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
138 lines
2.9 KiB
Go
138 lines
2.9 KiB
Go
package homedir
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import (
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"bytes"
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"errors"
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"os"
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"os/exec"
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"path/filepath"
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"runtime"
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"strconv"
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"strings"
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"sync"
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)
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// DisableCache will disable caching of the home directory. Caching is enabled
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// by default.
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var DisableCache bool
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var homedirCache string
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var cacheLock sync.RWMutex
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// Dir returns the home directory for the executing user.
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//
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// This uses an OS-specific method for discovering the home directory.
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// An error is returned if a home directory cannot be detected.
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func Dir() (string, error) {
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if !DisableCache {
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cacheLock.RLock()
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cached := homedirCache
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cacheLock.RUnlock()
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if cached != "" {
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return cached, nil
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}
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}
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cacheLock.Lock()
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defer cacheLock.Unlock()
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var result string
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var err error
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if runtime.GOOS == "windows" {
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result, err = dirWindows()
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} else {
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// Unix-like system, so just assume Unix
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result, err = dirUnix()
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}
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if err != nil {
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return "", err
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}
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homedirCache = result
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return result, nil
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}
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// Expand expands the path to include the home directory if the path
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// is prefixed with `~`. If it isn't prefixed with `~`, the path is
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// returned as-is.
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func Expand(path string) (string, error) {
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if len(path) == 0 {
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return path, nil
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}
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if path[0] != '~' {
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return path, nil
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}
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if len(path) > 1 && path[1] != '/' && path[1] != '\\' {
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return "", errors.New("cannot expand user-specific home dir")
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}
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dir, err := Dir()
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if err != nil {
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return "", err
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}
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return filepath.Join(dir, path[1:]), nil
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}
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func dirUnix() (string, error) {
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// First prefer the HOME environmental variable
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if home := os.Getenv("HOME"); home != "" {
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return home, nil
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}
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// If that fails, try getent
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var stdout bytes.Buffer
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cmd := exec.Command("getent", "passwd", strconv.Itoa(os.Getuid()))
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cmd.Stdout = &stdout
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if err := cmd.Run(); err != nil {
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// If the error is ErrNotFound, we ignore it. Otherwise, return it.
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if err != exec.ErrNotFound {
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return "", err
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}
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} else {
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if passwd := strings.TrimSpace(stdout.String()); passwd != "" {
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// username:password:uid:gid:gecos:home:shell
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passwdParts := strings.SplitN(passwd, ":", 7)
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if len(passwdParts) > 5 {
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return passwdParts[5], nil
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}
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}
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}
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// If all else fails, try the shell
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stdout.Reset()
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cmd = exec.Command("sh", "-c", "cd && pwd")
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cmd.Stdout = &stdout
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if err := cmd.Run(); err != nil {
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return "", err
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}
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result := strings.TrimSpace(stdout.String())
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if result == "" {
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return "", errors.New("blank output when reading home directory")
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}
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return result, nil
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}
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func dirWindows() (string, error) {
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// First prefer the HOME environmental variable
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if home := os.Getenv("HOME"); home != "" {
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return home, nil
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}
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drive := os.Getenv("HOMEDRIVE")
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path := os.Getenv("HOMEPATH")
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home := drive + path
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if drive == "" || path == "" {
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home = os.Getenv("USERPROFILE")
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}
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if home == "" {
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return "", errors.New("HOMEDRIVE, HOMEPATH, and USERPROFILE are blank")
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}
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return home, nil
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}
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