Limit to single inflight package syncing operation (#289)

tpaschalis · web-flow · commit 536037bfb323 · 2024-08-29T17:12:25.000-04:00
This PR revives work done in previous PRs (#118, #120) to make sure that only a single package syncing operation is ever in flight and also adds a test. The previous PRs did not account for needing to also protect `initStatuses` and `SetPackageStatuses`, so that's why the Lock and Unlock statements are not just paired in doSync. If you think the intent would be clearer using a sync.WaitGroup, let me know. The new test makes sure that the mutex correctly protects the local storage; if we comment out the calls to Lock/Unlock and run the test with the `-race` flag we can see the race condition taking place <details> ``` # Without using the mutex we can see the race condition of messages sent in parallel $ go test -run=TestPackageUpdatesInParallel -v -race -count=1 === RUN TestPackageUpdatesInParallel ================== WARNING: DATA RACE Write at 0x00c00003cdb0 by goroutine 10: github.com/open-telemetry/opamp-go/client/internal.(*InMemPackagesStore).SetLastReportedStatuses() /Users/tpaschalis/GitRepos/opamp-go/client/internal/inmempackagestore.go:95 +0x34 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).reportStatuses() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:335 +0x78 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).syncPackage() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:199 +0x4dc github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).doSync() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:132 +0x3b0 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).Sync.gowrap1() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:69 +0x4c Previous read at 0x00c00003cdb0 by goroutine 8: github.com/open-telemetry/opamp-go/client/internal.(*InMemPackagesStore).LastReportedStatuses() /Users/tpaschalis/GitRepos/opamp-go/client/internal/inmempackagestore.go:91 +0x30 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).initStatuses() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:88 +0x64 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).Sync() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:59 +0x78 github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel.func1() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:185 +0x68 github.com/open-telemetry/opamp-go/client/types.CallbacksStruct.OnMessage() /Users/tpaschalis/GitRepos/opamp-go/client/types/callbacks.go:161 +0x84 github.com/open-telemetry/opamp-go/client/types.(*CallbacksStruct).OnMessage() <autogenerated>:1 +0x20 github.com/open-telemetry/opamp-go/client/internal.(*receivedProcessor).ProcessReceivedMessage() /Users/tpaschalis/GitRepos/opamp-go/client/internal/receivedprocessor.go:160 +0xe94 github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel.func2() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:197 +0x4d0 Goroutine 10 (running) created at: github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).Sync() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:69 +0x15c github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel.func1() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:185 +0x68 github.com/open-telemetry/opamp-go/client/types.CallbacksStruct.OnMessage() /Users/tpaschalis/GitRepos/opamp-go/client/types/callbacks.go:161 +0x84 github.com/open-telemetry/opamp-go/client/types.(*CallbacksStruct).OnMessage() <autogenerated>:1 +0x20 github.com/open-telemetry/opamp-go/client/internal.(*receivedProcessor).ProcessReceivedMessage() /Users/tpaschalis/GitRepos/opamp-go/client/internal/receivedprocessor.go:160 +0xe94 github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel.func3() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:216 +0x4d0 Goroutine 8 (finished) created at: github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:196 +0x4b0 testing.tRunner() /opt/homebrew/Cellar/go/1.22.2/libexec/src/testing/testing.go:1689 +0x180 testing.(*T).Run.gowrap1() /opt/homebrew/Cellar/go/1.22.2/libexec/src/testing/testing.go:1742 +0x40 ================== ================== WARNING: DATA RACE Write at 0x00c0000999e0 by goroutine 11: runtime.mapaccess2_faststr() /opt/homebrew/Cellar/go/1.22.2/libexec/src/runtime/map_faststr.go:108 +0x42c github.com/open-telemetry/opamp-go/client/internal.(*InMemPackagesStore).CreatePackage() /Users/tpaschalis/GitRepos/opamp-go/client/internal/inmempackagestore.go:50 +0x74 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).syncPackage() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:203 +0x528 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).doSync() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:132 +0x3b0 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).Sync.gowrap1() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:69 +0x4c Previous read at 0x00c0000999e0 by goroutine 10: runtime.mapdelete() /opt/homebrew/Cellar/go/1.22.2/libexec/src/runtime/map.go:696 +0x43c github.com/open-telemetry/opamp-go/client/internal.