|
| 1 | +{ |
| 2 | + "cells": [ |
| 3 | + { |
| 4 | + "cell_type": "markdown", |
| 5 | + "metadata": {}, |
| 6 | + "source": [ |
| 7 | + "# How to cancel execution\n", |
| 8 | + "\n", |
| 9 | + "```{=mdx}\n", |
| 10 | + ":::info Prerequisites\n", |
| 11 | + "\n", |
| 12 | + "This guide assumes familiarity with the following concepts:\n", |
| 13 | + "\n", |
| 14 | + "- [LangChain Expression Language](/docs/concepts/#langchain-expression-language)\n", |
| 15 | + "- [Chains](/docs/how_to/sequence/)\n", |
| 16 | + "- [Streaming](/docs/how_to/streaming/)\n", |
| 17 | + "\n", |
| 18 | + ":::\n", |
| 19 | + "```\n", |
| 20 | + "\n", |
| 21 | + "When building longer-running chains or [LangGraph](https://langchain-ai.github.io/langgraphjs/) agents, you may want to interrupt execution in situations such as a user leaving your app or submitting a new query.\n", |
| 22 | + "\n", |
| 23 | + "[LangChain Expression Language (LCEL)](/docs/concepts#langchain-expression-language) supports aborting runnables that are in-progress via a runtime [signal](https://developer.mozilla.org/en-US/docs/Web/API/AbortController/signal) option.\n", |
| 24 | + "\n", |
| 25 | + "```{=mdx}\n", |
| 26 | + ":::caution Compatibility\n", |
| 27 | + "\n", |
| 28 | + "Built-in signal support requires `@langchain/core>=0.2.20`. Please see here for a [guide on upgrading](/docs/how_to/installation/#installing-integration-packages).\n", |
| 29 | + "\n", |
| 30 | + ":::\n", |
| 31 | + "```\n", |
| 32 | + "\n", |
| 33 | + "**Note:** Individual integrations like chat models or retrievers may have missing or differing implementations for aborting execution. Signal support as described in this guide will apply in between steps of a chain.\n", |
| 34 | + "\n", |
| 35 | + "To see how this works, construct a chain such as the one below that performs [retrieval-augmented generation](/docs/tutorials/rag). It answers questions by first searching the web using [Tavily](/docs/integrations/retrievers/tavily), then passing the results to a chat model to generate a final answer:\n", |
| 36 | + "\n", |
| 37 | + "```{=mdx}\n", |
| 38 | + "import ChatModelTabs from \"@theme/ChatModelTabs\";\n", |
| 39 | + "\n", |
| 40 | + "<ChatModelTabs />\n", |
| 41 | + "```" |
| 42 | + ] |
| 43 | + }, |
| 44 | + { |
| 45 | + "cell_type": "code", |
| 46 | + "execution_count": 1, |
| 47 | + "metadata": {}, |
| 48 | + "outputs": [], |
| 49 | + "source": [ |
| 50 | + "// @lc-docs-hide-cell\n", |
| 51 | + "import { ChatAnthropic } from \"@langchain/anthropic\";\n", |
| 52 | + "\n", |
| 53 | + "const llm = new ChatAnthropic({\n", |
| 54 | + " model: \"claude-3-5-sonnet-20240620\",\n", |
| 55 | + "});" |
| 56 | + ] |
| 57 | + }, |
| 58 | + { |
| 59 | + "cell_type": "code", |
| 60 | + "execution_count": 2, |
| 61 | + "metadata": {}, |
| 62 | + "outputs": [], |
| 63 | + "source": [ |
| 64 | + "import { TavilySearchAPIRetriever } from \"@langchain/community/retrievers/tavily_search_api\";\n", |
| 65 | + "import type { Document } from \"@langchain/core/documents\";\n", |
| 66 | + "import { StringOutputParser } from \"@langchain/core/output_parsers\";\n", |
| 67 | + "import { ChatPromptTemplate } from \"@langchain/core/prompts\";\n", |
| 68 | + "import { RunnablePassthrough, RunnableSequence } from \"@langchain/core/runnables\";\n", |
| 69 | + "\n", |
| 70 | + "const formatDocsAsString = (docs: Document[]) => {\n", |
| 71 | + " return docs.map((doc) => doc.pageContent).join(\"\\n\\n\")\n", |
| 72 | + "}\n", |
| 73 | + "\n", |
| 74 | + "const retriever = new TavilySearchAPIRetriever({\n", |
| 75 | + " k: 3,\n", |
| 76 | + "});\n", |
| 77 | + "\n", |
| 78 | + "const prompt = ChatPromptTemplate.fromTemplate(`\n", |
| 79 | + "Use the following context to answer questions to the best of your ability:\n", |
| 80 | + "\n", |
| 81 | + "<context>\n", |
| 82 | + "{context}\n", |
| 83 | + "</context>\n", |
| 84 | + "\n", |
| 85 | + "Question: {question}`)\n", |
| 86 | + "\n", |
| 87 | + "const chain = RunnableSequence.from([\n", |
| 88 | + " {\n", |
