Merge pull request #9608 from hashicorp/f-go-connlimit

Use go-connlimit to ratelimit with 429 responses

command/agent/http.go

@@ -40,6 +40,10 @@ const (
 	// MissingRequestID is a placeholder if we cannot retrieve a request
 	// UUID from context
 	MissingRequestID = "<missing request id>"
+
+	// HTTPConnStateFuncWriteTimeout is how long to try to write conn state errors
+	// before closing the connection
+	HTTPConnStateFuncWriteTimeout = 10 * time.Millisecond
 )
 
 var (
@@ -171,7 +175,7 @@ func makeConnState(isTLS bool, handshakeTimeout time.Duration, connLimit int) fu
 			// Still return the connection limiter
 			return connlimit.NewLimiter(connlimit.Config{
 				MaxConnsPerClientIP: connLimit,
-			}).HTTPConnStateFunc()
+			}).HTTPConnStateFuncWithDefault429Handler(HTTPConnStateFuncWriteTimeout)
 		}
 
 		return nil
@@ -183,7 +187,7 @@ func makeConnState(isTLS bool, handshakeTimeout time.Duration, connLimit int) fu
 
 		connLimiter := connlimit.NewLimiter(connlimit.Config{
 			MaxConnsPerClientIP: connLimit,
-		}).HTTPConnStateFunc()
+		}).HTTPConnStateFuncWithDefault429Handler(HTTPConnStateFuncWriteTimeout)
 
 		return func(conn net.Conn, state http.ConnState) {
 			switch state {

command/agent/http_test.go

@@ -14,6 +14,7 @@ import (
 	"net/http/httptest"
 	"net/url"
 	"os"
+	"strconv"
 	"strings"
 	"testing"
 	"time"
@@ -869,15 +870,24 @@ func TestHTTPServer_Limits_Error(t *testing.T) {
 	}
 }
 
+func limitStr(limit *int) string {
+	if limit == nil {
+		return "none"
+	}
+	return strconv.Itoa(*limit)
+}
+
 // TestHTTPServer_Limits_OK asserts that all valid limits combinations
 // (tls/timeout/conns) work.
 func TestHTTPServer_Limits_OK(t *testing.T) {
 	t.Parallel()
+
 	const (
 		cafile   = "../../helper/tlsutil/testdata/ca.pem"
 		foocert  = "../../helper/tlsutil/testdata/nomad-foo.pem"
 		fookey   = "../../helper/tlsutil/testdata/nomad-foo-key.pem"
 		maxConns = 10       // limit must be < this for testing
+		bufSize  = 1 * 1024 // enough for 429 error message
 	)
 
 	cases := []struct {
@@ -954,11 +964,14 @@ func TestHTTPServer_Limits_OK(t *testing.T) {
 
 		conn, err := net.DialTimeout("tcp", a.Server.Addr, deadline)
 		require.NoError(t, err)
-		defer conn.Close()
+		defer func() {
+			require.NoError(t, conn.Close())
+		}()
 
 		buf := []byte{0}
 		readDeadline := time.Now().Add(deadline)
-		conn.SetReadDeadline(readDeadline)
+		err = conn.SetReadDeadline(readDeadline)
+		require.NoError(t, err)
 		n, err := conn.Read(buf)
 		require.Zero(t, n)
 		if assertTimeout {
@@ -1011,12 +1024,12 @@ func TestHTTPServer_Limits_OK(t *testing.T) {
 		for i := 0; i < maxConns; i++ {
 			conns[i], err = net.DialTimeout("tcp", addr, 1*time.Second)
 			require.NoError(t, err)
-			defer conns[i].Close()
 
 			go func(i int) {
 				buf := []byte{0}
 				readDeadline := time.Now().Add(1 * time.Second)
-				conns[i].SetReadDeadline(readDeadline)
+				err = conns[i].SetReadDeadline(readDeadline)
+				require.NoError(t, err)
 				n, err := conns[i].Read(buf)
 				if n > 0 {
 					errCh <- fmt.Errorf("n > 0: %d", n)
@@ -1036,18 +1049,37 @@ func TestHTTPServer_Limits_OK(t *testing.T) {
 					"error does not wrap os.ErrDeadlineExceeded: (%T) %v", err, err)
 			}
 		}
+
+		for i := 0; i < maxConns; i++ {
+			require.NoError(t, conns[i].Close())
+		}
 	}
 