(*InMemPackagesStore).Packages() /Users/tpaschalis/GitRepos/opamp-go/client/internal/inmempackagestore.go:36 +0x64 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).deleteUnneededLocalPackages() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:303 +0x58 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).doSync() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:125 +0x1b4 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).Sync.gowrap1() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:69 +0x4c Goroutine 11 (running) created at: github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).Sync() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:69 +0x15c github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel.func1() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:185 +0x68 github.com/open-telemetry/opamp-go/client/types.CallbacksStruct.OnMessage() /Users/tpaschalis/GitRepos/opamp-go/client/types/callbacks.go:161 +0x84 github.com/open-telemetry/opamp-go/client/types.(*CallbacksStruct).OnMessage() <autogenerated>:1 +0x20 github.com/open-telemetry/opamp-go/client/internal.(*receivedProcessor).ProcessReceivedMessage() /Users/tpaschalis/GitRepos/opamp-go/client/internal/receivedprocessor.go:160 +0xe94 github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel.func2() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:197 +0x4d0 Goroutine 10 (running) created at: github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).Sync() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:69 +0x15c github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel.func1() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:185 +0x68 github.com/open-telemetry/opamp-go/client/types.CallbacksStruct.OnMessage() /Users/tpaschalis/GitRepos/opamp-go/client/types/callbacks.go:161 +0x84 github.com/open-telemetry/opamp-go/client/types.(*CallbacksStruct).OnMessage() <autogenerated>:1 +0x20 github.com/open-telemetry/opamp-go/client/internal.(*receivedProcessor).ProcessReceivedMessage() /Users/tpaschalis/GitRepos/opamp-go/client/internal/receivedprocessor.go:160 +0xe94 github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel.func3() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:216 +0x4d0 ================== ================== WARNING: DATA RACE Write at 0x00c00003cdb0 by goroutine 11: github.com/open-telemetry/opamp-go/client/internal.(*InMemPackagesStore).SetLastReportedStatuses() /Users/tpaschalis/GitRepos/opamp-go/client/internal/inmempackagestore.go:95 +0x34 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).reportStatuses() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:335 +0x78 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).syncPackage() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:229 +0x780 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).doSync() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:132 +0x3b0 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).Sync.gowrap1() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:69 +0x4c Previous write at 0x00c00003cdb0 by goroutine 10: github.com/open-telemetry/opamp-go/client/internal.(*InMemPackagesStore).SetLastReportedStatuses() /Users/tpaschalis/GitRepos/opamp-go/client/internal/inmempackagestore.go:95 +0x34 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).reportStatuses() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:335 +0x78 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).syncPackage() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:229 +0x780 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).doSync() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:132 +0x3b0 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).Sync.gowrap1() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:69 +0x4c Goroutine 11 (running) created at: github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).Sync() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:69 +0x15c github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel.func1() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:185 +0x68 github.com/open-telemetry/opamp-go/client/types.CallbacksStruct.OnMessage() /Users/tpaschalis/GitRepos/opamp-go/client/types/callbacks.go:161 +0x84 github.com/open-telemetry/opamp-go/client/types.(*CallbacksStruct).OnMessage() <autogenerated>:1 +0x20 github.com/open-telemetry/opamp-go/client/internal.