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fix(coderd): fix memory leak in watchWorkspaceAgentMetadata #10685

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Merged
merged 5 commits into from
Nov 16, 2023
Merged

fix(coderd): fix memory leak in watchWorkspaceAgentMetadata #10685

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e6ad02f
fix(coderd): fix memory leak in `watchWorkspaceAgentMetadata`
mafredri Nov 14, 2023
65a9899
fixes
mafredri Nov 15, 2023
ab3cea2
add test that can reproduce memory leak
mafredri Nov 15, 2023
1da56e6
remove unused testutil function
mafredri Nov 16, 2023
5bb2a4b
break out slice set merger into appendUnique
mafredri Nov 16, 2023
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125 changes: 82 additions & 43 deletions coderd/workspaceagents.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1767,10 +1767,10 @@ func (api *API) workspaceAgentUpdateMetadata(ctx context.Context, workspaceAgent

datum := database.UpdateWorkspaceAgentMetadataParams{
WorkspaceAgentID: workspaceAgent.ID,
Key: []string{},
Value: []string{},
Error: []string{},
CollectedAt: []time.Time{},
Key: make([]string, 0, len(req.Metadata)),
Value: make([]string, 0, len(req.Metadata)),
Error: make([]string, 0, len(req.Metadata)),
CollectedAt: make([]time.Time, 0, len(req.Metadata)),
}

for _, md := range req.Metadata {
Expand Down Expand Up @@ -1835,41 +1835,36 @@ func (api *API) workspaceAgentUpdateMetadata(ctx context.Context, workspaceAgent
// @Router /workspaceagents/{workspaceagent}/watch-metadata [get]
// @x-apidocgen {"skip": true}
func (api *API) watchWorkspaceAgentMetadata(rw http.ResponseWriter, r *http.Request) {
var (
ctx = r.Context()
workspaceAgent = httpmw.WorkspaceAgentParam(r)
log = api.Logger.Named("workspace_metadata_watcher").With(
slog.F("workspace_agent_id", workspaceAgent.ID),
)
// Allow us to interrupt watch via cancel.
ctx, cancel := context.WithCancel(r.Context())
defer cancel()
r = r.WithContext(ctx) // Rewire context for SSE cancellation.

workspaceAgent := httpmw.WorkspaceAgentParam(r)
log := api.Logger.Named("workspace_metadata_watcher").With(
slog.F("workspace_agent_id", workspaceAgent.ID),
)

// Send metadata on updates, we must ensure subscription before sending
// initial metadata to guarantee that events in-between are not missed.
update := make(chan workspaceAgentMetadataChannelPayload, 1)
cancelSub, err := api.Pubsub.Subscribe(watchWorkspaceAgentMetadataChannel(workspaceAgent.ID), func(_ context.Context, byt []byte) {
if ctx.Err() != nil {
return
}

var payload workspaceAgentMetadataChannelPayload
err := json.Unmarshal(byt, &payload)
if err != nil {
api.Logger.Error(ctx, "failed to unmarshal pubsub message", slog.Error(err))
log.Error(ctx, "failed to unmarshal pubsub message", slog.Error(err))
return
}

log.Debug(ctx, "received metadata update", "payload", payload)

select {
case prev := <-update:
// This update wasn't consumed yet, merge the keys.
newKeysSet := make(map[string]struct{})
for _, key := range payload.Keys {
newKeysSet[key] = struct{}{}
}
keys := prev.Keys
for _, key := range prev.Keys {
if _, ok := newKeysSet[key]; !ok {
keys = append(keys, key)
}
}
payload.Keys = keys
payload.Keys = appendUnique(prev.Keys, payload.Keys)
default:
}
// This can never block since we pop and merge beforehand.
Expand All @@ -1881,22 +1876,9 @@ func (api *API) watchWorkspaceAgentMetadata(rw http.ResponseWriter, r *http.Requ
}
defer cancelSub()

sseSendEvent, sseSenderClosed, err := httpapi.ServerSentEventSender(rw, r)
if err != nil {
httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
Message: "Internal error setting up server-sent events.",
Detail: err.Error(),
})
return
}
// Prevent handler from returning until the sender is closed.
defer func() {
<-sseSenderClosed
}()