-	assertLimit := func(t *testing.T, addr string, limit int) {
+	dial := func(t *testing.T, addr string, useTLS bool) net.Conn {
+		if useTLS {
+			cert, err := tls.LoadX509KeyPair(foocert, fookey)
+			require.NoError(t, err)
+			conn, err := tls.Dial("tcp", addr, &tls.Config{
+				Certificates:       []tls.Certificate{cert},
+				InsecureSkipVerify: true, // good enough
+			})
+			require.NoError(t, err)
+			return conn
+		} else {
+			conn, err := net.DialTimeout("tcp", addr, 1*time.Second)
+			require.NoError(t, err)
+			return conn
+		}
+	}
+
+	assertLimit := func(t *testing.T, addr string, limit int, useTLS bool) {
 		var err error
 
 		// Create limit connections
 		conns := make([]net.Conn, limit)
 		errCh := make(chan error, limit)
 		for i := range conns {
-			conns[i], err = net.DialTimeout("tcp", addr, 1*time.Second)
+			conns[i] = dial(t, addr, useTLS)
-			require.NoError(t, err)
-			defer conns[i].Close()
 
 			go func(i int) {
 				buf := []byte{0}
@@ -1067,26 +1099,30 @@ func TestHTTPServer_Limits_OK(t *testing.T) {
 		}
 
 		// Assert a new connection is dropped
-		conn, err := net.DialTimeout("tcp", addr, 1*time.Second)
+		conn := dial(t, addr, useTLS)
-		require.NoError(t, err)
+
-		defer conn.Close()
+		defer func() {
+			require.NoError(t, conn.Close())
+		}()
 
-		buf := []byte{0}
 		deadline := time.Now().Add(10 * time.Second)
-		conn.SetReadDeadline(deadline)
+		require.NoError(t, conn.SetReadDeadline(deadline))
-		n, err := conn.Read(buf)
-		require.Zero(t, n)
 
-		// Soft-fail as following assertion helps with debugging
+		buf := make([]byte, bufSize)
-		assert.Equal(t, io.EOF, err)
+		n, err := conn.Read(buf)
+
+		require.NoError(t, err)
+		require.NotZero(t, n)
+		require.True(t, strings.HasPrefix(string(buf), "HTTP/1.1 429 Too Many Requests"))
 
 		// Assert existing connections are ok
 		require.Len(t, errCh, 0)
 
 		// Cleanup
 		for _, conn := range conns {
-			conn.Close()
+			require.NoError(t, conn.Close())
 		}
+
 		for range conns {
 			err := <-errCh
 			require.Contains(t, err.Error(), "use of closed network connection")
@@ -1095,7 +1131,7 @@ func TestHTTPServer_Limits_OK(t *testing.T) {
 
 	for i := range cases {
 		tc := cases[i]
-		name := fmt.Sprintf("%d-tls-%t-timeout-%s-limit-%v", i, tc.tls, tc.timeout, tc.limit)
+		name := fmt.Sprintf("%d-tls-%t-timeout-%s-limit-%v", i, tc.tls, tc.timeout, limitStr(tc.limit))
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
 
@@ -1114,21 +1150,24 @@ func TestHTTPServer_Limits_OK(t *testing.T) {
 				}
 				c.Limits.HTTPSHandshakeTimeout = tc.timeout
 				c.Limits.HTTPMaxConnsPerClient = tc.limit
+				c.LogLevel = "ERROR"
 			})
-			defer s.Shutdown()
+			defer func() {
+				require.NoError(t, s.Shutdown())
+			}()
 
 			assertTimeout(t, s, tc.assertTimeout, tc.timeout)
 
 			if tc.assertLimit {
 				// There's a race between assertTimeout(false) closing
 				// its connection and the HTTP server noticing and
-				// untracking it. Since there's no way to coordiante
+				// untracking it. Since there's no way to coordinate
 				// when this occurs, sleeping is the only way to avoid
 				// asserting limits before the timed out connection is
 				// untracked.
 				time.Sleep(1 * time.Second)
 
