logcheck

README

This directory contains a linter for checking log calls. It was originally created to detect when unstructured logging calls like klog.Infof get added to files that should only use structured logging calls like klog.InfoS and now also supports other checks.

Installation

go install github.com/dims/logtools/logcheck

Usage

$logcheck.go <package_name> e.g $logcheck ./pkg/kubelet/lifecycle/

Configuration

Checks can be enabled or disabled globally via command line flags and env variables. In addition, the global setting for a check can be modified per file via a configuration file. That file contains lines in this format:

<checks> <regular expression>

<checks> is a comma-separated list of the names of checks that get enabled or disabled when a file name matches the regular expression. A check gets disabled when its name has - as prefix and enabled when there is no prefix or + as prefix. Only checks that are mentioned explicitly are modified. All regular expressions are checked in order, so later lines can override the previous ones.

In this example, checking for klog calls is enabled for all files under pkg/scheduler in the Kubernetes repo except for scheduler.go itself. Parameter checking is disabled everywhere.

klog,-parameters k8s.io/kubernetes/pkg/scheduler/.*
-klog k8s.io/kubernetes/pkg/scheduler/scheduler.go

The names of all supported checks are the ones used as sub-section titles in the next section.

Checks

structured (enabled by default)

Unstructured klog logging calls are flagged as error.

klog (disabled by default)

None of the klog logging methods may be used. This is even stricter than unstructured. Instead, code should retrieve a logr.Logger from klog and log through that.

parameters (enabled by default)

This ensures that if certain logging functions are allowed and are used, those functions are passed correct parameters.

all calls

Format strings are not allowed where plain strings are expected.

structured logging calls

Key/value parameters for logging calls are checked:

• For each key there must be a value.
• Keys must be constant strings.

This also warns about code that is valid, for example code that collects key/value pairs in an []interface variable before passing that on to a log call. Such valid code can use nolint:logcheck to disable the warning (when invoking logcheck through golangci-lint) or the parameters check can be disabled for the file.

with-helpers (disabled by default)

logr.Logger.WithName, logr.Logger.WithValues and logr.NewContext must not be used. The corresponding helper calls from k8s.io/klogr should be used instead. This is relevant when support contextual logging is disabled at runtime in klog.