ui, server: add a timeout per node while collecting hot ranges

Requests for hot ranges are serviced by a cluster wide fan-out,
where non-trivial work is done on each node to provide a response.
For each store, and for each hot range, we start a transaction with KV to look
up descriptor info.

Previously, there was no upper-bound set on the time a node could take
to provide a response. This commit introduces a per-node timeout
in the pagination logic, and is configurable with the new cluster setting
server.hot_ranges_request.node.timeout. A value of 0 will disable the timeout.

Error behavior and semantics are preserved. If a particular node times out,
The fan-out continues as before, as if a node failed to provide a response.

Informs cockroachdb#104269
Resolves cockroachdb#107627
Epic: none
Release note (ops change): Added a new cluster setting named
server.hot_ranges_request.node.timeout, with a default value of 5 minutes.
The setting controls the maximum amount of time that a hot ranges request
will spend waiting for a node to provide a response.
Set to 0 to disable timeouts.

Author: zachlite

docs/generated/settings/settings-for-tenants.txt

@@ -58,6 +58,7 @@ server.clock.persist_upper_bound_interval	duration	0s	the interval between persi
 server.eventlog.enabled	boolean	true	if set, logged notable events are also stored in the table system.eventlog	tenant-rw
 server.eventlog.ttl	duration	2160h0m0s	if nonzero, entries in system.eventlog older than this duration are periodically purged	tenant-rw
 server.host_based_authentication.configuration	string		host-based authentication configuration to use during connection authentication	tenant-rw
+server.hot_ranges_request.node.timeout	duration	5m0s	the duration allowed for a single node to return hot range data before the request is cancelled; if set to 0, there is no timeout	tenant-rw
 server.hsts.enabled	boolean	false	if true, HSTS headers will be sent along with all HTTP requests. The headers will contain a max-age setting of one year. Browsers honoring the header will always use HTTPS to access the DB Console. Ensure that TLS is correctly configured prior to enabling.	tenant-rw
 server.identity_map.configuration	string		system-identity to database-username mappings	tenant-rw
 server.log_gc.max_deletions_per_cycle	integer	1000	the maximum number of entries to delete on each purge of log-like system tables	tenant-rw

docs/generated/settings/settings.html

@@ -88,6 +88,7 @@
 <tr><td><div id="setting-server-eventlog-enabled" class="anchored"><code>server.eventlog.enabled</code></div></td><td>boolean</td><td><code>true</code></td><td>if set, logged notable events are also stored in the table system.eventlog</td><td>Serverless/Dedicated/Self-Hosted</td></tr>
 <tr><td><div id="setting-server-eventlog-ttl" class="anchored"><code>server.eventlog.ttl</code></div></td><td>duration</td><td><code>2160h0m0s</code></td><td>if nonzero, entries in system.eventlog older than this duration are periodically purged</td><td>Serverless/Dedicated/Self-Hosted</td></tr>
 <tr><td><div id="setting-server-host-based-authentication-configuration" class="anchored"><code>server.host_based_authentication.configuration</code></div></td><td>string</td><td><code></code></td><td>host-based authentication configuration to use during connection authentication</td><td>Serverless/Dedicated/Self-Hosted</td></tr>
+<tr><td><div id="setting-server-hot-ranges-request-node-timeout" class="anchored"><code>server.hot_ranges_request.node.timeout</code></div></td><td>duration</td><td><code>5m0s</code></td><td>the duration allowed for a single node to return hot range data before the request is cancelled; if set to 0, there is no timeout</td><td>Serverless/Dedicated/Self-Hosted</td></tr>
 <tr><td><div id="setting-server-hsts-enabled" class="anchored"><code>server.hsts.enabled</code></div></td><td>boolean</td><td><code>false</code></td><td>if true, HSTS headers will be sent along with all HTTP requests. The headers will contain a max-age setting of one year. Browsers honoring the header will always use HTTPS to access the DB Console. Ensure that TLS is correctly configured prior to enabling.</td><td>Serverless/Dedicated/Self-Hosted</td></tr>
 <tr><td><div id="setting-server-identity-map-configuration" class="anchored"><code>server.identity_map.configuration</code></div></td><td>string</td><td><code></code></td><td>system-identity to database-username mappings</td><td>Serverless/Dedicated/Self-Hosted</td></tr>
 <tr><td><div id="setting-server-log-gc-max-deletions-per-cycle" class="anchored"><code>server.log_gc.max_deletions_per_cycle</code></div></td><td>integer</td><td><code>1000</code></td><td>the maximum number of entries to delete on each purge of log-like system tables</td><td>Serverless/Dedicated/Self-Hosted</td></tr>

pkg/server/BUILD.bazel

@@ -27,6 +27,7 @@ go_library(
         "fanout_clients.go",
         "grpc_gateway.go",
         "grpc_server.go",
+        "hot_ranges.go",
         "import_ts.go",
         "index_usage_stats.go",
         "init.go",

pkg/server/api_v2_ranges.go

@@ -566,8 +566,9 @@ func (a *apiV2Server) listHotRanges(w http.ResponseWriter, r *http.Request) {
 		})
 	}
 