(*receivedProcessor).ProcessReceivedMessage() /Users/tpaschalis/GitRepos/opamp-go/client/internal/receivedprocessor.go:160 +0xe94 github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel.func2() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:197 +0x4d0 Goroutine 10 (running) created at: github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).Sync() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:69 +0x15c github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel.func1() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:185 +0x68 github.com/open-telemetry/opamp-go/client/types.CallbacksStruct.OnMessage() /Users/tpaschalis/GitRepos/opamp-go/client/types/callbacks.go:161 +0x84 github.com/open-telemetry/opamp-go/client/types.(*CallbacksStruct).OnMessage() <autogenerated>:1 +0x20 github.com/open-telemetry/opamp-go/client/internal.(*receivedProcessor).ProcessReceivedMessage() /Users/tpaschalis/GitRepos/opamp-go/client/internal/receivedprocessor.go:160 +0xe94 github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel.func3() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:216 +0x4d0 ================== ================== WARNING: DATA RACE Write at 0x00c00003cdb0 by goroutine 10: github.com/open-telemetry/opamp-go/client/internal.(*InMemPackagesStore).SetLastReportedStatuses() /Users/tpaschalis/GitRepos/opamp-go/client/internal/inmempackagestore.go:95 +0x34 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).reportStatuses() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:335 +0x78 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).doSync() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:151 +0x69c github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).Sync.gowrap1() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:69 +0x4c Previous write at 0x00c00003cdb0 by goroutine 11: github.com/open-telemetry/opamp-go/client/internal.(*InMemPackagesStore).SetLastReportedStatuses() /Users/tpaschalis/GitRepos/opamp-go/client/internal/inmempackagestore.go:95 +0x34 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).reportStatuses() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:335 +0x78 github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).doSync() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:151 +0x69c github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).Sync.gowrap1() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:69 +0x4c Goroutine 10 (running) created at: github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).Sync() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:69 +0x15c github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel.func1() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:185 +0x68 github.com/open-telemetry/opamp-go/client/types.CallbacksStruct.OnMessage() /Users/tpaschalis/GitRepos/opamp-go/client/types/callbacks.go:161 +0x84 github.com/open-telemetry/opamp-go/client/types.(*CallbacksStruct).OnMessage() <autogenerated>:1 +0x20 github.com/open-telemetry/opamp-go/client/internal.(*receivedProcessor).ProcessReceivedMessage() /Users/tpaschalis/GitRepos/opamp-go/client/internal/receivedprocessor.go:160 +0xe94 github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel.func3() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:216 +0x4d0 Goroutine 11 (running) created at: github.com/open-telemetry/opamp-go/client/internal.(*packagesSyncer).Sync() /Users/tpaschalis/GitRepos/opamp-go/client/internal/packagessyncer.go:69 +0x15c github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel.func1() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:185 +0x68 github.com/open-telemetry/opamp-go/client/types.CallbacksStruct.OnMessage() /Users/tpaschalis/GitRepos/opamp-go/client/types/callbacks.go:161 +0x84 github.com/open-telemetry/opamp-go/client/types.(*CallbacksStruct).OnMessage() <autogenerated>:1 +0x20 github.com/open-telemetry/opamp-go/client/internal.(*receivedProcessor).ProcessReceivedMessage() /Users/tpaschalis/GitRepos/opamp-go/client/internal/receivedprocessor.go:160 +0xe94 github.com/open-telemetry/opamp-go/client/internal.TestPackageUpdatesInParallel.func2() /Users/tpaschalis/GitRepos/opamp-go/client/internal/httpsender_test.go:197 +0x4d0 ================== testing.go:1398: race detected during execution of test --- FAIL: TestPackageUpdatesInParallel (0.10s) FAIL exit status 1 FAIL github.com/open-telemetry/opamp-go/client/internal 0.286s ``` </details> Fixes #84
diff --git a/client/httpclient.go b/client/httpclient.go
@@ -131,6 +131,7 @@ func (c *httpClient) runUntilStopped(ctx context.Context) {
 		&c.common.ClientSyncedState,
 		c.common.PackagesStateProvider,
 		c.common.Capabilities,
+		&c.common.PackageSyncMutex,
 	)
 }
 
