open-consul/agent/txn_endpoint.go

237 lines
6.4 KiB
Go

package agent
import (
"encoding/base64"
"fmt"
"net/http"
"strings"
"github.com/hashicorp/consul/agent/structs"
"github.com/hashicorp/consul/api"
)
const (
// maxTxnOps is used to set an upper limit on the number of operations
// inside a transaction. If there are more operations than this, then the
// client is likely abusing transactions.
maxTxnOps = 64
)
// decodeValue decodes the value member of the given operation.
func decodeValue(rawKV interface{}) error {
rawMap, ok := rawKV.(map[string]interface{})
if !ok {
return fmt.Errorf("unexpected raw KV type: %T", rawKV)
}
for k, v := range rawMap {
switch strings.ToLower(k) {
case "value":
// Leave the byte slice nil if we have a nil
// value.
if v == nil {
return nil
}
// Otherwise, base64 decode it.
s, ok := v.(string)
if !ok {
return fmt.Errorf("unexpected value type: %T", v)
}
decoded, err := base64.StdEncoding.DecodeString(s)
if err != nil {
return fmt.Errorf("failed to decode value: %v", err)
}
rawMap[k] = decoded
return nil
}
}
return nil
}
// fixupKVOp looks for non-nil KV operations and passes them on for
// value conversion.
func fixupKVOp(rawOp interface{}) error {
rawMap, ok := rawOp.(map[string]interface{})
if !ok {
return fmt.Errorf("unexpected raw op type: %T", rawOp)
}
for k, v := range rawMap {
switch strings.ToLower(k) {
case "kv":
if v == nil {
return nil
}
return decodeValue(v)
}
}
return nil
}
// fixupKVOps takes the raw decoded JSON and base64 decodes values in KV ops,
// replacing them with byte arrays.
func fixupKVOps(raw interface{}) error {
rawSlice, ok := raw.([]interface{})
if !ok {
return fmt.Errorf("unexpected raw type: %t", raw)
}
for _, rawOp := range rawSlice {
if err := fixupKVOp(rawOp); err != nil {
return err
}
}
return nil
}
// isWrite returns true if the given operation alters the state store.
func isWrite(op api.KVOp) bool {
switch op {
case api.KVSet, api.KVDelete, api.KVDeleteCAS, api.KVDeleteTree, api.KVCAS, api.KVLock, api.KVUnlock:
return true
}
return false
}
// convertOps takes the incoming body in API format and converts it to the
// internal RPC format. This returns a count of the number of write ops, and
// a boolean, that if false means an error response has been generated and
// processing should stop.
func (s *HTTPServer) convertOps(resp http.ResponseWriter, req *http.Request) (structs.TxnOps, int, bool) {
// Note the body is in API format, and not the RPC format. If we can't
// decode it, we will return a 400 since we don't have enough context to
// associate the error with a given operation.
var ops api.TxnOps
if err := decodeBody(req, &ops, fixupKVOps); err != nil {
resp.WriteHeader(http.StatusBadRequest)
fmt.Fprintf(resp, "Failed to parse body: %v", err)
return nil, 0, false
}
// Enforce a reasonable upper limit on the number of operations in a
// transaction in order to curb abuse.
if size := len(ops); size > maxTxnOps {
resp.WriteHeader(http.StatusRequestEntityTooLarge)
fmt.Fprintf(resp, "Transaction contains too many operations (%d > %d)",
size, maxTxnOps)
return nil, 0, false
}
// Convert the KV API format into the RPC format. Note that fixupKVOps
// above will have already converted the base64 encoded strings into
// byte arrays so we can assign right over.
var opsRPC structs.TxnOps
var writes int
var netKVSize int
for _, in := range ops {
if in.KV != nil {
size := len(in.KV.Value)
if size > maxKVSize {
resp.WriteHeader(http.StatusRequestEntityTooLarge)
fmt.Fprintf(resp, "Value for key %q is too large (%d > %d bytes)", in.KV.Key, size, maxKVSize)
return nil, 0, false
}
netKVSize += size
verb := api.KVOp(in.KV.Verb)
if isWrite(verb) {
writes++
}
out := &structs.TxnOp{
KV: &structs.TxnKVOp{
Verb: verb,
DirEnt: structs.DirEntry{
Key: in.KV.Key,
Value: in.KV.Value,
Flags: in.KV.Flags,
Session: in.KV.Session,
RaftIndex: structs.RaftIndex{
ModifyIndex: in.KV.Index,
},
},
},
}
opsRPC = append(opsRPC, out)
}
}
// Enforce an overall size limit to help prevent abuse.
if netKVSize > maxKVSize {
resp.WriteHeader(http.StatusRequestEntityTooLarge)
fmt.Fprintf(resp, "Cumulative size of key data is too large (%d > %d bytes)",
netKVSize, maxKVSize)
return nil, 0, false
}
return opsRPC, writes, true
}
// Txn handles requests to apply multiple operations in a single, atomic
// transaction. A transaction consisting of only read operations will be fast-
// pathed to an endpoint that supports consistency modes (but not blocking),
// and everything else will be routed through Raft like a normal write.
func (s *HTTPServer) Txn(resp http.ResponseWriter, req *http.Request) (interface{}, error) {
if req.Method != "PUT" {
return nil, MethodNotAllowedError{req.Method, []string{"PUT"}}
}
// Convert the ops from the API format to the internal format.
ops, writes, ok := s.convertOps(resp, req)
if !ok {
return nil, nil
}
// Fast-path a transaction with only writes to the read-only endpoint,
// which bypasses Raft, and allows for staleness.
conflict := false
var ret interface{}
if writes == 0 {
args := structs.TxnReadRequest{Ops: ops}
if done := s.parse(resp, req, &args.Datacenter, &args.QueryOptions); done {
return nil, nil
}
var reply structs.TxnReadResponse
if err := s.agent.RPC("Txn.Read", &args, &reply); err != nil {
return nil, err
}
// Since we don't do blocking, we only add the relevant headers
// for metadata.
setLastContact(resp, reply.LastContact)
setKnownLeader(resp, reply.KnownLeader)
ret, conflict = reply, len(reply.Errors) > 0
} else {
args := structs.TxnRequest{Ops: ops}
s.parseDC(req, &args.Datacenter)
s.parseToken(req, &args.Token)
var reply structs.TxnResponse
if err := s.agent.RPC("Txn.Apply", &args, &reply); err != nil {
return nil, err
}
ret, conflict = reply, len(reply.Errors) > 0
}
// If there was a conflict return the response object but set a special
// status code.
if conflict {
var buf []byte
var err error
buf, err = s.marshalJSON(req, ret)
if err != nil {
return nil, err
}
resp.Header().Set("Content-Type", "application/json")
resp.WriteHeader(http.StatusConflict)
resp.Write(buf)
return nil, nil
}
// Otherwise, return the results of the successful transaction.
return ret, nil
}