package consul import ( "fmt" "time" "github.com/armon/go-metrics" "github.com/hashicorp/consul/acl" "github.com/hashicorp/consul/agent/consul/structs" ) // Txn endpoint is used to perform multi-object atomic transactions. type Txn struct { srv *Server } // preCheck is used to verify the incoming operations before any further // processing takes place. This checks things like ACLs. func (t *Txn) preCheck(acl acl.ACL, ops structs.TxnOps) structs.TxnErrors { var errors structs.TxnErrors // Perform the pre-apply checks for any KV operations. for i, op := range ops { if op.KV != nil { ok, err := kvsPreApply(t.srv, acl, op.KV.Verb, &op.KV.DirEnt) if err != nil { errors = append(errors, &structs.TxnError{ OpIndex: i, What: err.Error(), }) } else if !ok { err = fmt.Errorf("failed to lock key %q due to lock delay", op.KV.DirEnt.Key) errors = append(errors, &structs.TxnError{ OpIndex: i, What: err.Error(), }) } } } return errors } // Apply is used to apply multiple operations in a single, atomic transaction. func (t *Txn) Apply(args *structs.TxnRequest, reply *structs.TxnResponse) error { if done, err := t.srv.forward("Txn.Apply", args, args, reply); done { return err } defer metrics.MeasureSince([]string{"consul", "txn", "apply"}, time.Now()) // Run the pre-checks before we send the transaction into Raft. acl, err := t.srv.resolveToken(args.Token) if err != nil { return err } reply.Errors = t.preCheck(acl, args.Ops) if len(reply.Errors) > 0 { return nil } // Apply the update. resp, err := t.srv.raftApply(structs.TxnRequestType, args) if err != nil { t.srv.logger.Printf("[ERR] consul.txn: Apply failed: %v", err) return err } if respErr, ok := resp.(error); ok { return respErr } // Convert the return type. This should be a cheap copy since we are // just taking the two slices. if txnResp, ok := resp.(structs.TxnResponse); ok { if acl != nil { txnResp.Results = FilterTxnResults(acl, txnResp.Results) } *reply = txnResp } else { return fmt.Errorf("unexpected return type %T", resp) } return nil } // Read is used to perform a read-only transaction that doesn't modify the state // store. This is much more scaleable since it doesn't go through Raft and // supports staleness, so this should be preferred if you're just performing // reads. func (t *Txn) Read(args *structs.TxnReadRequest, reply *structs.TxnReadResponse) error { if done, err := t.srv.forward("Txn.Read", args, args, reply); done { return err } defer metrics.MeasureSince([]string{"consul", "txn", "read"}, time.Now()) // We have to do this ourselves since we are not doing a blocking RPC. t.srv.setQueryMeta(&reply.QueryMeta) if args.RequireConsistent { if err := t.srv.consistentRead(); err != nil { return err } } // Run the pre-checks before we perform the read. acl, err := t.srv.resolveToken(args.Token) if err != nil { return err } reply.Errors = t.preCheck(acl, args.Ops) if len(reply.Errors) > 0 { return nil } // Run the read transaction. state := t.srv.fsm.State() reply.Results, reply.Errors = state.TxnRO(args.Ops) if acl != nil { reply.Results = FilterTxnResults(acl, reply.Results) } return nil }