Internal Replication Tasks

These metrics provide insights into the performance and health of replication processes, including merge activities, replica states, data insertion delays and partition configurations. 

• Active Merges: Count – Number of executing background merges.
• Readonly Replicas: Count – Number of Replicated tables that are currently in readonly state due to re-initialization after ZooKeeper session loss or due to startup without ZooKeeper configured.
• Delayed Inserts: Count – Number of INSERT queries that are throttled due to high number of active data parts for partition in a MergeTree table.
• Total Parts of MergeTree Tables: Count – Total amount of data parts in all tables of MergeTree family. Numbers larger than 10 000 will negatively affect the server startup time, and it may indicate unreasonable choice of the partition key.
• Max Part Count for Partition – Maximum number of parts per partition across all partitions of all tables of MergeTree family. Values larger than 300 indicates misconfiguration, overload, or massive data loading.
• Max Absolute Delay for Replicas: Second – Maximum difference in seconds between the most fresh replicated part and the most fresh data part still to be replicated, across Replicated tables. A very high value indicates a replica with no data.