open-consul/agent/consul/prepared_query_endpoint.go

871 lines
27 KiB
Go

// Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: MPL-2.0
package consul
import (
"fmt"
"strings"
"time"
"github.com/armon/go-metrics"
"github.com/armon/go-metrics/prometheus"
"github.com/hashicorp/go-hclog"
"github.com/hashicorp/go-memdb"
"github.com/hashicorp/go-uuid"
"github.com/hashicorp/consul/acl"
"github.com/hashicorp/consul/agent/consul/state"
"github.com/hashicorp/consul/agent/structs"
"github.com/hashicorp/consul/agent/structs/aclfilter"
"github.com/hashicorp/consul/logging"
)
var PreparedQuerySummaries = []prometheus.SummaryDefinition{
{
Name: []string{"prepared-query", "apply"},
Help: "Measures the time it takes to apply a prepared query update.",
},
{
Name: []string{"prepared-query", "explain"},
Help: "Measures the time it takes to process a prepared query explain request.",
},
{
Name: []string{"prepared-query", "execute"},
Help: "Measures the time it takes to process a prepared query execute request.",
},
{
Name: []string{"prepared-query", "execute_remote"},
Help: "Measures the time it takes to process a prepared query execute request that was forwarded to another datacenter.",
},
}
// PreparedQuery manages the prepared query endpoint.
type PreparedQuery struct {
srv *Server
logger hclog.Logger
}
// Apply is used to apply a modifying request to the data store. This should
// only be used for operations that modify the data. The ID of the session is
// returned in the reply.
func (p *PreparedQuery) Apply(args *structs.PreparedQueryRequest, reply *string) (err error) {
if done, err := p.srv.ForwardRPC("PreparedQuery.Apply", args, reply); done {
return err
}
defer metrics.MeasureSince([]string{"prepared-query", "apply"}, time.Now())
// Validate the ID. We must create new IDs before applying to the Raft
// log since it's not deterministic.
if args.Op == structs.PreparedQueryCreate {
if args.Query.ID != "" {
return fmt.Errorf("ID must be empty when creating a new prepared query")
}
// We are relying on the fact that UUIDs are random and unlikely
// to collide since this isn't inside a write transaction.
state := p.srv.fsm.State()
for {
if args.Query.ID, err = uuid.GenerateUUID(); err != nil {
return fmt.Errorf("UUID generation for prepared query failed: %v", err)
}
_, query, err := state.PreparedQueryGet(nil, args.Query.ID)
if err != nil {
return fmt.Errorf("Prepared query lookup failed: %v", err)
}
if query == nil {
break
}
}
}
*reply = args.Query.ID
// Get the ACL token for the request for the checks below.
authz, err := p.srv.ResolveToken(args.Token)
if err != nil {
return err
}
// If prefix ACLs apply to the incoming query, then do an ACL check. We
// need to make sure they have write access for whatever they are
// proposing.
if prefix, ok := args.Query.GetACLPrefix(); ok {
if err := authz.ToAllowAuthorizer().PreparedQueryWriteAllowed(prefix, nil); err != nil {
p.logger.Warn("Operation on prepared query denied due to ACLs", "query", args.Query.ID)
return err
}
}
// This is the second part of the check above. If they are referencing
// an existing query then make sure it exists and that they have write
// access to whatever they are changing, if prefix ACLs apply to it.
if args.Op != structs.PreparedQueryCreate {
state := p.srv.fsm.State()
_, query, err := state.PreparedQueryGet(nil, args.Query.ID)
if err != nil {
return fmt.Errorf("Prepared Query lookup failed: %v", err)
}
if query == nil {
return fmt.Errorf("Cannot modify non-existent prepared query: '%s'", args.Query.ID)
}
if prefix, ok := query.GetACLPrefix(); ok {
if err := authz.ToAllowAuthorizer().PreparedQueryWriteAllowed(prefix, nil); err != nil {
p.logger.Warn("Operation on prepared query denied due to ACLs", "query", args.Query.ID)
return err
}
}
}
// Parse the query and prep it for the state store.
switch args.Op {
case structs.PreparedQueryCreate, structs.PreparedQueryUpdate:
if err := parseQuery(args.Query); err != nil {
return fmt.Errorf("Invalid prepared query: %v", err)
}
case structs.PreparedQueryDelete:
// Nothing else to verify here, just do the delete (we only look
// at the ID field for this op).
default:
return fmt.Errorf("Unknown prepared query operation: %s", args.Op)
}
// Commit the query to the state store.