diff --git a/client/internal/clientcommon.go b/client/internal/clientcommon.go
@@ -41,6 +41,9 @@ type ClientCommon struct {
 	// PackagesStateProvider provides access to the local state of packages.
 	PackagesStateProvider types.PackagesStateProvider
 
+	// PackageSyncMutex makes sure only one package syncing operation happens at a time.
+	PackageSyncMutex sync.Mutex
+
 	// The transport-specific sender.
 	sender Sender
 
diff --git a/client/internal/httpsender.go b/client/internal/httpsender.go
@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"sync"
 	"sync/atomic"
 	"time"
 
@@ -91,10 +92,11 @@ func (h *HTTPSender) Run(
 	clientSyncedState *ClientSyncedState,
 	packagesStateProvider types.PackagesStateProvider,
 	capabilities protobufs.AgentCapabilities,
+	packageSyncMutex *sync.Mutex,
 ) {
 	h.url = url
 	h.callbacks = callbacks
-	h.receiveProcessor = newReceivedProcessor(h.logger, callbacks, h, clientSyncedState, packagesStateProvider, capabilities)
+	h.receiveProcessor = newReceivedProcessor(h.logger, callbacks, h, clientSyncedState, packagesStateProvider, capabilities, packageSyncMutex)
 
 	for {
 		pollingTimer := time.NewTimer(time.Millisecond * time.Duration(atomic.LoadInt64(&h.pollingIntervalMs)))
diff --git a/client/internal/httpsender_test.go b/client/internal/httpsender_test.go
@@ -183,7 +183,7 @@ func TestRequestInstanceUidFlagReset(t *testing.T) {
 	clientSyncedState := &ClientSyncedState{}
 	clientSyncedState.SetFlags(protobufs.AgentToServerFlags_AgentToServerFlags_RequestInstanceUid)
 	capabilities := protobufs.AgentCapabilities_AgentCapabilities_Unspecified
-	sender.receiveProcessor = newReceivedProcessor(&sharedinternal.NopLogger{}, sender.callbacks, sender, clientSyncedState, nil, capabilities)
+	sender.receiveProcessor = newReceivedProcessor(&sharedinternal.NopLogger{}, sender.callbacks, sender, clientSyncedState, nil, capabilities, new(sync.Mutex))
 
