AWS AppSync Events API
Serverless WebSocket pub/sub API that broadcasts events over channel namespaces to subscribed clients.
- Provider
- aws
- Category
- Edge
| property | type | values | required | kind default | this component |
|---|---|---|---|---|---|
| ackIntervalSeconds | integer | — | no | — | inherited |
| authorizationMode | enum | api-key | aws-iam | amazon-cognito-user-pools | openid-connect | aws-lambda | no | — | inherited |
| autoscaling | boolean | — | no | false | ▸ true |
| channelAssignment | enum | random | hash | sticky | no | random | inherited |
| drainOnScaleIn | boolean | — | no | false | inherited |
| managed | boolean | — | no | false | ▸ true |
| namespaceHandlers | boolean | — | no | false | inherited |
| protocol | enum | websocket | sse | long-poll | grpc-stream | udp-multicast | no | websocket | ▸ websocket |
| publishTransport | enum | http | websocket | no | http | inherited |
| pushFallback | boolean | — | no | false | ▸ false |
| sequenceNumbers | boolean | — | no | false | inherited |
| stampedeGuard | boolean | — | no | false | inherited |
| stateful | boolean | — | no | true | ▸ false |
| subscriptionsPerUser | integer | — | no | — | inherited |
| wildcardSubscriptions | boolean | — | no | true | inherited |
Every rule whose selector covers this component's kind or its category. Whether a rule fires depends on the design: its properties, its edges and its groups.
When a gateway holding millions of sockets restarts, every client reconnects at once and the gateway asks the coordination service about each of them. Without a stampede guard that lookup storm takes the coordination service down too.
- — all of these hold:
- — the node has at least one synchronous outgoing edge to a coordination-service
- — the node's `stampedeGuard` is false
With heavy-tail traffic a few channels carry most of the load. Assigning channels at random lands those hot channels on arbitrary hosts, and every tenant sharing a host suffers for it.
- — all of these hold:
- — the node's `channelAssignment` is "random"
- — the design requirement `traffic.skew` is "heavy-tail"
Scaling a gateway down kills every live WebSocket on the removed instance at once. Without a drain step those clients all reconnect together.
- — all of these hold:
- — the node's `autoscaling` is true
- — the node's `drainOnScaleIn` is false
nodes:
- { id: "appsync-events", component: "aws-appsync-events" }# yaml-language-server: $schema=../../schema/component.schema.json # AWS AppSync Events API: serverless WebSocket pub/sub over channel namespaces. "What is AWS # AppSync Events?" states AWS manages the WebSocket connections and scaling, clients publish over # HTTP or WebSocket and subscribe over WebSocket, and OnPublish/OnSubscribe handlers are optional. schemaVersion: "1" type: "component" id: "aws-appsync-events" kind: "realtime-gateway" provider: "aws" docs: "https://docs.aws.amazon.com/appsync/latest/eventapi/event-api-welcome.html" defaults: managed: true protocol: "websocket" stateful: false autoscaling: true pushFallback: false properties: authorizationMode: type: "enum" values: ["api-key", "aws-iam", "amazon-cognito-user-pools", "openid-connect", "aws-lambda"] publishTransport: type: "enum" values: ["http", "websocket"] default: "http" wildcardSubscriptions: type: "boolean" default: true namespaceHandlers: type: "boolean" default: false