MyCATApache/Mycat-Server · critical · ConfigException

[ node : ] in [ group: ] doesn't exist!

Error message

[ node :${s}] in [ group:${groupName}] doesn't exist!

What it means

ClusterConfig.loadGroup validates that every node listed in a group's nodeList exists in the parsed `nodes` map. If any referenced dataHost/node name is not defined earlier in the schema.xml configuration, ConfigException is thrown. Mycat refuses to start with an inconsistent cluster definition.

Solutions

  1. Fix the nodeList entry in schema.xml so every name exactly matches an existing <dataNode name=...> definition.
  2. Add the missing <dataNode> definition for the referenced node before the group is loaded.
  3. Remove stale node names from the group's nodeList if that node is no longer used.

Example fix

// before (schema.xml)
<group name="group1"><nodeList>dn1,dn9</nodeList></group>
// after
<group name="group1"><nodeList>dn1,dn2</nodeList></group>
Defensive patterns

Strategy: validation

Validate before calling

// Java: validate group nodeList before startup
for (String nodeName : groupNodeList.split(",")) {
    if (!nodes.containsKey(nodeName.trim())) {
        throw new IllegalArgumentException("nodeList references undefined node: " + nodeName);
    }
}

Try / catch

try { ClusterConfig.load(); } catch (ConfigException e) { LOG.error("Bad group/nodeList config: {}", e.getMessage()); throw new IllegalStateException("Fix schema.xml nodeList entries", e); }

Prevention

When it happens

Trigger: Loading schema.xml: a <group> element's nodeList attribute (comma-separated) references a node name that has no corresponding <dataNode> definition in the same file, so nodes.containsKey(s) is false.

Common situations: Typo in a node name inside nodeList; renaming or deleting a dataNode while the group still references the old name; splitting config across files and forgetting the node entry; copy-pasting group blocks from another deployment.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

AI-assisted analysis of MyCATApache/Mycat-Server@65f8d8beb7 (2026-09-11). Data as JSON: /api/errors/ca0e810579e448d1. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/io/mycat/config/model/ClusterConfig.java:128

                if (groups.containsKey(groupName)) {
                    throw new ConfigException("group duplicated : " + groupName);
                }

                Map<String, Object> props = ConfigUtil.loadElements(e);
                String value = (String) props.get("nodeList");
                if (null == value || "".equals(value)) {
                    throw new ConfigException("group should contain 'nodeList'");
                }

                String[] sList = SplitUtil.split(value, ',', true);

                if (null == sList || sList.length == 0) {
                    throw new ConfigException("group should contain 'nodeList'");
                }

                for (String s : sList) {
                    if (!nodes.containsKey(s)) {
                        throw new ConfigException("[ node :" + s + "] in [ group:" + groupName + "] doesn't exist!");
                    }
                }
                List<String> nodeList = Arrays.asList(sList);
                groups.put(groupName, nodeList);
            }
        }
        if (!groups.containsKey("default")) {
            List<String> nodeList = new ArrayList<String>(nodes.keySet());
            groups.put("default", nodeList);
        }
        return groups;
    }
}

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