_, err = p.srv.raftApply(structs.PreparedQueryRequestType, args)
if err != nil {
return fmt.Errorf("raft apply failed: %w", err)
}
return nil
}
// parseQuery makes sure the entries of a query are valid for a create or
// update operation. Some fields are not checked or are partially
// checked, as noted in the comments below. This also updates all the parsed
// fields of the query.
func parseQuery(query *structs.PreparedQuery) error {
// We skip a few fields:
// - ID is checked outside this fn.
// - Name is optional with no restrictions, except for uniqueness which
// is checked for integrity during the transaction. We also make sure
// names do not overlap with IDs, which is also checked during the
// transaction. Otherwise, people could "steal" queries that they don't
// have proper ACL rights to change.
// - Template is checked during the transaction since that's where we
// compile it.
// Anonymous queries require a session or need to be part of a template.
if query.Name == "" && query.Template.Type == "" && query.Session == "" {
return fmt.Errorf("Must be bound to a session")
}
// Token is checked when the query is executed, but we do make sure the
// user hasn't accidentally pasted-in the special redacted token name,
// which if we allowed in would be super hard to debug and understand.
if query.Token == aclfilter.RedactedToken {
return fmt.Errorf("Bad Token '%s', it looks like a query definition with a redacted token was submitted", query.Token)
}
// Parse the service query sub-structure.
if err := parseService(&query.Service); err != nil {
return err
}
// Parse the DNS options sub-structure.
if err := parseDNS(&query.DNS); err != nil {
return err
}
return nil
}
// parseService makes sure the entries of a query are valid for a create or
// update operation. Some of the fields are not checked or are partially
// checked, as noted in the comments below. This also updates all the parsed
// fields of the query.
func parseService(svc *structs.ServiceQuery) error {
// Service is required.
if svc.Service == "" {
return fmt.Errorf("Must provide a Service name to query")
}
failover := svc.Failover
// NearestN can be 0 which means "don't fail over by RTT".
if failover.NearestN < 0 {
return fmt.Errorf("Bad NearestN '%d', must be >= 0", svc.Failover.NearestN)
}
if (failover.NearestN != 0 || len(failover.Datacenters) != 0) && len(failover.Targets) != 0 {
return fmt.Errorf("Targets cannot be populated with NearestN or Datacenters")
}
// Make sure the metadata filters are valid
if err := structs.ValidateNodeMetadata(svc.NodeMeta, true); err != nil {
return err
}
if err := parseSameness(svc); err != nil {
return err
}
// We skip a few fields:
// - There's no validation for Datacenters; we skip any unknown entries
// at execution time.
// - OnlyPassing is just a boolean so doesn't need further validation.
// - Tags is a free-form list of tags and doesn't need further validation.
return nil
}
// parseDNS makes sure the entries of a query are valid for a create or
// update operation. This also updates all the parsed fields of the query.
func parseDNS(dns *structs.QueryDNSOptions) error {
if dns.TTL != "" {
ttl, err := time.ParseDuration(dns.TTL)
if err != nil {
return fmt.Errorf("Bad DNS TTL '%s': %v", dns.TTL, err)
}
if ttl < 0 {
return fmt.Errorf("DNS TTL '%d', must be >=0", ttl)
}
}
return nil
}
// Get returns a single prepared query by ID.
