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 .

Want to know more

TDengine Database

Specific details of , Welcome to

GitHub

View the relevant source code on .