[ddp] Call error: [ddp] sending without open connection

Hi,

I try to use your tool to perform load test of rocketch chat. But for 350 users app crash with error:

joining room: GENERAL
opening rooms

sending messages
done!
[ '[ddp] Call error: [ddp] sending without open connection' ]
/home/emikolajczak/rocket.chat.load.tester/src/server.js:65
        throw up;
        ^
Error: [ddp] sending without open connection
    at Promise (/home/emikolajczak/rocket.chat.load.tester/node_modules/@rocket.chat/src/lib/drivers/ddp.ts:212:35)
    at new Promise (<anonymous>)
    at Socket.<anonymous> (/home/emikolajczak/rocket.chat.load.tester/node_modules/@rocket.chat/src/lib/drivers/ddp.ts:211:12)
    at Generator.next (<anonymous>)
    at /home/emikolajczak/rocket.chat.load.tester/node_modules/@rocket.chat/sdk/lib/drivers/ddp.js:11:71
    at new Promise (<anonymous>)
    at __awaiter (/home/emikolajczak/rocket.chat.load.tester/node_modules/@rocket.chat/sdk/lib/drivers/ddp.js:7:12)
    at Socket.send (/home/emikolajczak/rocket.chat.load.tester/node_modules/@rocket.chat/sdk/lib/drivers/ddp.js:198:16)
    at Socket.<anonymous> (/home/emikolajczak/rocket.chat.load.tester/node_modules/@rocket.chat/src/lib/drivers/ddp.ts:256:33)
    at Generator.next (<anonymous>)
[nodemon] app crashed - waiting for file changes before starting...

My configuration is:

export HOST_URL=xxx
export PORT=3000
export REDIS_HOST=redis
export TRY_REGISTER=yes
export HOW_MANY=350
export SEATS_PER_ROOM=20000
export LOGIN_BATCH=10
export MESSAGE_SENDING_RATE=0.017
export ROOM_ID=GENERAL
export OPEN_ROOM=yes
export SSL_ENABLED=yes
export SEND_MESSAGES=yes
export CLIENT_TYPE=web
export USERS_USERNAME=tester-%s
export USERS_PASSWORD=tester-%s
export USERS_EMAIL=tester-%s@domain.com
export JOIN_ROOM=GENERAL
export LOG_IN=yes
export NO_SUBSCRIBE=no
export INITIAL_LOGIN_OFFSET=1
export LOGIN_OFFSET=1

Error occurs regardless number of running instances.

Server Setup Information:

• Version of Rocket.Chat Server: 3.0.12
• Operating System: Centos7
• Deployment Method: docker-compose
• Number of Running Instances: 25
• DB Replicaset Oplog: YES
• NodeJS Version: v12.14.0
• MongoDB Version: 4.0.16

Reproduce the failure with the supplied configuration, especially HOW_MANY=350, then start at src/server.js:65 and follow the stack into @rocket.chat/src/lib/drivers/ddp.ts at lines 212 and 256. Determine why sending occurs without an open connection; done means the load test no longer crashes with this error under the reported setup.