func (p *PreparedQuery) Get(args *structs.PreparedQuerySpecificRequest,
reply *structs.IndexedPreparedQueries) error {
if done, err := p.srv.ForwardRPC("PreparedQuery.Get", args, reply); done {
return err
}
return p.srv.blockingQuery(
&args.QueryOptions,
&reply.QueryMeta,
func(ws memdb.WatchSet, state *state.Store) error {
index, query, err := state.PreparedQueryGet(ws, args.QueryID)
if err != nil {
return err
}
if query == nil {
return structs.ErrQueryNotFound
}
// If no prefix ACL applies to this query, then they are
// always allowed to see it if they have the ID. We still
// have to filter the remaining object for tokens.
reply.Index = index
reply.Queries = structs.PreparedQueries{query}
if _, ok := query.GetACLPrefix(); !ok {
return p.srv.filterACL(args.Token, &reply.Queries[0])
}
// Otherwise, attempt to filter it the usual way.
if err := p.srv.filterACL(args.Token, reply); err != nil {
return err
}
// Since this is a GET of a specific query, if ACLs have
// prevented us from returning something that exists,
// then alert the user with a permission denied error.
if len(reply.Queries) == 0 {
p.logger.Warn("Request to get prepared query denied due to ACLs", "query", args.QueryID)
return acl.ErrPermissionDenied
}
return nil
})
}
// List returns all the prepared queries.
func (p *PreparedQuery) List(args *structs.DCSpecificRequest, reply *structs.IndexedPreparedQueries) error {
if done, err := p.srv.ForwardRPC("PreparedQuery.List", args, reply); done {
return err
}
return p.srv.blockingQuery(
&args.QueryOptions,
&reply.QueryMeta,
func(ws memdb.WatchSet, state *state.Store) error {
index, queries, err := state.PreparedQueryList(ws)
if err != nil {
return err
}
reply.Index, reply.Queries = index, queries
return p.srv.filterACL(args.Token, reply)
})
}
// Explain resolves a prepared query and returns the (possibly rendered template)
// to the caller. This is useful for letting operators figure out which query is
// picking up a given name. We can also add additional info about how the query
// will be executed here.
func (p *PreparedQuery) Explain(args *structs.PreparedQueryExecuteRequest,
reply *structs.PreparedQueryExplainResponse) error {
if done, err := p.srv.ForwardRPC("PreparedQuery.Explain", args, reply); done {
return err
}
defer metrics.MeasureSince([]string{"prepared-query", "explain"}, time.Now())
// We have to do this ourselves since we are not doing a blocking RPC.
p.srv.SetQueryMeta(&reply.QueryMeta, args.Token)
if args.RequireConsistent {
if err := p.srv.ConsistentRead(); err != nil {
return err
}
}
// Try to locate the query.
state := p.srv.fsm.State()
_, query, err := state.PreparedQueryResolve(args.QueryIDOrName, args.Agent)
if err != nil {
return err
}
if query == nil {
return structs.ErrQueryNotFound
}
// Place the query into a list so we can run the standard ACL filter on
// it.
queries := &structs.IndexedPreparedQueries{
Queries: structs.PreparedQueries{query},
}
if err := p.srv.filterACL(args.Token, queries); err != nil {
return err
}
// If the query was filtered out, return an error.
if len(queries.Queries) == 0 {
p.logger.Warn("Explain on prepared query denied due to ACLs", "query", query.ID)
return acl.ErrPermissionDenied
}
reply.Query = *(queries.Queries[0])
return nil
}
// Execute runs a prepared query and returns the results. This will perform the
// failover logic if no local results are available. This is typically called as
// part of a DNS lookup, or when executing prepared queries from the HTTP API.
func (p *PreparedQuery) Execute(args *structs.PreparedQueryExecuteRequest,
reply *structs.PreparedQueryExecuteResponse) error {
if done, err := p.srv.ForwardRPC("PreparedQuery.Execute", args, reply); done {
return err
}
defer metrics.MeasureSince([]string{"prepared-query", "execute"}, time.Now())
// We have to do this ourselves since we are not doing a blocking RPC.
