Catch fails on connection to Mongo

问题

the answer to this question: How to get node to exit when mongo connect fails contains async/wait code for a connection

however, my code (running on node v11.5.0 and mongodb v3.1.13) is failing to catch:

(async function() {
  let db; 
  try {
    db = await MongoClient.connect(uri, { useNewUrlParser: true }); 
    console.log("RETURN", db);
  } catch (err) {
    console.log('EXITING');
    process.exit(1);
  }
}());

to prove the point I intentionally give a uri without credentials:

mongodb://undefined@cluster0-shard-00-00-z4j9e.azure.mongodb.net:27017,cluster0-shard-00-01-z4j9e.azure.mongodb.net:27017,cluster0-shard-00-02-z4j9e.azure.mongodb.net:27017/test?ssl=true&replicaSet=Cluster0-shard-0&authSource=admin&retryWrites=true

and what I get is output like this:

/Users/ekkis/dev/mongo/node_modules/mongodb/lib/topologies/replset.js:346 throw err; ^

MongoError: password must be a string at passwordDigest (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/auth/scram.js:63:43) at ScramSHA1.ScramSHA.auth (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/auth/scram.js:175:25) at authenticate (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/connection/pool.js:232:17) at authenticateLiveConnections (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/connection/pool.js:819:7) at /Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/connection/pool.js:864:5 at waitForLogout (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/connection/pool.js:855:34) at Pool.auth (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/connection/pool.js:862:3) at Server.auth (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/topologies/server.js:931:20) at auth (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/topologies/replset.js:1474:19) at ReplSet.auth (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/topologies/replset.js:1492:5)

so if the error had been caught, the console should have displayed the word 'EXITING', but does not. additionally, I contend an exception was thrown because otherwise the returned value would have been printed, which it was not

how can this be? what do I need to do to get it to work?

* Appendix I *

In fact, the promises version of this exhibits the same odd behaviour, it doesn't catch:

MongoClient
  .connect(uri, { useNewUrlParser: true })
  .then(dbc => {
    console.log('SUCCESS');
    })
  .catch(err => {
    console.log('EXITING');
    process.exit(1);
  });

and yes, I tested the callback version, which also suffers the same malady. Incidentally, passing an empty string for the uri works well. I don't get it

* Appendix II *

In fact, the problem seems to be particular to the credentials passed i.e. if I pass:

mongodb://x:y@cluster0-shard-[...]

I catch a "MongoError: authentication fail" as expected. passing:

mongodb://@cluster0-shard-[...]

interestingly returns a connection but credentials missing a ":" fail in this odd way, so:

mongodb://ekkis@cluster0-shard-[...]

fails to catch

回答1:

Looks to me like it's a bug with however MongoClient is setting up its connections. You won't be able to use try & catch to handle asynchronously thrown errors within MongoClient code.

const {MongoClient} = require("mongodb");

process.on("uncaughtException", (err) => {
  console.log("process err", err);
  process.exit(1)
})

async function run () {
  let db;
  try {
    // connection url will throw because password isn't provided
    db = await MongoClient.connect("mongodb://myUsername:@localhost", { useNewUrlParser: true }); 
  } catch (err) {
    console.log('Exiting from thrown error', err);
    process.exit(1);
  }
}

run();

Here's a simplified example of what's happening -- the error will end up "uncaught" and caught by the uncaughtException handler

process.on("uncaughtException", (err) => console.log("uncaught", err));
try {
  setTimeout(() => {
    throw new Error("asynchronously thrown error");
  })
} catch (err) {
  console.log("Error will not be caught here")
}

来源：https://stackoverflow.com/questions/54737280/catch-fails-on-connection-to-mongo

标签

node.js

mongodb

try-catch