TLDR: After writing a JSON (successfully) to my Firestore, the next request will give me Internal Server Error (500). I have a suspicion that the problem is that inserting is not yet complete.
So basically, I have this code:
const jsonToDb = express();
exports.jsondb = functions.region('europe-west1').https.onRequest(jsonToDb);
jsonToDb.post('', (req, res) => {
let doc;
try {
doc = JSON.parse(req.body);
} catch(error) {
res.status(400).send(error.toString()).end();
return;
}
myDbFuncs.saveMyDoc(doc);
res.status(201).send("OK").end();
}
The database functions are in another JS file.
module.exports.saveMyDoc = function (myDoc) {
let newDoc = db.collection('insertedDocs').doc(new Date().toISOString());
newDoc.set(myDoc).then().catch();
return;
};
So I have several theories, maybe one of them is not wrong, but please help me with this. (Also if I made some mistakes in this little snippet, just tell me.)
Reproduction:
I send the first request => everything is OK, Json in the database.
I send a second request after the first request give me OK status => it does not do anything for a few secs, then 500: Internal Server Error.
Logs: Function execution took 4345 ms, finished with status: 'connection error'.
I just don't understand. Let's imagine I'm using this as an API, several requests simultaneously. Can't it handle? (I suppose it can handle, just I do something stupid.) Deliberately, I'm sending the second request after the first has finished and this occurs.
Should I make the saveMyDoc async?
saveMyDoc isn't returning a promise that resolves when all the async work is complete. If you lose track of a promise, Cloud Functions will shut down the work and clean up before the work is complete, making it look like it simply doesn't work. You should only send a response from an HTTP type function after all the work is fully complete.
Minimally, it should look more like this:
module.exports.saveMyDoc = function (myDoc) {
let newDoc = db.collection('insertedDocs').doc(new Date().toISOString());
return newDoc.set(myDoc);
};
Then you would use the promise in your main function:
myDbFuncs.saveMyDoc(doc).then(() => {
res.status(201).send("OK").end();
}
See how the response is only sent after the data is saved.
Read more about async programming in Cloud Functions in the documentation. Also watch this video series that talks about working with promises in Cloud Functions.
Related
I am currently building a data connector but would like to throw and error out to the user if the date range they have provided is not supported by my API endpoint (we don't have data for more than 90 days). I looked through the documentation and found this: https://developers.google.com/datastudio/connector/error-handling#user-facing-errors
And copied the code example exactly and tried to run it but my project still isn't showing the error dialog box back to the user.
I've also taken a look at how other people implement this in this repository (https://github.com/googledatastudio/community-connectors) but still can't see an issue with what I wrote.
function getData(request) {
try {
var dataSchema = getDataSchema(request);
var data = lookupRequestData(request, dataSchema);
} catch (e) {
console.log('pre throw');
// throw Error('some error!');
cc.newUserError()
.setDebugText('Error fetching data from API. Exception details: ' + e)
.setText('There was an error communicating with the service. Try again later, or file an issue if this error persists.')
.throwException();
console.log('post throw');
}
return {
schema: dataSchema,
rows: data
};
}
I can see both the pre throw and post throw strings in my log but there is still no error message being displayed. Just wondering if someone might be able to offer a bit of advice for other things to try.
Thanks
I am writing a private plugin for nodebb (open forum software). In the nodebb's webserver.js file there is a line that seems to be hogging all incoming json data.
app.use(bodyParser.json(jsonOpts));
I am trying to convert all incoming json data for one of my end-points into raw data. However the challenge is I cannot remove or modify the line above.
The following code works ONLY if I temporarily remove the line above.
var rawBodySaver = function (req, res, buf, encoding) {
if (buf && buf.length) {
req.rawBody = buf.toString(encoding || 'utf8');
}
}
app.use(bodyParser.json({ verify: rawBodySaver }));
However as soon as I put the app.use(bodyParser.json(jsonOpts)); middleware back into the webserver.js file it stops working. So it seems like body-parser only processes the first parser that matches the incoming data type and then skips all the rest?
How can I get around that? I could not find any information in their official documentation.
Any help is greatly appreciated.
