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fix: preserve multi-host HA DSN addresses (Go 1.26) #1946

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fix: preserve multi-host HA DSN addresses (Go 1.26) #1946

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2d729ff
fix: preserve multi-host HA DSN addresses (Go 1.26 / #1784)
sankalpsthakur Aug 1, 2026
c54255c
fix: address review - stdlib, docs, changelog and auth tests
sankalpsthakur Aug 5, 2026
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71 changes: 70 additions & 1 deletion clickhouse_options.go
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Original file line number Diff line number Diff line change
Expand Up @@ -200,7 +200,11 @@ func (o *Options) fromDSN(in string) error {
o.Auth.Username = dsn.User.Username()
o.Auth.Password, _ = dsn.User.Password()
}
o.Addr = append(o.Addr, strings.Split(dsn.Host, ",")...)
// Prefer hosts from the raw DSN authority so multi-host (HA) lists stay
// intact. net/url (and copies of it) can collapse multi-host IPv6 authorities
// to the last host; comma-split of Host also breaks when host values contain
// commas only as HA separators. See https://github.com/ClickHouse/clickhouse-go/issues/1784
o.Addr = append(o.Addr, dsnAddrList(in, dsn.Host)...)
var (
secure bool
params = dsn.Query()
Expand Down Expand Up @@ -398,6 +402,71 @@ func (o *Options) fromDSN(in string) error {
return nil
}

// dsnAddrList returns HA host addresses for a DSN.
// It extracts the authority host list from the raw DSN when possible so that
// multi-host URLs (including bracketed IPv6) are not lost to URL Host normalization.
// Falls back to splitting the already-parsed host on commas.
func dsnAddrList(rawDSN, parsedHost string) []string {
if addrs := addrListFromDSN(rawDSN); len(addrs) > 0 {
return addrs
}
if parsedHost == "" {
return nil
}
return strings.Split(parsedHost, ",")
}

// addrListFromDSN extracts host[:port] entries from the DSN authority.
// Supports comma-separated HA hosts and bracketed IPv6 literals.
func addrListFromDSN(raw string) []string {

@chernser chernser Aug 5, 2026

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There are already tools that can parse such form of url:

package main

import (
	"fmt"
	"net"
	"net/url"
	"strings"
)

type TargetHost struct {
	Host string
	Port string
}

func main() {
	rawURL := "clickhouse://user:pass@host1:9440,host2:9440/database?secure=true"

	// 1. Parse into a standard URL structure
	u, err := url.Parse(rawURL)
	if err != nil {
		panic(err)
	}

	// 2. Extract Username
	username := ""
	if u.User != nil {
		username = u.User.Username()
	}

	// 3. Extract the complete host cluster string
	// u.Host will contain "host1:9440,host2:9440"
	clusterStr := u.Host

	// 4. Split the individual hosts by comma
	hostTokens := strings.Split(clusterStr, ",")
	var hosts []TargetHost

	for _, token := range hostTokens {
		h, p, err := net.SplitHostPort(token)
		if err != nil {
			// Fallback if port is missing from a specific host token
			h = token
			p = ""
		}
		hosts = append(hosts, TargetHost{Host: h, Port: p})
	}

	// Output results
	fmt.Println("Username:", username)
	fmt.Println("Database:", strings.TrimPrefix(u.Path, "/"))
	fmt.Println("Hosts found:")
	for i, h := range hosts {
		fmt.Printf("  [%d] Host: %s, Port: %s\n", i, h.Host, h.Port)
	}
}

i := strings.Index(raw, "://")
if i < 0 {
return nil
}
rest := raw[i+3:]
if j := strings.IndexAny(rest, "?#"); j >= 0 {
rest = rest[:j]
}
if j := strings.Index(rest, "/"); j >= 0 {
rest = rest[:j]
}
if j := strings.LastIndex(rest, "@"); j >= 0 {
rest = rest[j+1:]
}
if rest == "" {
return nil
}
return splitHostList(rest)
}

// splitHostList splits a comma-separated host list without breaking bracketed IPv6 addresses.
func splitHostList(s string) []string {
var out []string
start := 0
depth := 0
for i := 0; i < len(s); i++ {
switch s[i] {
case '[':
depth++
case ']':
if depth > 0 {
depth--
}
case ',':
if depth == 0 {
if part := strings.TrimSpace(s[start:i]); part != "" {
out = append(out, part)
}
start = i + 1
}
}
}
if part := strings.TrimSpace(s[start:]); part != "" {
out = append(out, part)
}
return out
}

// receive copy of Options, so we don't modify original - so its reusable
func (o Options) setDefaults() *Options {
if len(o.Auth.Username) == 0 {
Expand Down
98 changes: 98 additions & 0 deletions clickhouse_options_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -563,6 +563,57 @@ func TestParseDSN(t *testing.T) {
},
"",
},
// Regression for https://github.com/ClickHouse/clickhouse-go/issues/1784

@chernser chernser Aug 5, 2026

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we do not name tests after issues - tests should match functionality
please remove.

