agentcfg/fetch.go

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// this work for additional information regarding copyright
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// the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

package agentcfg // import "github.com/elastic/opentelemetry-collector-components/internal/agentcfg"

import (
	"context"
)

// TransactionSamplingRateKey is the agent configuration key for the
// sampling rate. This is used by the Jaeger handler to adapt our agent
// configuration to the Jaeger remote sampler protocol.
const TransactionSamplingRateKey = "transaction_sample_rate"

// Fetcher defines a common interface to retrieving agent config.
type Fetcher interface {
	Fetch(context.Context, Query) (Result, error)
}

// AgentConfig holds an agent configuration definition.
type AgentConfig struct {
	// Config holds configuration settings that should be sent to
	// agents matching the above constraints.
	Config map[string]string
	// ServiceName holds the service name to which this agent configuration
	// applies. This is optional.
	ServiceName string
	// ServiceEnvironment holds the service environment to which this agent
	// configuration applies. This is optional.
	ServiceEnvironment string
	// AgentName holds the agent name to which this agent configuration
	// applies. This is optional, and is used for filtering configuration
	// settings for unauthenticated agents.
	AgentName string
	// Etag holds a unique ID for the configuration, which agents
	// will send along with their queries. The server uses this to
	// determine whether agent configuration has been applied.
	Etag string
}

// matchAgentConfig finds a matching AgentConfig based on the received Query.
// Order of precedence:
// - service.name and service.environment match an AgentConfig
// - service.name matches an AgentConfig, service.environment == ""
// - service.environment matches an AgentConfig, service.name == ""
// - an AgentConfig without a name or environment set
// Return an empty result if no matching result is found.
func matchAgentConfig(query Query, cfgs []AgentConfig) Result {
	name, env := query.Service.Name, query.Service.Environment
	result := zeroResult()
	var nameConf, envConf, defaultConf *AgentConfig

	for i, cfg := range cfgs {
		if cfg.ServiceName == name && cfg.ServiceEnvironment == env {
			nameConf = &cfgs[i]
			break
		} else if cfg.ServiceName == name && cfg.ServiceEnvironment == "" {
			nameConf = &cfgs[i]
		} else if cfg.ServiceName == "" && cfg.ServiceEnvironment == env {
			envConf = &cfgs[i]
		} else if cfg.ServiceName == "" && cfg.ServiceEnvironment == "" {
			defaultConf = &cfgs[i]
		}
	}

	if nameConf != nil {
		result = Result{Source{
			Settings: nameConf.Config,
			Etag:     nameConf.Etag,
			Agent:    nameConf.AgentName,
		}}
	} else if envConf != nil {
		result = Result{Source{
			Settings: envConf.Config,
			Etag:     envConf.Etag,
			Agent:    envConf.AgentName,
		}}
	} else if defaultConf != nil {
		result = Result{Source{
			Settings: defaultConf.Config,
			Etag:     defaultConf.Etag,
			Agent:    defaultConf.AgentName,
		}}
	}
	return result
}