FEATURE: add internal support for streaming mode (#42)

Also adds some tests around completions and supports additional params
such as top_p, temperature and max_tokens

This also migrates off Faraday to using Net::HTTP directly

lib/shared/inference/openai_completions.rb

@@ -3,31 +3,88 @@
 module ::DiscourseAi
   module Inference
     class OpenAiCompletions
+      TIMEOUT = 60
+
       CompletionFailed = Class.new(StandardError)
 
-      def self.perform!(messages, model = SiteSetting.ai_helper_model)
-        headers = {
-          "Authorization" => "Bearer #{SiteSetting.ai_openai_api_key}",
-          "Content-Type" => "application/json",
-        }
-
-        connection_opts = { request: { write_timeout: 60, read_timeout: 60, open_timeout: 60 } }
-
-        response =
-          Faraday.new(nil, connection_opts).post(
-            "https://api.openai.com/v1/chat/completions",
-            { model: model, messages: messages }.to_json,
-            headers,
+      def self.perform!(
+        messages,
+        model = SiteSetting.ai_helper_model,
+        temperature: nil,
+        top_p: nil,
+        max_tokens: nil,
+        stream: false,
+        &blk
       )
+        raise ArgumentError, "block must be supplied in streaming mode" if stream && !blk
 
-        if response.status != 200
+        url = URI("https://api.openai.com/v1/chat/completions")
+        headers = {
+          "Content-Type": "application/json",
+          Authorization: "Bearer #{SiteSetting.ai_openai_api_key}",
+        }
+        payload = { model: model, messages: messages }
+
+        payload[:temperature] = temperature if temperature
+        payload[:top_p] = top_p if top_p
+        payload[:max_tokens] = max_tokens if max_tokens
+        payload[:stream] = true if stream
+
+        Net::HTTP.start(
+          url.host,
+          url.port,
+          use_ssl: true,
+          read_timeout: TIMEOUT,
+          open_timeout: TIMEOUT,
+          write_timeout: TIMEOUT,
+        ) do |http|
+          request = Net::HTTP::Post.new(url, headers)
+          request.body = payload.to_json
+
+          response = http.request(request)
+
+          if response.code.to_i != 200
             Rails.logger.error(
-            "OpenAiCompletions: status: #{response.status} - body: #{response.body}",
+              "OpenAiCompletions: status: #{response.code.to_i} - body: #{response.body}",
             )
             raise CompletionFailed
           end
 
-        JSON.parse(response.body, symbolize_names: true)
+          if stream
+            stream(http, response, &blk)
+          else
+            JSON.parse(response.read_body, symbolize_names: true)
+          end
+        end
+      end
+
+      def self.stream(http, response)
+        cancelled = false
+        cancel = lambda { cancelled = true }
+
+        response.read_body do |chunk|
+          if cancelled
+            http.finish
+            break
+          end
+
+          chunk
+            .split("\n")
+            .each do |line|
+              data = line.split("data: ", 2)[1]
+
+              next if data == "[DONE]"
+
+              yield JSON.parse(data, symbolize_names: true), cancel if data
+
+              if cancelled
+                http.finish
+                break
+              end
+            end
+        end
+      rescue IOError
+        raise if !cancelled
       end
     end
   end

spec/shared/inference/openai_completions_spec.rb

@@ -0,0 +1,92 @@
+# frozen_string_literal: true
+require "rails_helper"
+
+describe DiscourseAi::Inference::OpenAiCompletions do
+  before { SiteSetting.ai_openai_api_key = "abc-123" }
+
+  it "can complete a trivial prompt" do
+    body = <<~JSON
+      {"id":"chatcmpl-74OT0yKnvbmTkqyBINbHgAW0fpbxc","object":"chat.completion","created":1681281718,"model":"gpt-3.5-turbo-0301","usage":{"prompt_tokens":12,"completion_tokens":13,"total_tokens":25},"choices":[{"message":{"role":"assistant","content":"1. Serenity\\n2. Laughter\\n3. Adventure"},"finish_reason":"stop","index":0}]}
+    JSON
+
+    stub_request(:post, "https://api.openai.com/v1/chat/completions").with(
+      body:
+        "{\"model\":\"gpt-3.5-turbo\",\"messages\":[{\"role\":\"user\",\"content\":\"write 3 words\"}],\"temperature\":0.5,\"top_p\":0.8,\"max_tokens\":700}",
+      headers: {
+        "Authorization" => "Bearer #{SiteSetting.ai_openai_api_key}",
+        "Content-Type" => "application/json",
+      },
+    ).to_return(status: 200, body: body, headers: {})
+
+    prompt = [role: "user", content: "write 3 words"]
+    completions =
+      DiscourseAi::Inference::OpenAiCompletions.perform!(
+        prompt,
+        "gpt-3.5-turbo",
+        temperature: 0.5,
+        top_p: 0.8,
+        max_tokens: 700,
+      )
+    expect(completions[:choices][0][:message][:content]).to eq(
+      "1. Serenity\n2. Laughter\n3. Adventure",
+    )
+  end
+
+  it "raises an error if attempting to stream without a block" do
+    expect do
+      DiscourseAi::Inference::OpenAiCompletions.perform!([], "gpt-3.5-turbo", stream: true)
+    end.to raise_error(ArgumentError)
+  end
+
+  def stream_line(finish_reason: nil, delta: {})
+    +"data: " << {
+      id: "chatcmpl-#{SecureRandom.hex}",
+      object: "chat.completion.chunk",
+      created: 1_681_283_881,
+      model: "gpt-3.5-turbo-0301",
+      choices: [{ delta: delta }],
+      finish_reason: finish_reason,
+      index: 0,
+    }.to_json
+  end
+
+  it "can operate in streaming mode" do
+    payload = [
+      stream_line(delta: { role: "assistant" }),
+      stream_line(delta: { content: "Mount" }),
+      stream_line(delta: { content: "ain" }),
+      stream_line(delta: { content: " " }),
+      stream_line(delta: { content: "Tree " }),
+      stream_line(delta: { content: "Frog" }),
+      stream_line(finish_reason: "stop"),
+      "[DONE]",
+    ].join("\n\n")
+
+    stub_request(:post, "https://api.openai.com/v1/chat/completions").with(
+      body:
+        "{\"model\":\"gpt-3.5-turbo\",\"messages\":[{\"role\":\"user\",\"content\":\"write 3 words\"}],\"stream\":true}",
+      headers: {
+        "Accept" => "*/*",
+        "Authorization" => "Bearer abc-123",
+        "Content-Type" => "application/json",
+        "Host" => "api.openai.com",
+      },
+    ).to_return(status: 200, body: payload, headers: {})
+
+    prompt = [role: "user", content: "write 3 words"]
+
+    content = +""
+
+    DiscourseAi::Inference::OpenAiCompletions.perform!(
+      prompt,
+      "gpt-3.5-turbo",
+      stream: true,
+    ) do |partial, cancel|
+      data = partial[:choices][0].dig(:delta, :content)
+      content << data if data
+      cancel.call if content.split(" ").length == 2
+    end
+
+    expect(content).to eq("Mountain Tree ")
+  end
+end

spec/support/openai_completions_inference_stubs.rb

@@ -94,7 +94,6 @@ class OpenAiCompletionsInferenceStubs
     end
 
     def stub_prompt(type)
-      prompt_builder = DiscourseAi::AiHelper::LlmPrompt.new
       text = type == TRANSLATE ? spanish_text : translated_response
 
       prompt_messages = CompletionPrompt.find_by(name: type).messages_with_user_input(text)