HadoopNameNodeDown

HadoopNameNodeDown #

The Hadoop NameNode service is unavailable.

Alert Rule
alert: HadoopNameNodeDown
annotations:
  description: |-
    The Hadoop NameNode service is unavailable.
      VALUE = {{ $value }}
      LABELS = {{ $labels }}    
  runbook: https://srerun.github.io/prometheus-alerts/runbooks/jmx_exporter/hadoopnamenodedown/
  summary: Hadoop Name Node Down (instance {{ $labels.instance }})
expr: up{job="hadoop-namenode"} == 0
for: 5m
labels:
  severity: critical

Here is a runbook for the HadoopNameNodeDown alert:

Meaning #

The HadoopNameNodeDown alert is triggered when the Hadoop NameNode service is unavailable. This indicates that the NameNode, which is a critical component of the Hadoop Distributed File System (HDFS), is not responding or is down. This can have significant implications for the overall health and functionality of the Hadoop cluster.

Impact #

The impact of this alert is high, as the unavailability of the NameNode can cause:

  • Data loss or corruption
  • Inability to write or read data from HDFS
  • Failure of dependent applications and services
  • Increased latency or timeouts for users and applications that rely on HDFS
  • Potential for catastrophic failure of the entire Hadoop cluster

Diagnosis #

To diagnose the issue, follow these steps:

  1. Check the NameNode logs for errors or exceptions that may indicate the cause of the failure.
  2. Verify that the NameNode process is running and that there are no issues with the underlying host or network.
  3. Check the Hadoop cluster’s overall health using tools such as the Hadoop Web UI or the hadoop dfsadmin command.
  4. Investigate any recent changes or updates to the Hadoop configuration or software that may have caused the issue.
  5. Check for any hardware or software failures, such as disk failures or network connectivity issues.

Mitigation #

To mitigate the issue, follow these steps:

  1. Restart the NameNode service to attempt to recover from the failure.
  2. Check for and resolve any underlying issues, such as disk space or network connectivity problems.
  3. If the issue persists, consider restarting the entire Hadoop cluster to ensure consistency and data integrity.
  4. Implement additional monitoring and alerting to detect potential issues before they cause a complete failure of the NameNode.
  5. Consider implementing a standby or redundant NameNode to provide high availability and minimize downtime in case of a failure.
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