-				assertLimit(t, s.Server.Addr, *tc.limit)
+				assertLimit(t, s.Server.Addr, *tc.limit, tc.tls)
 			} else {
 				assertNoLimit(t, s.Server.Addr)
 			}

go.mod

@@ -57,7 +57,7 @@ require (
 	github.com/hashicorp/cronexpr v1.1.1
 	github.com/hashicorp/go-checkpoint v0.0.0-20171009173528-1545e56e46de
 	github.com/hashicorp/go-cleanhttp v0.5.1
-	github.com/hashicorp/go-connlimit v0.2.0
+	github.com/hashicorp/go-connlimit v0.3.0
 	github.com/hashicorp/go-cty-funcs v0.0.0-20200930094925-2721b1e36840
 	github.com/hashicorp/go-discover v0.0.0-20200812215701-c4b85f6ed31f
 	github.com/hashicorp/go-envparse v0.0.0-20180119215841-310ca1881b22

go.sum

@@ -360,6 +360,8 @@ github.com/hashicorp/go-cleanhttp v0.5.1 h1:dH3aiDG9Jvb5r5+bYHsikaOUIpcM0xvgMXVo
 github.com/hashicorp/go-cleanhttp v0.5.1/go.mod h1:JpRdi6/HCYpAwUzNwuwqhbovhLtngrth3wmdIIUrZ80=
 github.com/hashicorp/go-connlimit v0.2.0 h1:OZjcfNxH/hPh/bT2Iw5yOJcLzz+zuIWpsp3I1S4Pjw4=
 github.com/hashicorp/go-connlimit v0.2.0/go.mod h1:OUj9FGL1tPIhl/2RCfzYHrIiWj+VVPGNyVPnUX8AqS0=
+github.com/hashicorp/go-connlimit v0.3.0 h1:oAojHGjFxUTTTA8c5XXnDqWJ2HLuWbDiBPTpWvNzvqM=
+github.com/hashicorp/go-connlimit v0.3.0/go.mod h1:OUj9FGL1tPIhl/2RCfzYHrIiWj+VVPGNyVPnUX8AqS0=
 github.com/hashicorp/go-cty-funcs v0.0.0-20200930094925-2721b1e36840 h1:kgvybwEeu0SXktbB2y3uLHX9lklLo+nzUwh59A3jzQc=
 github.com/hashicorp/go-cty-funcs v0.0.0-20200930094925-2721b1e36840/go.mod h1:Abjk0jbRkDaNCzsRhOv2iDCofYpX1eVsjozoiK63qLA=
 github.com/hashicorp/go-discover v0.0.0-20200812215701-c4b85f6ed31f h1:7WFMVeuJQp6BkzuTv9O52pzwtEFVUJubKYN+zez8eTI=

