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GODRIVER-2620 Fix hostname parsing for SRV polling. #1112

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merged 6 commits into from
Oct 28, 2022
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GODRIVER-2620 Fix hostname parsing for SRV polling. #1112

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cdaa715
GODRIVER-2620 Fix hostname parsing for SRV polling.
qingyang-hu Oct 28, 2022
7ad50fe
GODRIVER-2620 Enhance test cases to cover URIs both with and without …
qingyang-hu Oct 28, 2022
e675205
GODRIVER-2620 Minor polish.
qingyang-hu Oct 28, 2022
5b180ca
Label test helper.
qingyang-hu Oct 28, 2022
19a4154
Comment non-specification-required test.
qingyang-hu Oct 28, 2022
eae97a7
Indent code
qingyang-hu Oct 28, 2022
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2 changes: 1 addition & 1 deletion x/mongo/driver/topology/polling_srv_records_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -127,7 +127,7 @@ func compareHosts(t *testing.T, received []description.Server, expected []string
func TestPollingSRVRecordsSpec(t *testing.T) {
for _, tt := range srvPollingTests {
t.Run(tt.name, func(t *testing.T) {
uri := "mongodb+srv://test1.test.build.10gen.cc/?heartbeatFrequencyMS=100"
uri := "mongodb+srv://user:pass@test1.test.build.10gen.cc/?heartbeatFrequencyMS=100"
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Only testing with a URI containing a username/password may cause the same lack of test coverage as there is currently, but for URIs with no username/password.

Is there a way we can test with multiple URI formats? Could we include the URI in the test struct and add test cases for both with and without username/password?

cfg, err := NewConfig(options.Client().ApplyURI(uri), nil)
require.NoError(t, err, "error constructing topology configs: %v", err)

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28 changes: 19 additions & 9 deletions x/mongo/driver/topology/topology.go
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Expand Up @@ -14,6 +14,8 @@ import (
"context"
"errors"
"fmt"
"net"
"net/url"
"strings"
"sync"
"sync/atomic"
Expand Down Expand Up @@ -234,7 +236,22 @@ func (t *Topology) Connect() error {

t.serversLock.Unlock()
if t.pollingRequired {
go t.pollSRVRecords()
uri, err := url.Parse(t.cfg.URI)
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I'm concerned we don't have enough test coverage of MongoDB connection string formats in the SRV polling tests to assert that it's safe to use url.Parse.

Is every mongodb+srv:// connection string parseable with url.Parse?

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@qingyang-hu qingyang-hu Oct 28, 2022 •
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The package doc says url.Parse parses [scheme:][//[userinfo@]host][/]path[?query][#fragment].
It has been proven that mongodb+srv is parseable as a legal scheme, and covered in the test cases.
Mongo host in the connection string may be different from ordinary hostnames, e.g. a comma-separated host list. However, it is illegal for SRV, and should be sanity checked by topology.NewConfig before being passed in Connect().
Also, we don't need to parse the path string in this case so it doesn't impact us even though we may have special cases in the query parameters.

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Sounds good. I also tested out using url.Parse to parse a bunch of connection string formats and they all worked correctly (see here).

if err != nil {
return err
}
// sanity check before passing the hostname to resolver
parsedHosts := strings.Split(uri.Host, ",")
if len(parsedHosts) != 1 {
return fmt.Errorf("URI with SRV must include one and only one hostname")
}
_, _, err = net.SplitHostPort(parsedHosts[0])
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Suggested change
_, _, err = net.SplitHostPort(parsedHosts[0])
_, _, err = net.SplitHostPort(uri.Host)

[optional]: IMO this code reads better by using the uri to get the host, not the slice used in the sanity check.

if err == nil {
// we were able to successfully extract a port from the host,
// but should not be able to when using SRV
return fmt.Errorf("URI with srv must not include a port number")
}
go t.pollSRVRecords(parsedHosts[0])
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This refactor is a great idea!

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Suggested change
go t.pollSRVRecords(parsedHosts[0])
go t.pollSRVRecords(uri.Host)

[optional]: IMO this code reads better by using the uri to get the host, not the slice used in the sanity check.

t.pollingwg.Add(1)
}

Expand Down Expand Up @@ -556,7 +573,7 @@ func (t *Topology) selectServerFromDescription(desc description.Topology,
return suitable, nil
}

func (t *Topology) pollSRVRecords() {
func (t *Topology) pollSRVRecords(hosts string) {
defer t.pollingwg.Done()

serverConfig := newServerConfig(t.cfg.ServerOpts...)
Expand All @@ -573,13 +590,6 @@ func (t *Topology) pollSRVRecords() {
}
}()

// remove the scheme
uri := t.cfg.URI[14:]
hosts := uri
if idx := strings.IndexAny(uri, "/?@"); idx != -1 {
hosts = uri[:idx]
}

for {
select {
case <-pollTicker.C:
Expand Down