** Update **
The problem I am trying to solve is to correctly handle an incoming stripe webhook event. In the official stripe documentation they suggested I do the following:
// Match the raw body to content type application/json
app.post('/webhook', bodyParser.raw({type: 'application/json'}),
(request, response) => {
const sig = request.headers['stripe-signature'];
let event;
try {
event = stripe.webhooks.constructEvent(request.body, sig,
endpointSecret);
} catch (err) {
return response.status(400).send(Webhook Error:
${err.message});
}
Both methods, the original at the top of this post and the official stripe recommended way, construct the stripe event correctly but only if I remove the middleware in webserver. So my understanding now is that you cannot have multiple middleware to handle the same incoming data. I don't have much wiggle room when it comes to the first middleware except for being able to modify the argument (jsonOpts) that is being passed to it and comes from a .json file. I tried adding a verify field but I couldn't figure out how to add a function as its value. I hope this makes sense and sorry for not stating what problem I am trying to solve initially.
The only solution I can find without modifying the NodeBB code is to insert your middleware in a convenient hook (that will be later than you want) and then hack into the layer list in the app router to move that middleware earlier in the app layer list to get it in front of the things you want to be in front of.
This is a hack so if Express changes their internal implementation at some future time, then this could break. But, if they ever changed this part of the implementation, it would likely only be in a major revision (as in Express 4 ==> Express 5) and you could just adapt the code to fit the new scheme or perhaps NodeBB will have given you an appropriate hook by then.
The basic concept is as follows:
Get the router you need to modify. It appears it's the app router you want for NodeBB.
Insert your middleware/route as you normally would to allow Express to do all the normal setup for your middleware/route and insert it in the internal Layer list in the app router.
Then, reach into the list, take it off the end of the list (where it was just added) and insert it earlier in the list.
Figure out where to put it earlier in the list. You probably don't want it at the very start of the list because that would put it after some helpful system middleware that makes things like query parameter parsing work. So, the code looks for the first middleware that has a name we don't recognize from the built-in names we know and insert it right after that.
Here's the code for a function to insert your middleware.
function getAppRouter(app) {
// History:
// Express 4.x throws when accessing app.router and the router is on app._router
// But, the router is lazy initialized with app.lazyrouter()
// Express 5.x again supports app.router
// And, it handles the lazy construction of the router for you
let router;
try {
router = app.router; // Works for Express 5.x, Express 4.x will throw when accessing
} catch(e) {}
if (!router) {
// Express 4.x
if (typeof app.lazyrouter === "function") {
// make sure router has been created
app.lazyrouter();
}
router = app._router;
}
if (!router) {
throw new Error("Couldn't find app router");
}
return router;
}
// insert a method on the app router near the front of the list
function insertAppMethod(app, method, path, fn) {
let router = getAppRouter(app);
let stack = router.stack;
// allow function to be called with no path
// as insertAppMethod(app, metod, fn);
if (typeof path === "function") {
fn = path;
path = null;
}
// add the handler to the end of the list
if (path) {
app[method](path, fn);
} else {
app[method](fn);
}
// now remove it from the stack
let layerObj = stack.pop();
// now insert it near the front of the stack,
// but after a couple pre-built middleware's installed by Express itself
let skips = new Set(["query", "expressInit"]);
for (let i = 0; i < stack.length; i++) {
if (!skips.has(stack[i].name)) {
// insert it here before this item
stack.splice(i, 0, layerObj);
break;
}
}
}
You would then use this to insert your method like this from any NodeBB hook that provides you the app object sometime during startup. It will create your /webhook route handler and then insert it earlier in the layer list (before the other body-parser middleware).
let rawMiddleware = bodyParser.raw({type: 'application/json'});
insertAppMethod(app, 'post', '/webhook', (request, response, next) => {
rawMiddleware(request, response, (err) => {
if (err) {
next(err);
return;
}
const sig = request.headers['stripe-signature'];
let event;
try {
event = stripe.webhooks.constructEvent(request.body, sig, endpointSecret);
// you need to either call next() or send a response here
} catch (err) {
return response.status(400).send(`Webhook Error: ${err.message}`);
}
});
});
The bodyParser.json() middleware does the following:
Check the response type of an incoming request to see if it is application/json.