vendor/github.com/hashicorp/go-connlimit/LICENSE

@@ -0,0 +1,373 @@
+Mozilla Public License Version 2.0
+==================================
+
+1. Definitions
+--------------
+
+1.1. "Contributor"
+    means each individual or legal entity that creates, contributes to
+    the creation of, or owns Covered Software.
+
+1.2. "Contributor Version"
+    means the combination of the Contributions of others (if any) used
+    by a Contributor and that particular Contributor's Contribution.
+
+1.3. "Contribution"
+    means Covered Software of a particular Contributor.
+
+1.4. "Covered Software"
+    means Source Code Form to which the initial Contributor has attached
+    the notice in Exhibit A, the Executable Form of such Source Code
+    Form, and Modifications of such Source Code Form, in each case
+    including portions thereof.
+
+1.5. "Incompatible With Secondary Licenses"
+    means
+
+    (a) that the initial Contributor has attached the notice described
+        in Exhibit B to the Covered Software; or
+
+    (b) that the Covered Software was made available under the terms of
+        version 1.1 or earlier of the License, but not also under the
+        terms of a Secondary License.
+
+1.6. "Executable Form"
+    means any form of the work other than Source Code Form.
+
+1.7. "Larger Work"
+    means a work that combines Covered Software with other material, in
+    a separate file or files, that is not Covered Software.
+
+1.8. "License"
+    means this document.
+
+1.9. "Licensable"
+    means having the right to grant, to the maximum extent possible,
+    whether at the time of the initial grant or subsequently, any and
+    all of the rights conveyed by this License.
+
+1.10. "Modifications"
+    means any of the following:
+
+    (a) any file in Source Code Form that results from an addition to,
+        deletion from, or modification of the contents of Covered
+        Software; or
+
+    (b) any new file in Source Code Form that contains any Covered
+        Software.
+
+1.11. "Patent Claims" of a Contributor
+    means any patent claim(s), including without limitation, method,
+    process, and apparatus claims, in any patent Licensable by such
+    Contributor that would be infringed, but for the grant of the
+    License, by the making, using, selling, offering for sale, having
+    made, import, or transfer of either its Contributions or its
+    Contributor Version.
+
+1.12. "Secondary License"
+    means either the GNU General Public License, Version 2.0, the GNU
+    Lesser General Public License, Version 2.1, the GNU Affero General
+    Public License, Version 3.0, or any later versions of those
+    licenses.
+
+1.13. "Source Code Form"
+    means the form of the work preferred for making modifications.
+
+1.14. "You" (or "Your")
+    means an individual or a legal entity exercising rights under this
+    License. For legal entities, "You" includes any entity that
+    controls, is controlled by, or is under common control with You. For
+    purposes of this definition, "control" means (a) the power, direct
+    or indirect, to cause the direction or management of such entity,
+    whether by contract or otherwise, or (b) ownership of more than
+    fifty percent (50%) of the outstanding shares or beneficial
+    ownership of such entity.
+
+2. License Grants and Conditions
+--------------------------------
+
+2.1. Grants
+
+Each Contributor hereby grants You a world-wide, royalty-free,
+non-exclusive license:
+
+(a) under intellectual property rights (other than patent or trademark)
+    Licensable by such Contributor to use, reproduce, make available,
+    modify, display, perform, distribute, and otherwise exploit its
+    Contributions, either on an unmodified basis, with Modifications, or
+    as part of a Larger Work; and
+
+(b) under Patent Claims of such Contributor to make, use, sell, offer
+    for sale, have made, import, and otherwise transfer either its
+    Contributions or its Contributor Version.
+
+2.2. Effective Date
+
+The licenses granted in Section 2.1 with respect to any Contribution
+become effective for each Contribution on the date the Contributor first
+distributes such Contribution.
+
+2.3. Limitations on Grant Scope
+
+The licenses granted in this Section 2 are the only rights granted under
+this License. No additional rights or licenses will be implied from the
+distribution or licensing of Covered Software under this License.
+Notwithstanding Section 2.1(b) above, no patent license is granted by a
+Contributor:
+
+(a) for any code that a Contributor has removed from Covered Software;
+    or
+
+(b) for infringements caused by: (i) Your and any other third party's
+    modifications of Covered Software, or (ii) the combination of its
+    Contributions with other software (except as part of its Contributor
+    Version); or
+
+(c) under Patent Claims infringed by Covered Software in the absence of
+    its Contributions.
+
+This License does not grant any rights in the trademarks, service marks,
+or logos of any Contributor (except as may be necessary to comply with
+the notice requirements in Section 3.4).
+
+2.4. Subsequent Licenses
+
+No Contributor makes additional grants as a result of Your choice to
+distribute the Covered Software under a subsequent version of this
+License (see Section 10.2) or under the terms of a Secondary License (if
+permitted under the terms of Section 3.3).
+
+2.5. Representation
+
+Each Contributor represents that the Contributor believes its
+Contributions are its original creation(s) or it has sufficient rights
+to grant the rights to its Contributions conveyed by this License.
+
+2.6. Fair Use
+