if args.RequireConsistent {
if err := p.srv.ConsistentRead(); err != nil {
return err
}
}
// Try to locate the query.
state := p.srv.fsm.State()
_, query, err := state.PreparedQueryResolve(args.QueryIDOrName, args.Agent)
if err != nil {
return err
}
if query == nil {
return structs.ErrQueryNotFound
}
// If we have a sameness group, it controls the initial query and
// subsequent failover if required (Enterprise Only)
if query.Service.SamenessGroup != "" {
wrapper := newQueryServerWrapper(p.srv, p.ExecuteRemote)
if err := querySameness(wrapper, *query, args, reply); err != nil {
return err
}
} else {
// Execute the query for the local DC.
if err := p.execute(query, reply, args.Connect); err != nil {
return err
}
// If they supplied a token with the query, use that, otherwise use the
// token passed in with the request.
token := args.QueryOptions.Token
if query.Token != "" {
token = query.Token
}
if err := p.srv.filterACL(token, reply); err != nil {
return err
}
// TODO (slackpad) We could add a special case here that will avoid the
// fail over if we filtered everything due to ACLs. This seems like it
// might not be worth the code complexity and behavior differences,
// though, since this is essentially a misconfiguration.
// We have to do this ourselves since we are not doing a blocking RPC.
p.srv.SetQueryMeta(&reply.QueryMeta, token)
// Shuffle the results in case coordinates are not available if they
// requested an RTT sort.
reply.Nodes.Shuffle()
// Build the query source. This can be provided by the client, or by
// the prepared query. Client-specified takes priority.
qs := args.Source
if qs.Datacenter == "" {
qs.Datacenter = args.Agent.Datacenter
}
if query.Service.Near != "" && qs.Node == "" {
qs.Node = query.Service.Near
}
// Respect the magic "_agent" flag.
if qs.Node == "_agent" {
qs.Node = args.Agent.Node
} else if qs.Node == "_ip" {
if args.Source.Ip != "" {
_, nodes, err := state.Nodes(nil, structs.NodeEnterpriseMetaInDefaultPartition(), structs.TODOPeerKeyword)
if err != nil {
return err
}
for _, node := range nodes {
if args.Source.Ip == node.Address {
qs.Node = node.Node
break
}
}
} else {
p.logger.Warn("Prepared Query using near=_ip requires " +
"the source IP to be set but none was provided. No distance " +
"sorting will be done.")
}
// Either a source IP was given, but we couldn't find the associated node
// or no source ip was given. In both cases we should wipe the Node value
if qs.Node == "_ip" {
qs.Node = ""
}
}
// Perform the distance sort
err = p.srv.sortNodesByDistanceFrom(qs, reply.Nodes)
if err != nil {
return err
}
// If we applied a distance sort, make sure that the node queried for is in
// position 0, provided the results are from the same datacenter.
if qs.Node != "" && reply.Datacenter == qs.Datacenter {
for i, node := range reply.Nodes {
if strings.EqualFold(node.Node.Node, qs.Node) {
reply.Nodes[0], reply.Nodes[i] = reply.Nodes[i], reply.Nodes[0]
break
}
// Put a cap on the depth of the search. The local agent should
// never be further in than this if distance sorting was applied.
if i == 9 {
break
}
}
}
// Apply the limit if given.
if args.Limit > 0 && len(reply.Nodes) > args.Limit {
reply.Nodes = reply.Nodes[:args.Limit]
}
// In the happy path where we found some healthy nodes we go with that
// and bail out. Otherwise, we fail over and try remote DCs, as allowed
// by the query setup.
if len(reply.Nodes) == 0 {
wrapper := newQueryServerWrapper(p.srv, p.ExecuteRemote)
if err := queryFailover(wrapper, *query, args, reply); err != nil {
return err
}
}
}
return nil
}
// ExecuteRemote is used when a local node doesn't have any instances of a
// service available and needs to probe remote DCs. This sends the full query
// over since the remote side won't have it in its state store, and this doesn't
// do the failover logic since that's already being run on the originating DC.