| 89 | + " context: retriever.pipe(formatDocsAsString),\n", |
| 90 | + " question: new RunnablePassthrough(),\n", |
| 91 | + " },\n", |
| 92 | + " prompt,\n", |
| 93 | + " llm,\n", |
| 94 | + " new StringOutputParser(),\n", |
| 95 | + "]);" |
| 96 | + ] |
| 97 | + }, |
| 98 | + { |
| 99 | + "cell_type": "markdown", |
| 100 | + "metadata": {}, |
| 101 | + "source": [ |
| 102 | + "If you invoke it normally, you can see it returns up-to-date information:" |
| 103 | + ] |
| 104 | + }, |
| 105 | + { |
| 106 | + "cell_type": "code", |
| 107 | + "execution_count": 3, |
| 108 | + "metadata": {}, |
| 109 | + "outputs": [ |
| 110 | + { |
| 111 | + "name": "stdout", |
| 112 | + "output_type": "stream", |
| 113 | + "text": [ |
| 114 | + "Based on the provided context, the current weather in San Francisco is:\n", |
| 115 | + "\n", |
| 116 | + "Temperature: 17.6°C (63.7°F)\n", |
| 117 | + "Condition: Sunny\n", |
| 118 | + "Wind: 14.4 km/h (8.9 mph) from WSW direction\n", |
| 119 | + "Humidity: 74%\n", |
| 120 | + "Cloud cover: 15%\n", |
| 121 | + "\n", |
| 122 | + "The information indicates it's a sunny day with mild temperatures and light winds. The data appears to be from August 2, 2024, at 17:00 local time.\n" |
| 123 | + ] |
| 124 | + } |
| 125 | + ], |
| 126 | + "source": [ |
| 127 | + "await chain.invoke(\"what is the current weather in SF?\");" |
| 128 | + ] |
| 129 | + }, |
| 130 | + { |
| 131 | + "cell_type": "markdown", |
| 132 | + "metadata": {}, |
| 133 | + "source": [ |
| 134 | + "Now, let's interrupt it early. Initialize an [`AbortController`](https://developer.mozilla.org/en-US/docs/Web/API/AbortController) and pass its `signal` property into the chain execution. To illustrate the fact that the cancellation occurs as soon as possible, set a timeout of 100ms:" |
| 135 | + ] |
| 136 | + }, |
| 137 | + { |
| 138 | + "cell_type": "code", |
| 139 | + "execution_count": 4, |
| 140 | + "metadata": {}, |
| 141 | + "outputs": [ |
| 142 | + { |
| 143 | + "name": "stdout", |
| 144 | + "output_type": "stream", |
| 145 | + "text": [ |
| 146 | + "Error: Aborted\n", |
| 147 | + " at EventTarget.<anonymous> (/Users/jacoblee/langchain/langchainjs/langchain-core/dist/utils/signal.cjs:19:24)\n", |
| 148 | + " at [nodejs.internal.kHybridDispatch] (node:internal/event_target:825:20)\n", |
| 149 | + " at EventTarget.dispatchEvent (node:internal/event_target:760:26)\n", |
| 150 | + " at abortSignal (node:internal/abort_controller:370:10)\n", |
| 151 | + " at AbortController.abort (node:internal/abort_controller:392:5)\n", |
| 152 | + " at Timeout._onTimeout (evalmachine.<anonymous>:7:29)\n", |
| 153 | + " at listOnTimeout (node:internal/timers:573:17)\n", |
| 154 | + " at process.processTimers (node:internal/timers:514:7)\n", |
| 155 | + "timer1: 103.204ms\n" |
| 156 | + ] |
| 157 | + } |
| 158 | + ], |
| 159 | + "source": [ |
| 160 | + "const controller = new AbortController();\n", |
| 161 | + "\n", |
| 162 | + "const startTimer = console.time(\"timer1\");\n", |
| 163 | + "\n", |
| 164 | + "setTimeout(() => controller.abort(), 100);\n", |
| 165 | + "\n", |
| 166 | + "try {\n", |
| 167 | + " await chain.invoke(\"what is the current weather in SF?\", {\n", |
| 168 | + " signal: controller.signal,\n", |
| 169 | + " });\n", |
| 170 | + "} catch (e) {\n", |
| 171 | + " console.log(e);\n", |
| 172 | + "}\n", |
| 173 | + "\n", |
| 174 | + "console.timeEnd(\"timer1\");" |
| 175 | + ] |
| 176 | + }, |
| 177 | + { |
| 178 | + "cell_type": "markdown", |
| 179 | + "metadata": {}, |
| 180 | + "source": [ |
| 181 | + "And you can see that execution ends after just over 100ms. Looking at [this LangSmith trace](https://smith.langchain.com/public/63c04c3b-2683-4b73-a4f7-fb12f5cb9180/r), you can see that the model is never called.\n", |
| 182 | + "\n", |
| 183 | + "## Streaming\n", |
| 184 | + "\n", |
| 185 | + "You can pass a `signal` when streaming too. This gives you more control over using a `break` statement within the `for await... of` loop to cancel the current run, which will only trigger after final output has already started streaming. The below example uses a `break` statement - note the time elapsed before cancellation occurs:" |
