119 lines
5.1 KiB
Markdown
119 lines
5.1 KiB
Markdown
klog
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====
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klog is a permanent fork of https://github.com/golang/glog.
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## Why was klog created?
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The decision to create klog was one that wasn't made lightly, but it was necessary due to some
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drawbacks that are present in [glog](https://github.com/golang/glog). Ultimately, the fork was created due to glog not being under active development; this can be seen in the glog README:
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> The code in this repo [...] is not itself under development
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This makes us unable to solve many use cases without a fork. The factors that contributed to needing feature development are listed below:
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* `glog` [presents a lot "gotchas"](https://github.com/kubernetes/kubernetes/issues/61006) and introduces challenges in containerized environments, all of which aren't well documented.
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* `glog` doesn't provide an easy way to test logs, which detracts from the stability of software using it
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* A long term goal is to implement a logging interface that allows us to add context, change output format, etc.
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Historical context is available here:
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* https://github.com/kubernetes/kubernetes/issues/61006
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* https://github.com/kubernetes/kubernetes/issues/70264
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* https://groups.google.com/forum/#!msg/kubernetes-sig-architecture/wCWiWf3Juzs/hXRVBH90CgAJ
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* https://groups.google.com/forum/#!msg/kubernetes-dev/7vnijOMhLS0/1oRiNtigBgAJ
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## Release versioning
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Semantic versioning is used in this repository. It contains several Go modules
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with different levels of stability:
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- `k8s.io/klog/v2` - stable API, `vX.Y.Z` tags
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- `examples` - no stable API, no tags, no intention to ever stabilize
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Exempt from the API stability guarantee are items (packages, functions, etc.)
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which are marked explicitly as `EXPERIMENTAL` in their docs comment. Those
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may still change in incompatible ways or get removed entirely. This can only
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be used for code that is used in tests to avoid situations where non-test
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code from two different Kubernetes dependencies depends on incompatible
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releases of klog because an experimental API was changed.
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----
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How to use klog
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===============
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- Replace imports for `"github.com/golang/glog"` with `"k8s.io/klog/v2"`
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- Use `klog.InitFlags(nil)` explicitly for initializing global flags as we no longer use `init()` method to register the flags
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- You can now use `log_file` instead of `log_dir` for logging to a single file (See `examples/log_file/usage_log_file.go`)
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- If you want to redirect everything logged using klog somewhere else (say syslog!), you can use `klog.SetOutput()` method and supply a `io.Writer`. (See `examples/set_output/usage_set_output.go`)
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- For more logging conventions (See [Logging Conventions](https://github.com/kubernetes/community/blob/master/contributors/devel/sig-instrumentation/logging.md))
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- See our documentation on [pkg.go.dev/k8s.io](https://pkg.go.dev/k8s.io/klog).
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**NOTE**: please use the newer go versions that support semantic import versioning in modules, ideally go 1.11.4 or greater.
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### Coexisting with klog/v2
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See [this example](examples/coexist_klog_v1_and_v2/) to see how to coexist with both klog/v1 and klog/v2.
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### Coexisting with glog
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This package can be used side by side with glog. [This example](examples/coexist_glog/coexist_glog.go) shows how to initialize and synchronize flags from the global `flag.CommandLine` FlagSet. In addition, the example makes use of stderr as combined output by setting `alsologtostderr` (or `logtostderr`) to `true`.
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## Community, discussion, contribution, and support
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Learn how to engage with the Kubernetes community on the [community page](http://kubernetes.io/community/).
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You can reach the maintainers of this project at:
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- [Slack](https://kubernetes.slack.com/messages/klog)
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- [Mailing List](https://groups.google.com/forum/#!forum/kubernetes-sig-architecture)
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### Code of conduct
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Participation in the Kubernetes community is governed by the [Kubernetes Code of Conduct](code-of-conduct.md).
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----
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glog
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====
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Leveled execution logs for Go.
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This is an efficient pure Go implementation of leveled logs in the
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manner of the open source C++ package
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https://github.com/google/glog
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By binding methods to booleans it is possible to use the log package
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without paying the expense of evaluating the arguments to the log.
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Through the -vmodule flag, the package also provides fine-grained
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control over logging at the file level.
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The comment from glog.go introduces the ideas:
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Package glog implements logging analogous to the Google-internal
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C++ INFO/ERROR/V setup. It provides functions Info, Warning,
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Error, Fatal, plus formatting variants such as Infof. It
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also provides V-style logging controlled by the -v and
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-vmodule=file=2 flags.
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Basic examples:
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glog.Info("Prepare to repel boarders")
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glog.Fatalf("Initialization failed: %s", err)
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See the documentation of the V function for an explanation
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of these examples:
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if glog.V(2) {
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glog.Info("Starting transaction...")
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}
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glog.V(2).Infoln("Processed", nItems, "elements")
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The repository contains an open source version of the log package
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used inside Google. The master copy of the source lives inside
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Google, not here. The code in this repo is for export only and is not itself
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under development. Feature requests will be ignored.
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Send bug reports to golang-nuts@googlegroups.com.
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