 	// If we process a message with a nil AgentIdentification, or an incorrect NewInstanceUid.
 	sender.receiveProcessor.ProcessReceivedMessage(ctx,
@@ -208,3 +208,127 @@ func TestRequestInstanceUidFlagReset(t *testing.T) {
 	assert.Equal(t, sender.receiveProcessor.clientSyncedState.flags, protobufs.AgentToServerFlags_AgentToServerFlags_Unspecified)
 	cancel()
 }
+
+func TestPackageUpdatesInParallel(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	localPackageState := NewInMemPackagesStore()
+	sender := NewHTTPSender(&sharedinternal.NopLogger{})
+	blockSyncCh := make(chan struct{})
+	doneCh := make([]<-chan struct{}, 0)
+
+	// Use `ch` to simulate blocking behavior on the second call to Sync().
+	// This will allow both Sync() calls to be called in parallel; we will
+	// first make sure that both are inflight before manually releasing the
+	// channel so that both go through in sequence.
+	localPackageState.onAllPackagesHash = func() {
+		if localPackageState.lastReportedStatuses != nil {
+			<-blockSyncCh
+		}
+	}
+
+	var messages atomic.Int32
+	var mux sync.Mutex
+	sender.callbacks = types.CallbacksStruct{
+		OnMessageFunc: func(ctx context.Context, msg *types.MessageData) {
+			err := msg.PackageSyncer.Sync(ctx)
+			assert.NoError(t, err)
+			messages.Add(1)
+			doneCh = append(doneCh, msg.PackageSyncer.Done())
+		},
+	}
+
+	clientSyncedState := &ClientSyncedState{}
+	capabilities := protobufs.AgentCapabilities_AgentCapabilities_AcceptsPackages
+	sender.receiveProcessor = newReceivedProcessor(&sharedinternal.NopLogger{}, sender.callbacks, sender, clientSyncedState, localPackageState, capabilities, &mux)
+
+	sender.receiveProcessor.ProcessReceivedMessage(ctx,
+		&protobufs.ServerToAgent{
+			PackagesAvailable: &protobufs.PackagesAvailable{
+				Packages: map[string]*protobufs.PackageAvailable{
+					"package1": {
+						Type:    protobufs.PackageType_PackageType_TopLevel,
+						Version: "1.0.0",
+						File: &protobufs.DownloadableFile{
+							DownloadUrl: "foo",
+							ContentHash: []byte{4, 5},
+						},
+						Hash: []byte{1, 2, 3},
+					},
+				},
+				AllPackagesHash: []byte{1, 2, 3, 4, 5},
+			},
+		})
+	sender.receiveProcessor.ProcessReceivedMessage(ctx,
+		&protobufs.ServerToAgent{
+			PackagesAvailable: &protobufs.PackagesAvailable{
+				Packages: map[string]*protobufs.PackageAvailable{
+					"package22": {
+						Type:    protobufs.PackageType_PackageType_TopLevel,
+						Version: "1.0.0",
+						File: &protobufs.DownloadableFile{
+							DownloadUrl: "bar",
+							ContentHash: []byte{4, 5},
+						},
+						Hash: []byte{1, 2, 3},
+					},
+				},
+				AllPackagesHash: []byte{1, 2, 3, 4, 5},
+			},
+		})
+
+	// Make sure that both Sync calls have gone through _before_ releasing the first one.
+	// This means that they're both called in parallel, and that the race
+	// detector would always report a race condition, but proper locking makes
+	// sure that's not the case.
+	assert.Eventually(t, func() bool {
+		return messages.Load() == 2
+	}, 2*time.Second, 100*time.Millisecond, "both messages must have been processed successfully")
+
+	// Release the second Sync call so it can continue and wait for both of them to complete.
+	blockSyncCh <- struct{}{}
+	<-doneCh[0]
+	<-doneCh[1]
+
+	cancel()
+}
+
+func TestPackageUpdatesWithError(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	sender := NewHTTPSender(&sharedinternal.NopLogger{})
+
+	// We'll pass in a nil PackageStateProvider to force the Sync call to return with an error.
+	localPackageState := types.PackagesStateProvider(nil)
+	var messages atomic.Int32
+	var mux sync.Mutex
+	sender.callbacks = types.CallbacksStruct{
+		OnMessageFunc: func(ctx context.Context, msg *types.MessageData) {
+			// Make sure the call to Sync will return an error due to a nil PackageStateProvider
+			err := msg.PackageSyncer.Sync(ctx)
+			assert.Error(t, err)
+			messages.Add(1)
+		},
+	}
+
+	clientSyncedState := &ClientSyncedState{}
+
+	capabilities := protobufs.AgentCapabilities_AgentCapabilities_AcceptsPackages
+	sender.receiveProcessor = newReceivedProcessor(&sharedinternal.NopLogger{}, sender.callbacks, sender, clientSyncedState, localPackageState, capabilities, &mux)
+
+	// Send two messages in parallel.
+	sender.receiveProcessor.ProcessReceivedMessage(ctx,
+		&protobufs.ServerToAgent{
+			PackagesAvailable: &protobufs.PackagesAvailable{},
+		})
+	sender.receiveProcessor.ProcessReceivedMessage(ctx,
+		&protobufs.ServerToAgent{
+			PackagesAvailable: &protobufs.PackagesAvailable{},
+		})
+
+	// Make sure that even though the call to Sync errored out early, the lock
+	// was still released properly for both messages to be processed.
+	assert.Eventually(t, func() bool {
+		return messages.Load() == 2
+	}, 5*time.Second, 100*time.Millisecond, "both messages must have been processed successfully")
+
+	cancel()
+}
diff --git a/client/internal/inmempackagestore.go b/client/internal/inmempackagestore.go
@@ -15,6 +15,8 @@ type InMemPackagesStore struct {
 	fileContents         map[string][]byte
 	fileHashes           map[string][]byte
 	lastReportedStatuses *protobufs.PackageStatuses
+
+	onAllPackagesHash func()
 }
 
