Leveled execution logs for Go

Since the README file of this repository was 5 years old. I took the initiative of creating this update in formatting using markdown. If you need anything else please respond to this pull request so I can change it.

Leave your thoughts below about this change. I would appreciate it if my pull request is accepted since this is my first contribution to golang. I would certainly like to contribute more.

Best Regards

@robpike This is an export of an internal bug fix. The original author is @Sajmani

Fix problem that -log_dir will not be respected when anything is logged before flag.Parse().

Before this change, premature logging resulted into log files being put in the default location (e.g. /tmp), but not the one specified by the log_dir flag.

After this change, premature logging will not result into the creation of the log files yet. Instead, the log message will be printed to stderr.

It took me forever to figure out how to use the flag functionality; even in the generate godoc for glog, the instruction to call flag.Parse() is very easy to overlook.

By putting the information in the pull request in the README it will help prevent confusion to people either new to golang or who lack knowledge of the flag package.

Glogger contains a copy of the exported glog logging functions but it turns them into methods and allows adding prefixes to the logs. This allows "namespacing" the printout with something such as the name of the function that triggered it.

In case glog is called from the delegate, file name in log is always the name of the delgate go file.

New flag "fileNameStackDepth" added to get the right file name from the stack trace in case logger is delegated.

Please merge

Hi @robpike : The existing glog will rotate log file only when its size reach 1.8GB, but it is too large and not configurable, so I add the max-logfile-size flag in order to support custom configuration max log file size.

Adds "--logstashtype" and "--logstashurl" CLI options.

--logstashtype: logs generated will be sent to the logstash server with the provided type. Defaults to "" (disabled). Examples:

The following results in logs that can be queried with the "serviced-master" type in elastic search/kibana: serviced -master --logstashtype="serviced-master"

The following results in logs that can be queried with the "serviced-add-host-foo" type in elastic search/kibana: serviced add-template foo --logstashtype="serviced-add-host-foo"

--logstashurl: defines the logstash url and port. Defaults to "172.17.42.1:5042".

The purpose of this PR is to:

• Ensure the rules set on the main branch work as expected
• Get initial feedback on the changes made to include year in the timestamp

Example log output before adding year I0715 11:40:13.688222 77957 controller.go:839] NGINX is ready

Example log output after adding year I20220715 11:40:13.688222 77957 controller.go:839] NGINX is ready

Setting flags in init() can cause conflicts with user's flags. Using -v is very common in cmdline utilities, so rename it to -vlevel to prevent problems.

This problem has been reported quite a few times over the years; for example, see it reported at golang-nuts mailing list 1, and cue lang issue 2.

The problem is that, that glog package registers some flags in its init() function. The list of registered flags also includes the -v flag, which is usually used by developers either to control verbosity of their code-execution, or to show the software version. It's notable that all the complaints are regarding the -v flag, and none about the other flags, since those other flags are unlikely be used by any other developer.

The proposed fix allows the user of the glog package to change/prefix glog's flags' names, so that they will not conflict with any flags that they want to use.

This approach to the problem has a few advantages, compared to other options like, disabling all the flags in glog.

1. The default behaviour of the glog library is unchanged. So the current users of the library will not be affected.

2. Any new users who wish to use the -v, or other glog-occupied flag, can do so at build time.

3. The new users can still use the glog features/flags, albeit with a prefix.

4. We are not enforcing some specific prefix, which may also conflict.

5. The --help flag, correctly reports the changed/prefixed flag names.

$ ./main --help
Usage of ./main:

  ... other glog: prefixed flags ...

  -glog:v value
        log level for V logs
  -glog:vmodule value
        comma-separated list of pattern=N settings for file-filtered logging
  -v value
        Emit verbose execution progress

Please also see sample code 3 that demonstrates the problem, and how the patch fixes the problem.