Log level guidelines

Preliminary Remark:
Logging can be configured during setup and configuration phase, see General logging

TRACE - Anything at statement level like "start to calculate something", "query something", "loop x of y", etc… is logged at TRACE level.

DEBUG - Anything at method or request processing level e.g.

"method entered" or "return with ----" is logged at DEBUG level
"HTTP GET /someresource took 5 seconds status 200" but also 4xy statuses

INFO - In the following cases the information is logged at INFO level, e.g.

Process life cycle messages, like
- application started
- application ready
- shutdown application
Administrative events, like
- (re)load or flush caches
- (re)load configuration
- database migrations

WARN - Uncommon behaviour or situations, e.g.

unavailability of services
security related events (potentially malicious)
handled failures which prevent the application to work normally as long as the application is able to recover automatically

ERROR - Anything which potentially leads to unexpected behaviour or crashes, e.g.

unhandled failures
implementation failures

Examples

One Line Formatted LIFE-CYCLE Log Example

{"timestamp":"2017-08-01T07:48:09.916Z","environment":"AZURE","system":"PROD","product":"nexeed-pqm","application":"trinity-core-service","version":"1.0.1","instance":"3ae26cd4-7014-11e9-a923-1681be663d3e","thread":"thread-1","logger":"LIFE-CYCLE","loglevel":"INFO","status":"INITIALIZATION","message":"initialize masterdata cache"}

Pretty Printed LIFE-CYCLE Log Example

{
    "timestamp":    "2017-08-01T07:48:09.916Z",
    "environment":  "AZURE",
    "system":       "PROD",
    "product":      "nexeed-pqm",
    "application":  "trinity-core-service",
    "version":      "3.0.1",
    "instance":     "3ae26cd4-7014-11e9-a923-1681be663d3e",
    "thread":       "thread-1",
    "logger":       "LIFE-CYCLE",
    "loglevel":     "INFO",
    "status":       "INITIALIZATION",
    "message":      "initialize masterdata cache"
}