基于ScenarioID标签从InfluxDB查询标签值返回空值的问题

我通过脚本将遥测数据发送至InfluxDB，在Grafana中尝试通过标签值创建变量过滤数据时，查询ScenarioID标签值返回空结果，但相同方式查询requestName标签值却能正常工作，具体情况如下：

查询所有遥测数据 #

请求 #

http://localhost:8086/query?db=ApiGatewayManagement&q=SELECT * FROM JMeter_Result

输出 #

{    
    "results": [        
        {            
            "statement_id": 0,            
            "series": [                
                {                    
                    "name": "JMeter_Result",                    
                    "columns": [                        
                        "time",                        
                        "ScenarioID",                        
                        "errorCount",                        
                        "httpstatuscode",                        
                        "receivedBytes",                        
                        "requestName",                        
                        "responseMessage",                        
                        "responseTime",                        
                        "responsecode",                        
                        "samplecount",                        
                        "sentBytes",                        
                        "status"                    
                    ],                    
                    "values": [                        
                        [                            
                            "2023-02-23T15:54:51.529Z",                            
                            "ambratest_sprint_01",                            
                            0,                            
                            "200",                            
                            7978228,                            
                            "T01_LaunchApplication",                            
                            "Number of samples in transaction : 1, number of failing samples : 0",                            
                            6673,                            
                            "200",                            
                            1,                            
                            7000,                            
                            "Success"                        
                        ],                        
                        [                            
                            "2023-02-23T15:54:58.315Z",                            
                            "ambratest_sprint_01",                            
                            1,                            
                            "401",                            
                            1565,                            
                            "T02_Login",                            
                            "Number of samples in transaction : 2, number of failing samples : 1",                            
                            570,                            
                            "401",                            
                            1,                            
                            1168,                            
                            "Failure"                        
                        ],                        
                        [                            
                            "2023-02-23T16:04:38.904Z",                            
                            "ambratest_sprint_02",                            
                            0,                            
                            "200",                            
                            7978237,                            
                            "T01_LaunchApplication",                            
                            "Number of samples in transaction : 1, number of failing samples : 0",                            
                            9591,                            
                            "200",                            
                            1,                            
                            7000,                            
                            "Success"                        
                        ],                        
                        [                            
                            "2023-02-23T16:04:48.635Z",                            
                            "ambratest_sprint_02",                            
                            0,                            
                            "200",                            
                            10923,                            
                            "T02_Login",                            
                            "Number of samples in transaction : 6, number of failing samples : 0",                            
                            1942,                            
                            "200",                            
                            1,                            
                            3518,                            
                            "Success"                        
                        ]                    
                    ]                
                }            
            ]        
        }    
    ]
}

标签值查询尝试 #

查询ScenarioID标签值（返回空） #

请求

http://localhost:8086/query?db=ApiGatewayManagement&q=SHOW TAG VALUES FROM "JMeter_Result" WITH KEY=" ScenarioID"

输出

{    
    "results": [        
        {            
            "statement_id": 0        
        }    
    ]
}

查询requestName标签值（正常返回） #

请求

http://localhost:8086/query?db=ApiGatewayManagement&q=SHOW TAG VALUES FROM "JMeter_Result" WITH KEY="requestName"

输出

{    
    "results": [        
        {            
            "statement_id": 0,            
            "series": [                
                {                    
                    "name": "JMeter_Result",                    
                    "columns": [                        
                        "key",                        
                        "value"                    
                    ],                    
                    "values": [                        
                        [                            
                            "requestName",                            
                            "T01_LaunchApplication"                        
                        ],                        
                        [                            
                            "requestName",                            
                            "T02_Login"                        
                        ]                    
                    ]                
                }            
            ]        
        }    
    ]
}

问题原因及解决办法 #

1. 直接原因：查询语句中的空格错误
   你查询ScenarioID的请求里，KEY=" ScenarioID" 中ScenarioID前面多了一个空格。InfluxDB对标签名的匹配是严格区分字符的，多余的空格会导致系统找不到对应的标签，因此返回空结果。

   修正后的查询请求：

   http://localhost:8086/query?db=ApiGatewayManagement&q=SHOW TAG VALUES FROM "JMeter_Result" WITH KEY="ScenarioID"
   

2. 额外验证：确认ScenarioID是标签而非字段
   从你查询所有数据的输出看，ScenarioID出现在columns列表中，但InfluxDB的SELECT *会同时返回标签和字段。如果调整空格后仍无法查询到结果，需要检查写入数据的脚本，确认ScenarioID是被配置为**标签（Tag）**写入的，而不是字段（Field）。只有标签才能通过SHOW TAG VALUES查询，字段需要用SHOW FIELD KEYS或其他字段查询语句。如果是误设为字段，需要修改写入脚本，将ScenarioID设为标签后重新写入数据。

内容的提问来源于stack exchange，提问作者Jyoti Prakash Mallick