Notes for novice when deploying dolphin DB

Time:2021-3-6

Notes for novice when deploying dolphin DB

1. Why do Linux users have the error of “permission denied” when they start the control node or proxy node from the command line?

For Linux users, before starting dolphin dB, you need to execute the following command to modify the permissions of executable files, enter the server folder of the installation directory, and execute the following command:

chmod +x dolphindb
2. Why is the “status” column of the data node still red when you click the execute button on the Web cluster manager?

After clicking the execute button, you need to click the refresh button to refresh the status of the node. If the “status” column is still red after refreshing, there may be four reasons:

(1) The port is occupied. Click the view button in the "server log" column to view the log file of the data node. If "failed to bind the socket on xxxx" appears, the port number of the node to be started is the port number of the node to be started. This may be because the port number has been occupied by other programs. In this case, shut down other programs or reassign the port number to the dolphin DB node after restarting the node. It may also be that the node has just been shut down and the Linux kernel has not released the port number. In this case, wait 30 seconds, and then start the node.
(2) The firewall does not open the port. The firewall will restrict some ports. If these ports are used, they need to be opened or closed in the firewall.
(3) The IP address, port number or node alias in the configuration file is not written correctly. The IP address of the node needs to use LAN IP instead of "localhost".
(4) If the cluster is deployed in the cloud or k8s environment, you need to agent.cfg and cluster.cfg Add the configuration item lancluster = 0 in the file to start normally.
3. Why can’t the dolphin DB GUI start?

There are two reasons why the dolphin DB GUI can not be started: one is that Java is not installed; the other is that the installed java version is wrong. The environment for using the dolphin DB GUI requires Java 8 or above. Java download addresshttps://www.oracle.com/technetwork/java/javase/downloads/index.html

4. After defining variables on the web, why do you report the error of undefined variables after a period of time?

When using the dolphin DB notebook, if no command is executed within 10 minutes, the system will automatically close the session to release the dolphin DB system resources. It is recommended that users write and execute code in the dolphin DB GUI. The session of dolphin DB GUI will exist until the user closes down.

5. Why is there an error of “DFS is not enabled or the system is not a data node” when creating or accessing distributed tables?

The possible reason for this error is that code was executed on the control node or proxy node of the cluster. The control node is used to manage metadata and transactions of data nodes and distributed file systems, while the agent node is used to start and close data nodes, which is not used for computing. Users only need to switch to the data node to execute the code.

6. Why is there an error of “not granted to create or delete databases” when creating / deleting distributed tables?

Dolphin DB provides user rights management. Only users with corresponding rights can operate on databases and tables. If the user has the right to create / delete the distributed table, just log in with the login function. Default admin login:

login("admin", "123456")