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message_save_latency

Type: Histogram
Buckets: 0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1.0, 2.5, 5.0, 10.0
How many seconds it takes to save a message to spool.

This metric encompasses the elapsed time to saved either or both the meta and data portions of a message to spool.

High values indicate IO pressure which may be alleviated by tuning other constraints and/or RocksDB Parameters

Histogram

This metric is a histogram which means that it is exported as three underlying metrics:

  • message_save_latency_count - a counter tracking how many events have been accumulated into the histogram
  • message_save_latency_sum - a counter tracking the total value of all of the events have been accumulated into the histogram
  • message_save_latency_bucket - a counter tracking the number of events that fall within the various buckets shown above. This counter has an additional le label that indicates the bucket threshold. For example, the first bucket for this histogram will generate a label le="0.005" which will keep track of the number of events whose value was less-or-equal (le) that value.

The recommended visualization for a histogram is a heatmap based on message_save_latency_bucket.

While it is possible to calculate a mean average for message_save_latency by computing message_save_latency_sum / message_save_latency_count, it can be difficult to reason about what that value means if the traffic patterns are not uniform since the launch of the process. We strongly recommend using a heatmap visualization instead of computing an average value.