nathanmarz/storm · error · RuntimeException

No DRPC servers configured for topology

Error message

No DRPC servers configured for topology

What it means

DRPCSpout.open reads Config.DRPC_SERVERS from the topology conf to create DRPCInvocationsClient connections. If the list is null or empty it throws a RuntimeException because the spout has no servers to pull DRPC requests from.

Solutions

1. Set Config.DRPC_SERVERS in the topology conf to the list of DRPC server hosts.
2. Also set Config.DRPC_INVOCATIONS_PORT to the DRPC invocations port (default 3773).
3. Verify the config is not overwritten after being set (conf.putAll order).
4. For local testing, point DRPC_SERVERS at localhost and run a local DRPC server.

Example fix

// before
conf.put(Config.DRPC_INVOCATIONS_PORT, 3773);
// after
conf.put(Config.DRPC_INVOCATIONS_PORT, 3773);
conf.put(Config.DRPC_SERVERS, Arrays.asList("drpc1.example.com", "drpc2.example.com"));

List<String> servers = (List<String>) conf.get(Config.DRPC_SERVERS);
if (servers == null || servers.isEmpty()) {
    throw new IllegalStateException("Set " + Config.DRPC_SERVERS + " before submitting a DRPC topology");
}
if (!conf.containsKey(Config.DRPC_INVOCATIONS_PORT)) {
    throw new IllegalStateException("Set " + Config.DRPC_INVOCATIONS_PORT);
}

When it happens

Trigger: Building a topology containing DRPCSpout without setting Config.DRPC_SERVERS (or setting it to an empty list) in the conf, then running the topology (local or distributed).

Common situations: DRPC topologies submitted with a bare conf; conf key omitted after copying an example; DRPC_SERVERS accidentally cleared by code that overwrites the conf Map.

Understand the failure class

Background: "is required", "must be set", "missing required field": configuration validation errors across open-source libraries — this error's family across 36 libraries.

Related errors

• Must declare exactly one stream from last bolt in…
• Output stream of last component in LinearDRPCTopology must…
• Cannot join DRPC stream with streams originating from other…
• Each element of the list
• Field must be an Iterable of

AI-assisted analysis of nathanmarz/storm@cdb116e942 (2026-09-12). Data as JSON: /api/errors/ce6b8d83f7732e1a. Report an issue: GitHub.

Appendix: source

Thrown at storm-core/src/jvm/backtype/storm/drpc/DRPCSpout.java:79

        _function = function;
    }

    public DRPCSpout(String function, ILocalDRPC drpc) {
        _function = function;
        _local_drpc_id = drpc.getServiceId();
    }
    
    @Override
    public void open(Map conf, TopologyContext context, SpoutOutputCollector collector) {
        _collector = collector;
        if(_local_drpc_id==null) {
            int numTasks = context.getComponentTasks(context.getThisComponentId()).size();
            int index = context.getThisTaskIndex();

            int port = Utils.getInt(conf.get(Config.DRPC_INVOCATIONS_PORT));
            List<String> servers = (List<String>) conf.get(Config.DRPC_SERVERS);
            if(servers == null || servers.isEmpty()) {
                throw new RuntimeException("No DRPC servers configured for topology");   
            }
            if(numTasks < servers.size()) {
                for(String s: servers) {
                    _clients.add(new DRPCInvocationsClient(s, port));
                }
            } else {
                int i = index % servers.size();
                _clients.add(new DRPCInvocationsClient(servers.get(i), port));
            }
        }
        
    }

    @Override
    public void close() {
        for(DRPCInvocationsClient client: _clients) {
            client.close();
        }

View on GitHub (pinned to cdb116e942)