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FAQ

Last Updated: May 24, 2022

How do I select an instance type for a TSDB instance?

You can select an instance type for a Lindorm Time Series Database (TSDB) instance based on the following two metrics:

  • Number of time series: the number of data collection points on devices. A data collection point can be a sensor on a device. The data collected from a sensor is to be uploaded. The following formula is used: Number of time series = Number of devices x Number of data collection points or sensors on a device.

  • Write efficiency: the average number of data points or data records that need to be globally written to a TSDB database per second. The following formula is used: Write efficiency = Number of time series × Average number of data points that need to be written to a time series per second.

Note

If you need to write multivariate data points, the following formula is used: Total number of data points to write = Number of multivariate data points x Number of fields in each multivariate data point.

Can I connect to a TSDB instance over the Internet?

You can connect to a TSDB instance over the Internet. TSDB supports Internet access. Before you enable Internet access, make sure that the TSDB instance that you want to connect is created in a virtual private cloud (VPC). For more information about how to enable Internet access, see the "Internet connection" section in Network connection.

How does TSDB provide a visual display of data?

TSDB provides the following methods to visualize data:

You can connect a TSDB instance to Grafana to visualize data. For more information, see Connect a TSDB instance to Grafana.

What do I do if a connection to a TSDB instance times out and the error message "Connection timed out" is returned?

By default, a TSDB instance is deployed in a VPC. If the TSDB instance and the machine that you use to connect to the instance are deployed in different VPCs, the connection fails, and a timeout error occurs. You can use the following method to resolve the issue:

If the TSDB instance and the machine that you use to connect to the instance are deployed in the same region, you can add the machine to the NAT gateway that is associated with the VPC in which the TSDB instance is deployed. For more information, see Migrate an ECS instance.

What do I do if the error message "Exceed Max TS counter xxxx" is returned?

The error message is returned because the maximum number of time series that can be stored in the TSDB instance of the purchased specification is exceeded.

In this case, you must expand the instance. For more information, see Instance types and pricing.

What do I do if the error message "a null credential specified in the authorization field" is returned?

The error message is returned because the account management feature is enabled for your TSDB instance, but the request that you send does not contain account authentication information. For more information, see Manage accounts.

After the account management feature is enabled, we recommend that you adjust the business logic to ensure that each request that you send to write or query data contains the required account authentication information.

Effect of account management on read and write requests

What do I do if the error message "INTERNAL: Missing start time" is returned for a TSQL query?

When you run an SQL query on the TSQL Development page in the TSDB console, the following error message can occur:

Error in calling SQL restful api with error { "errorMessage" : "INTERNAL_ERROR ERROR: io.grpc.StatusRuntimeException: INTERNAL: Missing start time.\nTSDB query execution failure \n …… }

The error message is returned because the start time of the query is not specified in the WHERE clause. For example, the error message can occur if you execute the following statement:

select * from metric_name

If you do not specify a time range for an SQL query, TSDB performs a full table scan. In this case, if a large amount of data is scanned, the instance performance is degraded. To resolve this issue, TSDB V2.5.14 or later requires the start time of an SQL query. This works in the same manner as the start time of an HTTP request.

Before you execute an SQL statement, make sure that a start time is specified in the statement. For example, you can execute the following statement:

select * from metric_name where `timestamp` >= '2020-01-01 00:00:00 +0800'