// (Go 1.26 net/url multi-host / HA DSN). Also covers auth + query.
{
"HA multi-host with auth and secure (issue 1784)",
"clickhouse://user:pass@host1:9440,host2:9440/database?secure=true",

@chernser chernser Aug 5, 2026

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what user and password would be used for second host?
what if credentials are overridden in options?
There should be tests for all this cases.

&Options{
Protocol: Native,
TLS: &tls.Config{
InsecureSkipVerify: false,
},
Addr: []string{"host1:9440", "host2:9440"},
Settings: Settings{},
Auth: Auth{
Username: "user",
Password: "pass",
Database: "database",
},
scheme: "clickhouse",
},
"",
},
{
"HA multi-host HTTP scheme",
"http://host1:8123,host2:8123/db",
&Options{
Protocol: HTTP,
TLS: nil,
Addr: []string{"host1:8123", "host2:8123"},
Settings: Settings{},
Auth: Auth{
Database: "db",
},
scheme: "http",
},
"",
},
{
"HA multi-host IPv6",
"clickhouse://[::1]:9440,[2001:db8::1]:9440/test_database",
&Options{
Protocol: Native,
TLS: nil,
Addr: []string{"[::1]:9440", "[2001:db8::1]:9440"},
Settings: Settings{},
Auth: Auth{
Database: "test_database",
},
scheme: "clickhouse",
},
"",
},
}

for _, testCase := range testCases {
Expand All @@ -587,6 +638,53 @@ func parseURL(t *testing.T, v string) *url.URL {
return u
}

func TestDSNAddrList(t *testing.T) {
t.Parallel()
cases := []struct {
name string
raw string
parsedHost string
want []string
}{
{
name: "issue 1784 multi-host",
raw: "clickhouse://host1:9440,host2:9440/database",
parsedHost: "host1:9440,host2:9440",
want: []string{"host1:9440", "host2:9440"},
},
{
name: "multi-host with userinfo",
raw: "clickhouse://user:pass@host1:9440,host2:9440/db?secure=true",
parsedHost: "host1:9440,host2:9440",
want: []string{"host1:9440", "host2:9440"},
},
{
name: "bracketed IPv6 multi-host",
raw: "clickhouse://[::1]:9440,[2001:db8::1]:9440/db",
parsedHost: "[2001:db8::1]:9440", // parsers may keep only the last host
want: []string{"[::1]:9440", "[2001:db8::1]:9440"},
},
{
name: "fallback to parsed host",
raw: "not-a-url",
parsedHost: "only-host:9000",
want: []string{"only-host:9000"},
},
}
for _, tc := range cases {
t.Run(tc.name, func(t *testing.T) {
assert.Equal(t, tc.want, dsnAddrList(tc.raw, tc.parsedHost))
})
}
}

func TestSplitHostList(t *testing.T) {
t.Parallel()
assert.Equal(t, []string{"a:1", "b:2"}, splitHostList("a:1,b:2"))
assert.Equal(t, []string{"[::1]:1", "[::2]:2"}, splitHostList("[::1]:1,[::2]:2"))
assert.Equal(t, []string{"single"}, splitHostList("single"))
}

func TestLogger(t *testing.T) {
t.Run("debug=1 via DSN produces non-noop logger", func(t *testing.T) {
opts, err := ParseDSN("clickhouse://127.0.0.1/test?debug=1")
Expand Down
46 changes: 46 additions & 0 deletions lib/churl/churl_test.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,46 @@
package churl

import (
"testing"
)

// Multi-host (HA) DSNs must parse under churl so clickhouse-go remains compatible
// when net/url rejects or normalizes multi-host authorities (see Go 1.26 / #1784).
func TestParseMultiHost(t *testing.T) {
t.Parallel()
cases := []struct {
raw string
host string
path string
}{
{
raw: "clickhouse://host1:9440,host2:9440/database",
host: "host1:9440,host2:9440",
path: "/database",
},
{
raw: "clickhouse://user:pass@host1:9440,host2:9440/db?secure=true",
host: "host1:9440,host2:9440",
path: "/db",
},
{
raw: "http://host1:8123,host2:8123/db",
host: "host1:8123,host2:8123",
path: "/db",
},
}
for _, tc := range cases {
t.Run(tc.raw, func(t *testing.T) {
u, err := Parse(tc.raw)
if err != nil {
t.Fatalf("Parse(%q): %v", tc.raw, err)
}
if u.Host != tc.host {
t.Fatalf("Host: got %q want %q", u.Host, tc.host)
}
if u.Path != tc.path {
t.Fatalf("Path: got %q want %q", u.Path, tc.path)
}
})
}
}