consul/agent/consul/txn_endpoint.go

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package consul
import (
"fmt"
"time"
"github.com/armon/go-metrics"
"github.com/hashicorp/consul/acl"
"github.com/hashicorp/consul/agent/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 {
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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)
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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{"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{"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
}