// We don't want things to fan out further than one level.
func (p *PreparedQuery) ExecuteRemote(args *structs.PreparedQueryExecuteRemoteRequest,
reply *structs.PreparedQueryExecuteResponse) error {
if done, err := p.srv.ForwardRPC("PreparedQuery.ExecuteRemote", args, reply); done {
return err
}
defer metrics.MeasureSince([]string{"prepared-query", "execute_remote"}, time.Now())
// We have to do this ourselves since we are not doing a blocking RPC.
if args.RequireConsistent {
if err := p.srv.ConsistentRead(); err != nil {
return err
}
}
// Run the query locally to see what we can find.
if err := p.execute(&args.Query, reply, args.Connect); err != nil {
return err
}
// If they supplied a token with the query, use that, otherwise use the
// token passed in with the request.
token := args.QueryOptions.Token
if args.Query.Token != "" {
token = args.Query.Token
}
if err := p.srv.filterACL(token, reply); err != nil {
return err
}
// We have to do this ourselves since we are not doing a blocking RPC.
p.srv.SetQueryMeta(&reply.QueryMeta, token)
// We don't bother trying to do an RTT sort here since we are by
// definition in another DC. We just shuffle to make sure that we
// balance the load across the results.
reply.Nodes.Shuffle()
// Apply the limit if given.
if args.Limit > 0 && len(reply.Nodes) > args.Limit {
reply.Nodes = reply.Nodes[:args.Limit]
}
return nil
}
// execute runs a prepared query in the local DC without any failover. We don't
// apply any sorting options or ACL checks at this level - it should be done up above.
func (p *PreparedQuery) execute(query *structs.PreparedQuery,
reply *structs.PreparedQueryExecuteResponse,
forceConnect bool) error {
state := p.srv.fsm.State()
// If we're requesting Connect-capable services, then switch the
// lookup to be the Connect function.
f := state.CheckServiceNodes
if query.Service.Connect || forceConnect {
f = state.CheckConnectServiceNodes
}
_, nodes, err := f(nil, query.Service.Service, &query.Service.EnterpriseMeta, query.Service.Peer)
if err != nil {
return err
}
// Filter out any unhealthy nodes.
nodes = nodes.FilterIgnore(query.Service.OnlyPassing,
query.Service.IgnoreCheckIDs)
// Apply the node metadata filters, if any.
if len(query.Service.NodeMeta) > 0 {
nodes = nodeMetaFilter(query.Service.NodeMeta, nodes)
}
// Apply the service metadata filters, if any.
if len(query.Service.ServiceMeta) > 0 {
nodes = serviceMetaFilter(query.Service.ServiceMeta, nodes)
}
// Apply the tag filters, if any.
if len(query.Service.Tags) > 0 {
nodes = tagFilter(query.Service.Tags, nodes)
}
// Capture the nodes and pass the DNS information through to the reply.
reply.Service = query.Service.Service
reply.EnterpriseMeta = query.Service.EnterpriseMeta
reply.Nodes = nodes
reply.DNS = query.DNS
// Stamp the result with its this datacenter or peer.
if peerName := query.Service.Peer; peerName != "" {
reply.PeerName = peerName
reply.Datacenter = ""
} else {
reply.Datacenter = p.srv.config.Datacenter
}
return nil
}
// tagFilter returns a list of nodes who satisfy the given tags. Nodes must have
// ALL the given tags, and NONE of the forbidden tags (prefixed with !). Note
// for performance this modifies the original slice.
func tagFilter(tags []string, nodes structs.CheckServiceNodes) structs.CheckServiceNodes {
// Build up lists of required and disallowed tags.
