[azcosmos] tighten default HTTP client timeouts and increase pool size

sdk/data/azcosmos/CHANGELOG.md

@@ -10,6 +10,8 @@
 
 ### Other Changes
 
+* Set the default HTTP client connect (dial) timeout to 5 seconds (down from the azcore default of 30 seconds) and the default request timeout to 65 seconds (the azcore default was unbounded). The 65-second timeout applies to the entire HTTP round-trip, including response-body streaming. Increased the default idle connection pool size to 1000 total / 1000 per host (up from the azcore defaults of 100 / 10) to better support high-concurrency workloads against the Cosmos gateway. Callers that supply a custom `Transport` via `azcore.ClientOptions` are unaffected. See [PR 26856](https://github.com/Azure/azure-sdk-for-go/pull/26856).
+
 ## 1.5.0-beta.6 (2026-05-15)
 
 ### Features Added

sdk/data/azcosmos/cosmos_client.go

@@ -181,9 +181,7 @@ func NewClientFromConnectionString(connectionString string, o *ClientOptions) (*
 }
 
 func newClient(authPolicy policy.Policy, gem *globalEndpointManager, options *ClientOptions) (*azcore.Client, error) {
-	if options == nil {
-		options = &ClientOptions{}
-	}
+	options = withDefaultTransport(options)
 	return azcore.NewClient(moduleName, serviceLibVersion,
 		azruntime.PipelineOptions{
 			AllowedHeaders: getAllowedHeaders(),
@@ -207,9 +205,7 @@ func newClient(authPolicy policy.Policy, gem *globalEndpointManager, options *Cl
 }
 
 func newInternalPipeline(authPolicy policy.Policy, options *ClientOptions) azruntime.Pipeline {
-	if options == nil {
-		options = &ClientOptions{}
-	}
+	options = withDefaultTransport(options)
 	return azruntime.NewPipeline(moduleName, serviceLibVersion,
 		azruntime.PipelineOptions{
 			AllowedHeaders: getAllowedHeaders(),
@@ -220,6 +216,24 @@ func newInternalPipeline(authPolicy policy.Policy, options *ClientOptions) azrun
 		&options.ClientOptions)
 }
 
+// withDefaultTransport returns a *ClientOptions whose Transport is set to the
+// Cosmos default HTTP client when the caller has not supplied one. The
+// returned value is always non-nil and is safe to mutate without affecting
+// the caller's struct.
+func withDefaultTransport(options *ClientOptions) *ClientOptions {
+	if options == nil {
+		return &ClientOptions{
+			ClientOptions: azcore.ClientOptions{Transport: defaultCosmosHTTPClient},
+		}
+	}
+	if options.Transport != nil {
+		return options
+	}
+	clone := *options
+	clone.ClientOptions.Transport = defaultCosmosHTTPClient
+	return &clone
+}
+
 func createScopeFromEndpoint(endpoint *url.URL) ([]string, error) {
 	return []string{fmt.Sprintf("%s://%s/.default", endpoint.Scheme, endpoint.Hostname())}, nil
 }

sdk/data/azcosmos/cosmos_default_http_client.go

@@ -0,0 +1,63 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+package azcosmos
+
+import (
+	"crypto/tls"
+	"net"
+	"net/http"
+	"time"
+
+	"golang.org/x/net/http2"
+)
+
+const (
+	// defaultConnectTimeout is the default timeout for establishing a new TCP
+	// connection to the Cosmos service.
+	defaultConnectTimeout = 5 * time.Second
+
+	// defaultRequestTimeout is the default end-to-end timeout applied by the
+	// HTTP client to a single request, including connection setup, sending the
+	// request, and reading the entire response body. Callers that need a
+	// different bound can supply their own Transport via ClientOptions.
+	defaultRequestTimeout = 65 * time.Second
+)
+
+// defaultCosmosHTTPClient is the http.Client used by Cosmos clients when the
+// caller does not provide a custom Transport via ClientOptions. It mirrors the
+// azcore default transport but uses Cosmos-specific connect and request
+// timeouts.
+var defaultCosmosHTTPClient *http.Client
+
+func init() {
+	defaultCosmosHTTPClient = newDefaultCosmosHTTPClient()
+}
+
+func newDefaultCosmosHTTPClient() *http.Client {
+	transport := &http.Transport{
+		Proxy: http.ProxyFromEnvironment,
+		DialContext: (&net.Dialer{
+			Timeout:   defaultConnectTimeout,
+			KeepAlive: 30 * time.Second,
+		}).DialContext,
+		ForceAttemptHTTP2:     true,
+		MaxIdleConns:          1000,
+		MaxIdleConnsPerHost:   1000,
+		IdleConnTimeout:       90 * time.Second,
+		TLSHandshakeTimeout:   10 * time.Second,
+		ExpectContinueTimeout: 1 * time.Second,
+		TLSClientConfig: &tls.Config{
+			MinVersion:    tls.VersionTLS12,
+			Renegotiation: tls.RenegotiateFreelyAsClient,
+		},
+	}
+	if http2Transport, err := http2.ConfigureTransports(transport); err == nil {
+		http2Transport.ReadIdleTimeout = 2 * time.Second
+		http2Transport.PingTimeout = 1 * time.Second
+	}
+	return &http.Client{
+		Transport: transport,
+		Timeout:   defaultRequestTimeout,
+	}
+}

sdk/data/azcosmos/cosmos_default_http_client_test.go

@@ -0,0 +1,56 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+package azcosmos
+
+import (
+	"net/http"
+	"testing"
+	"time"
+
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore"
+	"github.com/Azure/azure-sdk-for-go/sdk/internal/mock"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDefaultCosmosHTTPClient_Timeouts(t *testing.T) {
+	require.Equal(t, 5*time.Second, defaultConnectTimeout)
+	require.Equal(t, 65*time.Second, defaultRequestTimeout)
+
+	c := newDefaultCosmosHTTPClient()
+	require.NotNil(t, c)
+	require.Equal(t, defaultRequestTimeout, c.Timeout)
+
+	transport, ok := c.Transport.(*http.Transport)
+	require.True(t, ok, "expected *http.Transport, got %T", c.Transport)
+	require.NotNil(t, transport.DialContext)
+}
+
+func TestWithDefaultTransport_NilOptions(t *testing.T) {
+	got := withDefaultTransport(nil)
+	require.NotNil(t, got)
+	require.Same(t, defaultCosmosHTTPClient, got.Transport)
+}
+
+func TestWithDefaultTransport_NoTransportSet(t *testing.T) {
+	in := &ClientOptions{
+		EnableContentResponseOnWrite: true,
+	}
+	got := withDefaultTransport(in)
+	require.NotSame(t, in, got, "expected withDefaultTransport to clone options")
+	require.Nil(t, in.Transport, "caller-supplied options must not be mutated")
+	require.Same(t, defaultCosmosHTTPClient, got.Transport)
+	require.True(t, got.EnableContentResponseOnWrite)
+}
+
+func TestWithDefaultTransport_PreservesCallerTransport(t *testing.T) {
+	srv, close := mock.NewServer()
+	defer close()
+
+	in := &ClientOptions{
+		ClientOptions: azcore.ClientOptions{Transport: srv},
+	}
+	got := withDefaultTransport(in)
+	require.Same(t, in, got, "expected withDefaultTransport to return same options when Transport is provided")
+	require.Same(t, srv, got.Transport)
+}