reorganization of _examples and add some new examples such as iris+groupcache+mysql+docker

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/database/mysql/cache/groupcache.go

@@ -0,0 +1,120 @@
+package cache
+
+import (
+	"context"
+	"encoding/json"
+	"net/url"
+	"strconv"
+	"time"
+
+	"myapp/entity"
+	"myapp/sql"
+
+	"github.com/mailgun/groupcache/v2"
+)
+
+// Service that cache will use to retrieve data.
+type Service interface {
+	RecordInfo() sql.Record
+	GetByID(ctx context.Context, dest interface{}, id int64) error
+	List(ctx context.Context, dest interface{}, opts sql.ListOptions) error
+}
+
+// Cache is a simple structure which holds the groupcache and the database service, exposes
+// `GetByID` and `List` which returns cached (or stores new) items.
+type Cache struct {
+	service Service
+	maxAge  time.Duration
+	group   *groupcache.Group
+}
+
+// Size default size to use on groupcache, defaults to 3MB.
+var Size int64 = 3 << (10 * 3)
+
+// New returns a new cache service which exposes `GetByID` and `List` methods to work with.
+// The "name" should be unique, "maxAge" for cache expiration.
+func New(service Service, name string, maxAge time.Duration) *Cache {
+	c := new(Cache)
+	c.service = service
+	c.maxAge = maxAge
+	c.group = groupcache.NewGroup(name, Size, c)
+	return c
+}
+
+const (
+	prefixID   = "#"
+	prefixList = "["
+)
+
+// Get implements the groupcache.Getter interface.
+// Use `GetByID` and `List` instead.
+func (c *Cache) Get(ctx context.Context, key string, dest groupcache.Sink) error {
+	if len(key) < 2 { // empty or missing prefix+key, should never happen.
+		return sql.ErrUnprocessable
+	}
+
+	var v interface{}
+
+	prefix := key[0:1]
+	key = key[1:]
+	switch prefix {
+	case prefixID:
+		// Get by ID.
+		id, err := strconv.ParseInt(key, 10, 64)
+		if err != nil || id <= 0 {
+			return err
+		}
+
+		switch c.service.RecordInfo().(type) {
+		case *entity.Category:
+			v = new(entity.Category)
+		case *entity.Product:
+			v = new(entity.Product)
+		}
+
+		err = c.service.GetByID(ctx, v, id)
+		if err != nil {
+			return err
+		}
+
+	case prefixList:
+		// Get a set of records, list.
+		q, err := url.ParseQuery(key)
+		if err != nil {
+			return err
+		}
+		opts := sql.ParseListOptions(q)
+
+		switch c.service.RecordInfo().(type) {
+		case *entity.Category:
+			v = new(entity.Categories)
+		case *entity.Product:
+			v = new(entity.Products)
+		}
+
+		err = c.service.List(ctx, v, opts)
+		if err != nil {
+			return err
+		}
+
+	default:
+		return sql.ErrUnprocessable
+	}
+
+	b, err := json.Marshal(v)
+	if err != nil {
+		return err
+	}
+
+	return dest.SetBytes(b, time.Now().Add(c.maxAge))
+}
+
+// GetByID binds an item to "dest" an item based on its "id".
+func (c *Cache) GetByID(ctx context.Context, id string, dest *[]byte) error {
+	return c.group.Get(ctx, prefixID+id, groupcache.AllocatingByteSliceSink(dest))
+}
+
+// List binds item to "dest" based on the "rawQuery" of `url.Values` for `ListOptions`.
+func (c *Cache) List(ctx context.Context, rawQuery string, dest *[]byte) error {
+	return c.group.Get(ctx, prefixList+rawQuery, groupcache.AllocatingByteSliceSink(dest))
+}