logger

go-logger

Logging library in GO, used for structural logging inside UPP (mostly required for monitoring publish events). It is based on the Logrus implementation.

Initialization

When working with this logger library, please make sure you use one of the init methods first (otherwise the logging will fail):

• InitLogger - requires a serviceName and a logLevel
• InitDefaultLogger - requires only the serviceName as a parameter

Note: You can still create your own standard logger by using the NewLogger function (check Logrus for more details).

Logging a Monitoring Event

The library is Logrus compatible, but it includes a few default fields, which help facilitate the monitoring of key application events (@time, transaction_id and service_name). You can add a monitoring event to a log entry by using the following method:

• WithMonitoringEvent - with transaction_id, eventName and contentType as parameters. A monitoring_event=true field will also be added to the entry. This message will be picked up by the monitoring services and dashboards.

Adding additional fields to the Entry

Beside the With... fields offered by the original Logrus Entry, the following methods can be used:

• WithTransactionID, to add a transaction ID to the log entry;
• WithUUID, to add a UUID to the log entry;
• WithTime, to set a custom time of the logging entry (this can be used to influence Splunk log time);
• WithValidFlag to mark if a message received by an application is valid or not. Invalid messages will be ignored by some of the monitoring statistics (SLAs).

Actual Logging

Use Logrus' default log methods, like Info, Warn, Error and others.

Examples

A monitoring log for a successful publish, with validation flag, can look like this:

logger.WithMonitoringEvent("Map", tid, "Annotations")
      .WithUUID(uuid)
      .WithValidFlag(true)
      .Info("Successfully mapped")

A monitoring log for a failed publish would log it as an error:

logger.WithMonitoringEvent("Map", tid, "Annotations")
      .WithUUID(uuid)
      .WithValidFlag(true)
      .WithError(err)
      .Error("Error decoding body")

Test Package

The test package has been introduced to check through unit tests that the application is logging relevant events properly. The example below shows how to check that an application is logging a specific monitoring event:

import (
    ...
    logTest "github.com/Financial-Times/go-logger/test"
    ...
)

func TestSomething(t *testing.T) {
    hook := logTest.NewTestHook("serviceName")
    ...
    Something()
    ...
    entry := hook.LastEntry()
    test.Assert(t, entry).HasMonitoringEvent("Map", "tid_test", "annotations").HasValidFlag(true)
}