PrometheusTsdbHeadTruncationsFailed

PrometheusTsdbHeadTruncationsFailed #

Prometheus encountered {{ $value }} TSDB head truncation failures

Alert Rule
alert: PrometheusTsdbHeadTruncationsFailed
annotations:
  description: |-
    Prometheus encountered {{ $value }} TSDB head truncation failures
      VALUE = {{ $value }}
      LABELS = {{ $labels }}    
  runbook: https://srerun.github.io/prometheus-alerts/runbooks/prometheus-self-monitoring-internal/prometheustsdbheadtruncationsfailed/
  summary: Prometheus TSDB head truncations failed (instance {{ $labels.instance }})
expr: increase(prometheus_tsdb_head_truncations_failed_total[1m]) > 0
for: 0m
labels:
  severity: critical

Meaning #

The PrometheusTsdbHeadTruncationsFailed alert is triggered when Prometheus encounters failures while truncating the time series database (TSDB) head. This indicates that Prometheus is unable to efficiently store and manage time series data, leading to potential data loss and performance issues.

Impact #

The impact of this alert can be severe, as it can lead to:

  • Data loss: Failed truncations can result in incomplete or missing data, making it challenging to monitor and troubleshoot systems.
  • Performance issues: Inefficient TSDB management can cause Prometheus to consume excessive resources, leading to slow query performance, high latency, and increased memory usage.
  • Alert fatigue: If left unaddressed, this issue can lead to a flood of false-positive alerts, desensitizing operators to legitimate issues and reducing the overall effectiveness of the monitoring system.

Diagnosis #

To diagnose the root cause of this issue, follow these steps:

  1. Check the Prometheus logs: Review the Prometheus logs to identify the specific error messages related to TSDB head truncations. This will help you understand the underlying cause of the failures.
  2. Verify disk space and resources: Ensure that the Prometheus instance has sufficient disk space, memory, and CPU resources to operate efficiently.
  3. Investigate TSDB configuration: Review the TSDB configuration to ensure it is properly tuned for the workload and data volume.
  4. Check for concurrent queries: Identify if there are any concurrent queries or high-load conditions that might be contributing to the TSDB head truncation failures.

Mitigation #

To mitigate this issue, follow these steps:

  1. Increase the disk space: Ensure that the Prometheus instance has sufficient disk space to store the TSDB files.
  2. Optimize TSDB configuration: Adjust the TSDB configuration to optimize performance, such as adjusting the max_chunk_age and retention settings.
  3. Restart Prometheus: Restart the Prometheus instance to clear any corrupted or stuck truncation operations.
  4. Implement monitoring and alerting: Set up monitoring and alerting for TSDB-related metrics, such as prometheus_tsdb_head_truncations_failed_total, to quickly identify and respond to future issues.
  5. Regularly maintain and upgrade Prometheus: Ensure that Prometheus is regularly maintained and upgraded to the latest version, which may include bug fixes and performance optimizations related to TSDB management.
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