syncthing/vendor/github.com/minio/cli/funcs.go
Jakob Borg 916ec63af6 cmd/stdiscosrv: New discovery server (fixes #4618)
This is a new revision of the discovery server. Relevant changes and
non-changes:

- Protocol towards clients is unchanged.

- Recommended large scale design is still to be deployed nehind nginx (I
  tested, and it's still a lot faster at terminating TLS).

- Database backend is leveldb again, only. It scales enough, is easy to
  setup, and we don't need any backend to take care of.

- Server supports replication. This is a simple TCP channel - protect it
  with a firewall when deploying over the internet. (We deploy this within
  the same datacenter, and with firewall.) Any incoming client announces
  are sent over the replication channel(s) to other peer discosrvs.
  Incoming replication changes are applied to the database as if they came
  from clients, but without the TLS/certificate overhead.

- Metrics are exposed using the prometheus library, when enabled.

- The database values and replication protocol is protobuf, because JSON
  was quite CPU intensive when I tried that and benchmarked it.

- The "Retry-After" value for failed lookups gets slowly increased from
  a default of 120 seconds, by 5 seconds for each failed lookup,
  independently by each discosrv. This lowers the query load over time for
  clients that are never seen. The Retry-After maxes out at 3600 after a
  couple of weeks of this increase. The number of failed lookups is
  stored in the database, now and then (avoiding making each lookup a
  database put).

All in all this means clients can be pointed towards a cluster using
just multiple A / AAAA records to gain both load sharing and redundancy
(if one is down, clients will talk to the remaining ones).

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4648
2018-01-14 08:52:31 +00:00

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Go

package cli
// BashCompleteFunc is an action to execute when the bash-completion flag is set
type BashCompleteFunc func(*Context)
// BeforeFunc is an action to execute before any subcommands are run, but after
// the context is ready if a non-nil error is returned, no subcommands are run
type BeforeFunc func(*Context) error
// AfterFunc is an action to execute after any subcommands are run, but after the
// subcommand has finished it is run even if Action() panics
type AfterFunc func(*Context) error
// ActionFunc is the action to execute when no subcommands are specified
type ActionFunc func(*Context) error
// CommandNotFoundFunc is executed if the proper command cannot be found
type CommandNotFoundFunc func(*Context, string)
// OnUsageErrorFunc is executed if an usage error occurs. This is useful for displaying
// customized usage error messages. This function is able to replace the
// original error messages. If this function is not set, the "Incorrect usage"
// is displayed and the execution is interrupted.
type OnUsageErrorFunc func(context *Context, err error, isSubcommand bool) error
// FlagStringFunc is used by the help generation to display a flag, which is
// expected to be a single line.
type FlagStringFunc func(Flag) string