Socket IO not working with multiple node js servers - node.js

Question

I have 3 servers on AWS.
When
user A connects with server 1 and
user B connects with server 2
they are unable to join or chat. But if both connects with same server then they are joining successfully.
What would be the best way to handle this situations
Over the AWS, I am using Load Balancer with Auto Scaling.

Answer 1

From socket.io's documentation:
Now that you have multiple Socket.IO nodes accepting connections, if you want to broadcast events to everyone (or even everyone in a certain room) you’ll need some way of passing messages between processes or computers.
The interface in charge of routing messages is what we call the Adapter. You can implement your own on top of the socket.io-adapter (by inheriting from it) or you can use the one we provide on top of Redis: socket.io-redis:
Implementing the Redis adaptor in our socket.io powered application for horizontal scaling is just a few lines of added code to the index.js file:
var io = require('socket.io')(3000);
var redis = require('socket.io-redis');
io.adapter(redis({ host: 'localhost', port: 6379 }));
To Enable AutoScaling in your application, add following line of code to the scaling-policy.yml file
# Enable autoscaling for the service
ScalableTarget:
Type: AWS::ApplicationAutoScaling::ScalableTarget
DependsOn: Service
Properties:
ServiceNamespace: 'ecs'
ScalableDimension: 'ecs:service:DesiredCount'
ResourceId:
Fn::Join:
- '/'
- - service
- Fn::ImportValue: !Join [':', [!Ref 'EnvironmentName', 'ClusterName']]
- !Ref 'ServiceName'
MinCapacity: 2
MaxCapacity: 10
RoleARN:
Fn::ImportValue:
!Join [':', [!Ref 'EnvironmentName', 'AutoscalingRole']]
# Create scaling policies for the service
ScaleDownPolicy:
Type: AWS::ApplicationAutoScaling::ScalingPolicy
DependsOn: ScalableTarget
Properties:
PolicyName:
Fn::Join:
- '/'
- - scale
- !Ref 'EnvironmentName'
- !Ref 'ServiceName'
- down
PolicyType: StepScaling
ResourceId:
Fn::Join:
- '/'
- - service
- Fn::ImportValue: !Join [':', [!Ref 'EnvironmentName', 'ClusterName']]
- !Ref 'ServiceName'
ScalableDimension: 'ecs:service:DesiredCount'
ServiceNamespace: 'ecs'
StepScalingPolicyConfiguration:
AdjustmentType: 'ChangeInCapacity'
StepAdjustments:
- MetricIntervalUpperBound: 0
ScalingAdjustment: -1
MetricAggregationType: 'Average'
Cooldown: 60
ScaleUpPolicy:
Type: AWS::ApplicationAutoScaling::ScalingPolicy
DependsOn: ScalableTarget
Properties:
PolicyName:
Fn::Join:
- '/'
- - scale
- !Ref 'EnvironmentName'
- !Ref 'ServiceName'
- up
PolicyType: StepScaling
ResourceId:
Fn::Join:
- '/'
- - service
- Fn::ImportValue: !Join [':', [!Ref 'EnvironmentName', 'ClusterName']]
- !Ref 'ServiceName'
ScalableDimension: 'ecs:service:DesiredCount'
ServiceNamespace: 'ecs'
StepScalingPolicyConfiguration:
AdjustmentType: 'ChangeInCapacity'
StepAdjustments:
- MetricIntervalLowerBound: 0
MetricIntervalUpperBound: 15
ScalingAdjustment: 1
- MetricIntervalLowerBound: 15
MetricIntervalUpperBound: 25
ScalingAdjustment: 2
- MetricIntervalLowerBound: 25
ScalingAdjustment: 3
MetricAggregationType: 'Average'
Cooldown: 60
# Create alarms to trigger these policies
LowCpuUsageAlarm:
Type: AWS::CloudWatch::Alarm
Properties:
AlarmName:
Fn::Join:
- '-'
- - low-cpu
- !Ref 'EnvironmentName'
- !Ref 'ServiceName'
AlarmDescription:
Fn::Join:
- ' '
- - "Low CPU utilization for service"
- !Ref 'ServiceName'
- "in stack"
- !Ref 'EnvironmentName'
MetricName: CPUUtilization
Namespace: AWS/ECS
Dimensions:
- Name: ServiceName
Value: !Ref 'ServiceName'
- Name: ClusterName
Value:
Fn::ImportValue: !Join [':', [!Ref 'EnvironmentName', 'ClusterName']]
Statistic: Average
Period: 60
EvaluationPeriods: 1
Threshold: 20
ComparisonOperator: LessThanOrEqualToThreshold
AlarmActions:
- !Ref ScaleDownPolicy
HighCpuUsageAlarm:
Type: AWS::CloudWatch::Alarm
Properties:
AlarmName:
Fn::Join:
- '-'
- - high-cpu
- !Ref 'EnvironmentName'
- !Ref 'ServiceName'
AlarmDescription:
Fn::Join:
- ' '
- - "High CPU utilization for service"
- !Ref 'ServiceName'
- "in stack"
- !Ref 'EnvironmentName'
MetricName: CPUUtilization
Namespace: AWS/ECS
Dimensions:
- Name: ServiceName
Value: !Ref 'ServiceName'
- Name: ClusterName
Value:
Fn::ImportValue: !Join [':', [!Ref 'EnvironmentName', 'ClusterName']]
Statistic: Average
Period: 60
EvaluationPeriods: 1
Threshold: 70
ComparisonOperator: GreaterThanOrEqualToThreshold
AlarmActions:
- !Ref ScaleUpPolicy