Heroku Key-Value Store Metrics Logs

Last updated April 25, 2025

Customers using Heroku Key-Value Store instances see Redis-related events on their app’s log stream. This can be useful for recording and analyzing usage over time.

Heroku Key-Value Store metrics which appear via heroku-redis are separate from standard alerts emitted from Redis itself that appear for all applications via -p [redis-addon-name], for example, -p redis-metric-98068.

Log Format

You can view Heroku Key-Value Store metrics logs with heroku logs.

You can filter for Heroku Key-Value Store metrics logs on a specific app.

For Cedar-generation apps:

$ heroku logs -p heroku-redis -a example-app

For Fir-generation apps:

$ heroku logs -s heroku-redis -a example-app

For example, the Heroku Key-Value Store metrics logs can look like:

2024-03-15T12:10:39.000000+00:00 app[heroku-redis]: source=REDIS addon=redis-metric-98068 sample#active-connections=404 sample#load-avg-1m=0.115 sample#load-avg-5m=0.075 sample#load-avg-15m=0.07 sample#read-iops=0 sample#write-iops=54.758 sample#memory-total=15405660kB sample#memory-free=12639520kB sample#memory-cached=1911724kB sample#memory-redis=343477584bytes sample#hit-rate=0.7 sample#evicted-keys=0

The following attributes appear in application logs for all plans:

  • source: The instance attachment name that the measurements relate to.
  • addon: The instance addon name that the measurements relate to.
  • The log line’s timestamp is the time at which the measurements were taken.

Key-Value Store Instance Metrics

These attributes apply to a particular Key-Value Store instance:

  • sample#active-connections: The number of connections established on the KVS instance.
  • sample#max-connections: The maximum number of connections available in the instance.
  • sample#connections-percentage-used: Percentage of connections used, between 0.0–1.0.
  • sample#memory-redis: Approximate amount of memory used by your KVS instance processes in bytes.
  • sample#hit-rate: The ratio of successful reads out of all read operations, rounded to five decimal points.
  • sample#evicted_keys: The number of evicted keys due to reaching your instance maxmemory limit.

Server Metrics

For multi-tenant plans, server metrics include other KVS instances running on the shared server, and may be misleading when diagnosing Redis performance.

Server metrics come directly from the server operating system:

  • sample#load-avg-1m, sample#load-avg-5m and sample#load-avg-15m: The average system load over a period of 1 minute, 5 minutes and 15 minutes, divided by the number of available CPUs. A load-avg of 1.0 indicates that, on average, processes were requesting CPU resources for 100% of the timespan. This number includes I/O wait.
  • sample#read-iops and sample#write-iops: Number of read or write operations in I/O sizes of 16-KB blocks.
  • sample#max-iops: The maximum number of IOPS available in the instance.
  • sample#iops-percentage-used: Percentage of IOPS used between read and write IOPS, between 0.0–1.0.
  • sample#memory-total: Total amount of server memory in use, in KB Capital This includes memory used by all Redis processes, OS memory, and disk cache.
  • sample#memory-free: Amount of free memory available in KB.
  • sample#memory-cached: Amount of memory being used the OS for page cache, in KB.
  • sample#memory-percentage-used: Percentage of server memory used on the instance, between 0.0–1.0.

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