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author | dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com> | 2020-08-27 08:22:37 +0000 |
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committer | Daniel J Walsh <dwalsh@redhat.com> | 2020-08-28 05:45:35 -0400 |
commit | 90a86cad3a6f007c6708406d8a78528fbb302a0a (patch) | |
tree | 4c6546079346d0ff39f7c9a4d076913457a6a417 /vendor/github.com/go-logr/logr/README.md | |
parent | d6b13d8a0993aced5e227e7a516aadbf37e14dbc (diff) | |
download | podman-90a86cad3a6f007c6708406d8a78528fbb302a0a.tar.gz podman-90a86cad3a6f007c6708406d8a78528fbb302a0a.tar.bz2 podman-90a86cad3a6f007c6708406d8a78528fbb302a0a.zip |
Bump k8s.io/apimachinery from 0.18.8 to 0.19.0
Bumps [k8s.io/apimachinery](https://github.com/kubernetes/apimachinery) from 0.18.8 to 0.19.0.
- [Release notes](https://github.com/kubernetes/apimachinery/releases)
- [Commits](https://github.com/kubernetes/apimachinery/compare/v0.18.8...v0.19.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>
Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>
Diffstat (limited to 'vendor/github.com/go-logr/logr/README.md')
-rw-r--r-- | vendor/github.com/go-logr/logr/README.md | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/vendor/github.com/go-logr/logr/README.md b/vendor/github.com/go-logr/logr/README.md new file mode 100644 index 000000000..aca17f382 --- /dev/null +++ b/vendor/github.com/go-logr/logr/README.md @@ -0,0 +1,181 @@ +# A more minimal logging API for Go + +Before you consider this package, please read [this blog post by the +inimitable Dave Cheney][warning-makes-no-sense]. I really appreciate what +he has to say, and it largely aligns with my own experiences. Too many +choices of levels means inconsistent logs. + +This package offers a purely abstract interface, based on these ideas but with +a few twists. Code can depend on just this interface and have the actual +logging implementation be injected from callers. Ideally only `main()` knows +what logging implementation is being used. + +# Differences from Dave's ideas + +The main differences are: + +1) Dave basically proposes doing away with the notion of a logging API in favor +of `fmt.Printf()`. I disagree, especially when you consider things like output +locations, timestamps, file and line decorations, and structured logging. I +restrict the API to just 2 types of logs: info and error. + +Info logs are things you want to tell the user which are not errors. Error +logs are, well, errors. If your code receives an `error` from a subordinate +function call and is logging that `error` *and not returning it*, use error +logs. + +2) Verbosity-levels on info logs. This gives developers a chance to indicate +arbitrary grades of importance for info logs, without assigning names with +semantic meaning such as "warning", "trace", and "debug". Superficially this +may feel very similar, but the primary difference is the lack of semantics. +Because verbosity is a numerical value, it's safe to assume that an app running +with higher verbosity means more (and less important) logs will be generated. + +This is a BETA grade API. + +There are implementations for the following logging libraries: + +- **github.com/google/glog**: [glogr](https://github.com/go-logr/glogr) +- **k8s.io/klog**: [klogr](https://git.k8s.io/klog/klogr) +- **go.uber.org/zap**: [zapr](https://github.com/go-logr/zapr) +- **log** (the Go standard library logger): + [stdr](https://github.com/go-logr/stdr) +- **github.com/sirupsen/logrus**: [logrusr](https://github.com/bombsimon/logrusr) + +# FAQ + +## Conceptual + +## Why structured logging? + +- **Structured logs are more easily queriable**: Since you've got + key-value pairs, it's much easier to query your structured logs for + particular values by filtering on the contents of a particular key -- + think searching request logs for error codes, Kubernetes reconcilers for + the name and namespace of the reconciled object, etc + +- **Structured logging makes it easier to have cross-referencable logs**: + Similarly to searchability, if you maintain conventions around your + keys, it becomes easy to gather all log lines related to a particular + concept. + +- **Structured logs allow better dimensions of filtering**: if you have + structure to your logs, you've got more precise control over how much + information is logged -- you might choose in a particular configuration + to log certain keys but not others, only log lines where a certain key + matches a certain value, etc, instead of just having v-levels