+	timeout := HotRangesRequestNodeTimeout.Get(&a.status.st.SV)
 	next, err := a.status.paginatedIterateNodes(
-		ctx, "hot ranges", limit, start, requestedNodes, dialFn,
+		ctx, "hot ranges", limit, start, requestedNodes, timeout, dialFn,
 		nodeFn, responseFn, errorFn)
 
 	if err != nil {

pkg/server/hot_ranges.go

@@ -0,0 +1,30 @@
+// Copyright 2023 The Cockroach Authors.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+package server
+
+import (
+	"time"
+
+	"github.com/cockroachdb/cockroach/pkg/settings"
+)
+
+// HotRangesRequestNodeTimeout controls the timeout of a serverpb.HotRangesRequest.
+// A default value of 5 minutes is meant to be an escape hatch for a node that is taking
+// too long to fulfill the request. The setting should be lowered for a faster response,
+// at the expense of possibly incomplete data, or raised for complete data, at the cost
+// of a possibly slower response.
+var HotRangesRequestNodeTimeout = settings.RegisterDurationSetting(
+	settings.TenantWritable,
+	"server.hot_ranges_request.node.timeout",
+	"the duration allowed for a single node to return hot range data before the request is cancelled; if set to 0, there is no timeout",
+	time.Minute*5,
+	settings.NonNegativeDuration,
+).WithPublic()

pkg/server/pagination.go

@@ -23,6 +23,7 @@ import (
 	"strings"
 	"sync"
 	"sync/atomic"
+	"time"
 
 	"github.com/cockroachdb/cockroach/pkg/base"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/liveness/livenesspb"
@@ -323,10 +324,14 @@ func (r *rpcNodePaginator) init() {
 	r.responseChan = make(chan paginatedNodeResponse, r.numNodes)
 }
 
+const noTimeout time.Duration = 0
+
 // queryNode queries the given node, and sends the responses back through responseChan
 // in order of idx (i.e. when all nodes with a lower idx have already sent theirs).
 // Safe for concurrent use.
-func (r *rpcNodePaginator) queryNode(ctx context.Context, nodeID roachpb.NodeID, idx int) {
+func (r *rpcNodePaginator) queryNode(
+	ctx context.Context, nodeID roachpb.NodeID, idx int, timeout time.Duration,
+) {
 	if atomic.LoadInt32(&r.done) != 0 {
 		// There are more values than we need. currentLen >= limit.
 		return
@@ -379,7 +384,18 @@ func (r *rpcNodePaginator) queryNode(ctx context.Context, nodeID roachpb.NodeID,
 		return
 	}
 
-	res, err := r.nodeFn(ctx, client, nodeID)
+	var res interface{}
+	var err error
+	if timeout == noTimeout {
+		res, err = r.nodeFn(ctx, client, nodeID)
+	} else {
+		err = timeutil.RunWithTimeout(ctx, "node fn", timeout, func(ctx context.Context) error {
+			var _err error
+			res, _err = r.nodeFn(ctx, client, nodeID)
+			return _err
+		})
+	}
+
 	if err != nil {
 		err = errors.Wrapf(err, "error requesting %s from node %d (%s)",
 			r.errorCtx, nodeID, r.nodeStatuses[serverID(nodeID)])

pkg/server/pagination_test.go

@@ -19,9 +19,11 @@ import (
 	"testing"
 	"time"
 
+	"github.com/cockroachdb/cockroach/pkg/base"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/liveness/livenesspb"
 	"github.com/cockroachdb/cockroach/pkg/roachpb"
 	"github.com/cockroachdb/cockroach/pkg/testutils/datapathutils"
+	"github.com/cockroachdb/cockroach/pkg/testutils/serverutils"
 	"github.com/cockroachdb/cockroach/pkg/util/leaktest"
 	"github.com/cockroachdb/cockroach/pkg/util/log"
 	"github.com/cockroachdb/datadriven"
@@ -389,7 +391,7 @@ func TestRPCPaginator(t *testing.T) {
 						// Issue requests in parallel.
 						for idx, nodeID := range nodesToQuery {
 							go func(nodeID roachpb.NodeID, idx int) {
-								paginator.queryNode(ctx, nodeID, idx)
+								paginator.queryNode(ctx, nodeID, idx, noTimeout)
 							}(nodeID, idx)
 						}
 
