From 343858d3ee27cc2d1c7672d64e537925ce349aaf Mon Sep 17 00:00:00 2001
From: Braden Bassingthwaite <bbassingthwaite@digitalocean.com>
Date: Thu, 1 Feb 2024 08:38:39 -0600
Subject: [PATCH] Go HTTP Filter: Expose envoy concurrency and request
 worker_id in public API (#32107)

Adds new functions to the Go SDK EnvoyConcurrency() and StreamInfo.WorkerID(). This information will allow Go HTTP plugins to optimize their performance in certain use cases. Follow up from #31987

cc @doujiang24

Commit Message:
Additional Description:
Risk Level:
Testing:
Docs Changes:
Release Notes:

Signed-off-by: Braden Bassingthwaite <bbassingthwaite@digitalocean.com>
---
 contrib/golang/common/go/api/filter.go        |  3 ++-
 .../filters/http/source/go/pkg/http/filter.go |  4 ++++
 .../filters/http/source/go/pkg/http/shim.go   | 19 +++++++++++++++++++
 .../network/source/go/pkg/network/filter.go   |  4 ++++
 4 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/contrib/golang/common/go/api/filter.go b/contrib/golang/common/go/api/filter.go
index 20e913cbb8ac..458193a77f76 100644
--- a/contrib/golang/common/go/api/filter.go
+++ b/contrib/golang/common/go/api/filter.go
@@ -139,7 +139,8 @@ type StreamInfo interface {
 	FilterState() FilterState
 	// VirtualClusterName returns the name of the virtual cluster which got matched
 	VirtualClusterName() (string, bool)
-
+	// WorkerID returns the ID of the Envoy worker thread
+	WorkerID() uint32
 	// Some fields in stream info can be fetched via GetProperty
 	// For example, startTime() is equal to GetProperty("request.time")
 }
diff --git a/contrib/golang/filters/http/source/go/pkg/http/filter.go b/contrib/golang/filters/http/source/go/pkg/http/filter.go
index b90629b2330c..029ebf612198 100644
--- a/contrib/golang/filters/http/source/go/pkg/http/filter.go
+++ b/contrib/golang/filters/http/source/go/pkg/http/filter.go
@@ -281,6 +281,10 @@ func (s *streamInfo) VirtualClusterName() (string, bool) {
 	return cAPI.HttpGetStringValue(unsafe.Pointer(s.request), ValueVirtualClusterName)
 }
 
+func (s *streamInfo) WorkerID() uint32 {
+	return uint32(s.request.req.worker_id)
+}
+
 type filterState struct {
 	request *httpRequest
 }
diff --git a/contrib/golang/filters/http/source/go/pkg/http/shim.go b/contrib/golang/filters/http/source/go/pkg/http/shim.go
index 44767a4c1a79..b02284cdc1ee 100644
--- a/contrib/golang/filters/http/source/go/pkg/http/shim.go
+++ b/contrib/golang/filters/http/source/go/pkg/http/shim.go
@@ -45,6 +45,23 @@ var ErrDupRequestKey = errors.New("dup request key")
 
 var Requests = &requestMap{}
 
+var (
+	initialized      = false
+	envoyConcurrency uint32
+)
+
+// EnvoyConcurrency returns the concurrency Envoy was set to run at. This can be used to optimize HTTP filters that need
+// memory per worker thread to avoid locks.
+//
+// Note: Do not use inside of an `init()` function, the value will not be populated yet. Use within the filters
+// `StreamFilterConfigFactory` or `StreamFilterConfigParser`
+func EnvoyConcurrency() uint32 {
+	if !initialized {
+		panic("concurrency has not yet been initialized, do not access within an init()")
+	}
+	return envoyConcurrency
+}
+
 type requestMap struct {
 	initOnce sync.Once
 	requests []map[*C.httpRequest]*httpRequest
@@ -52,6 +69,8 @@ type requestMap struct {
 
 func (f *requestMap) initialize(concurrency uint32) {
 	f.initOnce.Do(func() {
+		initialized = true
+		envoyConcurrency = concurrency
 		f.requests = make([]map[*C.httpRequest]*httpRequest, concurrency)
 		for i := uint32(0); i < concurrency; i++ {
 			f.requests[i] = map[*C.httpRequest]*httpRequest{}
diff --git a/contrib/golang/filters/network/source/go/pkg/network/filter.go b/contrib/golang/filters/network/source/go/pkg/network/filter.go
index 6a113fd5c662..22d1cf9aa63f 100644
--- a/contrib/golang/filters/network/source/go/pkg/network/filter.go
+++ b/contrib/golang/filters/network/source/go/pkg/network/filter.go
@@ -113,6 +113,10 @@ func (n *connectionCallback) VirtualClusterName() (string, bool) {
 	panic("implement me")
 }
 
+func (n *connectionCallback) WorkerID() uint32 {
+	panic("implement me")
+}
+
 type filterState struct {
 	wrapper unsafe.Pointer
 	setFunc func(envoyFilter unsafe.Pointer, key string, value string, stateType api.StateType, lifeSpan api.LifeSpan, streamSharing api.StreamSharing)