) {
         virReportSystemError(errno, "%s", _("could not close handshake fd"));
         goto cleanup;
@@ -1193,16 +1203,25 @@ int virLXCProcessStart(virConnectPtr conn,
     /* Connect to the controller as a client *first* because
      * this will block until the child has written their
      * pid file out to disk & created their cgroup */
-    if (!(priv->monitor = virLXCProcessConnectMonitor(driver, vm)))
+    if (!(priv->monitor = virLXCProcessConnectMonitor(driver, vm))) {
+        VIR_ERROR("Here");
+        /* Intentionally overwrite the real monitor error message,
+         * since a better one is almost always found in the logs
+         */
+        if (virLXCProcessReadLogOutput(vm, logfile, pos, ebuf, sizeof(ebuf)) > 0) {
+        VIR_ERROR("tHere");
+            virResetLastError();
+            virReportError(VIR_ERR_INTERNAL_ERROR,
+                           _("guest failed to start: %s"), ebuf);
+        }
         goto cleanup;
+    }
 
     /* And get its pid */
     if ((r = virPidFileRead(cfg->stateDir, vm->def->name, &vm->pid)) < 0) {
-        char out[1024];
-
-        if (virLXCProcessReadLogOutput(vm, logfile, pos, out, 1024) > 0)
+        if (virLXCProcessReadLogOutput(vm, logfile, pos, ebuf, sizeof(ebuf)) > 0)
             virReportError(VIR_ERR_INTERNAL_ERROR,
-                           _("guest failed to start: %s"), out);
+                           _("guest failed to start: %s"), ebuf);
         else
             virReportSystemError(-r,
                                  _("Failed to read pid file %s/%s.pid"),
-- 
1.8.3.1