Querying in ClickHouse CloudThe data in this system table is held locally on each node in ClickHouse Cloud. Obtaining a complete view of all data, therefore, requires the
clusterAllReplicas function. See here for further details.Description
Contains the historical values forsystem.asynchronous_metrics, which are saved once per time interval (one second by default). Enabled by default.
Key-value metrics of system.asynchronous_metrics (those broken down per CPU core, block device, network interface, or disk) are logged as one row per key, with the key in the key column. For scalar metrics the key column is empty.
Before version 26.8 every key was a separate scalar metric with the key mangled into its name (BlockReadBytes_sda). The asynchronous_metrics_key_values_mode server setting switches back to that form (legacy_names), or logs both forms at the same time (both) while the monitoring is being migrated.
Columns
hostname(LowCardinality(String)) — Hostname of the server executing the query.event_date(Date) — Event date.event_time(DateTime) — Event time.metric(LowCardinality(String)) — Metric name.key(LowCardinality(String)) — The key of a key-value metric, e.g. the CPU core number or the block device name. Empty for scalar metrics.value(Float64) — Metric value.
Example
- asynchronous_metric_log setting — Enabling and disabling the setting.
- system.asynchronous_metrics — Contains metrics, calculated periodically in the background.
- system.metric_log — Contains history of metrics values from tables
system.metricsandsystem.events, periodically flushed to disk.