Overview of the Dapr services on Dapr Docs

Dapr sidecar (daprd) overview

Mon, 01 Jan 0001 00:00:00 +0000

Dapr uses a sidecar pattern, meaning the Dapr APIs are run and exposed on a separate process, the Dapr sidecar, running alongside your application. The Dapr sidecar process is named daprd and is launched in different ways depending on the hosting environment.

The Dapr sidecar exposes:

Building block APIs used by your application business logic
A metadata API for discoverability of capabilities and to set attributes
A health API to determine health status and sidecar readiness and liveness

The Dapr sidecar will reach readiness state once the application is accessible on its configured port. The application cannot access the Dapr components during application start up/initialization.

Dapr Operator control plane service overview

Mon, 01 Jan 0001 00:00:00 +0000

When running Dapr in Kubernetes mode, a pod running the Dapr Operator service manages Dapr component updates and provides Kubernetes services endpoints for Dapr.

Running the operator service

The operator service is deployed as part of dapr init -k, or via the Dapr Helm charts. For more information on running Dapr on Kubernetes, visit the Kubernetes hosting page.

Additional configuration options

The operator service includes additional configuration options.

Injector watchdog

The operator service includes an injector watchdog feature which periodically polls all pods running in your Kubernetes cluster and confirms that the Dapr sidecar is injected in those which have the dapr.io/enabled=true annotation. It is primarily meant to address situations where the Injector service did not successfully inject the sidecar (the daprd container) into pods.

Dapr Placement control plane service overview

Mon, 01 Jan 0001 00:00:00 +0000

The Dapr Placement service is used to calculate and distribute distributed hash tables for the location of Dapr actors running in self-hosted mode or on Kubernetes. Grouped by namespace, the hash tables map actor types to pods or processes so a Dapr application can communicate with the actor. Anytime a Dapr application activates a Dapr actor, the Placement service updates the hash tables with the latest actor location.

Self-hosted mode

The Placement service Docker container is started automatically as part of dapr init. It can also be run manually as a process if you are running in slim-init mode.

Dapr Scheduler control plane service overview

Mon, 01 Jan 0001 00:00:00 +0000

The Dapr Scheduler service is used to schedule different types of jobs, running in self-hosted mode or on Kubernetes.

Jobs created through the Jobs API
Actor reminder jobs (used by the actor reminders)
Actor reminder jobs created by the Workflow API (which uses actor reminders)

There is no concept of a leader Scheduler instance. All Scheduler service replicas are considered peers. All receive jobs to be scheduled for execution and the jobs are allocated between the available Scheduler service replicas for load balancing of the trigger events.

Dapr Sentry control plane service overview

Mon, 01 Jan 0001 00:00:00 +0000

The Dapr Sentry service manages mTLS between services and acts as a certificate authority. It generates mTLS certificates and distributes them to any running sidecars. This allows sidecars to communicate with encrypted, mTLS traffic. For more information read the sidecar-to-sidecar communication overview.

Self-hosted mode

The Sentry service Docker container is not started automatically as part of dapr init. However it can be executed manually by following the instructions for setting up mutual TLS.

Dapr Sidecar Injector control plane service overview

Mon, 01 Jan 0001 00:00:00 +0000

When running Dapr in Kubernetes mode, a pod is created running the Dapr Sidecar Injector service, which looks for pods initialized with the Dapr annotations, and then creates another container in that pod for the daprd service

Running the sidecar injector

The sidecar injector service is deployed as part of dapr init -k, or via the Dapr Helm charts. For more information on running Dapr on Kubernetes, visit the Kubernetes hosting page.