GODRIVER-89 Implement Initial DNS Seedlist discovery spec

.evergreen/.evg.yml

@@ -342,6 +342,10 @@ tasks:
       tags: ["test", "replicaset"]
       commands:
         - func: bootstrap-mongo-orchestration
+          vars:
+            TOPOLOGY: "replica_set"
+            AUTH: "noauth"
+            SSL: "nossl"
         - func: run-tests
           vars:
             TOPOLOGY: "replica_set"

Makefile

@@ -67,6 +67,10 @@ update-bson-corpus-tests:
 update-connection-string-tests:
 	etc/update-spec-tests.sh connection-string
 
+.PHONY: update-initial-dns-seedlist-discovery-tests
+update-initial-dns-seedlist-discovery-tests:
+	etc/update-spec-tests.sh initial-dns-seedlist-discovery
+
 .PHONY: update-max-staleness-tests
 update-max-staleness-tests:
 	etc/update-spec-tests.sh max-staleness

data/initial-dns-seedlist-discovery/README.rst

@@ -0,0 +1,57 @@
+====================================
+Initial DNS Seedlist Discovery tests
+====================================
+
+This directory contains platform-independent tests that drivers can use
+to prove their conformance to the Initial DNS Seedlist Discovery spec.
+
+Test Setup
+----------
+
+Start a three-node replica set on localhost, on ports 27017, 27018, and 27019,
+with replica set name "repl0".
+
+To run the tests that accompany this spec, you need to configure the SRV and
+TXT records with a real name server. The following records are required for
+these tests::
+
+  Record                                    TTL    Class   Port   Target
+  _mongodb._tcp.test1.test.build.10gen.cc.  86400  IN SRV  27017  localhost.build.10gen.cc.
+  _mongodb._tcp.test1.test.build.10gen.cc.  86400  IN SRV  27018  localhost.build.10gen.cc.
+  _mongodb._tcp.test2.test.build.10gen.cc.  86400  IN SRV  27018  localhost.build.10gen.cc.
+  _mongodb._tcp.test2.test.build.10gen.cc.  86400  IN SRV  27019  localhost.build.10gen.cc.
+  _mongodb._tcp.test3.test.build.10gen.cc.  86400  IN SRV  27017  localhost.build.10gen.cc.
+  _mongodb._tcp.test5.test.build.10gen.cc.  86400  IN SRV  27017  localhost.build.10gen.cc.
+  _mongodb._tcp.test6.test.build.10gen.cc.  86400  IN SRV  27017  localhost.build.10gen.cc.
+
+  Record                                    TTL    Class   Text
+  test5.test.build.10gen.cc.                86400  IN TXT  "connectTimeoutMS=300000&socketTimeoutMS=300000"
+  test6.test.build.10gen.cc.                86400  IN TXT  "connectTimeoutMS=200000"
+  test6.test.build.10gen.cc.                86400  IN TXT  "socketTimeoutMS=200000"
+
+Note that ``test4`` is omitted deliberately to test what happens with no SRV
+record.
+
+In our tests we have used "localhost.build.10gen.cc" as the domain, and then
+configured "localhost.build.10gen.cc" to resolve to 127.0.0.1.
+
+You need to adapt the records shown above to replace ``build.10gen.cc`` with
+your own domain name, and update the "uri" field in the YAML or JSON files in
+this directory with the actual domain.
+
+Test Format and Use
+-------------------
+
+These YAML and JSON files contain the following fields:
+
+- ``uri``: a mongodb+srv connection string
+- ``seeds``: the expected set of initial seeds discovered from the SRV record
+- ``hosts``: the discovered topology's list of hosts once SDAM completes a scan
+- ``options``: the parsed connection string options as discovered from URI and
+  TXT records
+
+For each file, create MongoClient initialized with the mongodb+srv connection
+string. You SHOULD verify that the client's initial seed list matches the list of
+seeds. You MUST verify that the set of ServerDescriptions in the client's
+TopologyDescription eventually matches the list of hosts. You MUST verify that
+the set of Connection String Options matches the client's parsed set.

data/initial-dns-seedlist-discovery/no-results.json

@@ -0,0 +1,5 @@
+{
+  "uri": "mongodb+srv://test4.test.build.10gen.cc/",
+  "seeds": [],
+  "hosts": []
+}

data/initial-dns-seedlist-discovery/no-results.yml

@@ -0,0 +1,3 @@
+uri: "mongodb+srv://test4.test.build.10gen.cc/"
+seeds: []
+hosts: []

data/initial-dns-seedlist-discovery/one-result-default-port.json

@@ -0,0 +1,11 @@
+{
+  "uri": "mongodb+srv://test3.test.build.10gen.cc/?replicaSet=repl0",
+  "seeds": [
+    "localhost.build.10gen.cc:27017"
+  ],
+  "hosts": [
+    "localhost:27017",
+    "localhost:27018",
+    "localhost:27019"
+  ]
+}

