Cache connection failures

src/libstore/remote-store.cc

@@ -44,13 +44,26 @@ RemoteStore::RemoteStore(const Params & params)
     : Store(params)
     , connections(make_ref<Pool<Connection>>(
             std::max(1, std::stoi(get(params, "max-connections", "1"))),
-            [this]() { return openConnection(); },
+            [this]() { return openConnectionWrapper(); },
             [](const ref<Connection> & r) { return r->to.good() && r->from.good(); }
             ))
 {
 }
 
 
+ref<RemoteStore::Connection> RemoteStore::openConnectionWrapper()
+{
+    if (failed)
+        throw Error("opening a connection to remote store ‘%s’ previously failed", getUri());
+    try {
+        return openConnection();
+    } catch (...) {
+        failed = true;
+        throw;
+    }
+}
+
+
 UDSRemoteStore::UDSRemoteStore(const Params & params)
     : Store(params)
     , LocalFSStore(params)

src/libstore/remote-store.hh

@@ -98,6 +98,8 @@ protected:
         void processStderr(Sink * sink = 0, Source * source = 0);
     };
 
+    ref<Connection> openConnectionWrapper();
+
     virtual ref<Connection> openConnection() = 0;
 
     void initConnection(Connection & conn);
@@ -106,6 +108,8 @@ protected:
 
 private:
 
+    std::atomic_bool failed{false};
+
     void setOptions(Connection & conn);
 };