The default RPC transport now requests wire compression in Node

.changeset/six-olives-hang.md

@@ -0,0 +1,5 @@
+---
+'@solana/rpc': patch
+---
+
+Enabled Brotli, gzip, and Deflate compression by default when running in Node.js, where compression headers are not added by the runtime like they are in browsers

packages/rpc/src/__tests__/rpc-transport-header-config-test.ts

@@ -5,6 +5,31 @@ import { createDefaultRpcTransport } from '../rpc-transport';
 jest.mock('@solana/rpc-transport-http');
 
 describe('createDefaultRpcTransport', () => {
+    if (__NODEJS__) {
+        it('adds default compression headers', () => {
+            createDefaultRpcTransport({ url: 'fake://url' });
+            expect(createHttpTransportForSolanaRpc).toHaveBeenCalledWith(
+                expect.objectContaining({
+                    headers: expect.objectContaining({
+                        'accept-encoding': 'br,gzip,deflate',
+                    }),
+                }),
+            );
+        });
+        it('allows the override of the default compression headers', () => {
+            createDefaultRpcTransport({
+                headers: { 'aCcEpT-eNcOdInG': 'zstd' },
+                url: 'fake://url',
+            });
+            expect(createHttpTransportForSolanaRpc).toHaveBeenCalledWith(
+                expect.objectContaining({
+                    headers: expect.objectContaining({
+                        'accept-encoding': 'zstd',
+                    }),
+                }),
+            );
+        });
+    }
     it('adds configured headers to each request with downcased property names', () => {
         createDefaultRpcTransport({
             headers: { aUtHoRiZaTiOn: 'Picard, 4 7 Alpha Tango' },

packages/rpc/src/rpc-transport.ts

@@ -31,6 +31,13 @@ export function createDefaultRpcTransport<TClusterUrl extends ClusterUrl>(
         createHttpTransportForSolanaRpc({
             ...config,
             headers: {
+                ...(__NODEJS__ &&
+                    ({
+                        // Keep these headers lowercase so they will be overriden by any user-supplied headers below.
+                        'accept-encoding':
+                            // Natively supported by Node LTS v20.18.0 and above.
+                            'br,gzip,deflate', // Brotli, gzip, and Deflate, in that order.
+                    } as { [overrideHeader: string]: string })),
                 ...(config.headers ? normalizeHeaders(config.headers) : undefined),
                 ...({
                     // Keep these headers lowercase so they will override any user-supplied headers above.