Rename Random to Jitter and introduce timeouts

This patch renames the `Random` parameter of the leadership flag to
`Jitter` because it reflects better what it is used for.

The patch also introduces timeouts for the database operations so that
the flag will recover faster when database connection packets are
silently dropped.

Note that the `lib/pq` doesn't always respect timeouts, in particular it
doesn't respect them when packags are dropped. To effectively respect
those timeouts it is necessary to switch to the `pgx` family of
libraries. In order to make that easier this patch also adds some
functions to abstract the differences, like the `database.ErrorCode`
that extracts the error code from a database error and works with both
`lib/pq` and `pgx`.

Signed-off-by: Juan Hernandez <[email protected]>

Author: jhernand

database/error_code.go

@@ -0,0 +1,47 @@
+/*
+Copyright (c) 2021 Red Hat, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package database
+
+import (
+	"reflect"
+)
+
+// ErrorCode extracts the error code from the given error returned by a database operation. It uses
+// reflection to get the value of the `Code` field in order to avoid having to import the `lib/pq`
+// and `pgx` packages. It returns an empty string if the passed error is nil or it hasn't the `Code`
+// field.
+func ErrorCode(err error) string {
+	if err == nil {
+		return ""
+	}
+	value := reflect.ValueOf(err)
+	if value.Type().Kind() != reflect.Ptr {
+		return ""
+	}
+	elem := value.Elem()
+	if elem.Type().Kind() != reflect.Struct {
+		return ""
+	}
+	field := elem.FieldByName("Code")
+	if !field.IsValid() {
+		return ""
+	}
+	if field.Type().Kind() != reflect.String {
+		return ""
+	}
+	return field.String()
+}

database/error_code_test.go

@@ -0,0 +1,59 @@
+/*
+Copyright (c) 2021 Red Hat, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package database
+
+import (
+	"io"
+
+	. "github.com/onsi/ginkgo/extensions/table" // nolint
+	. "github.com/onsi/gomega"                  // nolint
+
+	"github.com/jackc/pgconn"
+	"github.com/lib/pq"
+)
+
+var _ = DescribeTable(
+	"Error code extraction",
+	func(err error, expected string) {
+		actual := ErrorCode(err)
+		Expect(actual).To(Equal(expected))
+	},
+	Entry(
+		"Nil",
+		nil,
+		"",
+	),
+	Entry(
+		"From 'pq'",
+		&pq.Error{
+			Code: "123",
+		},
+		"123",
+	),
+	Entry(
+		"From 'pgconn'",
+		&pgconn.PgError{
+			Code: "123",
+		},
+		"123",
+	),
+	Entry(
+		"Non SQL error",
+		io.EOF,
+		"",
+	),
+)

database/main_test.go

@@ -0,0 +1,29 @@
+/*
+Copyright (c) 2021 Red Hat, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package database
+
+import (
+	"testing"
+
+	. "github.com/onsi/ginkgo" // nolint
+	. "github.com/onsi/gomega" // nolint
+)
+
+func TestDatabase(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "Database")
+}

go.mod

@@ -9,15 +9,15 @@ require (
 	github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b
 	github.com/google/uuid v1.2.0
 	github.com/grokify/html-strip-tags-go v0.0.0-20200322061010-ea0c1cf2f119
+	github.com/jackc/pgconn v1.9.0
+	github.com/jackc/pgx/v4 v4.12.0
 	github.com/json-iterator/go v1.1.10
 	github.com/lib/pq v1.10.2
 	github.com/onsi/ginkgo v1.11.0
 	github.com/onsi/gomega v1.7.0
 	github.com/prometheus/client_golang v1.9.0
 	gitlab.com/c0b/go-ordered-json v0.0.0-20171130231205-49bbdab258c2
 	golang.org/x/net v0.0.0-20210226172049-e18ecbb05110
-	golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4 // indirect
-	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
 	gopkg.in/yaml.v3 v3.0.0-20200615113413-eeeca48fe776
 	k8s.io/api v0.18.5
 	k8s.io/apimachinery v0.18.5