[libvirt PATCH v4 15/31] qemu: log error output from nbdkit

[Jonathon Jongsma <jjongsma@xxxxxxxxxx>]

log stderr and stdout from nbdkit into its own log so that
nbdkit-related issues can be debugged more easily.

Signed-off-by: Jonathon Jongsma <jjongsma@xxxxxxxxxx>
---
 src/qemu/qemu_nbdkit.c | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/src/qemu/qemu_nbdkit.c b/src/qemu/qemu_nbdkit.c
index 34462f784a..7a7b9a6a54 100644
--- a/src/qemu/qemu_nbdkit.c
+++ b/src/qemu/qemu_nbdkit.c
@@ -848,15 +848,24 @@ qemuNbdkitProcessStart(qemuNbdkitProcess *proc,
     int rc;
     int exitstatus = 0;
     int cmdret = 0;
-    VIR_AUTOCLOSE errfd = -1;
     virTimeBackOffVar timebackoff;
     bool socketCreated = false;
+    g_autofree char *basename = g_strdup_printf("%s-nbdkit-%i", vm->def->name, proc->source->id);
+    int logfd = -1;
+    g_autoptr(qemuLogContext) logContext = NULL;
+    g_autofree char *errmsg = NULL;
+    g_autoptr(virURI) uri = NULL;
+    g_autofree char *uristring = NULL;
 
     if (!(cmd = qemuNbdkitProcessBuildCommand(proc)))
         return -1;
 
+    logContext = qemuLogContextNew(driver, vm, basename);
+    logfd = qemuLogContextGetWriteFD(logContext);
+
     VIR_DEBUG("starting nbdkit process for %s", proc->source->nodestorage);
-    virCommandSetErrorFD(cmd, &errfd);
+    virCommandSetErrorFD(cmd, &logfd);
+    virCommandSetOutputFD(cmd, &logfd);
     virCommandSetPidFile(cmd, proc->pidfile);
 
     if (qemuExtDeviceLogCommand(driver, vm, cmd, "nbdkit") < 0)
@@ -900,12 +909,15 @@ qemuNbdkitProcessStart(qemuNbdkitProcess *proc,
     return 0;
 
  error:
-    if (errfd > 0) {
-        g_autofree char *errbuf = g_new0(char, 1024);
-        if (read(errfd, errbuf, 1024) > 0)
-            virReportError(VIR_ERR_OPERATION_FAILED,
-                           _("nbdkit failed to start and reported: %s"), errbuf);
-    }
+    if (qemuLogContextReadFiltered(logContext, &errmsg, 1024) < 0)
+        VIR_WARN("Unable to read from nbdkit log");
+
+    uri = qemuBlockStorageSourceGetURI(proc->source);
+    uristring = virURIFormat(uri);
+    virReportError(VIR_ERR_INTERNAL_ERROR,
+                   _("Failed to connect to nbdkit for '%s': %s"),
+                   uristring, errmsg);
+
     qemuNbdkitProcessStop(proc);
     return -1;
 }
-- 
2.39.0