+This License is not intended to limit any rights You have under
+applicable copyright doctrines of fair use, fair dealing, or other
+equivalents.
+
+2.7. Conditions
+
+Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted
+in Section 2.1.
+
+3. Responsibilities
+-------------------
+
+3.1. Distribution of Source Form
+
+All distribution of Covered Software in Source Code Form, including any
+Modifications that You create or to which You contribute, must be under
+the terms of this License. You must inform recipients that the Source
+Code Form of the Covered Software is governed by the terms of this
+License, and how they can obtain a copy of this License. You may not
+attempt to alter or restrict the recipients' rights in the Source Code
+Form.
+
+3.2. Distribution of Executable Form
+
+If You distribute Covered Software in Executable Form then:
+
+(a) such Covered Software must also be made available in Source Code
+    Form, as described in Section 3.1, and You must inform recipients of
+    the Executable Form how they can obtain a copy of such Source Code
+    Form by reasonable means in a timely manner, at a charge no more
+    than the cost of distribution to the recipient; and
+
+(b) You may distribute such Executable Form under the terms of this
+    License, or sublicense it under different terms, provided that the
+    license for the Executable Form does not attempt to limit or alter
+    the recipients' rights in the Source Code Form under this License.
+
+3.3. Distribution of a Larger Work
+
+You may create and distribute a Larger Work under terms of Your choice,
+provided that You also comply with the requirements of this License for
+the Covered Software. If the Larger Work is a combination of Covered
+Software with a work governed by one or more Secondary Licenses, and the
+Covered Software is not Incompatible With Secondary Licenses, this
+License permits You to additionally distribute such Covered Software
+under the terms of such Secondary License(s), so that the recipient of
+the Larger Work may, at their option, further distribute the Covered
+Software under the terms of either this License or such Secondary
+License(s).
+
+3.4. Notices
+
+You may not remove or alter the substance of any license notices
+(including copyright notices, patent notices, disclaimers of warranty,
+or limitations of liability) contained within the Source Code Form of
+the Covered Software, except that You may alter any license notices to
+the extent required to remedy known factual inaccuracies.
+
+3.5. Application of Additional Terms
+
+You may choose to offer, and to charge a fee for, warranty, support,
+indemnity or liability obligations to one or more recipients of Covered
+Software. However, You may do so only on Your own behalf, and not on
+behalf of any Contributor. You must make it absolutely clear that any
+such warranty, support, indemnity, or liability obligation is offered by
+You alone, and You hereby agree to indemnify every Contributor for any
+liability incurred by such Contributor as a result of warranty, support,
+indemnity or liability terms You offer. You may include additional
+disclaimers of warranty and limitations of liability specific to any
+jurisdiction.
+
+4. Inability to Comply Due to Statute or Regulation
+---------------------------------------------------
+
+If it is impossible for You to comply with any of the terms of this
+License with respect to some or all of the Covered Software due to
+statute, judicial order, or regulation then You must: (a) comply with
+the terms of this License to the maximum extent possible; and (b)
+describe the limitations and the code they affect. Such description must
+be placed in a text file included with all distributions of the Covered
+Software under this License. Except to the extent prohibited by statute
+or regulation, such description must be sufficiently detailed for a
+recipient of ordinary skill to be able to understand it.
+
+5. Termination
+--------------
+
+5.1. The rights granted under this License will terminate automatically
+if You fail to comply with any of its terms. However, if You become
+compliant, then the rights granted under this License from a particular
+Contributor are reinstated (a) provisionally, unless and until such
+Contributor explicitly and finally terminates Your grants, and (b) on an
+ongoing basis, if such Contributor fails to notify You of the
+non-compliance by some reasonable means prior to 60 days after You have
+come back into compliance. Moreover, Your grants from a particular
+Contributor are reinstated on an ongoing basis if such Contributor
+notifies You of the non-compliance by some reasonable means, this is the
+first time You have received notice of non-compliance with this License
+from such Contributor, and You become compliant prior to 30 days after
+Your receipt of the notice.
+
+5.2. If You initiate litigation against any entity by asserting a patent
+infringement claim (excluding declaratory judgment actions,
+counter-claims, and cross-claims) alleging that a Contributor Version
+directly or indirectly infringes any patent, then the rights granted to
+You by any and all Contributors for the Covered Software under Section
+2.1 of this License shall terminate.
+
+5.3. In the event of termination under Sections 5.1 or 5.2 above, all
+end user license agreements (excluding distributors and resellers) which
+have been validly granted by You or Your distributors under this License
+prior to termination shall survive termination.
+
+************************************************************************
+*                                                                      *
+*  6. Disclaimer of Warranty                                           *
