feat: Add weighted fair receiver

Makefile

@@ -9,7 +9,7 @@ lint: init
 	golangci-lint run ./...
 
 test: init
-	go test -race -v ./...
+	go test -race ./...
 
 tools:
 	curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b $(GOPATH)/bin v1.17.0

docs/decisions/2024-07-08-multiserver.md

@@ -0,0 +1,19 @@
+---
+Date: 2024/07/08
+Authors: @Xopherus, @shezadkhan137
+Status: Accepted
+---
+
+# Multi-Server Fair Weighted Queues
+
+## Context
+
+ZeroFox needs to prioritize messages within SQS queues, especially when services receive data from multiple sources with varying latency requirements. Prioritization is key to meeting SLAs for high-priority messages while ensuring lower-priority messages are not starved. Additionally, we need to dynamically allocate throughput based on message priority to ensure fairness and efficiency.
+
+## Decisions
+
+1. Implement an experimental Weighted Fair Queue algorithm as a decorator for the go-msg library (receiver). 
+This decorator, called `WeightedFairReceiver`, will enable message prioritization based on assigned weights.
+
+2. Implement a `MultiServer` wrapper around `WeightedFairReceiver`. 
+This server will consume messages from multiple underlying servers into a single receiver, guaranteeing consumption in proportion to assigned weights.

go.mod

@@ -3,20 +3,29 @@ module github.com/zerofox-oss/go-msg
 go 1.21
 
 require (
+	github.com/JimWen/gods-generic v0.10.2
+	github.com/asecurityteam/rolling v2.0.4+incompatible
 	github.com/google/go-cmp v0.6.0
 	github.com/pierrec/lz4/v4 v4.1.8
+	github.com/stretchr/testify v1.8.4
 	go.opencensus.io v0.24.0
 	go.opentelemetry.io/otel v1.24.0
 	go.opentelemetry.io/otel/bridge/opencensus v1.24.0
 	go.opentelemetry.io/otel/sdk v1.24.0
 	go.opentelemetry.io/otel/trace v1.24.0
+	golang.org/x/sync v0.0.0-20190423024810-112230192c58
+	pgregory.net/rapid v1.1.0
 )
 