If it is that type, then read the body from the incoming stream to get all the data from the stream.
When it has all the data from the stream, parse it as JSON and put the result into req.body so follow-on request handlers can access the already-read and already-parsed data there.
Because it reads the data from the stream, there is no longer any more data in the stream. Unless it saves the raw data somewhere (I haven't looked to see if it does), then the original RAW data is gone - it's been read from the stream already. This is why you can't have multiple different middleware all trying to process the same request body. Whichever one goes first reads the data from the incoming stream and then the original data is no longer there in the stream.
To help you find a solution, we need to know what end-problem you're really trying to solve? You will not be able to have two middlewares both looking for the same content-type and both reading the request body. You could replace bodyParser.json() that does both what it does now and does something else for your purpose in the same middleware, but not in separate middleware.
I see that JSON.stringify and JSON.parse are both sycnhronous.
I would like to know if there a simple npm library that does this in an asynchonous way .
Thank you
You can make anything "asynchronous" by using Promises:
function asyncStringify(str) {
return new Promise((resolve, reject) => {
resolve(JSON.stringify(str));
});
}
Then you can use it like any other promise:
asyncStringfy(str).then(ajaxSubmit);
Note that because the code is not asynchronous, the promise will be resolved right away (there's no blocking operation on stringifying a JSON, it doesn't require any system call).
You can also use the async/await API if your platform supports it:
async function asyncStringify(str) {
return JSON.stringify(str);
}
Then you can use it the same way:
asyncStringfy(str).then(ajaxSubmit);
// or use the "await" API
const strJson = await asyncStringify(str);
ajaxSubmit(strJson);
Edited: One way of adding true asynchrnous parsing/stringifying (maybe because we're parsing something too complex) is to pass the job to another process (or service) and wait on the response.
You can do this in many ways (like creating a new service that shares a REST API), I will demonstrate here a way of doing this with message passing between processes:
First create a file that will take care of doing the parsing/stringifying. Call it async-json.js for the sake of the example:
// async-json.js
function stringify(value) {
return JSON.stringify(value);
}
function parse(value) {
return JSON.parse(value);
}
process.on('message', function(message) {
let result;
if (message.method === 'stringify') {
result = stringify(message.value)
} else if (message.method === 'parse') {
result = parse(message.value);
}
process.send({ callerId: message.callerId, returnValue: result });
});
All this process does is wait a message asking to stringify or parse a JSON and then respond with the right value.
Now, on your code, you can fork this script and send messages back and forward. Whenever a request is sent, you create a new promise, whenever a response comes back to that request, you can resolve the promise:
const fork = require('child_process').fork;
const asyncJson = fork(__dirname + '/async-json.js');
const callers = {};
asyncJson.on('message', function(response) {
callers[response.callerId].resolve(response.returnValue);
});
function callAsyncJson(method, value) {
const callerId = parseInt(Math.random() * 1000000);
const callPromise = new Promise((resolve, reject) => {
callers[callerId] = { resolve: resolve, reject: reject };
asyncJson.send({ callerId: callerId, method: method, value: value });
});
return callPromise;
}
function JsonStringify(value) {
return callAsyncJson('stringify', value);
}
function JsonParse(value) {
return callAsyncJson('parse', value);
}
JsonStringify({ a: 1 }).then(console.log.bind(console));
JsonParse('{ "a": "1" }').then(console.log.bind(console));
Note: this is just one example, but knowing this you can figure out other improvements or other ways to do it. Hope this is helpful.
Check this out, another npm package-
async-json is a library that provides an asynchronous version of the standard JSON.stringify.
Install-
npm install async-json
Example-
var asyncJSON = require('async-json');
asyncJSON.stringify({ some: "data" }, function (err, jsonValue) {
if (err) {
throw err;
}
jsonValue === '{"some":"data"}';
});
Note-Didn't test it, you need to manually check it's dependency and
required packages.
By asynchronous I assume you actually mean non-blocking asynchronous - i.e., if you have a large (megabytes large) JSON string, and you stringify, you don't want your web server to hard freeze and block newly incoming web requests for 500+ milliseconds while it processes the object.