must, not := make([]string, 0), make([]string, 0)
for _, tag := range tags {
tag = strings.ToLower(tag)
if strings.HasPrefix(tag, "!") {
tag = tag[1:]
not = append(not, tag)
} else {
must = append(must, tag)
}
}
n := len(nodes)
for i := 0; i < n; i++ {
node := nodes[i]
// Index the tags so lookups this way are cheaper.
index := make(map[string]struct{})
if node.Service != nil {
for _, tag := range node.Service.Tags {
tag = strings.ToLower(tag)
index[tag] = struct{}{}
}
}
// Bail if any of the required tags are missing.
for _, tag := range must {
if _, ok := index[tag]; !ok {
goto DELETE
}
}
// Bail if any of the disallowed tags are present.
for _, tag := range not {
if _, ok := index[tag]; ok {
goto DELETE
}
}
// At this point, the service is ok to leave in the list.
continue
DELETE:
nodes[i], nodes[n-1] = nodes[n-1], structs.CheckServiceNode{}
n--
i--
}
return nodes[:n]
}
// nodeMetaFilter returns a list of the nodes who satisfy the given metadata filters. Nodes
// must have ALL the given tags.
func nodeMetaFilter(filters map[string]string, nodes structs.CheckServiceNodes) structs.CheckServiceNodes {
var filtered structs.CheckServiceNodes
for _, node := range nodes {
if structs.SatisfiesMetaFilters(node.Node.Meta, filters) {
filtered = append(filtered, node)
}
}
return filtered
}
func serviceMetaFilter(filters map[string]string, nodes structs.CheckServiceNodes) structs.CheckServiceNodes {
var filtered structs.CheckServiceNodes
for _, node := range nodes {
if structs.SatisfiesMetaFilters(node.Service.Meta, filters) {
filtered = append(filtered, node)
}
}
return filtered
}
type stateLookuper interface {
samenessGroupLookup(name string, entMeta acl.EnterpriseMeta) (uint64, *structs.SamenessGroupConfigEntry, error)
}
type stateLookup struct {
srv *Server
}
// queryServer is a wrapper that makes it easier to test the failover logic.
type queryServer interface {
GetLogger() hclog.Logger
GetOtherDatacentersByDistance() ([]string, error)
GetLocalDC() string
ExecuteRemote(args *structs.PreparedQueryExecuteRemoteRequest, reply *structs.PreparedQueryExecuteResponse) error
GetSamenessGroupFailoverTargets(name string, entMeta acl.EnterpriseMeta) ([]structs.QueryFailoverTarget, error)
}
// queryServerWrapper applies the queryServer interface to a Server.
type queryServerWrapper struct {
srv *Server
sl stateLookuper
executeRemote func(args *structs.PreparedQueryExecuteRemoteRequest, reply *structs.PreparedQueryExecuteResponse) error
}
func newQueryServerWrapper(srv *Server, executeRemote func(args *structs.PreparedQueryExecuteRemoteRequest, reply *structs.PreparedQueryExecuteResponse) error) *queryServerWrapper {
return &queryServerWrapper{
srv: srv,
executeRemote: executeRemote,
sl: stateLookup{srv},
}
}
// GetLocalDC returns the name of the local datacenter.
func (q *queryServerWrapper) GetLocalDC() string {
return q.srv.config.Datacenter
}
// ExecuteRemote calls ExecuteRemote on PreparedQuery.
func (q *queryServerWrapper) ExecuteRemote(args *structs.PreparedQueryExecuteRemoteRequest, reply *structs.PreparedQueryExecuteResponse) error {
return q.executeRemote(args, reply)
}
// GetLogger returns the server's logger.
func (q *queryServerWrapper) GetLogger() hclog.Logger {
return q.srv.loggers.Named(logging.PreparedQuery)
}
// GetOtherDatacentersByDistance calls into the server's fn and filters out the
// server's own DC.
func (q *queryServerWrapper) GetOtherDatacentersByDistance() ([]string, error) {
// TODO (slackpad) - We should cache this result since it's expensive to
// compute.
