[systemd-devel] [PATCH v5] bus-util: be more verbose if dbus job fails

[Michal Sekletar]

Users might have hard time figuring out why exactly their systemctl request
failed. If dbus job fails try to figure out more details about failure by
examining Result property of the service.

https://bugzilla.redhat.com/show_bug.cgi?id=1016680
---

Changes in v5:
        * simplified code for retrieval of Result property
        * in case unknown service Result is retrieved from systemd don't abort but print generic error message
        * fixed grammar error
        
 src/libsystemd/sd-bus/bus-util.c | 79 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 72 insertions(+), 7 deletions(-)

diff --git a/src/libsystemd/sd-bus/bus-util.c b/src/libsystemd/sd-bus/bus-util.c
index ea2379d..fcb14a4 100644
--- a/src/libsystemd/sd-bus/bus-util.c
+++ b/src/libsystemd/sd-bus/bus-util.c
@@ -30,6 +30,7 @@
 #include "path-util.h"
 #include "missing.h"
 #include "set.h"
+#include "unit-name.h"
 
 #include "sd-bus.h"
 #include "bus-error.h"
@@ -1708,6 +1709,68 @@ static int bus_process_wait(sd_bus *bus) {
         }
 }
 
+static int bus_job_get_service_result(BusWaitForJobs *d, char **result) {
+        _cleanup_free_ char *dbus_path = NULL;
+
+        assert(d);
+        assert(d->name);
+        assert(result);
+
+        dbus_path = unit_dbus_path_from_name(d->name);
+        if (!dbus_path)
+                return -ENOMEM;
+
+        return sd_bus_get_property_string(d->bus,
+                                          "org.freedesktop.systemd1",
+                                          dbus_path,
+                                          "org.freedesktop.systemd1.Service",
+                                          "Result",
+                                          NULL,
+                                          result);
+}
+
+static const struct {
+        const char *result, *explanation;
+} explanations [] = {
+        { "resources", "configured resource limit was exceeded" },
+        { "timeout", "timeout was exceeded" },
+        { "exit-code", "control process exited with error code" },
+        { "signal", "fatal signal was delivered to the control process" },
+        { "core-dump", "fatal signal was delivered to the control process. Core dumped" },
+        { "watchdog", "service failed to send watchdog ping" },
+        { "start-limit", "start of the service was attempted too often too quickly" }
+};
+
+static void log_job_error_with_service_result(const char* service, const char *result) {
+        unsigned i;
+        _cleanup_free_ char *service_shell_quoted = NULL;
+
+        assert(service);
+        assert(result);
+
+        service_shell_quoted = shell_maybe_quote(service);
+
+        for (i = 0; i < ELEMENTSOF(explanations); ++i)
+                if (streq(result, explanations[i].result))
+                        break;
+
+        if (i < ELEMENTSOF(explanations))
+                log_error("Job for %s failed because %s. See \"systemctl status %s\" and \"journalctl -xe\" for details.\n",
+                          service,
+                          explanations[i].explanation,
+                          strna(service_shell_quoted));
+        else
+                log_error("Job for %s failed. See \"systemctl status %s\" and \"journalctl -xe\" for details.\n",
+                          service,
+                          strna(service_shell_quoted));
+
+        /* For some results maybe additional explanation is required */
+        if (streq_ptr(result, "start-limit"))
+                log_info("To force a start please invoke \"systemctl reset-failed %s\" followed by \"systemctl start %s\" again.",
+                         strna(service_shell_quoted),
+                         strna(service_shell_quoted));
+}
+
 static int check_wait_response(BusWaitForJobs *d, bool quiet) {
         int r = 0;
 
@@ -1727,15 +1790,17 @@ static int check_wait_response(BusWaitForJobs *d, bool quiet) {
                 else if (streq(d->result, "unsupported"))
                         log_error("Operation on or unit type of %s not supported on this system.", strna(d->name));
                 else if (!streq(d->result, "done") && !streq(d->result, "skipped")) {
-                        _cleanup_free_ char *quoted = NULL;
+                        if (d->name) {
+                                int q;
+                                _cleanup_free_ char *result = NULL;
 
-                        if (d->name)
-                                quoted = shell_maybe_quote(d->name);
+                                q = bus_job_get_service_result(d, &result);
+                                if (q < 0)
+                                        log_debug_errno(q, "Failed to get Result property of service %s: %m", d->name);
 
-                        if (quoted)
-                                log_error("Job for %s failed. See 'systemctl status %s' and 'journalctl -xe' for details.", d->name, quoted);
-                        else
-                                log_error("Job failed. See 'journalctl -xe' for details.");
+                                log_job_error_with_service_result(d->name, result);
+                        } else
+                                log_error("Job failed. See \"journalctl -xe\" for details.");
                 }
         }
 
-- 
2.3.4