data/initial-dns-seedlist-discovery/one-result-default-port.yml

@@ -0,0 +1,7 @@
+uri: "mongodb+srv://test3.test.build.10gen.cc/?replicaSet=repl0"
+seeds:
+    - localhost.build.10gen.cc:27017
+hosts:
+    - localhost:27017
+    - localhost:27018
+    - localhost:27019

data/initial-dns-seedlist-discovery/one-txt-record.json

@@ -0,0 +1,16 @@
+{
+  "uri": "mongodb+srv://test5.test.build.10gen.cc/?replicaSet=repl0",
+  "seeds": [
+    "localhost.build.10gen.cc:27017"
+  ],
+  "hosts": [
+    "localhost:27017",
+    "localhost:27018",
+    "localhost:27019"
+  ],
+  "options": {
+    "connectTimeoutMS": 300000,
+    "replicaSet": "repl0",
+    "socketTimeoutMS": 300000
+  }
+}

data/initial-dns-seedlist-discovery/one-txt-record.yml

@@ -0,0 +1,11 @@
+uri: "mongodb+srv://test5.test.build.10gen.cc/?replicaSet=repl0"
+seeds:
+    - localhost.build.10gen.cc:27017
+hosts:
+    - localhost:27017
+    - localhost:27018
+    - localhost:27019
+options:
+    connectTimeoutMS: 300000
+    replicaSet: repl0
+    socketTimeoutMS: 300000

data/initial-dns-seedlist-discovery/two-results-default-port.json

@@ -0,0 +1,12 @@
+{
+  "uri": "mongodb+srv://test1.test.build.10gen.cc/?replicaSet=repl0",
+  "seeds": [
+    "localhost.build.10gen.cc:27017",
+    "localhost.build.10gen.cc:27018"
+  ],
+  "hosts": [
+    "localhost:27017",
+    "localhost:27018",
+    "localhost:27019"
+  ]
+}

data/initial-dns-seedlist-discovery/two-results-default-port.yml

@@ -0,0 +1,8 @@
+uri: "mongodb+srv://test1.test.build.10gen.cc/?replicaSet=repl0"
+seeds:
+    - localhost.build.10gen.cc:27017
+    - localhost.build.10gen.cc:27018
+hosts:
+    - localhost:27017
+    - localhost:27018
+    - localhost:27019

data/initial-dns-seedlist-discovery/two-results-nonstandard-port.json

@@ -0,0 +1,12 @@
+{
+  "uri": "mongodb+srv://test2.test.build.10gen.cc/?replicaSet=repl0",
+  "seeds": [
+    "localhost.build.10gen.cc:27018",
+    "localhost.build.10gen.cc:27019"
+  ],
+  "hosts": [
+    "localhost:27017",
+    "localhost:27018",
+    "localhost:27019"
+  ]
+}

data/initial-dns-seedlist-discovery/two-results-nonstandard-port.yml

@@ -0,0 +1,8 @@
+uri: "mongodb+srv://test2.test.build.10gen.cc/?replicaSet=repl0"
+seeds:
+    - localhost.build.10gen.cc:27018
+    - localhost.build.10gen.cc:27019
+hosts:
+    - localhost:27017
+    - localhost:27018
+    - localhost:27019

data/initial-dns-seedlist-discovery/two-txt-records-with-override.json

@@ -0,0 +1,16 @@
+{
+  "uri": "mongodb+srv://test6.test.build.10gen.cc/?replicaSet=repl0&connectTimeoutMS=250000",
+  "seeds": [
+    "localhost.build.10gen.cc:27017"
+  ],
+  "hosts": [
+    "localhost:27017",
+    "localhost:27018",
+    "localhost:27019"
+  ],
+  "options": {
+    "connectTimeoutMS": 250000,
+    "replicaSet": "repl0",
+    "socketTimeoutMS": 200000
+  }
+}

data/initial-dns-seedlist-discovery/two-txt-records-with-override.yml

@@ -0,0 +1,11 @@
+uri: "mongodb+srv://test6.test.build.10gen.cc/?replicaSet=repl0&connectTimeoutMS=250000"
+seeds:
+    - localhost.build.10gen.cc:27017
+hosts:
+    - localhost:27017
+    - localhost:27018
+    - localhost:27019
+options:
+    connectTimeoutMS: 250000
+    replicaSet: repl0
+    socketTimeoutMS: 200000

data/initial-dns-seedlist-discovery/two-txt-records.json

@@ -0,0 +1,16 @@
+{
+  "uri": "mongodb+srv://test6.test.build.10gen.cc/?replicaSet=repl0",
+  "seeds": [
+    "localhost.build.10gen.cc:27017"
+  ],
+  "hosts": [
+    "localhost:27017",
+    "localhost:27018",
+    "localhost:27019"
+  ],
+  "options": {
+    "connectTimeoutMS": 200000,
+    "replicaSet": "repl0",
+    "socketTimeoutMS": 200000
+  }
+}

