Feature/sse (#3125)

* Base changes for ServerSide Events (instead of socket.io)

* lint fixes

* adding of interface and separate methods for streaming events

* lint

* first draft, handles both internal and external prediction end points.

* lint fixes

* additional internal end point for streaming and associated changes

* return streamresponse as true to build agent flow

* 1) JSON formatting for internal events
2) other fixes

* 1) convert internal event to metadata to maintain consistency with external response

* fix action and metadata streaming

* fix for error when agent flow is aborted

* prevent subflows from streaming and other code cleanup

* prevent streaming from enclosed tools

* add fix for preventing chaintool streaming

* update lock file

* add open when hidden to sse

* Streaming errors

* Streaming errors

* add fix for showing error message

---------

Co-authored-by: Henry <hzj94@hotmail.com>

packages/components/nodes/chains/LLMChain/LLMChain.ts

@@ -4,7 +4,15 @@ import { HumanMessage } from '@langchain/core/messages'
 import { ChatPromptTemplate, FewShotPromptTemplate, HumanMessagePromptTemplate, PromptTemplate } from '@langchain/core/prompts'
 import { OutputFixingParser } from 'langchain/output_parsers'
 import { LLMChain } from 'langchain/chains'
-import { IVisionChatModal, ICommonObject, INode, INodeData, INodeOutputsValue, INodeParams } from '../../../src/Interface'
+import {
+    IVisionChatModal,
+    ICommonObject,
+    INode,
+    INodeData,
+    INodeOutputsValue,
+    INodeParams,
+    IServerSideEventStreamer
+} from '../../../src/Interface'
 import { additionalCallbacks, ConsoleCallbackHandler, CustomChainHandler } from '../../../src/handler'
 import { getBaseClasses, handleEscapeCharacters } from '../../../src/utils'
 import { checkInputs, Moderation, streamResponse } from '../../moderation/Moderation'
@@ -162,18 +170,22 @@ const runPrediction = async (
     const loggerHandler = new ConsoleCallbackHandler(options.logger)
     const callbacks = await additionalCallbacks(nodeData, options)
 
-    const isStreaming = !disableStreaming && options.socketIO && options.socketIOClientId
-    const socketIO = isStreaming ? options.socketIO : undefined
-    const socketIOClientId = isStreaming ? options.socketIOClientId : ''
     const moderations = nodeData.inputs?.inputModeration as Moderation[]
 
+    // this is true if the prediction is external and the client has requested streaming='true'
+    const shouldStreamResponse = !disableStreaming && options.shouldStreamResponse
+    const sseStreamer: IServerSideEventStreamer = options.sseStreamer as IServerSideEventStreamer
+    const chatId = options.chatId
+
     if (moderations && moderations.length > 0) {
         try {
             // Use the output of the moderation chain as input for the LLM chain
             input = await checkInputs(moderations, input)
         } catch (e) {
             await new Promise((resolve) => setTimeout(resolve, 500))
-            streamResponse(isStreaming, e.message, socketIO, socketIOClientId)
+            if (shouldStreamResponse) {
+                streamResponse(sseStreamer, chatId, e.message)
+            }
             return formatResponse(e.message)
         }
     }
@@ -245,8 +257,8 @@ const runPrediction = async (
         if (seen.length === 0) {
             // All inputVariables have fixed values specified
             const options = { ...promptValues }
-            if (isStreaming) {
-                const handler = new CustomChainHandler(socketIO, socketIOClientId)
+            if (shouldStreamResponse) {
+                const handler = new CustomChainHandler(sseStreamer, chatId)
                 const res = await chain.call(options, [loggerHandler, handler, ...callbacks])
                 return formatResponse(res?.text)
             } else {
@@ -261,8 +273,8 @@ const runPrediction = async (
                 ...promptValues,
                 [lastValue]: input
             }
-            if (isStreaming) {
-                const handler = new CustomChainHandler(socketIO, socketIOClientId)
+            if (shouldStreamResponse) {
+                const handler = new CustomChainHandler(sseStreamer, chatId)
                 const res = await chain.call(options, [loggerHandler, handler, ...callbacks])
                 return formatResponse(res?.text)
             } else {
@@ -273,8 +285,9 @@ const runPrediction = async (
             throw new Error(`Please provide Prompt Values for: ${seen.join(', ')}`)
         }
     } else {
-        if (isStreaming) {
-            const handler = new CustomChainHandler(socketIO, socketIOClientId)
+        if (shouldStreamResponse) {
+            const handler = new CustomChainHandler(sseStreamer, chatId)
+
             const res = await chain.run(input, [loggerHandler, handler, ...callbacks])
             return formatResponse(res)
         } else {