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
116 lines
2.6 KiB
Go
116 lines
2.6 KiB
Go
package cli
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import (
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"fmt"
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"io"
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"os"
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"strings"
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)
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// OsExiter is the function used when the app exits. If not set defaults to os.Exit.
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var OsExiter = os.Exit
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// ErrWriter is used to write errors to the user. This can be anything
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// implementing the io.Writer interface and defaults to os.Stderr.
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var ErrWriter io.Writer = os.Stderr
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// MultiError is an error that wraps multiple errors.
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type MultiError struct {
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Errors []error
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}
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// NewMultiError creates a new MultiError. Pass in one or more errors.
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func NewMultiError(err ...error) MultiError {
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return MultiError{Errors: err}
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}
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// Error implements the error interface.
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func (m MultiError) Error() string {
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errs := make([]string, len(m.Errors))
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for i, err := range m.Errors {
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errs[i] = err.Error()
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}
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return strings.Join(errs, "\n")
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}
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type ErrorFormatter interface {
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Format(s fmt.State, verb rune)
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}
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// ExitCoder is the interface checked by `App` and `Command` for a custom exit
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// code
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type ExitCoder interface {
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error
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ExitCode() int
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}
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// ExitError fulfills both the builtin `error` interface and `ExitCoder`
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type ExitError struct {
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exitCode int
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message interface{}
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}
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// NewExitError makes a new *ExitError
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func NewExitError(message interface{}, exitCode int) *ExitError {
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return &ExitError{
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exitCode: exitCode,
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message: message,
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}
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}
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// Error returns the string message, fulfilling the interface required by
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// `error`
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func (ee *ExitError) Error() string {
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return fmt.Sprintf("%v", ee.message)
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}
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// ExitCode returns the exit code, fulfilling the interface required by
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// `ExitCoder`
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func (ee *ExitError) ExitCode() int {
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return ee.exitCode
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}
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// HandleExitCoder checks if the error fulfills the ExitCoder interface, and if
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// so prints the error to stderr (if it is non-empty) and calls OsExiter with the
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// given exit code. If the given error is a MultiError, then this func is
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// called on all members of the Errors slice and calls OsExiter with the last exit code.
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func HandleExitCoder(err error) {
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if err == nil {
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return
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}
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if exitErr, ok := err.(ExitCoder); ok {
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if err.Error() != "" {
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if _, ok := exitErr.(ErrorFormatter); ok {
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fmt.Fprintf(ErrWriter, "%+v\n", err)
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} else {
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fmt.Fprintln(ErrWriter, err)
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}
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}
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OsExiter(exitErr.ExitCode())
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return
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}
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if multiErr, ok := err.(MultiError); ok {
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code := handleMultiError(multiErr)
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OsExiter(code)
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return
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}
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}
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func handleMultiError(multiErr MultiError) int {
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code := 1
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for _, merr := range multiErr.Errors {
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if multiErr2, ok := merr.(MultiError); ok {
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code = handleMultiError(multiErr2)
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} else {
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fmt.Fprintln(ErrWriter, merr)
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if exitErr, ok := merr.(ExitCoder); ok {
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code = exitErr.ExitCode()
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}
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}
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}
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return code
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}
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