Merge branch 'development' into moveOutDocGenerator

* development: (36 commits)
  Fix english translations
  Fix footer on mobile
  re-add google analytics code
  Fix Russian translation
  Move all dependencies on @0xproject/types out of devDependencies
  Slight improvement to footer
  Fix a few Korean translations
  Address feedback
  Use source tree hash instead of compile flag
  Fix race condition
  Update CHANGELOG
  Delete artifacts directory
  Add generated contract artifacts to gitignore
  Check dependencies when determining if should be recompiled
  Update CHANGELOG
  Remove unused CHANGELOG entry
  Remove unused import
  Change assert.doesConformToShema interface
  Remove a type assertion
  Publish
  ...

6 files changed, 58 insertions, 7 deletions

diff --git a/packages/connect/src/http_client.ts b/packages/connect/src/http_client.ts
index 9e5f0f448..cf0aaef0d 100644
--- a/packages/connect/src/http_client.ts
+++ b/packages/connect/src/http_client.ts
@@ -172,13 +172,12 @@ export class HttpClient implements Client {
             body: JSON.stringify(payload),
             headers,
         });
-        const json = await response.json();
+        const text = await response.text();
         if (!response.ok) {
-            const errorString = `${response.status} - ${response.statusText}\n${requestType} ${url}\n${JSON.stringify(
-                json,
-            )}`;
+            const errorString = `${response.status} - ${response.statusText}\n${requestType} ${url}\n${text}`;
             throw Error(errorString);
         }
-        return json;
+        const result = !_.isEmpty(text) ? JSON.parse(text) : undefined;
+        return result;
     }
 }
diff --git a/packages/connect/src/index.ts b/packages/connect/src/index.ts
index 344a32e28..bb42384f9 100644
--- a/packages/connect/src/index.ts
+++ b/packages/connect/src/index.ts
@@ -17,4 +17,5 @@ export {
     TokenPairsItem,
     TokenPairsRequestOpts,
     TokenTradeInfo,
+    WebSocketOrderbookChannelConfig,
 } from './types';
diff --git a/packages/connect/src/schemas/schemas.ts b/packages/connect/src/schemas/schemas.ts
index 0b8b798a9..b9a8472fb 100644
--- a/packages/connect/src/schemas/schemas.ts
+++ b/packages/connect/src/schemas/schemas.ts
@@ -3,6 +3,7 @@ import { orderBookRequestSchema } from './orderbook_request_schema';
 import { ordersRequestOptsSchema } from './orders_request_opts_schema';
 import { pagedRequestOptsSchema } from './paged_request_opts_schema';
 import { tokenPairsRequestOptsSchema } from './token_pairs_request_opts_schema';
+import { webSocketOrderbookChannelConfigSchema } from './websocket_orderbook_channel_config_schema';
 
 export const schemas = {
     feesRequestSchema,
@@ -10,4 +11,5 @@ export const schemas = {
     ordersRequestOptsSchema,
     pagedRequestOptsSchema,
     tokenPairsRequestOptsSchema,
+    webSocketOrderbookChannelConfigSchema,
 };
diff --git a/packages/connect/src/schemas/websocket_orderbook_channel_config_schema.ts b/packages/connect/src/schemas/websocket_orderbook_channel_config_schema.ts
new file mode 100644
index 000000000..81c0cac9c
--- /dev/null
+++ b/packages/connect/src/schemas/websocket_orderbook_channel_config_schema.ts
@@ -0,0 +1,10 @@
+export const webSocketOrderbookChannelConfigSchema = {
+    id: '/WebSocketOrderbookChannelConfig',
+    type: 'object',
+    properties: {
+        heartbeatIntervalMs: {
+            type: 'number',
+            minimum: 10,
+        },
+    },
+};
diff --git a/packages/connect/src/types.ts b/packages/connect/src/types.ts
index 970eff498..5f837b0b3 100644
--- a/packages/connect/src/types.ts
+++ b/packages/connect/src/types.ts
@@ -44,6 +44,13 @@ export interface OrderbookChannel {
 }
 
 /*
+ * heartbeatInterval: Interval in milliseconds that the orderbook channel should ping the underlying websocket. Default: 15000
+ */
+export interface WebSocketOrderbookChannelConfig {
+    heartbeatIntervalMs?: number;
+}
+
+/*
  * baseTokenAddress: The address of token designated as the baseToken in the currency pair calculation of price
  * quoteTokenAddress: The address of token designated as the quoteToken in the currency pair calculation of price
  * snapshot: If true, a snapshot of the orderbook will be sent before the updates to the orderbook
diff --git a/packages/connect/src/ws_orderbook_channel.ts b/packages/connect/src/ws_orderbook_channel.ts
index 822a022f4..5aa730d8f 100644
--- a/packages/connect/src/ws_orderbook_channel.ts
+++ b/packages/connect/src/ws_orderbook_channel.ts
@@ -3,6 +3,7 @@ import { schemas } from '@0xproject/json-schemas';
 import * as _ from 'lodash';
 import * as WebSocket from 'websocket';
 
