Connection ignoring the compressors option

[M-Gonzalo]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Mongoose version

8.6.1

Node.js version

latest

MongoDB server version

6.8.0

Typescript version (if applicable)

No response

Description

I tried configuring my connection to use network compression with the following option:

{
  compressors: ['zstd', 'snappy', 'zlib']
}

and then verifying it is actually applied using

mongoose.connection.db!.command({ hello: 1 })

but there is no compressors section at all. These are the top level properties of the output (not showing the whole thing for security reasons):

[
  "$clusterTime", "connectionId", "electionId", "hosts", "isWritablePrimary", "lastWrite", "localTime",
  "logicalSessionTimeoutMinutes", "maxBsonObjectSize", "maxMessageSizeBytes", "maxWireVersion",
  "maxWriteBatchSize", "me", "minWireVersion", "ok", "operationTime", "primary", "readOnly", "secondary",
  "setName", "setVersion", "tags", "topologyVersion"
]

Steps to Reproduce

As shown in description

Expected Behavior

I should be seeing the actual compression algorithm negotiated between de driver and the server

[M-Gonzalo]

I've seen this ranging from node 16 and mongoose 5, to the latest bun canary and mongoose@latest

[vkarpov15]

I'm unable to repro. RUnning the following script:

const mongoose = require('mongoose');

mongoose.connect('mongodb://127.0.0.1:27017/mongoose_test?replicaSet=rs', { compressors: ['zstd'] }).then(() => {
  return mongoose.connection.db.command({ hello: 1 })
}).then(res => console.log(res, Object.keys(res)));

and I get the following output, which includes the compression option:

{
  topologyVersion: { processId: new ObjectId('66e2f9b7243537af4ef88862'), counter: 6 },
  hosts: [ 'localhost:27017', 'localhost:27018', 'localhost:27019' ],
  setName: 'rs',
  setVersion: 1,
  isWritablePrimary: true,
  secondary: false,
  primary: 'localhost:27017',
  me: 'localhost:27017',
  electionId: new ObjectId('7fffffff0000000000000001'),
  lastWrite: {
    opTime: { ts: new Timestamp({ t: 1726151108, i: 7 }), t: 1 },
    lastWriteDate: 2024-09-12T14:25:08.000Z,
    majorityOpTime: { ts: new Timestamp({ t: 1726151108, i: 7 }), t: 1 },
    majorityWriteDate: 2024-09-12T14:25:08.000Z
  },
  maxBsonObjectSize: 16777216,
  maxMessageSizeBytes: 48000000,
  maxWriteBatchSize: 100000,
  localTime: 2024-09-12T14:25:10.883Z,
  logicalSessionTimeoutMinutes: 30,
  connectionId: 41,
  minWireVersion: 0,
  maxWireVersion: 13,
  readOnly: false,
  compression: [ 'zstd' ],
  ok: 1,
  '$clusterTime': {
    clusterTime: new Timestamp({ t: 1726151108, i: 7 }),
    signature: {
      hash: Binary.createFromBase64('AAAAAAAAAAAAAAAAAAAAAAAAAAA=', 0),
      keyId: 0
    }
  },
  operationTime: new Timestamp({ t: 1726151108, i: 7 })
} [
  'topologyVersion',
  'hosts',
  'setName',
  'setVersion',
  'isWritablePrimary',
  'secondary',
  'primary',
  'me',
  'electionId',
  'lastWrite',
  'maxBsonObjectSize',
  'maxMessageSizeBytes',
  'maxWriteBatchSize',
  'localTime',
  'logicalSessionTimeoutMinutes',
  'connectionId',
  'minWireVersion',
  'maxWireVersion',
  'readOnly',
  'compression',
  'ok',
  '$clusterTime',
  'operationTime'
]

Can you please clarify what you mean by "configuring my connection to use network compression" with a code sample?

[M-Gonzalo]

Can you please clarify what you mean by "configuring my connection to use network compression" with a code sample?

const options = mongoURI.includes('localhost') ?
    {} : { compressors: ['zstd', 'snappy', 'zlib'] } as ConnectOptions

export default (startTime: number) => mongoose.connect(mongoURI, options)
    .then(async mongoose => {
        const serverStatus = await mongoose.connection.db!.command({ hello: 1 })
        console.log(Object.keys(serverStatus).includes('compressors') ? '🟢 Compression enabled' : '🔴 Compression disabled')
    })
    .then(() => console.log(`🟢 Connected to MongoDB in ${(performance.now() - startTime).toFixed(2)}ms`))
    .catch((err) => { console.error('❌ MongoDB connection error:', err, '\nQuiting now... 💀'); process.exit(2) })

Result:

[M-Gonzalo]

OK, I can see the problem is in the URL, actually... I'll try to post it while anonymizing it

mongodb+srv://[REDACTED]:[REDACTED]@[REDACTED].mongodb.net/DATABASE-NAME?retryWrites=true&w=majority

Maybe that URL is malformed or somehow impedes the compressors config? Because in localhost compression works just fine

[vkarpov15]

Is it possible that your mongoURI includes localhost? I presume you've tried printing out mongoURI?

[M-Gonzalo]

Is it possible that your mongoURI includes localhost? I presume you've tried printing out mongoURI?

No, it's a Mongo Atlas URL. No "localhost" there

[vkarpov15]

Have you tried setting compressors option in your query string instead of as connection options? See MongoDB docs. You might have better luck with that, although both query string and connect options work on my end with Atlas.

[M-Gonzalo]

Have you tried setting compressors option in your query string instead of as connection options? See MongoDB docs. You might have better luck with that, although both query string and connect options work on my end with Atlas.

Yes I have. Same results.

[vkarpov15]

What permissions and roles does the database user have on your Atlas DB? Maybe for some reason compression doesn't get sent back if you don't have admin permissions?

[M-Gonzalo]

What permissions and roles does the database user have on your Atlas DB? Maybe for some reason compression doesn't get sent back if you don't have admin permissions?

It's the driver actually who rejects the compressors option. It's like it doesn't know it, but it clearly should.

[vkarpov15]

Ah ok I see what the issue might be. You're checking for the compressors option, but the runCommand result includes the compression result as a compression property, and 'compressors' !== 'compression'. Can you try that?