server/placement: add placement constraint config parser (#1256)

server/placement/constraint.go

@@ -0,0 +1,38 @@
+// Copyright 2018 PingCAP, 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,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package placement
+
+// Config is consist of a list of constraints.
+type Config struct {
+	Constraints []*Constraint
+}
+
+// Constraint represents a user-defined region placement rule. Each constraint
+// is configured as an expression, for example 'count(zone:z1,rack:r1,host)>=3'.
+type Constraint struct {
+	Function string   // One of "count", "label_values", "count_leader", "isolation_level".
+	Filters  []Filter // "key:value" formed parameters.
+	Labels   []string // "key" formed parameters.
+	Op       string   // One of "<", "<=", "=", ">=", ">".
+	Value    int      // Expected expression evaluate value.
+}
+
+// Filter is used for filtering replicas of a region. The form in the
+// configuration is "key:value", which appears in the function argument of the
+// expression.
+type Filter struct {
+	Key, Value string
+}
+
+var functionList = []string{"count", "label_values", "count_leader", "isolation_level"}

server/placement/parser.go

@@ -0,0 +1,130 @@
+// Copyright 2018 PingCAP, 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,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package placement
+
+import (
+	"regexp"
+	"strconv"
+	"strings"
+
+	"github.com/pkg/errors"
+)
+
+// ParseConfig parses a user configuration string.
+func ParseConfig(str string) (*Config, error) {
+	var config Config
+	for _, sub := range strings.Split(str, ";") {
+		if len(sub) > 0 {
+			c, err := parseConstraint(sub)
+			if err != nil {
+				return nil, err
+			}
+			config.Constraints = append(config.Constraints, c)
+		}
+	}
+	return &config, nil
+}
+
+func parseConstraint(str string) (*Constraint, error) {
+	re := regexp.MustCompile(`^(.+)\((.*)\)\s*([<>=]+)\s*([\+\-0-9]+)\s*$`)
+	matches := re.FindStringSubmatch(str)
+	if len(matches) != 5 {
+		return nil, errors.Errorf("bad format constraint '%s'", str)
+	}
+	function, err := parserFunctionName(matches[1])
+	if err != nil {
+		return nil, err
+	}
+	filters, labels, err := parseArguments(matches[2])
+	if err != nil {
+		return nil, err
+	}
+	op, err := parseOp(matches[3])
+	if err != nil {
+		return nil, err
+	}
+	value, err := parseValue(matches[4])
+	if err != nil {
+		return nil, err
+	}
+	return &Constraint{
+		Function: function,
+		Filters:  filters,
+		Labels:   labels,
+		Op:       op,
+		Value:    value,
+	}, nil
+}
+
+func parserFunctionName(str string) (string, error) {
+	str = strings.TrimSpace(str)
+	for _, f := range functionList {
+		if str == f {
+			return str, nil
+		}
+	}
+	return "", errors.Errorf("unexpected function name '%s'", str)
+}
+
+func parseArguments(str string) (filters []Filter, labels []string, err error) {
+	str = strings.TrimSpace(str)
+	if len(str) == 0 {
+		return nil, nil, nil
+	}
+	for _, sub := range strings.Split(str, ",") {
+		if idx := strings.Index(sub, ":"); idx != -1 {
+			key, err := parseArgument(sub[:idx])
+			if err != nil {
+				return nil, nil, err
+			}
+			value, err := parseArgument(sub[idx+1:])
+			if err != nil {
+				return nil, nil, err
+			}
+			filters = append(filters, Filter{Key: key, Value: value})
+		} else {
+			label, err := parseArgument(sub)
+			if err != nil {
+				return nil, nil, err
+			}
+			labels = append(labels, label)
+		}
+	}
+	return
+}
+
+func parseArgument(str string) (string, error) {
+	str = strings.TrimSpace(str)
+	if ok, _ := regexp.MatchString(`^[a-zA-Z0-9_\-.]+$`, str); !ok {
+		return "", errors.Errorf("invalid argument '%s'", str)
+	}
+	return str, nil
+}
+
+func parseOp(str string) (string, error) {
+	str = strings.TrimSpace(str)
+	switch str {
+	case "<", "<=", "=", ">=", ">":
+		return str, nil
+	}
+	return "", errors.Errorf(`expect one of "<", "<=", "=", ">=", ">", but got '%s'`, str)
+}
+
+func parseValue(str string) (int, error) {
+	n, err := strconv.Atoi(strings.TrimSpace(str))
+	if err != nil {
+		return 0, errors.Errorf("expected integer, but got '%s'", str)
+	}
+	return n, nil
+}

server/placement/placement_test.go

@@ -0,0 +1,95 @@
+// Copyright 2018 PingCAP, 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,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package placement
+
+import (
+	"testing"
+
+	. "github.com/pingcap/check"
+)
+
+func TestPlacement(t *testing.T) {
+	TestingT(t)
+}
+
+var _ = Suite(&testPlacementSuite{})
+
+type testPlacementSuite struct{}
+
+func (s *testPlacementSuite) TestConfigParse(c *C) {
+	cases := []struct {
+		source string
+		config *Config
+	}{
+		{source: ``, config: &Config{}},
+		{source: `;`, config: &Config{}},
+		{
+			source: `count()=3`,
+			config: s.config(s.constraint("count", "=", 3)),
+		},
+		{
+			source: `count(zone:z1,region:r3)>=5`,
+			config: s.config(s.constraint("count", ">=", 5, "zone", "z1", "region", "r3")),
+		},
+		{
+			source: `count()>5;label_values(zone:z1,host,ssd)>-1`,
+			config: s.config(s.constraint("count", ">", 5), s.constraint("label_values", ">", -1, "zone", "z1", "host", "", "ssd", "")),
+		},
+		{
+			source: " count ( )  <5 ;; \tlabel_values\t ( zone : z1 , \thost , ssd ) > -1 ;;;",
+			config: s.config(s.constraint("count", "<", 5), s.constraint("label_values", ">", -1, "zone", "z1", "host", "", "ssd", "")),
+		},
+		// Wrong format configs.
+		{source: "count=3"},
+		{source: "count()=abc"},
+		{source: "count()=<3"},
+		{source: "count()"},
+		{source: "+count()"},
+		{source: "count(a=b)=1"},
+		{source: "count(a;b;c)=1"},
+	}
+
+	for _, t := range cases {
+		config, err := ParseConfig(t.source)
+		if t.config != nil {
+			c.Assert(err, IsNil)
+			c.Assert(config, DeepEquals, t.config)
+		} else {
+			c.Assert(err, NotNil)
+		}
+	}
+}
+
+func (s *testPlacementSuite) constraint(function string, op string, value int, argPairs ...string) *Constraint {
+	var filters []Filter
+	var labels []string
+	for i := 0; i < len(argPairs); i += 2 {
+		if argPairs[i+1] == "" {
+			labels = append(labels, argPairs[i])
+		} else {
+			filters = append(filters, Filter{Key: argPairs[i], Value: argPairs[i+1]})
+		}
+	}
+	return &Constraint{
+		Function: function,
+		Filters:  filters,
+		Labels:   labels,
+		Op:       op,
+		Value:    value,
+	}
+}
+
+func (s *testPlacementSuite) config(constraints ...*Constraint) *Config {
+	return &Config{Constraints: constraints}
+}