Option 1
The generic answer is to iterate through your object piece by piece, and to then call setImmedate whenever a threshold is reached. This then allows other functions in the event queue to run for a bit.
For JSON (de)serialization, the yieldable-json library does this very well. It does however drastically sacrifice JSON processing time (which is somewhat intentional).
Usage example from the yieldable-json readme:
const yj = require('yieldable-json')
yj.stringifyAsync({key:"value"}, (err, data) => {
if (!err)
console.log(data)
})
Option 2
If processing speed is extremely important (such as with real-time data), you may want to consider spawning multiple Node threads instead. I've used used the PM2 Process Manager with great success, although initial setup was quite daunting. Once it works however, the final result is magic, and does not require modifying your source code, just your package.json file. It acts as a proxy, load balancer, and monitoring tool for Node applications. It's somewhat analogous to Docker swarm, but bare metal, and does not require a special client on the server.
I've read the Feathers book, so I know that to create an error response I simply instantiate the appropriate feathers-errors class:
import {BadRequest} from 'feathers-errors';
const errorResponse = new BadRequest(`foo`, `bar`);
However, I'm having difficulty returning that error response to the user. Even when I create an endpoint that does nothing but return an error response ...
class SomeService {
create(data) {
return new BadRequest(`foo`, `bar`);
}
}
it doesn't work: instead of getting an error response, I get no response, and inside the Chrome debugger I can see that the response is pending (until it eventually times out and becomes an ERR_EMPTY_RESPONSE).
I tried reading about Express error handling, and in the examples I saw people used next to wrap the the response. However, next comes from the error handler, and I'm not sure where in my Feathers code I can get that next function.
If anyone could help explain (using next or not) how I can return a complete, not pending, error response, I would greatly appreciate it.
Your services have to return a promise. If your code is not asynchronous you can turn it into a promise with Promise.resolve and Promise.reject:
class SomeService {
create(data) {
return Promise.reject(new BadRequest(`foo`, `bar`));
}
}
Also make sure you registered the Express error handler to get nicely formatted errors:
const errorHandler = require('feathers-errors/handler');
// Last in the chain
app.use(errorHandler);
There is also more information in the error handling chapter.
First, I need to tell you that I am very new to the wonders of nodejs, socketstream, angularjs and JavaScript in general. I come from a Java background and this might explain my ignorance of the correct way of doing things async.
To toy around with things I installed the ss-angular-demo from americanyak. My problem is now that the Rpc seems to be a synchronous interface and my call the the mysql database has an asynchronous interface. How can I return the database results upon a call of the Rpc?
Here is what I did so far with socketstream 0.3:
In app.js I successfully tell ss to allow my mysql database connection to be accessed by putting ss.api.add('coolStore',mysqlConn); in there at the right place (as explained in the socketstream docs). I use the mysql npm, so I can call mysql within the Rpc
server/rpc/coolRpc.js
exports.actions = function (req, res, ss) {
// use session middleware
req.use('session');
return {
get: function(threshold){
var sql = "SELECT cool.id, cool.score, cool.data FROM cool WHERE cool.score > " + threshold;
if (!ss.arbStore) {
console.log("connecting to mysql arb data store");
ss.coolStore = ss.coolStore.connect();
}
ss.coolStore.query(sql, function(err, rows, fields) {
if(err) {
console.log("error fetching stuff", err);
} else {
console.log("first row = "+rows[0].id);
}
});
var db_rows = ???
return res(null, db_rows || []);
}
}
The console logs the id of my database entry, as expected. However, I am clueless how I can make the Rpc's return statement return the rows of my query. What is the right way of addressing this sort of problem?
Thanks for your help. Please be friendly with me, because this is also my first question on stackoverflow.
It's not synchronous. When your results are ready, you can send them back:
exports.actions = function (req, res, ss) {
// use session middleware
req.use('session');
return {
get: function(threshold){
...
ss.coolStore.query(sql, function(err, rows, fields) {
res(err, rows || []);
});
}
}
};
You need to make sure that you always call res(...) from an RPC function, even when an error occurs, otherwise you might get dangling requests (where the client code keeps waiting for a response that's never generated). In the code above, the error is forwarded to the client so it can be handled there.