 require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/go-logr/logr v1.4.2 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
+	github.com/kr/text v0.2.0 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 	go.opentelemetry.io/otel/metric v1.24.0 // indirect
 	go.opentelemetry.io/otel/sdk/metric v1.24.0 // indirect
 	golang.org/x/sys v0.20.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -1,8 +1,13 @@
 cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/JimWen/gods-generic v0.10.2 h1:ib/BF6W5+ANQJinlNxHYETH1BtxZASkBOV3v4mHSYYY=
+github.com/JimWen/gods-generic v0.10.2/go.mod h1:ukDWk4Hb0hovQbhqitDTeOK4Hz+IK0y3q5QKQdri3as=
+github.com/asecurityteam/rolling v2.0.4+incompatible h1:WOSeokINZT0IDzYGc5BVcjLlR9vPol08RvI2GAsmB0s=
+github.com/asecurityteam/rolling v2.0.4+incompatible/go.mod h1:2D4ba5ZfYCWrIMleUgTvc8pmLExEuvu3PDwl+vnG58Q=
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
 github.com/cncf/udpa/go v0.0.0-20191209042840-269d4d468f6f/go.mod h1:M8M6+tZqaGXZJjfX53e64911xZQV5JYwmTeXPW+k8Sc=
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -11,8 +16,6 @@ github.com/envoyproxy/go-control-plane v0.9.1-0.20191026205805-5f8ba28d4473/go.m
 github.com/envoyproxy/go-control-plane v0.9.4/go.mod h1:6rpuAdCZL397s3pYoYcLgu1mIlRU8Am5FuJP05cCM98=
 github.com/envoyproxy/protoc-gen-validate v0.1.0/go.mod h1:iSmxcyjqTsJpI2R4NaDN7+kN2VEUnK/pcBlmesArF7c=
 github.com/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
-github.com/go-logr/logr v1.4.1 h1:pKouT5E8xu9zeFC39JXRDukb6JFQPXM5p5I91188VAQ=
-github.com/go-logr/logr v1.4.1/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
 github.com/go-logr/logr v1.4.2 h1:6pFjapn8bFcIbiKo3XT4j/BhANplGihG6tvd+8rYgrY=
 github.com/go-logr/logr v1.4.2/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
 github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
@@ -40,6 +43,10 @@ github.com/google/go-cmp v0.5.3/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/uuid v1.1.2/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
+github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/pierrec/lz4/v4 v4.1.8 h1:ieHkV+i2BRzngO4Wd/3HGowuZStgq6QkPsD1eolNAO4=
 github.com/pierrec/lz4/v4 v4.1.8/go.mod h1:gZWDp/Ze/IJXGXf23ltt2EXimqmTUXEy0GFuRQyBid4=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
@@ -52,46 +59,21 @@ github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
-github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
-github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 go.opencensus.io v0.24.0 h1:y73uSU6J157QMP2kn2r30vwW1A2W2WFwSCGnAVxeaD0=
 go.opencensus.io v0.24.0/go.mod h1:vNK8G9p7aAivkbmorf4v+7Hgx+Zs0yY+0fOtgBfjQKo=
 go.opentelemetry.io/otel v1.24.0 h1:0LAOdjNmQeSTzGBzduGe/rU4tZhMwL5rWgtp9Ku5Jfo=
 go.opentelemetry.io/otel v1.24.0/go.mod h1:W7b9Ozg4nkF5tWI5zsXkaKKDjdVjpD4oAt9Qi/MArHo=
-go.opentelemetry.io/otel v1.25.0 h1:gldB5FfhRl7OJQbUHt/8s0a7cE8fbsPAtdpRaApKy4k=
-go.opentelemetry.io/otel v1.25.0/go.mod h1:Wa2ds5NOXEMkCmUou1WA7ZBfLTHWIsp034OVD7AO+Vg=
-go.opentelemetry.io/otel v1.26.0 h1:LQwgL5s/1W7YiiRwxf03QGnWLb2HW4pLiAhaA5cZXBs=
-go.opentelemetry.io/otel v1.26.0/go.mod h1:UmLkJHUAidDval2EICqBMbnAd0/m2vmpf/dAM+fvFs4=
 go.opentelemetry.io/otel/bridge/opencensus v1.24.0 h1:Vlhy5ee5k5R0zASpH+9AgHiJH7xnKACI3XopO1tUZfY=
 go.opentelemetry.io/otel/bridge/opencensus v1.24.0/go.mod h1:jRjVXV/X38jyrnHtvMGN8+9cejZB21JvXAAvooF2s+Q=
-go.opentelemetry.io/otel/bridge/opencensus v1.25.0 h1:0o/9KwAgxjK+3pMV0pwIF5toYHqDsPmQhfrBvKaG6mU=
