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Logs

Nebula Graph uses glog to print logs, uses gflags to control the severity level of the log, and provides an HTTP interface to dynamically change the log level at runtime to facilitate tracking.

Log directory

The default log directory is /usr/local/nebula/logs/.

If the log directory is deleted while Nebula Graph is running, the log would not continue to be printed. However, this operation will not affect the services. To recover the logs, restart the services.

Parameter descriptions

  • minloglevel: Specifies the minimum level of the log. That is, no logs below this level will be printed. Optional values are 0 (INFO), 1 (WARNING), 2 (ERROR), 3 (FATAL). It is recommended to set it to 0 during debugging and 1 in a production environment. If it is set to 4, Nebula Graph will not print any logs.
  • v: Specifies the detailed level of the log. The larger the value, the more detailed the log is. Optional values are 0, 1, 2, 3.

The default severity level for the metad, graphd, and storaged logs can be found in their respective configuration files. The default path is /usr/local/nebula/etc/.

Check the severity level

Check all the flag values (log values included) of the current gflags with the following command.

$ curl <ws_ip>:<ws_port>/flags
Parameter Description
ws_ip The IP address for the HTTP service, which can be found in the configuration files above. The default value is 127.0.0.1.
ws_port The port for the HTTP service, which can be found in the configuration files above. The default values are 19559(Meta), 19669(Graph), and 19779(Storage) respectively.

Examples are as follows:

  • Check the current minloglevel in the Meta service:
    $ curl 127.0.0.1:19559/flags | grep 'minloglevel'
  • Check the current v in the Storage service:
    $ curl 127.0.0.1:19779/flags | grep -w 'v'

Change the severity level

Change the severity level of the log with the following command.

$ curl -X PUT -H "Content-Type: application/json" -d '{"<key>":<value>[,"<key>":<value>]}' "<ws_ip>:<ws_port>/flags"
Parameter Description
key The type of the log to be changed. For optional values, see Parameter descriptions.
value The level of the log. For optional values, see Parameter descriptions.
ws_ip The IP address for the HTTP service, which can be found in the configuration files above. The default value is 127.0.0.1.
ws_port The port for the HTTP service, which can be found in the configuration files above. The default values are 19559(Meta), 19669(Graph), and 19779(Storage) respectively.

Examples are as follows:

$ curl -X PUT -H "Content-Type: application/json" -d '{"minloglevel":0,"v":3}' "127.0.0.1:19779/flags" # storaged
$ curl -X PUT -H "Content-Type: application/json" -d '{"minloglevel":0,"v":3}' "127.0.0.1:19669/flags" # graphd
$ curl -X PUT -H "Content-Type: application/json" -d '{"minloglevel":0,"v":3}' "127.0.0.1:19559/flags" # metad

If the log level is changed while Nebula Graph is running, it will be restored to the level set in the configuration file after restarting the service. To permanently modify it, see Configuration files.

RocksDB logs

RocksDB logs are usually used to debug RocksDB parameters and stored in /usr/local/nebula/data/storage/nebula/$id/data/LOG. $id is the ID of the example.

Last update: September 2, 2021
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