TAS Log Rate Limits

README.md

TAS 4.0.20+ has ability to limit the log rate (bytes/sec) of applications to avoid having a single application overwhelm the logging system in Cloud Foundry.

The general settings or ways to configure logging limits are:

• "Default log rate limit per app" in the TAS tile under App Developer Controls
• CF org/space quotas
• log-rate-limit-per-second app setting

Default log rate limit per app

The global default setting is just that, a default. It's the same as setting the per-app log-rate-limit-per-second on every single app in the foundation. This is not a way to keep devs from overriding this value. Devs can override the global default value with a higher or lower log-rate-limit-per-second value.

NOTE - If you've implemented quotas with log rate limits, it's important this setting isn't too large compared to the quota or you may unintentionally cause cf push to fail for entire orgs/spaces.

CF org/space quotas

The log rate quota value behaves just like any other quota value, setting a cap on shared resources within an org/space.

Setting a log rate limit in a quota is not the same as setting a log-rate-limit-per-second value. The quota value is the MAX value the log-rate-limit-per-second can be set to and since the global default is essentially the same as setting this per app, the quota applies to the global setting as well.

What does that mean? If you set an org log quota of 2048 bytes/sec but you set the global default to 4096 bytes/sec, you'll get a cf push error "organization's log rate limit exceeded: staging requires 4096 bytes per second".

The other thing to note about the quota log rate limit value is that it takes into account all apps within the assigned org/space when calculating whether you have enough headroom. If you set an org log quota of 2048 bytes/sec and have two apps with a log-rate-limit-per-second of 1024 bytes/sec - everything is fine (1024 + 1024 = 2048), at least until you try to push a 3rd app (1024 + 1024 + 1024 = 3072).

Just remember the quota is not implementing the log rate limit, it's capping the log rate limit settings within the org/space.

log-rate-limit-per-second App Setting

This is the value that can be set per app in the application manifest as log-rate-limit-per-second or via the cf scale command after the fact. This value by default is unlimited (unset) unless a default global log rate limit has been set. A dev can override this value to any setting below or even above the default value - the global value is just a default. The important thing to keep in mind is that cf quotas can limit the max this value can be set to, and needs to fit within the org/space quota alongside all other apps within the org/space.

test-output.txt

Global default limit: 2048b
Org quota limit: not set
App limit: not set
Result: App uses default global limit, "app instance exceeded log rate limit (2048 bytes/sec)"


Global default limit: 2048b
Org quota limit: 3000b
App limit: not set
Result: App uses default global limit, "app instance exceeded log rate limit (2048 bytes/sec)"


Global default limit: 2700b
Org quota limit: 2048b
App limit: not set
Result: Can't push the app, "organization's log rate limit exceeded: staging requires 2700 bytes per second"


Global default limit: 2700b
Org quota limit: 2701b
App limit: not set
Result: App uses default global limit, "app instance exceeded log rate limit (2700 bytes/sec)"


Global default limit: 2700b
Org quota limit: 2701b
App limit: 2800b
Result: Can't push the app, "organization's log rate limit exceeded: staging requires 2800 bytes per second"


Global default limit: 2700b
Org quota limit: 2800b
App limit: 2750b
Result: App uses the app limit, "app instance exceeded log rate limit (2750 bytes/sec)"


Global default limit: 2700b
Org quota limit: unlimited
App limit: 2750b
Result: App uses the app limit, "app instance exceeded log rate limit (2750 bytes/sec)"


Global default limit: 2700b
Org quota limit: unlimited
App limit: 2048b
Result: App uses the app limit, "app instance exceeded log rate limit (2048 bytes/sec)"


Global default limit: 2700b
Org quota limit: unlimited
App limit: 2800b
Result: App uses the app limit, "app instance exceeded log rate limit (2800 bytes/sec)"