Understanding Heroku Data for Redis Log Statements and Common Errors
Last updated March 24, 2023
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Heroku Data for Redis logs to the logplex which collates and publishes your application’s log-stream. You can isolate Heroku Data for Redis events with the heroku logs command by filtering for the redis process.
Logs are a premium-tier feature. They aren’t available on Essential-tier databases.
$ heroku logs -p heroku-redis -t
Besides seeing system-level Redis activity, these logs are also useful for understanding your application’s use of Redis and for diagnosing common errors. This article lists common log statements, their purpose, and any action that must be taken.
REPLICA OF …
2022-08-18T17:29:39Z app[redis]: [maturing-daily-1187] * REPLICAOF would result into synchronization with the master we are already connected with. No operation performed.
This log statement indicates that Heroku Data for Redis is ensuring your HA standby is following your primary Redis instances.
CONFIG REWRITE
2022-08-18T17:29:39Z app[redis]: [maturing-daily-1187] # CONFIG REWRITE executed with success.
This log statement indicates that Heroku Data for Redis has proceeded to rewrite your Redis instance configuration. This statement happens whenever we must change your instance configuration or when you trigger a configuration change.
Database Memory Close to the Limit
2022-09-12T07:27:33+00:00 app[heroku-redis]: source=REDIS_URL sample#used_memory_over_limit=10435336.0bytes message=Database memory close to the limit. Please upgrade your database plan or change your maxmemory policy.
This log is seen when a Redis instance is using more than 90% of its plan memory limit. Since you can see this log before you actually exceed the limit, you can monitor this log to make an alert.