Configuration Parameters

In this chapter, all the configuration parameters on both server and client side are described thoroughly.

Configuration File on Server Side

On the server side, the actual service of TDengine is provided by an executable taosd whose parameters can be configured in file taos.cfg to meet the requirements of different use cases. The default location of taos.cfg is /etc/taos, but can be changed by using -c parameter on the CLI of taosd. For example, the configuration file can be put under /home/user and used like below

taosd -c /home/user

Parameter -C can be used on the CLI of taosd to show its configuration, like below:

taosd -C

Configuration File on Client Side

TDengine CLI taos is the tool for users to interact with TDengine. It can share same configuration file as taosd or use a separate configuration file. When launching taos, parameter -c can be used to specify the location where its configuration file is. For example taos -c /home/cfg means /home/cfg/taos.cfg will be used. If -c is not used, the default location of the configuration file is /etc/taos. For more details please use taos --help to get.

From version 2.0.10.0 below commands can be used to show the configuration parameters of the client side.

taos -C

taos --dump-config

Configuration Parameters

note

taosd needs to be restarted for the parameters changed in the configuration file to take effect.

Connection Parameters

firstEp

secondEp

fqdn

serverPort

note

TDengine uses 13 continuous ports, both TCP and UDP, starting with the port specified by serverPort. You should ensure, in your firewall rules, that these ports are kept open. Below table describes the ports used by TDengine in details.

maxShellConns

maxConnections

rpcForceTcp

Monitoring Parameters

monitor

monitorInterval

telemetryReporting

Query Parameters

queryBufferSize

ratioOfQueryCores

maxNumOfDistinctRes

Locale Parameters

timezone

info

To handle the data insertion and data query from multiple timezones, Unix Timestamp is used and stored in TDengine. The timestamp generated from any timezones at same time is same in Unix timestamp. To make sure the time on client side can be converted to Unix timestamp correctly, the timezone must be set properly.

On Linux system, TDengine clients automatically obtain timezone from the host. Alternatively, the timezone can be configured explicitly in configuration file taos.cfg like below.

timezone UTC-7
timezone GMT-8
timezone Asia/Shanghai

The above examples are all proper configuration for the timezone of UTC+8. On Windows system, however, timezone Asia/Shanghai is not supported, it must be set as timezone UTC-8.

The setting for timezone impacts strings that are not in Unix timestamp format and keywords or functions related to date/time. For example:

SELECT count(*) FROM table_name WHERE TS<'2019-04-11 12:01:08';

If the timezone is UTC+8, the above SQL statement is equal to:

SELECT count(*) FROM table_name WHERE TS<1554955268000;

If the timezone is UTC, it’s equal to

SELECT count(*) FROM table_name WHERE TS<1554984068000;

To avoid the problems of using time strings, Unix timestamp can be used directly. Furthermore, time strings with timezone can be used in SQL statements. For example “2013-04-12T15:52:01.123+08:00” in RFC3339 format or “2013-04-12T15:52:01.123+0800” in ISO-8601 format are not influenced by timezone setting when converted to Unix timestamp.

locale

info

A specific type “nchar” is provided in TDengine to store non-ASCII characters such as Chinese, Japanese, and Korean. The characters to be stored in nchar type are firstly encoded in UCS4-LE before sending to server side. To store non-ASCII characters correctly, the encoding format of the client side needs to be set properly.

The characters input on the client side are encoded using the default system encoding, which is UTF-8 on Linux, or GB18030 or GBK on some systems in Chinese, POSIX in docker, CP936 on Windows in Chinese. The encoding of the operating system in use must be set correctly so that the characters in nchar type can be converted to UCS4-LE.

