Two week selection of tdengine community issues | phase II

Hi,TDengine database My user friends , In order to prevent too many common problems from bothering everyone , Convenient for everyone to learn 、 Absorb experience , We will select the common problems encountered by users in the community recently 、 Summary , Share with you . This is the second issue of this column , I will share the following common questions ：

One . How to troubleshoot connection problems at the fastest speed ？（ Include connector ）

First of all, we need to clarify a few points ：

1. When the network can be interconnected , Whether client or connector , All connection problems to the database basically belong to configuration problems ;

2. After encountering connector connection problems , Please check first  TDengine  Whether the client can work normally （ The specific confirmation method is to ensure that the client can successfully query the sub tables of each database server ）;

3. The specific errors of connection problems are mainly ：

1) “Unable to establish connection”;

2) “Unable to resolve FQDN”;

Next is the specific troubleshooting method ：

1. Run on the server taosd | grep -i fqdn , perhaps cat Data file directory （ The default is /var/lib/taos）/dnode/dnodeEps.json | grep -i fqdn, Get output fqdn Parameter values .

2. On the client server hosts In file , Check whether you have the right fqdn Parameter value and database server ip write .

3. If step 1 The output of is localhost, When the client initiates connection resolution, it will connect to itself 127.0.0.1 Thus, the connection fails , So at this point , Need to pass through taos.cfg（ The default path /etc/taos） The server fqdn Change the parameter value to other values , Then in the data file directory （ The default is /var/lib/taos）/dnode/dnodeEps.json Next sync update dnodeFqdn Value , Then restart the database service to load the new configuration , Back to step 1.

If step 1 The output of is not localhost, Continue with step 4.

4. The client relaunches the connection .

5. If there is still a problem with the connection , Please check the port rules of the firewall , ECS should also pay attention to the rules of security groups .

6. If you can't solve it after full try , Please be there. gitHub Or feedback in wechat Group , It will be handled with the assistance of official staff .

Two . 2.0 edition TDengine How to do data migration between different machines ？

1. Log in to the old database service first ,show dnodes Record each dnode Of ID Corresponding End Point And IP;

2. Plan the new database service nodes fqdn And IP Address , And the corresponding relationship with the nodes of the old system ;

3. Copy the data files of each node of the old system to the data file directory of the corresponding node of the new system ;

4. Connect the nodes of the old system taos.cfg Copy to the corresponding nodes of the new system , And make corresponding modifications ：firstEP/fqdn/dataDir/logDir wait ;

5. Edit the data folder of each node of the new system dnodeEps.json, Will be one of the dnodeFqdn Change to the existing fqdn Parameter values ,dnodePort Change to the existing serverPort Parameter values （ All in all , Make sure that the configuration of this file is the same as ours taos.cfg The actual configuration is consistent ）;

6. Start the new system , Migration complete ;

3、 ... and . How to modify the data file directory dataDir？

1. Stop database service ;

2. modify taos.cfg Under the dataDir The value is the new directory path we need ;

3. Move all the original data files to the new directory , Make sure that in the new dataDir Next , Can see the previous dnode,mnode,vnode,vnode_bak;

4. Start the service again ;

Four . vnode_bak What's the use of directories ？

Under the data file directory vnode_bak It is used to store the data files of the deleted database , If the database is deleted by mistake , You can contact our enterprise team to provide data recovery services .

5、 ... and . Which parameters need to be restarted to take effect ？ Which parameters can be hotter ？

https://docs.taosdata.com/operation/optimize： Here you can see the specific description of database level parameters .

https://docs.taosdata.com/taos-sql/database： Here you can see the operation details of the hotter parameters .

Parameters for database service level , Unified in taos.cfg Revision in China , The modification takes effect after restarting the database service . Be careful ： stay taos.cfg among , Some parameters that coincide with database level parameters , It only represents the default value of the parameter of the newly created database .

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