calloptions.go

// Copyright (c) 2015 Uber Technologies, Inc.

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// THE SOFTWARE.

package tchannel

// Format is the arg scheme used for a specific call.
type Format string

// The list of formats supported by tchannel.
const (
	HTTP   Format = "http"
	JSON   Format = "json"
	Raw    Format = "raw"
	Thrift Format = "thrift"
)

func (f Format) String() string {
	return string(f)
}

// CallOptions are options for a specific call.
type CallOptions struct {
	// Format is arg scheme used for this call, sent in the "as" header.
	// This header is only set if the Format is set.
	Format Format

	// ShardKey determines where this call request belongs, used with ringpop applications.
	ShardKey string

	// RequestState stores request state across retry attempts.
	RequestState *RequestState

	// RoutingKey identifies the destined traffic group. Relays may favor the
	// routing key over the service name to route the request to a specialized
	// traffic group.
	RoutingKey string

	// RoutingDelegate identifies a traffic group capable of routing a request
	// to an instance of the intended service.
	RoutingDelegate string

	// CallerName defaults to the channel's service name for an outbound call.
	// Optionally override this field to support transparent proxying when inbound
	// caller names vary across calls.
	CallerName string
}

var defaultCallOptions = &CallOptions{}

func (c *CallOptions) setHeaders(headers transportHeaders) {
	headers[ArgScheme] = Raw.String()
	c.overrideHeaders(headers)
}

// overrideHeaders sets headers if the call options contains non-default values.
func (c *CallOptions) overrideHeaders(headers transportHeaders) {
	if c.Format != "" {
		headers[ArgScheme] = c.Format.String()
	}
	if c.ShardKey != "" {
		headers[ShardKey] = c.ShardKey
	}
	if c.RoutingKey != "" {
		headers[RoutingKey] = c.RoutingKey
	}
	if c.RoutingDelegate != "" {
		headers[RoutingDelegate] = c.RoutingDelegate
	}
	if c.CallerName != "" {
		headers[CallerName] = c.CallerName
	}
}

// setResponseHeaders copies some headers from the incoming call request to the response.
func setResponseHeaders(reqHeaders, respHeaders transportHeaders) {
	respHeaders[ArgScheme] = reqHeaders[ArgScheme]
}