Merge pull request #6144 from dachary/wip-13339-hammer

mon: check for store writeablility before participating in election

Reviewed-by: Sage Weil <sage@redhat.com>

src/mon/Elector.cc

@@ -78,8 +78,15 @@ void Elector::start()
   init();
 
   // start by trying to elect me
-  if (epoch % 2 == 0) 
+  if (epoch % 2 == 0) {
     bump_epoch(epoch+1);  // odd == election cycle
+  } else {
+    // do a trivial db write just to ensure it is writeable.
+    MonitorDBStore::TransactionRef t(new MonitorDBStore::Transaction);
+    t->put(Monitor::MONITOR_NAME, "election_writeable_test", rand());
+    int r = mon->store->apply_transaction(t);
+    assert(r >= 0);
+  }
   start_stamp = ceph_clock_now(g_ceph_context);
   electing_me = true;
   acked_me[mon->rank] = CEPH_FEATURES_ALL;

src/mon/MonitorDBStore.h

@@ -291,6 +291,8 @@ class MonitorDBStore
 	  db->compact_range_async(compact.front().first, compact.front().second.first, compact.front().second.second);
 	compact.pop_front();
       }
+    } else {
+      assert(0 == "failed to write to db");
     }
     return r;
   }
@@ -568,7 +570,8 @@ class MonitorDBStore
     for (iter = prefixes.begin(); iter != prefixes.end(); ++iter) {
       dbt->rmkeys_by_prefix((*iter));
     }
-    db->submit_transaction_sync(dbt);
+    int r = db->submit_transaction_sync(dbt);
+    assert(r >= 0);
   }
 
   int open(ostream &out) {