+*  -------------------------                                           *
+*                                                                      *
+*  Covered Software is provided under this License on an "as is"       *
+*  basis, without warranty of any kind, either expressed, implied, or  *
+*  statutory, including, without limitation, warranties that the       *
+*  Covered Software is free of defects, merchantable, fit for a        *
+*  particular purpose or non-infringing. The entire risk as to the     *
+*  quality and performance of the Covered Software is with You.        *
+*  Should any Covered Software prove defective in any respect, You     *
+*  (not any Contributor) assume the cost of any necessary servicing,   *
+*  repair, or correction. This disclaimer of warranty constitutes an   *
+*  essential part of this License. No use of any Covered Software is   *
+*  authorized under this License except under this disclaimer.         *
+*                                                                      *
+************************************************************************
+
+************************************************************************
+*                                                                      *
+*  7. Limitation of Liability                                          *
+*  --------------------------                                          *
+*                                                                      *
+*  Under no circumstances and under no legal theory, whether tort      *
+*  (including negligence), contract, or otherwise, shall any           *
+*  Contributor, or anyone who distributes Covered Software as          *
+*  permitted above, be liable to You for any direct, indirect,         *
+*  special, incidental, or consequential damages of any character      *
+*  including, without limitation, damages for lost profits, loss of    *
+*  goodwill, work stoppage, computer failure or malfunction, or any    *
+*  and all other commercial damages or losses, even if such party      *
+*  shall have been informed of the possibility of such damages. This   *
+*  limitation of liability shall not apply to liability for death or   *
+*  personal injury resulting from such party's negligence to the       *
+*  extent applicable law prohibits such limitation. Some               *
+*  jurisdictions do not allow the exclusion or limitation of           *
+*  incidental or consequential damages, so this exclusion and          *
+*  limitation may not apply to You.                                    *
+*                                                                      *
+************************************************************************
+
+8. Litigation
+-------------
+
+Any litigation relating to this License may be brought only in the
+courts of a jurisdiction where the defendant maintains its principal
+place of business and such litigation shall be governed by laws of that
+jurisdiction, without reference to its conflict-of-law provisions.
+Nothing in this Section shall prevent a party's ability to bring
+cross-claims or counter-claims.
+
+9. Miscellaneous
+----------------
+
+This License represents the complete agreement concerning the subject
+matter hereof. If any provision of this License is held to be
+unenforceable, such provision shall be reformed only to the extent
+necessary to make it enforceable. Any law or regulation which provides
+that the language of a contract shall be construed against the drafter
+shall not be used to construe this License against a Contributor.
+
+10. Versions of the License
+---------------------------
+
+10.1. New Versions
+
+Mozilla Foundation is the license steward. Except as provided in Section
+10.3, no one other than the license steward has the right to modify or
+publish new versions of this License. Each version will be given a
+distinguishing version number.
+
+10.2. Effect of New Versions
+
+You may distribute the Covered Software under the terms of the version
+of the License under which You originally received the Covered Software,
+or under the terms of any subsequent version published by the license
+steward.
+
+10.3. Modified Versions
+
+If you create software not governed by this License, and you want to
+create a new license for such software, you may create and use a
+modified version of this License if you rename the license and remove
+any references to the name of the license steward (except to note that
+such modified license differs from this License).
+
+10.4. Distributing Source Code Form that is Incompatible With Secondary
+Licenses
+
+If You choose to distribute Source Code Form that is Incompatible With
+Secondary Licenses under the terms of this version of the License, the
+notice described in Exhibit B of this License must be attached.
+
+Exhibit A - Source Code Form License Notice
+-------------------------------------------
+
+  This Source Code Form is subject to the terms of the Mozilla Public
+  License, v. 2.0. If a copy of the MPL was not distributed with this
+  file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+If it is not possible or desirable to put the notice in a particular
+file, then You may include the notice in a location (such as a LICENSE
+file in a relevant directory) where a recipient would be likely to look
+for such a notice.
+
+You may add additional accurate notices of copyright ownership.
+
+Exhibit B - "Incompatible With Secondary Licenses" Notice
+---------------------------------------------------------
+
+  This Source Code Form is "Incompatible With Secondary Licenses", as
+  defined by the Mozilla Public License, v. 2.0.