-go.opentelemetry.io/otel/bridge/opencensus v1.25.0/go.mod h1:rZyTdpmRqoV+PpUn6QlruxJp/kE4765rPy0pP6mRDk8=
-go.opentelemetry.io/otel/bridge/opencensus v1.26.0 h1:DZzxj9QjznMVoehskOJnFP2gsTCWtDTFBDvFhPAY7nc=
-go.opentelemetry.io/otel/bridge/opencensus v1.26.0/go.mod h1:rJiX0KrF5m8Tm1XE8jLczpAv5zUaDcvhKecFG0ZoFG4=
 go.opentelemetry.io/otel/metric v1.24.0 h1:6EhoGWWK28x1fbpA4tYTOWBkPefTDQnb8WSGXlc88kI=
 go.opentelemetry.io/otel/metric v1.24.0/go.mod h1:VYhLe1rFfxuTXLgj4CBiyz+9WYBA8pNGJgDcSFRKBco=
-go.opentelemetry.io/otel/metric v1.25.0 h1:LUKbS7ArpFL/I2jJHdJcqMGxkRdxpPHE0VU/D4NuEwA=
-go.opentelemetry.io/otel/metric v1.25.0/go.mod h1:rkDLUSd2lC5lq2dFNrX9LGAbINP5B7WBkC78RXCpH5s=
-go.opentelemetry.io/otel/metric v1.26.0 h1:7S39CLuY5Jgg9CrnA9HHiEjGMF/X2VHvoXGgSllRz30=
-go.opentelemetry.io/otel/metric v1.26.0/go.mod h1:SY+rHOI4cEawI9a7N1A4nIg/nTQXe1ccCNWYOJUrpX4=
 go.opentelemetry.io/otel/sdk v1.24.0 h1:YMPPDNymmQN3ZgczicBY3B6sf9n62Dlj9pWD3ucgoDw=
 go.opentelemetry.io/otel/sdk v1.24.0/go.mod h1:KVrIYw6tEubO9E96HQpcmpTKDVn9gdv35HoYiQWGDFg=
-go.opentelemetry.io/otel/sdk v1.25.0 h1:PDryEJPC8YJZQSyLY5eqLeafHtG+X7FWnf3aXMtxbqo=
-go.opentelemetry.io/otel/sdk v1.25.0/go.mod h1:oFgzCM2zdsxKzz6zwpTZYLLQsFwc+K0daArPdIhuxkw=
-go.opentelemetry.io/otel/sdk v1.26.0 h1:Y7bumHf5tAiDlRYFmGqetNcLaVUZmh4iYfmGxtmz7F8=
-go.opentelemetry.io/otel/sdk v1.26.0/go.mod h1:0p8MXpqLeJ0pzcszQQN4F0S5FVjBLgypeGSngLsmirs=
 go.opentelemetry.io/otel/sdk/metric v1.24.0 h1:yyMQrPzF+k88/DbH7o4FMAs80puqd+9osbiBrJrz/w8=
 go.opentelemetry.io/otel/sdk/metric v1.24.0/go.mod h1:I6Y5FjH6rvEnTTAYQz3Mmv2kl6Ek5IIrmwTLqMrrOE0=
-go.opentelemetry.io/otel/sdk/metric v1.25.0 h1:7CiHOy08LbrxMAp4vWpbiPcklunUshVpAvGBrdDRlGw=
-go.opentelemetry.io/otel/sdk/metric v1.25.0/go.mod h1:LzwoKptdbBBdYfvtGCzGwk6GWMA3aUzBOwtQpR6Nz7o=
-go.opentelemetry.io/otel/sdk/metric v1.26.0 h1:cWSks5tfriHPdWFnl+qpX3P681aAYqlZHcAyHw5aU9Y=
-go.opentelemetry.io/otel/sdk/metric v1.26.0/go.mod h1:ClMFFknnThJCksebJwz7KIyEDHO+nTB6gK8obLy8RyE=
 go.opentelemetry.io/otel/trace v1.24.0 h1:CsKnnL4dUAr/0llH9FKuc698G04IrpWV0MQA/Y1YELI=
 go.opentelemetry.io/otel/trace v1.24.0/go.mod h1:HPc3Xr/cOApsBI154IU0OI0HJexz+aw5uPdbs3UCjNU=
-go.opentelemetry.io/otel/trace v1.25.0 h1:tqukZGLwQYRIFtSQM2u2+yfMVTgGVeqRLPUYx1Dq6RM=
-go.opentelemetry.io/otel/trace v1.25.0/go.mod h1:hCCs70XM/ljO+BeQkyFnbK28SBIJ/Emuha+ccrCRT7I=
-go.opentelemetry.io/otel/trace v1.26.0 h1:1ieeAUb4y0TE26jUFrCIXKpTuVK7uJGN9/Z/2LP5sQA=
-go.opentelemetry.io/otel/trace v1.26.0/go.mod h1:4iDxvGDQuUkHve82hJJ8UqrwswHYsZuWCBllGV2U2y0=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
@@ -107,6 +89,7 @@ golang.org/x/net v0.0.0-20201110031124-69a78807bb2b/go.mod h1:sp8m0HH+o8qH0wwXwY
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58 h1:8gQV6CLnAEikrhgkHFbMAEhagSSnXWGV915qUMm9mrU=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
@@ -142,8 +125,12 @@ google.golang.org/protobuf v1.23.0/go.mod h1:EGpADcykh3NcUnDUJcl1+ZksZNG86OlYog2
 google.golang.org/protobuf v1.23.1-0.20200526195155-81db48ad09cc/go.mod h1:EGpADcykh3NcUnDUJcl1+ZksZNG86OlYog2l/sGQquU=
 google.golang.org/protobuf v1.25.0/go.mod h1:9JNX74DMeImyA3h4bdi1ymwjUzf21/xIlbajtzgsN7c=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 honnef.co/go/tools v0.0.0-20190523083050-ea95bdfd59fc/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
+pgregory.net/rapid v1.1.0 h1:CMa0sjHSru3puNx+J0MIAuiiEV4N0qj8/cMWGBBCsjw=
+pgregory.net/rapid v1.1.0/go.mod h1:PY5XlDGj0+V1FCq0o192FdRhpKHGTRIWBgqjDBTrq04=