 var _ types.PackagesStateProvider = (*InMemPackagesStore)(nil)
@@ -28,6 +30,9 @@ func NewInMemPackagesStore() *InMemPackagesStore {
 }
 
 func (l *InMemPackagesStore) AllPackagesHash() ([]byte, error) {
+	if l.onAllPackagesHash != nil {
+		l.onAllPackagesHash()
+	}
 	return l.allPackagesHash, nil
 }
 
diff --git a/client/internal/packagessyncer.go b/client/internal/packagessyncer.go
@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"sync"
 
 	"github.com/open-telemetry/opamp-go/client/types"
 	"github.com/open-telemetry/opamp-go/protobufs"
@@ -20,6 +21,7 @@ type packagesSyncer struct {
 	sender            Sender
 
 	statuses *protobufs.PackageStatuses
+	mux      *sync.Mutex
 	doneCh   chan struct{}
 }
 
@@ -30,6 +32,7 @@ func NewPackagesSyncer(
 	sender Sender,
 	clientSyncedState *ClientSyncedState,
 	packagesStateProvider types.PackagesStateProvider,
+	mux *sync.Mutex,
 ) *packagesSyncer {
 	return &packagesSyncer{
 		logger:            logger,
@@ -38,6 +41,7 @@ func NewPackagesSyncer(
 		clientSyncedState: clientSyncedState,
 		localState:        packagesStateProvider,
 		doneCh:            make(chan struct{}),
+		mux:               mux,
 	}
 }
 
@@ -49,15 +53,24 @@ func (s *packagesSyncer) Sync(ctx context.Context) error {
 	}()
 
 	// Prepare package statuses.
+	// Grab a lock to make sure that package statuses are not overriden by
+	// another call to Sync running in parallel.
+	// In case Sync returns early with an error, take care of unlocking the
+	// mutex in this goroutine; otherwise it will be unlocked at the end
+	// of the sync operation.
+	s.mux.Lock()
 	if err := s.initStatuses(); err != nil {
+		s.mux.Unlock()
 		return err
 	}
 
 	if err := s.clientSyncedState.SetPackageStatuses(s.statuses); err != nil {
+		s.mux.Unlock()
 		return err
 	}
 
-	// Now do the actual syncing in the background.
+	// Now do the actual syncing in the background and release the lock from
+	// inside of the goroutine.
 	go s.doSync(ctx)
 
 	return nil
@@ -99,6 +112,10 @@ func (s *packagesSyncer) initStatuses() error {
 
 // doSync performs the actual syncing process.
 func (s *packagesSyncer) doSync(ctx context.Context) {
+	// Once doSync returns  in a separate goroutine, make sure to release the
+	// mutex so that a new syncing process can take place.
+	defer s.mux.Unlock()
+
 	hash, err := s.localState.AllPackagesHash()
 	if err != nil {
 		s.logger.Errorf(ctx, "Package syncing failed: %V", err)
diff --git a/client/internal/receivedprocessor.go b/client/internal/receivedprocessor.go
@@ -3,6 +3,7 @@ package internal
 import (
 	"context"
 	"fmt"
+	"sync"
 
