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Add support for SRV records for memcache clients
This allows MEMCAHE_SRV to be specified as an SRV record from
which multiple memcache hosts can be resolved. For example:
MEMCACHE_SRV=_memcache._tcp.mylovelydomain.com
This can be used instead of MEMCACHE_HOST_PORT.
This will then be resolved and whatever set of servers it represents
will be used as the set of memcache servers to connect to. At this
stage neither priority or weight is supported, though weight could
be fairly straightforwardly in future.
The SRV can be polled periodically for new servers by setting the
following env var (with 0 meaning "never check"):
MEMCACHE_SRV_REFRESH=600s # supports standard go durations
Signed-off-by: Peter Marsh <[email protected]>- Loading branch information
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,49 @@ | ||
| package srv | ||
|
|
||
| import ( | ||
| "errors" | ||
| "fmt" | ||
| "net" | ||
| "regexp" | ||
|
|
||
| logger "github.com/sirupsen/logrus" | ||
| ) | ||
|
|
||
| var srvRegex = regexp.MustCompile(`^_(.+?)\._(.+?)\.(.+)$`) | ||
|
|
||
| func ParseSrv(srv string) (string, string, string, error) { | ||
| matches := srvRegex.FindStringSubmatch(srv) | ||
| if matches == nil { | ||
| errorText := fmt.Sprintf("could not parse %s to SRV parts", srv) | ||
| logger.Errorf(errorText) | ||
| return "", "", "", errors.New(errorText) | ||
| } | ||
| return matches[1], matches[2], matches[3], nil | ||
| } | ||
|
|
||
| func ServerStringsFromSrv(srv string) ([]string, error) { | ||
| service, proto, name, err := ParseSrv(srv) | ||
|
|
||
| if err != nil { | ||
| logger.Errorf("failed to parse SRV: %s", err) | ||
| return nil, err | ||
| } | ||
|
|
||
| _, srvs, err := net.LookupSRV(service, proto, name) | ||
|
|
||
| if err != nil { | ||
| logger.Errorf("failed to lookup SRV: %s", err) | ||
| return nil, err | ||
| } | ||
|
|
||
| logger.Debugf("found %v servers(s) from SRV", len(srvs)) | ||
|
|
||
| serversFromSrv := make([]string, len(srvs)) | ||
| for i, srv := range srvs { | ||
| server := fmt.Sprintf("%s:%v", srv.Target, srv.Port) | ||
| logger.Debugf("server from srv[%v]: %s", i, server) | ||
| serversFromSrv[i] = fmt.Sprintf("%s:%v", srv.Target, srv.Port) | ||
| } | ||
|
|
||
| return serversFromSrv, nil | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,56 @@ | ||
| package srv | ||
|
|
||
| import ( | ||
| "errors" | ||
| "net" | ||
| "testing" | ||
|
|
||
| "github.com/envoyproxy/ratelimit/src/srv" | ||
| "github.com/stretchr/testify/assert" | ||
| ) | ||
|
|
||
| func TestParseSrv(t *testing.T) { | ||
| service, proto, name, err := srv.ParseSrv("_something._tcp.example.org.") | ||
| assert.Equal(t, service, "something") | ||
| assert.Equal(t, proto, "tcp") | ||
| assert.Equal(t, name, "example.org.") | ||
| assert.Nil(t, err) | ||
|
|
||
| service, proto, name, err = srv.ParseSrv("_something-else._udp.example.org") | ||
| assert.Equal(t, service, "something-else") | ||
| assert.Equal(t, proto, "udp") | ||
| assert.Equal(t, name, "example.org") | ||
| assert.Nil(t, err) | ||
|
|
||
| _, _, _, err = srv.ParseSrv("example.org") | ||
| assert.Equal(t, err, errors.New("could not parse example.org to SRV parts")) | ||
| } | ||
|
|
||
| func TestServerStringsFromSrvWhenSrvIsNotWellFormed(t *testing.T) { | ||
| _, err := srv.ServerStringsFromSrv("example.org") | ||
| assert.Equal(t, err, errors.New("could not parse example.org to SRV parts")) | ||
| } | ||
|
|
||
| func TestServerStringsFromSevWhenSrvIsWellFormedButNotLookupable(t *testing.T) { | ||
| _, err := srv.ServerStringsFromSrv("_something._tcp.example.invalid") | ||
| var e *net.DNSError | ||
| if errors.As(err, &e) { | ||
| assert.Equal(t, e.Err, "no such host") | ||
| assert.Equal(t, e.Name, "_something._tcp.example.invalid") | ||
| assert.False(t, e.IsTimeout) | ||
| assert.False(t, e.IsTemporary) | ||
| assert.True(t, e.IsNotFound) | ||
| } else { | ||
| t.Fail() | ||
| } | ||
| } | ||
|
|
||
| func TestServerStrings(t *testing.T) { | ||
| // it seems reasonable to think _xmpp-server._tcp.gmail.com will be available for a long time! | ||
| servers, err := srv.ServerStringsFromSrv("_xmpp-server._tcp.gmail.com.") | ||
| assert.True(t, len(servers) > 0) | ||
| for _, s := range servers { | ||
| assert.Regexp(t, `^.*xmpp-server.*google.com.:\d+$`, s) | ||
| } | ||
| assert.Nil(t, err) | ||
| } |