Logs in Managed Service for ClickHouse®

DoubleCloud maintains a log of events taking place in managed clusters that you can use for monitoring activity and debugging issues.

You can access logs in the Logs tab on the cluster page, or you can configure log export to external log management providers.

Log entries

Log entry records status or describes certain events in your cluster. These messages tell you that certain events occur in the cluster or show something is wrong and needs attention.

Log entry structure

A log entry contains the complete information on a logged event and consists of the following segments:

Date and time stamp in the YYYY/MM/DD, HH:MM:SS format.
Log level indicator.
Log entry text.

Log levels

Log level is a status that tells how important a log entry is.

DoubleCloud clusters support the following log levels:

Level	Description
TRACE	Detailed diagnostics information
DEBUG	Debugging information
INFO	Diagnostics information for statistics
WARNING	Warning about a non-critical malfunction, investigate further
ERROR	Error report
FATAL	Possible system failure, service shutdown

Default values for system log tables

DoubleCloud Managed Service for ClickHouse® allows you to manage system.*_log tables:

Enable and disable the tables (except system.query_log and system.part_log).
Change the disk space allowed for the table (in bytes) - retention_size.
Change the table partition's retention time (in seconds) - retention_time.

This parameter is used after conversion into days by the following formula:
```
(ceil (table_retention_time / (60 * 60 * 24)))
```
The resulting number determines the limit of partitions for the table. Each table has one partition per day.

Log tables cleanup schedule

Log tables are cleaned up once every 24 hours, after 0:00 according to the timezone of the cluster's region. This allows the peak usage to exceed the set limits.

system.query_log

You can't turn off this table

You can't apply system.query_log_enabled: false, only change the size and time.

Parameter	Default value
`query_log_retention_size`	`1073741824`
`query_log_retention_time`	`2592000`

system.query_thread_log

Parameter	Default value
`query_thread_log_enabled`	`true`
`query_thread_log_retention_size`	`536870912`
`query_thread_log_retention_time`	`2592000`

system.query_views_log

Parameter	Default value
`query_views_log_enabled`	`false`
`query_views_log_retention_size`	`0`
`query_views_log_retention_time`	`2592000`

system.part_log

You can't turn off this table

You can't apply system.part_log_enabled: false, only change the size and time.

Parameter	Default value
`part_log_retention_size`	`536870912`
`part_log_retention_time`	`2592000`

system.metric_log

Parameter	Default value
`metric_log_enabled`	`true`
`metric_log_retention_size`	`536870912`
`metric_log_retention_time`	`2592000`

system.asynchronous_metric_log:

Parameter	Default value
`asynchronous_metric_log_enabled`	`false`
`asynchronous_metric_log_retention_size`	`0`
`asynchronous_metric_log_retention_time`	`2592000`

system.text_log

Parameter	Default value
`text_log_enabled`	`false`
`text_log_retention_size`	`536870912`
`text_log_retention_time`	`2592000`
`text_log_level`	`Trace`

system.trace_log

Parameter	Default value
`trace_log_enabled`	`true`
`trace_log_retention_size`	`536870912`
`trace_log_retention_time`	`2592000`

system.opentelemetry_span_log

Parameter	Default value
`opentelemetry_span_log_enabled`	`false`
`opentelemetry_span_log_retention_size`	`0`
`opentelemetry_span_log_retention_time`	`2592000`

system.session_log

Parameter	Default value
`session_log_enabled`	`false`
`session_log_retention_size`	`0`
`session_log_retention_time`	`2592000`

system.zookeeper_log

Parameter	Default value
`zookeeper_log_enabled`	`false`
`zookeeper_log_retention_size`	`0`
`zookeeper_log_retention_time`	`2592000`

system.asynchronous_insert_log

Parameter	Default value
`asynchronous_insert_log_enabled`	`false`
`asynchronous_insert_log_retention_size`	`0`
`asynchronous_insert_log_retention_time`	`2592000`