 	"github.com/open-telemetry/opamp-go/client/types"
 	"github.com/open-telemetry/opamp-go/protobufs"
@@ -24,6 +25,9 @@ type receivedProcessor struct {
 
 	packagesStateProvider types.PackagesStateProvider
 
+	// packageSyncMutex protects against multiple package syncing operations at the same time.
+	packageSyncMutex *sync.Mutex
+
 	// Agent's capabilities defined at Start() time.
 	capabilities protobufs.AgentCapabilities
 }
@@ -35,6 +39,7 @@ func newReceivedProcessor(
 	clientSyncedState *ClientSyncedState,
 	packagesStateProvider types.PackagesStateProvider,
 	capabilities protobufs.AgentCapabilities,
+	packageSyncMutex *sync.Mutex,
 ) receivedProcessor {
 	return receivedProcessor{
 		logger:                logger,
@@ -43,6 +48,7 @@ func newReceivedProcessor(
 		clientSyncedState:     clientSyncedState,
 		packagesStateProvider: packagesStateProvider,
 		capabilities:          capabilities,
+		packageSyncMutex:      packageSyncMutex,
 	}
 }
 
@@ -122,6 +128,7 @@ func (r *receivedProcessor) ProcessReceivedMessage(ctx context.Context, msg *pro
 					r.sender,
 					r.clientSyncedState,
 					r.packagesStateProvider,
+					r.packageSyncMutex,
 				)
 			} else {
 				r.logger.Debugf(ctx, "Ignoring PackagesAvailable, agent does not have AcceptsPackages capability")
diff --git a/client/internal/wsreceiver.go b/client/internal/wsreceiver.go
@@ -3,6 +3,7 @@ package internal
 import (
 	"context"
 	"fmt"
+	"sync"
 
 	"github.com/gorilla/websocket"
 	"github.com/open-telemetry/opamp-go/client/types"
@@ -32,13 +33,14 @@ func NewWSReceiver(
 	clientSyncedState *ClientSyncedState,
 	packagesStateProvider types.PackagesStateProvider,
 	capabilities protobufs.AgentCapabilities,
+	packageSyncMutex *sync.Mutex,
 ) *wsReceiver {
 	w := &wsReceiver{
 		conn:      conn,
 		logger:    logger,
 		sender:    sender,
 		callbacks: callbacks,
-		processor: newReceivedProcessor(logger, callbacks, sender, clientSyncedState, packagesStateProvider, capabilities),
+		processor: newReceivedProcessor(logger, callbacks, sender, clientSyncedState, packagesStateProvider, capabilities, packageSyncMutex),
 		stopped:   make(chan struct{}),
 	}
 
diff --git a/client/internal/wsreceiver_test.go b/client/internal/wsreceiver_test.go
diff --git a/client/wsclient.go b/client/wsclient.go

Original file line number	Diff line number	Diff line change
`@@ -131,6 +131,7 @@ func (c *httpClient) runUntilStopped(ctx context.Context) {`
`131`	`131`	`&c.common.ClientSyncedState,`
`132`	`132`	`c.common.PackagesStateProvider,`
`133`	`133`	`c.common.Capabilities,`
	`134`	`+ &c.common.PackageSyncMutex,`
`134`	`135`	`)`
`135`	`136`	`}`
`136`	`137`
Original file line number	Diff line number	Diff line change
`@@ -15,6 +15,8 @@ type InMemPackagesStore struct {`
`15`	`15`	`fileContents map[string][]byte`
`16`	`16`	`fileHashes map[string][]byte`
`17`	`17`	`lastReportedStatuses *protobufs.PackageStatuses`
	`18`	`+`
	`19`	`+ onAllPackagesHash func()`
`18`	`20`	`}`
`19`	`21`
`20`	`22`	`var _ types.PackagesStateProvider = (*InMemPackagesStore)(nil)`
`@@ -28,6 +30,9 @@ func NewInMemPackagesStore() *InMemPackagesStore {`
`28`	`30`	`}`
`29`	`31`
`30`	`32`	`func (l *InMemPackagesStore) AllPackagesHash() ([]byte, error) {`
	`33`	`+ if l.onAllPackagesHash != nil {`
	`34`	`+ l.onAllPackagesHash()`
	`35`	`+ }`
`31`	`36`	`return l.allPackagesHash, nil`
`32`	`37`	`}`
`33`	`38`