Add XDC RPC failover for identifier verification

src/server/networks.js

@@ -61,7 +61,7 @@ export default once(() => {
       network_id: 50,
       web3Transport: 'HttpProvider',
       // eslint-disable-next-line prettier/prettier
-      httpWeb3Provider: xdcRpc ? xdcRpc : 'https://rpc.xdc.org/',
+      httpWeb3Provider: xdcRpc ? xdcRpc : 'https://rpc.xdc.org/,https://erpc.xinfin.network',
       websocketWeb3Provider: '',
       explorer: xdcExplorers
     },

src/server/utils/__tests__/eth-provider.test.js

@@ -0,0 +1,31 @@
+jest.mock('@ambire/signature-validator', () => ({
+  verifyMessage: jest.fn().mockResolvedValue(true)
+}))
+
+import { ethers } from 'ethers'
+import { verifyMessage } from '@ambire/signature-validator'
+import { verifyIdentifier } from '../eth'
+
+describe('verifyIdentifier RPC fallback', () => {
+  test('uses multiple default XDC RPC endpoints', async () => {
+    const configuredRpc = process.env.XDC_RPC
+    delete process.env.XDC_RPC
+
+    try {
+      await verifyIdentifier(`0x${'11'.repeat(65)}`, '0x0000000000000000000000000000000000000001', 50)
+    } finally {
+      if (configuredRpc === undefined) {
+        delete process.env.XDC_RPC
+      } else {
+        process.env.XDC_RPC = configuredRpc
+      }
+    }
+
+    const { provider } = verifyMessage.mock.calls[0][0]
+    expect(provider).toBeInstanceOf(ethers.providers.FallbackProvider)
+    expect(provider.providerConfigs.map(({ provider: rpc }) => rpc.connection.url)).toEqual([
+      'https://rpc.xdc.org/',
+      'https://erpc.xinfin.network'
+    ])
+  })
+})

src/server/utils/eth.js

@@ -59,11 +59,18 @@ export const verifyIdentifier = async (fvsig, gdAddress, chainId = 42220) => {
   // const celoProvider = new ethers.providers.JsonRpcProvider('https://forno.celo.org')
   // const xdcProvider = new ethers.providers.JsonRpcProvider('https://rpc.ankr.com/')
 
-  const rpc = networks[chainId]?.httpWeb3Provider?.split(',')[0]
-  const provider = rpc ? new ethers.providers.JsonRpcProvider(rpc) : null
-  if (!provider) {
+  const rpcs = networks[chainId]?.httpWeb3Provider?.split(',') || []
+  const rpc = rpcs[0]
+  if (!rpc) {
     throw new Error(`verifyIdentifier: no RPC for chainId ${chainId} for FV identifier verification`)
   }
+  const provider =
+    rpcs.length > 1
+      ? new ethers.providers.FallbackProvider(
+          rpcs.map(endpoint => new ethers.providers.JsonRpcProvider(endpoint, chainId)),
+          1
+        )
+      : new ethers.providers.JsonRpcProvider(rpc)
 
   try {
     const verifyResult = await verifyMessage({