+import { schemas as clientSchemas } from './schemas/schemas';
 import {
     OrderbookChannel,
     OrderbookChannelHandler,
@@ -10,9 +11,13 @@ import {
     OrderbookChannelSubscriptionOpts,
     WebsocketClientEventType,
     WebsocketConnectionEventType,
+    WebSocketOrderbookChannelConfig,
 } from './types';
 import { orderbookChannelMessageParser } from './utils/orderbook_channel_message_parser';
 
+const DEFAULT_HEARTBEAT_INTERVAL_MS = 15000;
+const MINIMUM_HEARTBEAT_INTERVAL_MS = 10;
+
 /**
  * This class includes all the functionality related to interacting with a websocket endpoint
  * that implements the standard relayer API v0
@@ -21,15 +26,25 @@ export class WebSocketOrderbookChannel implements OrderbookChannel {
     private _apiEndpointUrl: string;
     private _client: WebSocket.client;
     private _connectionIfExists?: WebSocket.connection;
+    private _heartbeatTimerIfExists?: NodeJS.Timer;
     private _subscriptionCounter = 0;
+    private _heartbeatIntervalMs: number;
     /**
      * Instantiates a new WebSocketOrderbookChannel instance
      * @param   url                 The relayer API base WS url you would like to interact with
+     * @param   config              The configuration object. Look up the type for the description.
      * @return  An instance of WebSocketOrderbookChannel
      */
-    constructor(url: string) {
+    constructor(url: string, config?: WebSocketOrderbookChannelConfig) {
         assert.isUri('url', url);
+        if (!_.isUndefined(config)) {
+            assert.doesConformToSchema('config', config, clientSchemas.webSocketOrderbookChannelConfigSchema);
+        }
         this._apiEndpointUrl = url;
+        this._heartbeatIntervalMs =
+            _.isUndefined(config) || _.isUndefined(config.heartbeatIntervalMs)
+                ? DEFAULT_HEARTBEAT_INTERVAL_MS
+                : config.heartbeatIntervalMs;
         this._client = new WebSocket.client();
     }
     /**
@@ -63,7 +78,7 @@ export class WebSocketOrderbookChannel implements OrderbookChannel {
                 connection.on(WebsocketConnectionEventType.Error, wsError => {
                     handler.onError(this, subscriptionOpts, wsError);
                 });
-                connection.on(WebsocketConnectionEventType.Close, () => {
+                connection.on(WebsocketConnectionEventType.Close, (code: number, desc: string) => {
                     handler.onClose(this, subscriptionOpts);
                 });
                 connection.on(WebsocketConnectionEventType.Message, message => {
@@ -80,6 +95,9 @@ export class WebSocketOrderbookChannel implements OrderbookChannel {
         if (!_.isUndefined(this._connectionIfExists)) {
             this._connectionIfExists.close();
         }
+        if (!_.isUndefined(this._heartbeatTimerIfExists)) {
+            clearInterval(this._heartbeatTimerIfExists);
+        }
     }
     private _getConnection(callback: (error?: Error, connection?: WebSocket.connection) => void) {
         if (!_.isUndefined(this._connectionIfExists) && this._connectionIfExists.connected) {
@@ -87,6 +105,20 @@ export class WebSocketOrderbookChannel implements OrderbookChannel {
         } else {
             this._client.on(WebsocketClientEventType.Connect, connection => {
                 this._connectionIfExists = connection;
+                if (this._heartbeatIntervalMs >= MINIMUM_HEARTBEAT_INTERVAL_MS) {
+                    this._heartbeatTimerIfExists = setInterval(() => {
+                        connection.ping('');
+                    }, this._heartbeatIntervalMs);
+                } else {
+                    callback(
+                        new Error(
+                            `Heartbeat interval is ${
+                                this._heartbeatIntervalMs
+                            }ms which is less than the required minimum of ${MINIMUM_HEARTBEAT_INTERVAL_MS}ms`,
+                        ),
+                        undefined,
+                    );
+                }
                 callback(undefined, this._connectionIfExists);
             });
             this._client.on(WebsocketClientEventType.ConnectFailed, error => {