and names + to key off of. + +- **Structured logs better represent structured data**: sometimes, the + data that you want to log is inherently structured (think tuple-link + objects). Structured logs allow you to preserve that structure when + outputting. + +## Why V-levels? + +**V-levels give operators an easy way to control the chattiness of log +operations**. V-levels provide a way for a given package to distinguish +the relative importance or verbosity of a given log message. Then, if +a particular logger or package is logging too many messages, the user +of the package can simply change the v-levels for that library. + +## Why not more named levels, like Warning? + +Read [Dave Cheney's post][warning-makes-no-sense]. Then read [Differences +from Dave's ideas](#differences-from-daves-ideas). + +## Why not allow format strings, too? + +**Format strings negate many of the benefits of structured logs**: + +- They're not easily searchable without resorting to fuzzy searching, + regular expressions, etc + +- They don't store structured data well, since contents are flattened into + a string + +- They're not cross-referencable + +- They don't compress easily, since the message is not constant + +(unless you turn positional parameters into key-value pairs with numerical +keys, at which point you've gotten key-value logging with meaningless +keys) + +## Practical + +## Why key-value pairs, and not a map? + +Key-value pairs are *much* easier to optimize, especially around +allocations. Zap (a structured logger that inspired logr's interface) has +[performance measurements](https://github.com/uber-go/zap#performance) +that show this quite nicely. + +While the interface ends up being a little less obvious, you get +potentially better performance, plus avoid making users type +`map[string]string{}` every time they want to log. + +## What if my V-levels differ between libraries? + +That's fine. Control your V-levels on a per-logger basis, and use the +`WithName` function to pass different loggers to different libraries. + +Generally, you should take care to ensure that you have relatively +consistent V-levels within a given logger, however, as this makes deciding +on what verbosity of logs to request easier. + +## But I *really* want to use a format string! + +That's not actually a question. Assuming your question is "how do +I convert my mental model of logging with format strings to logging with +constant messages": + +1. figure out what the error actually is, as you'd write in a TL;DR style, + and use that as a message + +2. For every place you'd write a format specifier, look to the word before + it, and add that as a key value pair + +For instance, consider the following examples (all taken from spots in the +Kubernetes codebase): + +- `klog.V(4).Infof("Client is returning errors: code %v, error %v", + responseCode, err)` becomes `logger.Error(err, "client returned an + error", "code", responseCode)` + +- `klog.V(4).Infof("Got a Retry-After %ds response for attempt %d to %v", + seconds, retries, url)` becomes `logger.V(4).Info("got a retry-after + response when requesting url", "attempt", retries, "after + seconds", seconds, "url", url)` + +If you *really* must use a format string, place it as a key value, and +call `fmt.Sprintf` yourself -- for instance, `log.Printf("unable to +reflect over type %T")` becomes `logger.Info("unable to reflect over +type", "type", fmt.Sprintf("%T"))`. In general though, the cases where +this is necessary should be few and far between. + +## How do I choose my V-levels? + +This is basically the only hard constraint: increase V-levels to denote +more verbose or more debug-y logs. + +Otherwise, you can start out with `0` as "you always want to see this", +`1` as "common logging that you might *possibly* want to turn off", and +`10` as "I would like to performance-test your log collection stack". + +Then gradually choose levels in between as you need them, working your way +down from 10 (for debug and trace style logs) and up from 1 (for chattier +info-type logs). + +## How do I choose my keys + +- make your keys human-readable +- constant keys are generally a good idea +- be consistent across your codebase +- keys should naturally match parts of the message string + +While key names are mostly unrestricted (and spaces are acceptable), +it's generally a good idea to stick to printable ascii characters, or at +least match the general character set of your log lines. + +[warning-makes-no-sense]: http://dave.cheney.net/2015/11/05/lets-talk-about-logging |