x/README.md

@@ -3,4 +3,4 @@
 This directory holds experimental packages ([decision record](../docs/decisions/2024-07-09-experimental-changes)).
 The intent is to introduce new features which may or may not become a part of the core library.
 
-Code in this directory may not be backwards compatible. 
+Code in this directory may not be backwards compatible. 

x/multiserver/README.md

@@ -0,0 +1,65 @@
+# Multiserver
+
+The `multiserver` package provides a `MultiServer` that can serve messages from multiple underlying servers to a single receiver. The server will consume messages from the underlying servers in the ratio of the weights provided.
+
+### Example
+
+```go
+package main
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/zerofox-oss/go-msg"
+	"github.com/zerofox-oss/go-msg/backends/mem"
+	"github.com/zerofox-oss/go-msg/x/multiserver"
+)
+
+func main() {
+	// Create memory servers
+	server1 := mem.NewServer(make(chan *msg.Message, 100), 10)
+	server2 := mem.NewServer(make(chan *msg.Message, 100), 10)
+
+	// Define server weights
+	serverWeights := []multiserver.ServerWeight{
+		{Server: server1, Weight: 1.0},
+		{Server: server2, Weight: 2.0},
+	}
+
+	// Create MultiServer
+	mserver, err := multiserver.NewMultiServer(10, serverWeights)
+	if err != nil {
+		fmt.Println("Error creating MultiServer:", err)
+		return
+	}
+
+	// Start serving messages
+	go func() {
+		mserver.Serve(msg.ReceiverFunc(func(ctx context.Context, m *msg.Message) error {
+			fmt.Println("Received message:", m)
+			return nil
+		}))
+	}()
+
+	// Simulate sending messages
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	go func() {
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case server1.C <- &msg.Message{Body: bytes.NewBuffer([]byte("message from server1"))}:
+			case server2.C <- &msg.Message{Body: bytes.NewBuffer([]byte("message from server2"))}:
+			}
+		}
+	}()
+
+	<-ctx.Done()
+	mserver.Shutdown(context.Background())
+}
+```

x/multiserver/multiserver.go

@@ -0,0 +1,108 @@
+package multiserver
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	msg "github.com/zerofox-oss/go-msg"
+	"golang.org/x/sync/errgroup"
+)
+
+// MultiServer is a server that can serve messages from multiple underlying servers
+// to as single receiver. The server will consume messages from the underlying servers
+// in the ratio of the weights provided.
+type MultiServer struct {
+	servers       []msg.Server
+	weights       []float64
+	concurrency   int
+	queueWaitTime time.Duration
+	wfr           *WeightedFairReceiver
+}
+
+type ServerWeight struct {
+	Server msg.Server
+	Weight float64
+}
+
+// MultiServerOption is a functional option for the MultiServer.
+type MultiServerOption func(*MultiServer)
+
+// WithQueueWaitTime sets the time to wait for a message to arrive.
+func WithQueueWaitTime(queueWaitTime time.Duration) MultiServerOption {
+	return func(m *MultiServer) {
+		m.queueWaitTime = queueWaitTime
+	}
+}
+
+// NewMultiServer creates a new MultiServer with the given concurrency.
+// The server will distribute the messages to underlying receiver from
+// the given servers in the ratio of the weights provided.
+func NewMultiServer(concurrency int, serverWeights []ServerWeight, opts ...MultiServerOption) (*MultiServer, error) {
+	if len(serverWeights) == 0 {
+		return nil, errors.New("serverWeights must not be empty")
+	}
+
+	if concurrency <= 0 {
+		return nil, errors.New("concurrency must be greater than 0")
+	}
+
+	servers := make([]msg.Server, 0, len(serverWeights))
+	weights := make([]float64, 0, len(serverWeights))
+
+	for _, s := range serverWeights {
+		servers = append(servers, s.Server)
+		weights = append(weights, s.Weight)
+	}
+
+	server := &MultiServer{
+		concurrency:   concurrency,
+		servers:       servers,
+		weights:       weights,
+		queueWaitTime: 1 * time.Millisecond,
+	}
+
+	for _, opt := range opts {
+		opt(server)
+	}
+
+	return server, nil
+}
+
+// Serve serves messages to the underlying servers.
+func (m *MultiServer) Serve(msg msg.Receiver) error {
+	m.wfr = NewWeightedFairReceiver(
+		m.weights,
+		m.concurrency,
+		m.queueWaitTime,
+		msg,
+	)
+
+	g := errgroup.Group{}
+	for i, s := range m.servers {
+		s := s
+		i := i
+		g.Go(func() error {
+			return s.Serve(m.wfr.WithPriorityReceiver(i))
+		})
+	}
+
+	return g.Wait()
+}
+
+// Shutdown shuts down the server.
+func (m *MultiServer) Shutdown(ctx context.Context) error {
+	g := errgroup.Group{}
+	for _, s := range m.servers {
+		s := s
+		g.Go(func() error {
+			return s.Shutdown(ctx)
+		})
+	}
+	err := g.Wait()
+	if err != nil {
+		return err
+	}
+
+	return m.wfr.Close(ctx)
+}