From 6682639b73779a2795cb13f10b7ebae1dd807476 Mon Sep 17 00:00:00 2001
From: Tim Ross <tim.ross@goteleport.com>
Date: Fri, 26 Jan 2024 17:52:18 -0500
Subject: [PATCH] Use cache for listing app sessions

ListAppSessions was never added to the `auth.Cache` interface or
implemented by `cache.Cache` which means all session listing was
using the backend as the data source. This could cause backend
throttling if the number of sessions was large enough.
---
 lib/auth/api.go          |  3 +++
 lib/cache/cache.go       | 13 +++++++++++++
 lib/cache/collections.go |  1 +
 3 files changed, 17 insertions(+)

diff --git a/lib/auth/api.go b/lib/auth/api.go
index e3259efd5c40a..04fcdb2424ec6 100644
--- a/lib/auth/api.go
+++ b/lib/auth/api.go
@@ -923,6 +923,9 @@ type Cache interface {
 	// GetAppSession gets an application web session.
 	GetAppSession(context.Context, types.GetAppSessionRequest) (types.WebSession, error)
 
+	// ListAppSessions returns a page of application web sessions.
+	ListAppSessions(ctx context.Context, pageSize int, pageToken, user string) ([]types.WebSession, string, error)
+
 	// GetSnowflakeSession gets a Snowflake web session.
 	GetSnowflakeSession(context.Context, types.GetSnowflakeSessionRequest) (types.WebSession, error)
 
diff --git a/lib/cache/cache.go b/lib/cache/cache.go
index fa4374df7366d..3e51e0bc39193 100644
--- a/lib/cache/cache.go
+++ b/lib/cache/cache.go
@@ -2152,6 +2152,19 @@ func (c *Cache) GetAppSession(ctx context.Context, req types.GetAppSessionReques
 	return sess, trace.Wrap(err)
 }
 
+// ListAppSessions returns a page of application web sessions.
+func (c *Cache) ListAppSessions(ctx context.Context, pageSize int, pageToken, user string) ([]types.WebSession, string, error) {
+	ctx, span := c.Tracer.Start(ctx, "cache/ListAppSessions")
+	defer span.End()
+
+	rg, err := readCollectionCache(c, c.collections.appSessions)
+	if err != nil {
+		return nil, "", trace.Wrap(err)
+	}
+	defer rg.Release()
+	return rg.reader.ListAppSessions(ctx, pageSize, pageToken, user)
+}
+
 // GetSnowflakeSession gets Snowflake web session.
 func (c *Cache) GetSnowflakeSession(ctx context.Context, req types.GetSnowflakeSessionRequest) (types.WebSession, error) {
 	ctx, span := c.Tracer.Start(ctx, "cache/GetSnowflakeSession")
diff --git a/lib/cache/collections.go b/lib/cache/collections.go
index 48296ce219464..8c1bd704ea527 100644
--- a/lib/cache/collections.go
+++ b/lib/cache/collections.go
@@ -1427,6 +1427,7 @@ func (appSessionExecutor) getReader(cache *Cache, cacheOK bool) appSessionGetter
 
 type appSessionGetter interface {
 	GetAppSession(ctx context.Context, req types.GetAppSessionRequest) (types.WebSession, error)
+	ListAppSessions(ctx context.Context, pageSize int, pageToken, user string) ([]types.WebSession, string, error)
 }
 
 var _ executor[types.WebSession, appSessionGetter] = appSessionExecutor{}