forked from hashicorp/consul
/
prepared_query.go
50 lines (39 loc) · 1.29 KB
/
prepared_query.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
package cachetype
import (
"fmt"
"github.com/hashicorp/consul/agent/cache"
"github.com/hashicorp/consul/agent/structs"
)
// Recommended name for registration.
const PreparedQueryName = "prepared-query"
// PreparedQuery supports fetching discovering service instances via prepared
// queries.
type PreparedQuery struct {
RPC RPC
}
func (c *PreparedQuery) Fetch(opts cache.FetchOptions, req cache.Request) (cache.FetchResult, error) {
var result cache.FetchResult
// The request should be a PreparedQueryExecuteRequest.
reqReal, ok := req.(*structs.PreparedQueryExecuteRequest)
if !ok {
return result, fmt.Errorf(
"Internal cache failure: request wrong type: %T", req)
}
// Allways allow stale - there's no point in hitting leader if the request is
// going to be served from cache and endup arbitrarily stale anyway. This
// allows cached service-discover to automatically read scale across all
// servers too.
reqReal.AllowStale = true
// Fetch
var reply structs.PreparedQueryExecuteResponse
if err := c.RPC.RPC("PreparedQuery.Execute", reqReal, &reply); err != nil {
return result, err
}
result.Value = &reply
result.Index = reply.QueryMeta.Index
return result, nil
}
func (c *PreparedQuery) SupportsBlocking() bool {
// Prepared queries don't support blocking.
return false
}