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cleanup - wrap block comments @ 80 columns
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@ginayeh
ginayeh committed Jun 27, 2023
1 parent 64419cd commit 4bec8f2
Showing 1 changed file with 37 additions and 25 deletions.
62 changes: 37 additions & 25 deletions internal/resolver/dns/dns_resolver.go
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Expand Up @@ -62,7 +62,8 @@ const (
defaultPort = "443"
defaultDNSSvrPort = "53"
golang = "GO"
// txtPrefix is the prefix string to be prepended to the host name for txt record lookup.
// txtPrefix is the prefix string to be prepended to the host name for txt
// record lookup.
txtPrefix = "_grpc_config."
// In DNS, service config is encoded in a TXT record via the mechanism
// described in RFC-1464 using the attribute name grpc_config.
Expand Down Expand Up @@ -114,7 +115,8 @@ func NewBuilder() resolver.Builder {

type dnsBuilder struct{}

// Build creates and starts a DNS resolver that watches the name resolution of the target.
// Build creates and starts a DNS resolver that watches the name resolution of
// the target.
func (b *dnsBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) {
host, port, err := parseTarget(target.Endpoint(), defaultPort)
if err != nil {
Expand Down Expand Up @@ -180,19 +182,22 @@ type dnsResolver struct {
ctx context.Context
cancel context.CancelFunc
cc resolver.ClientConn
// rn channel is used by ResolveNow() to force an immediate resolution of the target.
// rn channel is used by ResolveNow() to force an immediate resolution of the
// target.
rn chan struct{}
// wg is used to enforce Close() to return after the watcher() goroutine has finished.
// Otherwise, data race will be possible. [Race Example] in dns_resolver_test we
// replace the real lookup functions with mocked ones to facilitate testing.
// If Close() doesn't wait for watcher() goroutine finishes, race detector sometimes
// will warns lookup (READ the lookup function pointers) inside watcher() goroutine
// has data race with replaceNetFunc (WRITE the lookup function pointers).
// wg is used to enforce Close() to return after the watcher() goroutine has
// finished. Otherwise, data race will be possible. [Race Example] in
// dns_resolver_test we replace the real lookup functions with mocked ones to
// facilitate testing. If Close() doesn't wait for watcher() goroutine
// finishes, race detector sometimes will warns lookup (READ the lookup
// function pointers) inside watcher() goroutine has data race with
// replaceNetFunc (WRITE the lookup function pointers).
wg sync.WaitGroup
disableServiceConfig bool
}

// ResolveNow invoke an immediate resolution of the target that this dnsResolver watches.
// ResolveNow invoke an immediate resolution of the target that this
// dnsResolver watches.
func (d *dnsResolver) ResolveNow(resolver.ResolveNowOptions) {
select {
case d.rn <- struct{}{}:
Expand Down Expand Up @@ -220,8 +225,8 @@ func (d *dnsResolver) watcher() {

var timer *time.Timer
if err == nil {
// Success resolving, wait for the next ResolveNow. However, also wait 30 seconds at the very least
// to prevent constantly re-resolving.
// Success resolving, wait for the next ResolveNow. However, also wait 30
// seconds at the very least to prevent constantly re-resolving.
backoffIndex = 1
timer = newTimerDNSResRate(minDNSResRate)
select {
Expand All @@ -231,7 +236,8 @@ func (d *dnsResolver) watcher() {
case <-d.rn:
}
} else {
// Poll on an error found in DNS Resolver or an error received from ClientConn.
// Poll on an error found in DNS Resolver or an error received from
// ClientConn.
timer = newTimer(backoff.DefaultExponential.Backoff(backoffIndex))
backoffIndex++
}
Expand Down Expand Up @@ -278,7 +284,8 @@ func (d *dnsResolver) lookupSRV() ([]resolver.Address, error) {
}

func handleDNSError(err error, lookupType string) error {
if dnsErr, ok := err.(*net.DNSError); ok && !dnsErr.IsTimeout && !dnsErr.IsTemporary {
dnsErr, ok := err.(*net.DNSError)
if ok && !dnsErr.IsTimeout && !dnsErr.IsTemporary {
// Timeouts and temporary errors should be communicated to gRPC to
// attempt another DNS query (with backoff). Other errors should be
// suppressed (they may represent the absence of a TXT record).
Expand Down Expand Up @@ -307,10 +314,12 @@ func (d *dnsResolver) lookupTXT() *serviceconfig.ParseResult {
res += s
}

// TXT record must have "grpc_config=" attribute in order to be used as service config.
// TXT record must have "grpc_config=" attribute in order to be used as
// service config.
if !strings.HasPrefix(res, txtAttribute) {
logger.Warningf("dns: TXT record %v missing %v attribute", res, txtAttribute)
// This is not an error; it is the equivalent of not having a service config.
// This is not an error; it is the equivalent of not having a service
// config.
return nil
}
sc := canaryingSC(strings.TrimPrefix(res, txtAttribute))
Expand Down Expand Up @@ -352,9 +361,10 @@ func (d *dnsResolver) lookup() (*resolver.State, error) {
return &state, nil
}

// formatIP returns ok = false if addr is not a valid textual representation of an IP address.
// If addr is an IPv4 address, return the addr and ok = true.
// If addr is an IPv6 address, return the addr enclosed in square brackets and ok = true.
// formatIP returns ok = false if addr is not a valid textual representation of
// an IP address. If addr is an IPv4 address, return the addr and ok = true.
// If addr is an IPv6 address, return the addr enclosed in square brackets and
// ok = true.
func formatIP(addr string) (addrIP string, ok bool) {
ip := net.ParseIP(addr)
if ip == nil {
Expand All @@ -366,10 +376,10 @@ func formatIP(addr string) (addrIP string, ok bool) {
return "[" + addr + "]", true
}

// parseTarget takes the user input target string and default port, returns formatted host and port info.
// If target doesn't specify a port, set the port to be the defaultPort.
// If target is in IPv6 format and host-name is enclosed in square brackets, brackets
// are stripped when setting the host.
// parseTarget takes the user input target string and default port, returns
// formatted host and port info. If target doesn't specify a port, set the port
// to be the defaultPort. If target is in IPv6 format and host-name is enclosed
// in square brackets, brackets are stripped when setting the host.
// examples:
// target: "www.google.com" defaultPort: "443" returns host: "www.google.com", port: "443"
// target: "ipv4-host:80" defaultPort: "443" returns host: "ipv4-host", port: "80"
Expand All @@ -385,12 +395,14 @@ func parseTarget(target, defaultPort string) (host, port string, err error) {
}
if host, port, err = net.SplitHostPort(target); err == nil {
if port == "" {
// If the port field is empty (target ends with colon), e.g. "[::1]:", this is an error.
// If the port field is empty (target ends with colon), e.g. "[::1]:",
// this is an error.
return "", "", errEndsWithColon
}
// target has port, i.e ipv4-host:port, [ipv6-host]:port, host-name:port
if host == "" {
// Keep consistent with net.Dial(): If the host is empty, as in ":80", the local system is assumed.
// Keep consistent with net.Dial(): If the host is empty, as in ":80",
// the local system is assumed.
host = "localhost"
}
return host, port, nil
Expand Down

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