dcs, err := q.srv.router.GetDatacentersByDistance()
if err != nil {
return nil, err
}
var result []string
for _, dc := range dcs {
if dc != q.srv.config.Datacenter {
result = append(result, dc)
}
}
return result, nil
}
// queryFailover runs an algorithm to determine which DCs to try and then calls
// them to try to locate alternative services.
func queryFailover(q queryServer, query structs.PreparedQuery,
args *structs.PreparedQueryExecuteRequest,
reply *structs.PreparedQueryExecuteResponse) error {
// Pull the list of other DCs. This is sorted by RTT in case the user
// has selected that.
nearest, err := q.GetOtherDatacentersByDistance()
if err != nil {
return err
}
// This will help us filter unknown targets supplied by the user.
known := make(map[string]struct{})
for _, dc := range nearest {
known[dc] = struct{}{}
}
// Build a candidate list of failover targets to try, starting with the nearest N target
// from RTTs.
var targets []structs.QueryFailoverTarget
index := make(map[string]struct{})
if query.Service.Failover.NearestN > 0 {
for i, dc := range nearest {
if !(i < query.Service.Failover.NearestN) {
break
}
targets = append(targets, structs.QueryFailoverTarget{Datacenter: dc})
index[dc] = struct{}{}
}
}
// Then add any targets explicitly listed that weren't selected above.
for _, target := range query.Service.Failover.AsTargets() {
// This will prevent a log of other log spam if we do not
// attempt to talk to datacenters we don't know about.
if dc := target.Datacenter; dc != "" {
if _, ok := known[dc]; !ok {
q.GetLogger().Debug("Skipping unknown datacenter in prepared query", "datacenter", dc)
continue
}
// This will make sure we don't re-try something that fails
// from the NearestN list.
if _, ok := index[dc]; !ok {
targets = append(targets, target)
continue
}
}
if target.Peer != "" || target.PartitionOrEmpty() != "" || target.NamespaceOrEmpty() != "" {
targets = append(targets, target)
}
}
// Now try the selected targets in priority order.
failovers := 0
for _, target := range targets {
// This keeps track of how many iterations we actually run.
failovers++
err = targetSelector(q, query, args, target, reply)
if err != nil {
continue
}
// We can stop if we found some nodes.
if len(reply.Nodes) > 0 {
break
}
}
// Set this at the end because the response from the remote doesn't have
// this information.
reply.Failovers = failovers
return nil
}
func targetSelector(q queryServer,
query structs.PreparedQuery,
args *structs.PreparedQueryExecuteRequest,
target structs.QueryFailoverTarget,
reply *structs.PreparedQueryExecuteResponse) error {
// Be super paranoid and set the nodes slice to nil since it's
// the same slice we used before. We know there's nothing in
// there, but the underlying msgpack library has a policy of
// updating the slice when it's non-nil, and that feels dirty.
// Let's just set it to nil so there's no way to communicate
// through this slice across successive RPC calls.
reply.Nodes = nil
// Reset Peer, because it may have been set by a previous failover
// target.
query.Service.Peer = target.Peer
query.Service.EnterpriseMeta = target.EnterpriseMeta
dc := target.Datacenter
if target.Peer != "" {
dc = q.GetLocalDC()
}
// Note that we pass along the limit since may be applied
// remotely to save bandwidth. We also pass along the consistency
// mode information and token we were given, so that applies to
// the remote query as well.
remote := &structs.PreparedQueryExecuteRemoteRequest{
Datacenter: dc,
Query: query,
Limit: args.Limit,
QueryOptions: args.QueryOptions,
Connect: args.Connect,
}
var err error
if err = q.ExecuteRemote(remote, reply); err != nil {
q.GetLogger().Warn("Failed querying for service in datacenter",
"service", query.Service.Service,
"peerName", query.Service.Peer,
"datacenter", dc,
"enterpriseMeta", query.Service.EnterpriseMeta,
"error", err,
)
return err
}
return nil
}