tracing setup has wrong logger syntax

[grantr]

pkg/tracing/opencensus.go

Lines 126 to 129 in 73daad6

	case config.Zipkin:
	zipEP, err := zipkin.NewEndpoint(name, ":80")
	if err != nil {
	logger.Errorw("error building zipkin endpoint", err)

Line 129 uses logger.Errorw incorrectly. It should actually be

logger.Errorw("error building zipkin endpoint", "error", err)

The effect is that whenever an error occurs in zipkin.NewEndpoint, the actual error message is not present in the log line. (Zap also logs a warning "key without a value is ignored").

/cc @mattmoor @grac3gao

@Harwayne this is in-the-wild evidence that SugaredLogger is problematic. If this line were using the Logger type, this bug would be impossible.

[vagababov]

Sugared logger has its benefits, but does require consistent usange
/assign

[vagababov]

/assign @vagababov

[grac3gao-zz]

after correcting the syntax, the error message shows "error building zipkin endpointlookup : no such host"

[vagababov]

well that is the error...