// We always use the original Request context because it contains
// the RBAC actor.
md, err := api.Database.GetWorkspaceAgentMetadata(ctx, database.GetWorkspaceAgentMetadataParams{
initialMD, err := api.Database.GetWorkspaceAgentMetadata(ctx, database.GetWorkspaceAgentMetadataParams{
WorkspaceAgentID: workspaceAgent.ID,
Keys: nil,
})
Expand All @@ -1908,15 +1890,45 @@ func (api *API) watchWorkspaceAgentMetadata(rw http.ResponseWriter, r *http.Requ
return
}

metadataMap := make(map[string]database.WorkspaceAgentMetadatum)
for _, datum := range md {
log.Debug(ctx, "got initial metadata", "num", len(initialMD))

metadataMap := make(map[string]database.WorkspaceAgentMetadatum, len(initialMD))
for _, datum := range initialMD {
metadataMap[datum.Key] = datum
}
//nolint:ineffassign // Release memory.
initialMD = nil
Comment on lines +1899 to +1900
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My understanding here is that we only need the initial slice of metadata from the DB once in order to massage it into a map.
Without this, I assume the initial slice would stay around for the duration of the SSE request?


sseSendEvent, sseSenderClosed, err := httpapi.ServerSentEventSender(rw, r)
if err != nil {
httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
Message: "Internal error setting up server-sent events.",
Detail: err.Error(),
})
return
}
// Prevent handler from returning until the sender is closed.
defer func() {
cancel()
<-sseSenderClosed
}()
// Synchronize cancellation from SSE -> context, this lets us simplify the
// cancellation logic.
go func() {
select {
case <-ctx.Done():
case <-sseSenderClosed:
cancel()
}
}()

var lastSend time.Time
sendMetadata := func() {
lastSend = time.Now()
values := maps.Values(metadataMap)

log.Debug(ctx, "sending metadata", "num", len(values))

_ = sseSendEvent(ctx, codersdk.ServerSentEvent{
Type: codersdk.ServerSentEventTypeData,
Data: convertWorkspaceAgentMetadata(values),
Expand All @@ -1935,10 +1947,11 @@ func (api *API) watchWorkspaceAgentMetadata(rw http.ResponseWriter, r *http.Requ
fetchedMetadata := make(chan []database.WorkspaceAgentMetadatum)
go func() {
defer close(fetchedMetadata)
defer cancel()

for {
select {
case <-sseSenderClosed:
case <-ctx.Done():
return
case payload := <-update:
md, err := api.Database.GetWorkspaceAgentMetadata(ctx, database.GetWorkspaceAgentMetadataParams{
Expand All @@ -1948,24 +1961,35 @@ func (api *API) watchWorkspaceAgentMetadata(rw http.ResponseWriter, r *http.Requ
if err != nil {
if !errors.Is(err, context.Canceled) {
log.Error(ctx, "failed to get metadata", slog.Error(err))
_ = sseSendEvent(ctx, codersdk.ServerSentEvent{
Type: codersdk.ServerSentEventTypeError,
Data: codersdk.Response{
Message: "Failed to get metadata.",
Detail: err.Error(),
},
})
}
return
}
select {
case <-sseSenderClosed:
case <-ctx.Done():
return
// We want to block here to avoid constantly pinging the
// database when the metadata isn't being processed.
case fetchedMetadata <- md:
log.Debug(ctx, "fetched metadata update for keys", "keys", payload.Keys, "num", len(md))
}
}
}
}()
defer func() {
<-fetchedMetadata
}()

pendingChanges := true
for {
select {
case <-sseSenderClosed:
case <-ctx.Done():
return
case md, ok := <-fetchedMetadata:
if !ok {
Expand All @@ -1989,9 +2013,24 @@ func (api *API) watchWorkspaceAgentMetadata(rw http.ResponseWriter, r *http.Requ
}
}

// appendUnique is like append and adds elements from src to dst,
// skipping any elements that already exist in dst.
func appendUnique[T comparable](dst, src []T) []T {
exists := make(map[T]struct{}, len(dst))
for _, key := range dst {
exists[key] = struct{}{}
}
for _, key := range src {
if _, ok := exists[key]; !ok {
dst = append(dst, key)
}
}
return dst
}

func convertWorkspaceAgentMetadata(db []database.WorkspaceAgentMetadatum) []codersdk.WorkspaceAgentMetadata {
// An empty array is easier for clients to handle than a null.
result := []codersdk.WorkspaceAgentMetadata{}
result := make([]codersdk.WorkspaceAgentMetadata, 0, len(db))
for _, datum := range db {
result = append(result, codersdk.WorkspaceAgentMetadata{
Result: codersdk.WorkspaceAgentMetadataResult{
Expand Down
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