feat(relayer): Support defining inventory config externally (#1316)

This allows the inventory config to be defined in a separate JSON file,
where it's much easier to update and mainintain. To use this, define
RELAYER_EXTERNAL_INVENTORY_CONFIG=<path-to-file>.

src/relayer/RelayerClientHelper.ts

@@ -1,4 +1,4 @@
-import { utils as sdkUtils } from "@across-protocol/sdk-v2";
+import { typeguards, utils as sdkUtils } from "@across-protocol/sdk-v2";
 import winston from "winston";
 import { AcrossApiClient, BundleDataClient, InventoryClient, ProfitClient, TokenClient } from "../clients";
 import { AdapterManager, CrossChainTransferClient } from "../clients/bridges";
@@ -11,7 +11,7 @@ import {
   updateSpokePoolClients,
 } from "../common";
 import { SpokePoolClientsByChain } from "../interfaces";
-import { Signer } from "../utils";
+import { isDefined, readFile, Signer } from "../utils";
 import { RelayerConfig } from "./RelayerConfig";
 
 export interface RelayerClients extends Clients {
@@ -107,12 +107,31 @@ export async function constructRelayerClients(
     configStoreClient.getChainIdIndicesForBlock(),
     config.blockRangeEndBlockBuffer
   );
+
   const crossChainAdapterSupportedChains = adapterManager.supportedChains();
   const crossChainTransferClient = new CrossChainTransferClient(
     logger,
     enabledChainIds.filter((chainId) => crossChainAdapterSupportedChains.includes(chainId)),
     adapterManager
   );
+
+  // If an external inventory configuration was defined, read it in now before instantiating the InventoryClient.
+  if (isDefined(config.externalInventoryConfig)) {
+    const _inventoryConfig = await readFile(config.externalInventoryConfig);
+    try {
+      config.inventoryConfig = JSON.parse(_inventoryConfig);
+    } catch (err) {
+      const msg = typeguards.isError(err) ? err.message : (err as Record<string, unknown>)?.code;
+      throw new Error(`Inventory config error in ${config.externalInventoryConfig} (${msg ?? "unknown error"})`);
+    }
+    logger.debug({
+      at: "Relayer#constructRelayerClients",
+      message: "Updated Inventory config.",
+      source: config.externalInventoryConfig,
+      inventoryConfig: config.inventoryConfig,
+    });
+  }
+
   const inventoryClient = new InventoryClient(
     signerAddr,
     logger,

src/relayer/RelayerConfig.ts

@@ -1,10 +1,12 @@
-import { BigNumber, toBNWei, assert, toBN, replaceAddressCase, ethers } from "../utils";
+import { BigNumber, toBNWei, assert, isDefined, toBN, replaceAddressCase, ethers } from "../utils";
 import { CommonConfig, ProcessEnv } from "../common";
 import * as Constants from "../common/Constants";
 import { InventoryConfig } from "../interfaces";
 
 export class RelayerConfig extends CommonConfig {
-  readonly inventoryConfig: InventoryConfig;
+  readonly externalInventoryConfig?: string;
+  inventoryConfig: InventoryConfig;
+
   readonly debugProfitability: boolean;
   // Whether token price fetch failures will be ignored when computing relay profitability.
   // If this is false, the relayer will throw an error when fetching prices fails.
@@ -41,6 +43,7 @@ export class RelayerConfig extends CommonConfig {
       RELAYER_GAS_MESSAGE_MULTIPLIER,
       RELAYER_GAS_MULTIPLIER,
       RELAYER_GAS_PADDING,
+      RELAYER_EXTERNAL_INVENTORY_CONFIG,
       RELAYER_INVENTORY_CONFIG,
       RELAYER_TOKENS,
       SEND_RELAYS,
@@ -67,7 +70,14 @@ export class RelayerConfig extends CommonConfig {
     this.slowDepositors = SLOW_DEPOSITORS
       ? JSON.parse(SLOW_DEPOSITORS).map((depositor) => ethers.utils.getAddress(depositor))
       : [];
-    this.inventoryConfig = RELAYER_INVENTORY_CONFIG ? JSON.parse(RELAYER_INVENTORY_CONFIG) : {};
+
+    assert(
+      !isDefined(RELAYER_EXTERNAL_INVENTORY_CONFIG) || !isDefined(RELAYER_INVENTORY_CONFIG),
+      "Concurrent inventory management configurations detected."
+    );
+    this.externalInventoryConfig = RELAYER_EXTERNAL_INVENTORY_CONFIG;
+    this.inventoryConfig = JSON.parse(RELAYER_INVENTORY_CONFIG ?? "{}");
+
     this.minRelayerFeePct = toBNWei(MIN_RELAYER_FEE_PCT || Constants.RELAYER_MIN_FEE_PCT);
 
     if (Object.keys(this.inventoryConfig).length > 0) {

src/utils/fsUtils.ts

@@ -0,0 +1,12 @@
+import * as fs from "fs/promises";
+import { typeguards } from "@across-protocol/sdk-v2";
+
+export async function readFile(fileName: string): Promise<string> {
+  try {
+    return await fs.readFile(fileName, { encoding: "utf8" });
+  } catch (err) {
+    // @dev fs methods can return errors that are not Error objects (i.e. errno).
+    const msg = typeguards.isError(err) ? err.message : (err as Record<string, unknown>)?.code;
+    throw new Error(`Unable to read ${fileName} (${msg ?? "unknown error"})`);
+  }
+}

src/utils/index.ts

@@ -49,6 +49,7 @@ export {
 // Utils specifically for this bot.
 export * from "./SDKUtils";
 export * from "./chains";
+export * from "./fsUtils";
 export * from "./ProviderUtils";
 export * from "./SignerUtils";
 export * from "./DepositUtils";