The locale definition standard on Linux is: <Language>_<Region>.<charset>, for example, in “zh_CN.UTF-8”, “zh” means Chinese, “CN” means China mainland, “UTF-8” means charset. On Linux and Mac OSX, the charset can be set by locale in the system. On Windows system another configuration parameter charset must be used to configure charset because the locale used on Windows is not POSIX standard. Of course, charset can also be used on Linux to specify the charset.

charset

info

On Linux, if charset is not set in taos.cfg, when taos is started, the charset is obtained from system locale. If obtaining charset from system locale fails, taos would fail to start. So on Linux system, if system locale is set properly, it’s not necessary to set charset in taos.cfg. For example:

locale zh_CN.UTF-8

On a Linux system, if the charset contained in locale is not consistent with that set by charset, the later setting in the configuration file takes precedence.

locale zh_CN.UTF-8
charset GBK

charset GBK
locale zh_CN.UTF-8

On Windows system, it’s not possible to obtain charset from system locale. If it’s not set in configuration file taos.cfg, it would be default to CP936, same as set as below in taos.cfg. For example

charset CP936

Storage Parameters

dataDir

cache

blocks

days

keep

minRows

maxRows

walLevel

fsync

update

cacheLast

minimalTmpDirGB

minimalDataDirGB

vnodeBak

Cluster Parameters

numOfMnodes

replica

quorum

role

balance

balanceInterval

arbitrator

Time Parameters

precision

rpcTimer

rpcMaxTime

statusInterval

shellActivityTimer

tableMetaKeepTimer

maxTmrCtrl

offlineThreshold

Performance Optimization Parameters

numOfThreadsPerCore

ratioOfQueryThreads

maxVgroupsPerDb

maxTablesPerVnode

minTablesPerVnode

tableIncStepPerVnode

maxNumOfOrderedRes

mnodeEqualVnodeNum

numOfCommitThreads

Compression Parameters

comp

tsdbMetaCompactRatio

compressMsgSize

compressColData

lossyColumns

fPrecision

dPrecision

Continuous Query Parameters

stream

minSlidingTime

minIntervalTime

maxStreamCompDelay

maxFirstStreamCompDelay

retryStreamCompDelay

streamCompDelayRatio

info

To prevent system resource from being exhausted by multiple concurrent streams, a random delay is applied on each stream automatically. maxFirstStreamCompDelay is the maximum delay time before a continuous query is started the first time. streamCompDelayRatio is the ratio for calculating delay time, with the size of the time window as base. maxStreamCompDelay is the maximum delay time. The actual delay time is a random time not bigger than maxStreamCompDelay. If a continuous query fails, retryStreamComDelay is the delay time before retrying it, also not bigger than maxStreamCompDelay.

HTTP Parameters

note

HTTP service was provided by taosd prior to version 2.4.0.0 and is provided by taosAdapter after version 2.4.0.0. The parameters described in this section are only application in versions prior to 2.4.0.0. If you are using any version from 2.4.0.0, please refer to taosAdapter.

http

httpEnableRecordSql

httpMaxThreads

restfulRowLimit

httpDBNameMandatory

Log Parameters

logDir

minimalLogDirGB

numOfLogLines

asyncLog

logKeepDays

debugFlag

mDebugFlag

dDebugFlag

sDebugFlag

wDebugFlag

sdbDebugFlag

rpcDebugFlag

tmrDebugFlag

cDebugFlag

jniDebugFlag

odbcDebugFlag

uDebugFlag

httpDebugFlag

mqttDebugFlag

monitorDebugFlag

qDebugFlag

vDebugFlag

tsdbDebugFlag

cqDebugFlag

Client Only

maxSQLLength

tscEnableRecordSql

maxBinaryDisplayWidth

info

If the length of value exceeds maxBinaryDisplayWidth, then the actual display width is max(column name, maxBinaryDisplayLength); otherwise the actual display width is max(length of column name, length of column value). This parameter can also be changed dynamically using set max_binary_display_width <nn\> in TDengine CLI taos.

maxWildCardsLength

clientMerge

maxRegexStringLen

Other Parameters

enableCoreFile