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Heroku Postgres Metrics Logs

Last Updated: 17 February 2014

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Heroku Postgres Standard and Premium Tier database users will see database-related events on their app’s log stream. This can be useful for recording and analyzing usage over time.

Heroku Postgres Metrics which appear via `heroku-postgres` are separate from standard alerts emitted from Postgres itself which appear for all applications via `postgres`.

Log format

2013-05-07T17:41:06+00:00 source=HEROKU_POSTGRESQL_VIOLET sample#current_transaction=1873 sample#db_size=26219348792bytes sample#tables=13 sample#active-connections=92 sample#waiting-connections=1 sample#index-cache-hit-rate=0.99723 sample#table-cache-hit-rate=0.99118 sample#load-avg-1m=1.42 sample#load-avg-5m=1.45 sample#load-avg-15m=1.34 sample#read-iops=0 sample#write-iops=2.875 sample#memory-total=1692568kB sample#memory-free=73876kB sample#memory-cached=1344128kB sample#memory-postgres=22388kB

The attributes found on the log are, for all standard and premium tier databases:

  • source: The database name the measurements relate to.
  • The log line’s timestamp is the time at which the measurements were taken.
  • sample#db_size: The number of bytes contained in the database. This includes all table and index data on disk, including database bloat.
  • sample#tables: The number of tables in the database.
  • sample#active-connections: The number of connections established on the database.
  • sample#current_transaction: The current transaction ID, which can be used to track writes over time.
  • sample#index-cache-hit-rate: Rate of index lookups served from shared buffer cache, rounded to five decimal points.
  • sample#table-cache-hit-rate: Rate of table lookups served from shared buffer cache, rounded to five decimal points.
  • sample#waiting-connections: Number of connections waiting on a lock to be acquired. If many connections are waiting, this can be a sign of mishandled database concurrency.
  • 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 cpu.
  • sample#read-iops and sample#write-iops: Number of reads or writes operations in I/O sizes of 16KB blocks.
  • sample#memory-total: Total amount of memory available in kB.
  • sample#memory-free: Amount of free memory available in kB.
  • sample#memory-cached: Amount of cached memory in kB.
  • sample#memory-postgres: Approximate amount of memory used by PostgreSQL in kB.