MyCATApache/Mycat-Server · error · RuntimeException

can not find the data node with name

Error message

can not find the data node with name:{dataNode}

What it means

Before fetching, SequenceVal resolves the data host config for the sequence's dataNode from MycatConfig. If conf.getDataNodes() has no entry for this.dataNode, it throws a RuntimeException naming the missing data node. This is a configuration-resolution failure, not a runtime DB failure.

Solutions

1. Verify the dataNode name in the sequence/table config matches a <dataNode name="..."> entry in schema.xml.
2. Fix the typo or add the missing dataNode definition, then restart/reload Mycat.
3. Check that the config Mycat loaded at runtime is the file you edited (correct conf directory).

Example fix

// before (schema.xml)
<table name="t" dataNode="dnX"/> <!-- dnX not defined -->
// after
<dataNode name="dn1" dataHost="host1" database="db1"/>
<table name="t" dataNode="dn1"/>

if (!MycatServer.getInstance().getConfig().getDataNodes().containsKey(dataNode)) {
    throw new IllegalArgumentException("dataNode not defined: " + dataNode);
}

try { seqVal.fetchSequenceFromDB(); } catch (RuntimeException e) { log.error("missing dataNode for sequence", e); }

When it happens

Trigger: SequenceVal constructed with a dataNode name that is not declared in schema.xml's <dataNode> definitions (typo, dataNode removed, config not reloaded).

Common situations: Sequence configured under a table whose dataNode was renamed; stale Mycat config after editing schema.xml without restart/reload.

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

• dataNode name is null
• invalid table dataNodes
• invalid param ,connection request db is
• SelfCheck### user all node is empty!
• SelfCheck### users node within the item is empty!

AI-assisted analysis of MyCATApache/Mycat-Server@65f8d8beb7 (2026-09-11). Data as JSON: /api/errors/11454c1af9c7ce08. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/io/mycat/route/sequence/handler/SequenceVal.java:231

						con.close();
						pstmt.close();
						rs.close();
					} catch (SQLException e) {
						e.printStackTrace();
					}
				}
			}
		}
		LOGGER.error("get sequence:" + this.seqName + " value failure, please check the sequence config");
		this.fetching.compareAndSet(true, false);
		return null;
	}

	private DataHostConfig getDBHostConfig() {
		MycatConfig conf = MycatServer.getInstance().getConfig();
		PhysicalDBNode mysqlDN = conf.getDataNodes().get(this.dataNode);
		if (mysqlDN == null) {
			throw new RuntimeException("can not find the data node with name:" + this.dataNode);
		}
		PhysicalDatasource physicalDatasource = mysqlDN.getDbPool().getSource();
		return physicalDatasource.getHostConfig();
	}

	public void sleep(long time) {
		try {
			Thread.sleep(time);
		} catch (InterruptedException e) {
			IncrSequenceMySQLHandler.LOGGER
					.warn("wait db fetch sequnce err " + e);
		}
	}
	//是否成功返回。
	public boolean isSuccessFetched() {
		return successFetched;
	}
	//下一个可用的id

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