netlify-lambda/lib/serve.js

var express = require("express");
var bodyParser = require("body-parser");
var expressLogging = require("express-logging");
var queryString = require("querystring");
var path = require("path");
var conf = require("./config");
var jwtDecode = require("jwt-decode");

function handleErr(err, response) {
  response.statusCode = 500;
  response.write("Function invocation failed: " + err.toString());
  response.end();
  console.log("Error during invocation: ", err);
  return;
}

function handleInvocationTimeout(response, timeout) {
  response.statusCode = 500;
  response.write(`Function invocation took longer than ${timeout} seconds.`);
  response.end();
  console.log(
    `Your lambda function took longer than ${timeout} seconds to finish.
If you need a longer execution time, you can increase the timeout using the -t or --timeout flag.
Please note that default function invocation is 10 seconds, check our documentation for more information (https://www.netlify.com/docs/functions/#custom-deployment-options).
`
  );
}

function createCallback(response) {
  return function callback(err, lambdaResponse) {
    if (err) {
      return handleErr(err, response);
    }

    response.statusCode = lambdaResponse.statusCode;
    for (const key in lambdaResponse.headers) {
      response.setHeader(key, lambdaResponse.headers[key]);
    }

    if (lambdaResponse.body) {
      response.write(
        lambdaResponse.isBase64Encoded
          ? Buffer.from(lambdaResponse.body, "base64")
          : lambdaResponse.body
      );
    } else {
      if (
        process.env.CONTEXT !== "production" ||
        !process.env.SILENCE_EMPTY_LAMBDA_WARNING
      )
        console.log(
          `Your lambda function didn't return a body, which may be a mistake. Check our Usage docs for examples (https://github.com/netlify/netlify-lambda#usage). 
          If this is intentional, you can silence this warning by setting process.ENV.SILENCE_EMPTY_LAMBDA_WARNING to a truthy value or process.env.CONTEXT to 'production'`
        );
    }
    response.end();
  };
}

function promiseCallback(promise, callback) {
  if (!promise) return;
  if (typeof promise.then !== "function") return;
  if (typeof callback !== "function") return;

  return promise.then(
    function(data) {
      callback(null, data);
    },
    function(err) {
      callback(err, null);
    }
  );
}

function buildClientContext(headers) {
  // inject a client context based on auth header https://github.com/netlify/netlify-lambda/pull/57
  if (!headers["authorization"]) return;

  const parts = headers["authorization"].split(" ");
  if (parts.length !== 2 || parts[0] !== "Bearer") return;

  try {
    return {
      identity: {
        url: "NETLIFY_LAMBDA_LOCALLY_EMULATED_IDENTITY_URL",
        token: "NETLIFY_LAMBDA_LOCALLY_EMULATED_IDENTITY_TOKEN"
      },
      user: jwtDecode(parts[1])
    };
  } catch (e) {
    return; // Ignore errors - bearer token is not a JWT, probably not intended for us
  }
}

function createHandler(dir, static, timeout) {
  return function(request, response) {
    // handle proxies without path re-writes (http-servr)
    var cleanPath = request.path.replace(/^\/.netlify\/functions/, "");

    var func = cleanPath.split("/").filter(e => !!e)[0];
    if (typeof func === "undefined") {
      console.error(
        `Something went wrong and the function path derived from ${cleanPath} (raw form: ${
          request.path
        }) was undefined. Please doublecheck your function naming and toml configuration.`
      );
    }
    if (typeof dir === "undefined") {
      console.error(
        `Something went wrong and the function directory ${dir} was undefined. Please doublecheck your toml configuration.`
      );
    }
    var module = path.join(process.cwd(), dir, func);
    if (static) {
      delete require.cache[require.resolve(module)];
    }
    var handler;
    try {
      handler = require(module);
    } catch (err) {
      handleErr(err, response);
      return;
    }

    var isBase64 =
      request.body &&
      !(request.headers["content-type"] || "").match(
        /text|application|multipart\/form-data/
      );
    var lambdaRequest = {
      path: request.path,
      httpMethod: request.method,
      queryStringParameters: queryString.parse(request.url.split(/\?(.+)/)[1]),
      headers: request.headers,
      body: isBase64
        ? Buffer.from(request.body.toString(), "utf8").toString("base64")
        : request.body,
      isBase64Encoded: isBase64
    };

    var callback = createCallback(response);

    var promise = handler.handler(
      lambdaRequest,
      { clientContext: buildClientContext(request.headers) || {} },
      callback
    );

    var invocationTimeoutRef = null;

    Promise.race([
      promiseCallback(promise, callback),
      new Promise(function(resolve) {
        invocationTimeoutRef = setTimeout(function() {
          handleInvocationTimeout(response, timeout);
          resolve();
        }, timeout * 1000);
      })
    ]).then(
      result => {
        clearTimeout(invocationTimeoutRef);
        return result; // not used, but writing this to avoid future footguns
      },
      err => {
        clearTimeout(invocationTimeoutRef);
        throw err;
      }
    );
  };
}

exports.listen = function(port, static, timeout) {
  var config = conf.load();
  var app = express();
  var dir = config.build.functions || config.build.Functions;
  app.use(bodyParser.raw({ limit: "6mb" }));
  app.use(bodyParser.text({ limit: "6mb", type: "*/*" }));
  app.use(
    expressLogging(console, {
      blacklist: ["/favicon.ico"]
    })
  );

  app.get("/favicon.ico", function(req, res) {
    res.status(204).end();
  });
  app.get("/", function(req, res) {
    res
      .status(404)
      .send(
        `You have requested the root of http://localhost:${port}. This is likely a mistake. netlify-lambda serves functions at htttp://localhost:${port}/.netlify/functions/your-function-name, please fix your code.`
      );
  });
  app.all("*", createHandler(dir, static, timeout));

  app.listen(port, function(err) {
    if (err) {
      console.error("Unable to start lambda server: ", err);
      process.exit(1);
    }

    console.log(`Lambda server is listening on ${port}`);
  });

  return {
    clearCache: function(chunk) {
      var module = path.join(process.cwd(), dir, chunk);
      delete require.cache[require.resolve(module)];
    }
  };
};