vendor/github.com/hashicorp/go-connlimit/NOTICE.md

@@ -0,0 +1,3 @@
+Copyright © 2020 HashiCorp, Inc.
+
+This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this project, you can obtain one at http://mozilla.org/MPL/2.0/.

vendor/github.com/hashicorp/go-connlimit/README.md

@@ -11,7 +11,7 @@ the resources that can be consumed by a single client.
 
 ### TCP Server
 
-```
+```go
 // During server setup:
 s.limiter = NewLimiter(Config{
   MaxConnsPerClientIP: 10,
@@ -19,7 +19,7 @@ s.limiter = NewLimiter(Config{
 
 ```
 
-```
+```go
 // handleConn is called in its own goroutine for each net.Conn accepted by
 // a net.Listener.
 func (s *Server) handleConn(conn net.Conn) {
@@ -53,7 +53,7 @@ func (s *Server) handleConn(conn net.Conn) {
 
 ### HTTP Server
 
-```
+```go
 lim := NewLimiter(Config{
   MaxConnsPerClientIP: 10,
 })

vendor/github.com/hashicorp/go-connlimit/connlimit.go

@@ -2,16 +2,23 @@ package connlimit
 
 import (
 	"errors"
+	"fmt"
 	"net"
 	"net/http"
 	"sync"
 	"sync/atomic"
+	"time"
 )
 
 var (
 	// ErrPerClientIPLimitReached is returned if accepting a new conn would exceed
 	// the per-client-ip limit set.
 	ErrPerClientIPLimitReached = errors.New("client connection limit reached")
+	tooManyConnsMsg            = "Your IP is issuing too many concurrent connections, please rate limit your calls\n"
+	tooManyRequestsResponse    = []byte(fmt.Sprintf("HTTP/1.1 429 Too Many Requests\r\n"+
+		"Content-Type: text/plain\r\n"+
+		"Content-Length: %d\r\n"+
+		"Connection: close\r\n\r\n%s", len(tooManyConnsMsg), tooManyConnsMsg))
 )
 
 // Limiter implements a simple limiter that tracks the number of connections
@@ -173,7 +180,7 @@ func (l *Limiter) SetConfig(c Config) {
 	l.cfg.Store(c)
 }
 
-// HTTPConnStateFunc returns a func that can be passed as the ConnState field of
+// HTTPConnStateFuncWithErrorHandler returns a func that can be passed as the ConnState field of
 // an http.Server. This intercepts new HTTP connections to the server and
 // applies the limiting to new connections.
 //
@@ -181,13 +188,15 @@ func (l *Limiter) SetConfig(c Config) {
 // in the limiter as if it was closed. Servers that use Hijacking must implement
 // their own calls if they need to continue limiting the number of concurrent
 // hijacked connections.
-func (l *Limiter) HTTPConnStateFunc() func(net.Conn, http.ConnState) {
+// errorHandler MUST close the connection itself
+func (l *Limiter) HTTPConnStateFuncWithErrorHandler(errorHandler func(error, net.Conn)) func(net.Conn, http.ConnState) {
+
 	return func(conn net.Conn, state http.ConnState) {
 		switch state {
 		case http.StateNew:
 			_, err := l.Accept(conn)
 			if err != nil {
-				conn.Close()
+				errorHandler(err, conn)
 			}
 		case http.StateHijacked:
 			l.freeConn(conn)
@@ -199,3 +208,26 @@ func (l *Limiter) HTTPConnStateFunc() func(net.Conn, http.ConnState) {
 		}
 	}
 }
+
+// HTTPConnStateFunc is here for ascending compatibility reasons.
+func (l *Limiter) HTTPConnStateFunc() func(net.Conn, http.ConnState) {
+	return l.HTTPConnStateFuncWithErrorHandler(func(err error, conn net.Conn) {
+		conn.Close()
+	})
+}
+
+// HTTPConnStateFuncWithDefault429Handler return an HTTP 429 if too many connections occur.
+// BEWARE that returning HTTP 429 is done on critical path, you might choose to use
+// HTTPConnStateFuncWithErrorHandler if you want to use a non-blocking strategy.
+func (l *Limiter) HTTPConnStateFuncWithDefault429Handler(writeDeadlineMaxDelay time.Duration) func(net.Conn, http.ConnState) {
+	return l.HTTPConnStateFuncWithErrorHandler(func(err error, conn net.Conn) {
+		if err == ErrPerClientIPLimitReached {
+			// We don't care about slow players
+			if writeDeadlineMaxDelay > 0 {
+				conn.SetDeadline(time.Now().Add(writeDeadlineMaxDelay))
+			}
+			conn.Write(tooManyRequestsResponse)
+		}
+		conn.Close()
+	})
+}

vendor/modules.txt

@@ -384,7 +384,7 @@ github.com/hashicorp/go-checkpoint
 # github.com/hashicorp/go-cleanhttp v0.5.1
 ## explicit
 github.com/hashicorp/go-cleanhttp
-# github.com/hashicorp/go-connlimit v0.2.0
+# github.com/hashicorp/go-connlimit v0.3.0
 ## explicit
 github.com/hashicorp/go-connlimit
 # github.com/hashicorp/go-cty-funcs v0.0.0-20200930094925-2721b1e36840