From 73a5e7df21681038912cccfddf8aec484d3cfe20 Mon Sep 17 00:00:00 2001
From: rrossi-sc <riccardo.rossi@safetyculture.io>
Date: Mon, 6 Jul 2026 15:10:39 +1000
Subject: [PATCH] feat: add configurable gRPC message size limits

Add MaxRecvMsgSize and MaxSendMsgSize options to GRPCServerConfig
to allow configuring server-side gRPC message size limits.

This enables operators to increase the default 4MiB limit for both
external API calls and internal dispatch operations.

New flags:
- --grpc-max-recv-msg-size (default: 4194304)
- --grpc-max-send-msg-size (default: 4194304)
- --dispatch-cluster-max-recv-msg-size (default: 4194304)
- --dispatch-cluster-max-send-msg-size (default: 4194304)

Use case: LookupSubjects with complex permission schemas involving
recursive relations (e.g., group#downwards_member) and set operations
can exceed the default limit due to internal CollectingDispatchStream
buffering during Union/Intersection/Exclusion operations.

Fixes #3213
---
 pkg/cmd/util/util.go                 | 29 +++++++++++++++++++---------
 pkg/cmd/util/zz_generated.options.go | 18 +++++++++++++++++
 2 files changed, 38 insertions(+), 9 deletions(-)

diff --git a/pkg/cmd/util/util.go b/pkg/cmd/util/util.go
index 197dc9a635..497b3fcb19 100644
--- a/pkg/cmd/util/util.go
+++ b/pkg/cmd/util/util.go
@@ -32,15 +32,17 @@ import (
 const BufferedNetwork string = "buffnet"
 
 type GRPCServerConfig struct {
-	Address      string        `debugmap:"visible"`
-	Network      string        `debugmap:"visible" default:"tcp"`
-	TLSCertPath  string        `debugmap:"visible"`
-	TLSKeyPath   string        `debugmap:"visible"`
-	MaxConnAge   time.Duration `debugmap:"visible" default:"30s"`
-	Enabled      bool          `debugmap:"visible"`
-	BufferSize   int           `debugmap:"visible"`
-	ClientCAPath string        `debugmap:"visible"`
-	MaxWorkers   uint32        `debugmap:"visible"`
+	Address        string        `debugmap:"visible"`
+	Network        string        `debugmap:"visible" default:"tcp"`
+	TLSCertPath    string        `debugmap:"visible"`
+	TLSKeyPath     string        `debugmap:"visible"`
+	MaxConnAge     time.Duration `debugmap:"visible" default:"30s"`
+	Enabled        bool          `debugmap:"visible"`
+	BufferSize     int           `debugmap:"visible"`
+	ClientCAPath   string        `debugmap:"visible"`
+	MaxWorkers     uint32        `debugmap:"visible"`
+	MaxRecvMsgSize int           `debugmap:"visible" default:"4194304"`
+	MaxSendMsgSize int           `debugmap:"visible" default:"4194304"`
 
 	flagPrefix string
 }
@@ -64,6 +66,8 @@ func RegisterGRPCServerFlags(flags *pflag.FlagSet, config *GRPCServerConfig, fla
 	flags.DurationVar(&config.MaxConnAge, flagPrefix+"-max-conn-age", 30*time.Second, "how long a connection serving "+serviceName+" should be able to live")
 	flags.BoolVar(&config.Enabled, flagPrefix+"-enabled", defaultEnabled, "enable "+serviceName+" gRPC server")
 	flags.Uint32Var(&config.MaxWorkers, flagPrefix+"-max-workers", 0, "set the number of workers for this server (0 value means 1 worker per request)")
+	flags.IntVar(&config.MaxRecvMsgSize, flagPrefix+"-max-recv-msg-size", 4*1024*1024, "maximum size in bytes of gRPC messages the server can receive")
+	flags.IntVar(&config.MaxSendMsgSize, flagPrefix+"-max-send-msg-size", 4*1024*1024, "maximum size in bytes of gRPC messages the server can send")
 }
 
 // Complete takes a set of default options and returns a completed server
@@ -78,6 +82,13 @@ func (c *GRPCServerConfig) Complete(level zerolog.Level, svcRegistrationFn func(
 		MaxConnectionAge: c.MaxConnAge,
 	}), grpc.NumStreamWorkers(c.MaxWorkers))
 
+	if c.MaxRecvMsgSize > 0 {
+		opts = append(opts, grpc.MaxRecvMsgSize(c.MaxRecvMsgSize))
+	}
+	if c.MaxSendMsgSize > 0 {
+		opts = append(opts, grpc.MaxSendMsgSize(c.MaxSendMsgSize))
+	}
+
 	tlsOpts, certWatcher, err := c.tlsOpts()
 	if err != nil {
 		return nil, err
diff --git a/pkg/cmd/util/zz_generated.options.go b/pkg/cmd/util/zz_generated.options.go
index 1c44dd3d6f..836a40ed56 100644
--- a/pkg/cmd/util/zz_generated.options.go
+++ b/pkg/cmd/util/zz_generated.options.go
@@ -39,6 +39,8 @@ func (g *GRPCServerConfig) ToOption() GRPCServerConfigOption {
 		to.BufferSize = g.BufferSize
 		to.ClientCAPath = g.ClientCAPath
 		to.MaxWorkers = g.MaxWorkers
+		to.MaxRecvMsgSize = g.MaxRecvMsgSize
+		to.MaxSendMsgSize = g.MaxSendMsgSize
 	}
 }
 
@@ -80,6 +82,8 @@ func (g *GRPCServerConfig) DebugMap() map[string]any {
 		debugMap["ClientCAPath"] = g.ClientCAPath
 	}
 	debugMap["MaxWorkers"] = g.MaxWorkers
+	debugMap["MaxRecvMsgSize"] = g.MaxRecvMsgSize
+	debugMap["MaxSendMsgSize"] = g.MaxSendMsgSize
 	return debugMap
 }
 
@@ -183,6 +187,20 @@ func WithMaxWorkers(maxWorkers uint32) GRPCServerConfigOption {
 	}
 }
 
+// WithMaxRecvMsgSize returns an option that can set MaxRecvMsgSize on a GRPCServerConfig
+func WithMaxRecvMsgSize(maxRecvMsgSize int) GRPCServerConfigOption {
+	return func(g *GRPCServerConfig) {
+		g.MaxRecvMsgSize = maxRecvMsgSize
+	}
+}
+
+// WithMaxSendMsgSize returns an option that can set MaxSendMsgSize on a GRPCServerConfig
+func WithMaxSendMsgSize(maxSendMsgSize int) GRPCServerConfigOption {
+	return func(g *GRPCServerConfig) {
+		g.MaxSendMsgSize = maxSendMsgSize
+	}
+}
+
 type HTTPServerConfigOption func(h *HTTPServerConfig)
 
 // NewHTTPServerConfigWithOptions creates a new HTTPServerConfig with the passed in options set