| 186 | + ] |
| 187 | + }, |
| 188 | + { |
| 189 | + "cell_type": "code", |
| 190 | + "execution_count": 5, |
| 191 | + "metadata": {}, |
| 192 | + "outputs": [ |
| 193 | + { |
| 194 | + "name": "stdout", |
| 195 | + "output_type": "stream", |
| 196 | + "text": [ |
| 197 | + "chunk \n", |
| 198 | + "timer2: 3.990s\n" |
| 199 | + ] |
| 200 | + } |
| 201 | + ], |
| 202 | + "source": [ |
| 203 | + "const startTimer2 = console.time(\"timer2\");\n", |
| 204 | + "\n", |
| 205 | + "const stream = await chain.stream(\"what is the current weather in SF?\");\n", |
| 206 | + "\n", |
| 207 | + "for await (const chunk of stream) {\n", |
| 208 | + " console.log(\"chunk\", chunk);\n", |
| 209 | + " break;\n", |
| 210 | + "}\n", |
| 211 | + "\n", |
| 212 | + "console.timeEnd(\"timer2\");" |
| 213 | + ] |
| 214 | + }, |
| 215 | + { |
| 216 | + "cell_type": "markdown", |
| 217 | + "metadata": {}, |
| 218 | + "source": [ |
| 219 | + "Now compare this to using a signal. Note that you will need to wrap the stream in a `try/catch` block:" |
| 220 | + ] |
| 221 | + }, |
| 222 | + { |
| 223 | + "cell_type": "code", |
| 224 | + "execution_count": 6, |
| 225 | + "metadata": {}, |
| 226 | + "outputs": [ |
| 227 | + { |
| 228 | + "name": "stdout", |
| 229 | + "output_type": "stream", |
| 230 | + "text": [ |
| 231 | + "Error: Aborted\n", |
| 232 | + " at EventTarget.<anonymous> (/Users/jacoblee/langchain/langchainjs/langchain-core/dist/utils/signal.cjs:19:24)\n", |
| 233 | + " at [nodejs.internal.kHybridDispatch] (node:internal/event_target:825:20)\n", |
| 234 | + " at EventTarget.dispatchEvent (node:internal/event_target:760:26)\n", |
| 235 | + " at abortSignal (node:internal/abort_controller:370:10)\n", |
| 236 | + " at AbortController.abort (node:internal/abort_controller:392:5)\n", |
| 237 | + " at Timeout._onTimeout (evalmachine.<anonymous>:7:38)\n", |
| 238 | + " at listOnTimeout (node:internal/timers:573:17)\n", |
| 239 | + " at process.processTimers (node:internal/timers:514:7)\n", |
| 240 | + "timer3: 100.684ms\n" |
| 241 | + ] |
| 242 | + } |
| 243 | + ], |
| 244 | + "source": [ |
| 245 | + "const controllerForStream = new AbortController();\n", |
| 246 | + "\n", |
| 247 | + "const startTimer3 = console.time(\"timer3\");\n", |
| 248 | + "\n", |
| 249 | + "setTimeout(() => controllerForStream.abort(), 100);\n", |
| 250 | + "\n", |
| 251 | + "try {\n", |
| 252 | + " const streamWithSignal = await chain.stream(\"what is the current weather in SF?\", {\n", |
| 253 | + " signal: controllerForStream.signal\n", |
| 254 | + " });\n", |
| 255 | + " for await (const chunk of streamWithSignal) {\n", |
| 256 | + " console.log(chunk);\n", |
| 257 | + " break;\n", |
| 258 | + " } \n", |
| 259 | + "} catch (e) {\n", |
| 260 | + " console.log(e); \n", |
| 261 | + "}\n", |
| 262 | + "\n", |
| 263 | + "console.timeEnd(\"timer3\");" |
| 264 | + ] |
| 265 | + }, |
| 266 | + { |
| 267 | + "cell_type": "markdown", |
| 268 | + "metadata": {}, |
| 269 | + "source": [ |
| 270 | + "## Related\n", |
| 271 | + "\n", |
| 272 | + "- [Pass through arguments from one step to the next](/docs/how_to/passthrough)\n", |
| 273 | + "- [Dispatching custom events](/docs/how_to/callbacks_custom_events)" |
| 274 | + ] |
| 275 | + } |
| 276 | + ], |
| 277 | + "metadata": { |
| 278 | + "kernelspec": { |
| 279 | + "display_name": "TypeScript", |
| 280 | + "language": "typescript", |
| 281 | + "name": "tslab" |
| 282 | + }, |
| 283 | + "language_info": { |
| 284 | + "codemirror_mode": { |
| 285 | + "mode": "typescript", |
| 286 | + "name": "javascript", |
| 287 | + "typescript": true |
| 288 | + }, |
| 289 | + "file_extension": ".ts", |
| 290 | + "mimetype": "text/typescript", |
| 291 | + "name": "typescript", |
| 292 | + "version": "3.7.2" |
| 293 | + } |
| 294 | + }, |
| 295 | + "nbformat": 4, |
| 296 | + "nbformat_minor": 2 |
| 297 | +} |
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