release-21.1: util/log,server/debug: fixes to logging and the logspy api endpoint

[mikeCRL]

cockroachdb/cockroach#66328 --- Release note (api change): The /debug/logspy API does not any more enable maximum logging verbosity automatically. To change the verbosity, use the new /debug/vmodule endpoint or pass the &vmodule= query parameter to the /debug/logspy endpoint. For example, suppose you wish to run a 20s logspy session: - Before: curl %2527https://.../debug/logspy?duration=20s&...%2527 - Now: curl %2527https://.../debug/logspy?duration=20s&vmodule=...%2527 OR curl %2527https://.../debug/vmodule?duration=22s&vmodule=...%2527 curl %2527https://.../debug/logspy?duration=20s%2527 As for the regular vmodule command-line flag, the maximum verbosity across all the source code can be selected with the pattern *=4. Note: at most one in-flight HTTP API request is allowed to modify the vmodule parameter. This maintain the invariant that the configuration restored at the end of each request is the same as when the request started. Release note (api change): The new /debug/vmodule API makes it possible for an operator to configure the logging verbosity in a similar way as the SQL built-in function crdb_internal.set_vmodule(), or to query the current configuration as in crdb_internal.get_vmodule(). Additionally, any configuration change performed via this API can be automatically reverted after a configurable delay. The API forms are: - /debug/vmodule - retrieve the current configuration. - /debug/vmodule?set=[vmodule config]&duration=[duration] - change the configuration to [vmodule config] . The previous configuration at the time the /debug/vmodule request started is restored after [duration]. This duration, if not specified, defaults to twice the default duration of a logspy request (currently, the logspy default duration is 5s, so the vmodule default duration is 10s). If the duration is zero or negative, the previous configuration is never restored.

[mikeCRL]

Created during a test of an issue-creation script. Issue is not needed. Closing.