data/initial-dns-seedlist-discovery/two-txt-records.yml

@@ -0,0 +1,11 @@
+uri: "mongodb+srv://test6.test.build.10gen.cc/?replicaSet=repl0"
+seeds:
+    - localhost.build.10gen.cc:27017
+hosts:
+    - localhost:27017
+    - localhost:27018
+    - localhost:27019
+options:
+    connectTimeoutMS: 200000
+    replicaSet: repl0
+    socketTimeoutMS: 200000

mongo/connstring/connstring.go

@@ -82,17 +82,21 @@ type parser struct {
 
 func (p *parser) parse(original string) error {
 	p.Original = original
-
 	uri := original
+
 	var err error
-	// scheme
-	if !strings.HasPrefix(uri, "mongodb://") {
-		return fmt.Errorf("scheme must be \"mongodb\"")
+	var isSRV bool
+	if strings.HasPrefix(uri, "mongodb+srv://") {
+		isSRV = true
+		// remove the scheme
+		uri = uri[14:]
+	} else if strings.HasPrefix(uri, "mongodb://") {
+		// remove the scheme
+		uri = uri[10:]
+	} else {
+		return fmt.Errorf("scheme must be \"mongodb\" or \"mongodb+srv\"")
 	}
 
-	// user info
-	uri = uri[10:]
-
 	if idx := strings.Index(uri, "@"); idx != -1 {
 		userInfo := uri[:idx]
 		uri = uri[idx+1:]
@@ -128,10 +132,9 @@ func (p *parser) parse(original string) error {
 				return internal.WrapErrorf(err, "invalid password")
 			}
 		}
-
 	}
 
-	// hosts
+	// fetch the hosts field
 	hosts := uri
 	if idx := strings.IndexAny(uri, "/?@"); idx != -1 {
 		if uri[idx] == '@' {
@@ -140,17 +143,36 @@ func (p *parser) parse(original string) error {
 		if uri[idx] == '?' {
 			return fmt.Errorf("must have a / before the query ?")
 		}
-
 		hosts = uri[:idx]
 	}
 
-	for _, host := range strings.Split(hosts, ",") {
+	var connectionArgsFromTXT []string
+	parsedHosts := strings.Split(hosts, ",")
+
+	if isSRV {
+		parsedHosts = strings.Split(hosts, ",")
+		if len(parsedHosts) != 1 {
+			return fmt.Errorf("URI with SRV must include one and only one hostname")
+		}
+		parsedHosts, err = fetchSeedlistFromSRV(parsedHosts[0])
+		if err != nil {
+			return err
+		}
+
+		// error ignored because finding a TXT record should not be
+		// considered an error.
+		recordsFromTXT, _ := net.LookupTXT(hosts)
+		for _, recordFromTXT := range recordsFromTXT {
+			connectionArgsFromTXT = append(connectionArgsFromTXT, strings.FieldsFunc(recordFromTXT, func(r rune) bool { return r == ';' || r == '&' })...)
+		}
+	}
+
+	for _, host := range parsedHosts {
 		err = p.addHost(host)
 		if err != nil {
 			return internal.WrapErrorf(err, "invalid host \"%s\"", host)
 		}
 	}
-
 	if len(p.Hosts) == 0 {
 		return fmt.Errorf("must have at least 1 host")
 	}
@@ -195,7 +217,10 @@ func (p *parser) parse(original string) error {
 		return nil
 	}
 
-	for _, pair := range strings.FieldsFunc(uri, func(r rune) bool { return r == ';' || r == '&' }) {
+	connectionArgsFromQueryString := strings.FieldsFunc(uri, func(r rune) bool { return r == ';' || r == '&' })
+	connectionArgPairs := append(connectionArgsFromTXT, connectionArgsFromQueryString...)
+
+	for _, pair := range connectionArgPairs {
 		err = p.addOption(pair)
 		if err != nil {
 			return err
@@ -205,6 +230,29 @@ func (p *parser) parse(original string) error {
 	return nil
 }
 
+func fetchSeedlistFromSRV(host string) ([]string, error) {
+	var err error
+
+	_, _, err = net.SplitHostPort(host)
+
+	if err == nil {
+		// we were able to successfully extract a port from the host,
+		// but should not be able to when using SRV
+		return nil, fmt.Errorf("URI with srv must not include a port number")
+	}
+
+	_, addresses, err := net.LookupSRV("mongodb", "tcp", host)
+	if err != nil {
+		return nil, err
+	}
+	parsedHosts := make([]string, len(addresses))
+	for i, address := range addresses {
+		parsedHosts[i] = fmt.Sprintf("%s:%d", strings.TrimSuffix(address.Target, "."), address.Port)
+	}
+
+	return parsedHosts, nil
+}
+
 func (p *parser) addHost(host string) error {
 	if host == "" {
 		return nil