@@ -412,3 +414,54 @@ func TestRPCPaginator(t *testing.T) {
 	}
 
 }
+
+func TestRPCPaginatorWithTimeout(t *testing.T) {
+	defer leaktest.AfterTest(t)()
+	defer log.Scope(t).Close(t)
+	ctx := context.Background()
+	server := serverutils.StartServerOnly(t, base.TestServerArgs{})
+	defer server.Stopper().Stop(ctx)
+
+	s := server.StatusServer().(*systemStatusServer)
+
+	dialFn := func(ctx context.Context, nodeID roachpb.NodeID) (interface{}, error) {
+		client, err := s.dialNode(ctx, nodeID)
+		return client, err
+	}
+	nodeFn := func(ctx context.Context, client interface{}, nodeID roachpb.NodeID) (interface{}, error) {
+		select {
+		case <-time.After(time.Second * 10):
+		case <-ctx.Done():
+			break
+		}
+
+		// Return an error that mimics the error returned when a rpc's context is cancelled:
+		return nil, errors.New("some error")
+	}
+	responseFn := func(nodeID roachpb.NodeID, resp interface{}) {
+		// noop
+	}
+
+	var timeoutError error
+	errorFn := func(nodeID roachpb.NodeID, err error) {
+		timeoutError = err
+		log.Infof(ctx, "error from node %d: %v", nodeID, err)
+	}
+
+	pagState := paginationState{}
+
+	_, _ = s.paginatedIterateNodes(
+		ctx,
+		"test-paginate-with-timeout",
+		1000,
+		pagState,
+		[]roachpb.NodeID{},
+		time.Second*2,
+		dialFn,
+		nodeFn,
+		responseFn,
+		errorFn,
+	)
+
+	require.ErrorContains(t, timeoutError, "operation \"node fn\" timed out")
+}

pkg/server/status.go

@@ -2809,8 +2809,9 @@ func (s *systemStatusServer) HotRangesV2(
 		response.ErrorsByNodeID[nodeID] = err.Error()
 	}
 
+	timeout := HotRangesRequestNodeTimeout.Get(&s.st.SV)
 	next, err := s.paginatedIterateNodes(
-		ctx, "hotRanges", size, start, requestedNodes, dialFn,
+		ctx, "hotRanges", size, start, requestedNodes, timeout, dialFn,
 		nodeFn, responseFn, errorFn)
 
 	if err != nil {
@@ -3087,12 +3088,14 @@ func (s *statusServer) iterateNodes(
 // and nodeError on every error result. It returns the next `limit` results
 // after `start`. If `requestedNodes` is specified and non-empty, iteration is
 // only done on that subset of nodes in addition to any nodes already in pagState.
+// If non-zero, nodeFn will run with a timeout specified by nodeFnTimeout.
 func (s *statusServer) paginatedIterateNodes(
 	ctx context.Context,
 	errorCtx string,
 	limit int,
 	pagState paginationState,
 	requestedNodes []roachpb.NodeID,
+	nodeFnTimeout time.Duration,
 	dialFn func(ctx context.Context, nodeID roachpb.NodeID) (interface{}, error),
 	nodeFn func(ctx context.Context, client interface{}, nodeID roachpb.NodeID) (interface{}, error),
 	responseFn func(nodeID roachpb.NodeID, resp interface{}),
@@ -3154,7 +3157,9 @@ func (s *statusServer) paginatedIterateNodes(
 				Sem:        sem,
 				WaitForSem: true,
 			},
-			func(ctx context.Context) { paginator.queryNode(ctx, nodeID, idx) },
+			func(ctx context.Context) {
+				paginator.queryNode(ctx, nodeID, idx, nodeFnTimeout)
+			},
 		); err != nil {
 			return pagState, err
 		}
@@ -3208,7 +3213,7 @@ func (s *statusServer) listSessionsHelper(
 	var err error
 	var pagState paginationState
 	if pagState, err = s.paginatedIterateNodes(
-		ctx, "session list", limit, start, nil, dialFn, nodeFn, responseFn, errorFn); err != nil {
+		ctx, "session list", limit, start, nil, noTimeout, dialFn, nodeFn, responseFn, errorFn); err != nil {
 		err := serverpb.ListSessionsError{Message: err.Error()}
 		response.Errors = append(response.Errors, err)
 	}

pkg/ui/workspaces/db-console/src/views/hotRanges/index.tsx

@@ -55,16 +55,6 @@ const HotRangesPage = () => {
     }
   }, [dispatch, isValid]);
 
-  useEffect(() => {
-    dispatch(
-      refreshHotRanges(
-        new HotRangesRequest({
-          page_size: 1000,
-        }),
-      ),
-    );
-  }, [dispatch]);
-
   const [filteredHotRanges, setFilteredHotRanges] =
     useState<HotRange[]>(hotRanges);