README
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Bindings
Bindings provide a common way to trigger an application with events from external systems, or invoke an external system with optional data payloads. Bindings are great for event-driven, on-demand compute and help reduce boilerplate code.
To get started with bindings visit the How To Guide.
To view all the currently supported bindings visit: Dapr bindings.
For detailed binding specs visit Dapr binding specs.
Implementing a new binding
A compliant binding needs to implement one or more interfaces, depending on the type of binding (Input or Output):
Input binding:
type InputBinding interface {
Init(metadata Metadata) error
Read(handler func(*ReadResponse) error) error
}
Output binding:
An output binding can be used to invoke an external system and also to return data from it.
Each output binding can decide which operations it supports. This information is communicated to the caller via the Operations() method.
type OutputBinding interface {
Init(metadata Metadata) error
Invoke(req *InvokeRequest) (*InvokeResponse, error)
Operations() []OperationKind
}
When creating an Output Binding, a list of OperationKind items needs to be returned.
For example, if running a component that takes in a SQL query and returns a result set, the OperationKind can be query.
While components are not restricted to a list of supported operations, it's best to use common ones if the operation kind falls under that operation definition. The list of common operations can be found here.
After implementing a binding, the specification docs need to be updated via a PR: Dapr docs.
Documentation
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Index ¶
Constants ¶
const (
// TTLMetadataKey defines the metadata key for setting a time to live (in seconds)
TTLMetadataKey = "ttlInSeconds"
)
Variables ¶
This section is empty.
Functions ¶
Types ¶
type AppResponse ¶
type AppResponse struct {
Data interface{} `json:"data"`
To []string `json:"to"`
StoreName string `json:"storeName"`
State []state.SetRequest `json:"state"`
Concurrency string `json:"concurrency"`
}
AppResponse is the object describing the response from user code after a bindings event
type InputBinding ¶
type InputBinding interface {
// Init passes connection and properties metadata to the binding implementation
Init(metadata Metadata) error
// Read is a blocking method that triggers the callback function whenever an event arrives
Read(handler func(*ReadResponse) error) error
}
InputBinding is the interface to define a binding that triggers on incoming events
type InvokeRequest ¶
type InvokeRequest struct {
Data []byte `json:"data"`
Metadata map[string]string `json:"metadata"`
Operation OperationKind `json:"operation"`
}
InvokeRequest is the object given to a dapr output binding
type InvokeResponse ¶
type InvokeResponse struct {
Data []byte `json:"data"`
Metadata map[string]string `json:"metadata"`
}
InvokeResponse is the response object returned from an output binding
type OperationKind ¶
type OperationKind string
OperationKind defines an output binding operation
const ( GetOperation OperationKind = "get" CreateOperation OperationKind = "create" DeleteOperation OperationKind = "delete" ListOperation OperationKind = "list" )
Non exhaustive list of operations. A binding can add operations that are not in this list.
type OutputBinding ¶
type OutputBinding interface {
Init(metadata Metadata) error
Invoke(req *InvokeRequest) (*InvokeResponse, error)
Operations() []OperationKind
}
OutputBinding is the interface for an output binding, allowing users to invoke remote systems with optional payloads
type ReadResponse ¶
ReadResponse is an the return object from an dapr input binding
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