Keepalives support

[marselester]

Proposing to add keepalives and keepalives_interval parameters support #360.

By default KeepAlive is set to 15 seconds https://godoc.org/net#Dialer.

type Dialer struct {
    ...
    // KeepAlive specifies the interval between keep-alive
    // probes for an active network connection.
    // If zero, keep-alive probes are sent with a default value
    // (currently 15 seconds), if supported by the protocol and operating
    // system. Network protocols or operating systems that do
    // not support keep-alives ignore this field.
    // If negative, keep-alive probes are disabled.
    KeepAlive time.Duration
    ...
}

From what I understand, on Linux that would set

• TCP_KEEPIDLE=15 (idle time) the time (in seconds) the connection needs to remain idle before TCP starts sending keepalive probes.
• TCP_KEEPINTVL=15 (retry interval) the time (in seconds) between individual keepalive probes.

If TCP_KEEPCNT=8 (the maximum number of keepalive probes TCP should send before dropping the connection), then
the total timeout would be TCP_KEEPIDLE + TCP_KEEPINTVL * TCP_KEEPCNT = 15 seconds + 15 seconds * 8 pings = 135 seconds.

[marselester]

Go 1.13 tests fail because I used if !errors.Is(err, tc.want) { ... } 🤔

FAIL: TestKeepaliveError/keepalives_interval_float (0.00s)

connector_test.go:133: expected: invalid syntax, got: invalid value for parameter keepalives_interval: strconv.ParseInt: parsing "1.1": invalid syntax

FAIL: TestKeepaliveError/keepalives_interval_whitespace (0.00s)

connector_test.go:133: expected: invalid syntax, got: invalid value for parameter keepalives_interval: strconv.ParseInt: parsing " ": invalid syntax

[alok87]

I am running the go process in a debian 8 OS. The connections does not get auto cleaned for me until i restart the go process. I am assuming it was because of bad connections not getting terminated.

By default 15 seconds do you mean Keep-alives in linux system with lib/pq are already working? And this PR makes it configurable?

[marselester]

By default 15 seconds do you mean Keep-alives in linux system with lib/pq are already working?

They should be working golang/go#23459. You can check the number of probes with sysctl net.ipv4.tcp_keepalive_probes.

[alok87]

Its 9 for me, let me check why the connections are not getting cleaned.

$ sudo sysctl net.ipv4.tcp_keepalive_probes
net.ipv4.tcp_keepalive_probes = 9

[alok87]

Confirmed mine was a connection leak, db.Stats() helped a great deal !

[marselester]

I haven't tried these changes on prod, but at least keepalives_interval=5 works in a simple demo https://github.com/marselester/pg-keepalive, i.e., sql.Open("postgres", dsn) and sql.OpenDB(connector).

setsockopt(3, SOL_SOCKET, SO_KEEPALIVE, [1], 4) = 0
setsockopt(3, SOL_TCP, TCP_KEEPINTVL, [5], 4) = 0
setsockopt(3, SOL_TCP, TCP_KEEPIDLE, [5], 4) = 0