-
-
Save pecigonzalo/7ae8be959875a45b2832655c850d9a0a to your computer and use it in GitHub Desktop.
Get dynamically mapped host port from within ECS container
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| package main | |
| import ( | |
| "encoding/json" | |
| "io/ioutil" | |
| "log" | |
| "net/http" | |
| "os" | |
| "bufio" | |
| "fmt" | |
| "github.com/aws/aws-sdk-go/aws" | |
| "github.com/aws/aws-sdk-go/aws/ec2metadata" | |
| "github.com/aws/aws-sdk-go/aws/session" | |
| "github.com/aws/aws-sdk-go/service/ecs" | |
| "path" | |
| "strings" | |
| ) | |
| type EcsAgentMetadata struct { | |
| Cluster string `json:"Cluster"` | |
| } | |
| type EcsAgentTaskMetadata struct { | |
| Tasks []struct { | |
| Arn string `json:"Arn"` | |
| Containers []struct { | |
| DockerId string `json:"DockerId"` | |
| } `json:"Containers"` | |
| } `json:"Tasks"` | |
| } | |
| func check(err error) { | |
| if err != nil { | |
| log.Panic(err) | |
| } | |
| } | |
| // See | |
| // https://github.com/aws/amazon-ecs-agent/issues/258 | |
| // https://github.com/aws/amazon-ecs-agent/pull/709 | |
| func ecsAgentTaskMetadata() (EcsAgentTaskMetadata, error) { | |
| response, err := http.Get("http://172.17.0.1:51678/v1/tasks") | |
| if err != nil { | |
| return EcsAgentTaskMetadata{}, err | |
| } | |
| defer response.Body.Close() | |
| body, err := ioutil.ReadAll(response.Body) | |
| if err != nil { | |
| return EcsAgentTaskMetadata{}, err | |
| } | |
| metadata := EcsAgentTaskMetadata{} | |
| err = json.Unmarshal(body, &metadata) | |
| if err != nil { | |
| return EcsAgentTaskMetadata{}, err | |
| } | |
| return metadata, nil | |
| } | |
| func ecsAgentMetadata() (EcsAgentMetadata, error) { | |
| response, err := http.Get("http://172.17.0.1:51678/v1/metadata") | |
| if err != nil { | |
| return EcsAgentMetadata{}, err | |
| } | |
| defer response.Body.Close() | |
| body, err := ioutil.ReadAll(response.Body) | |
| if err != nil { | |
| return EcsAgentMetadata{}, err | |
| } | |
| metadata := EcsAgentMetadata{} | |
| err = json.Unmarshal(body, &metadata) | |
| if err != nil { | |
| return EcsAgentMetadata{}, err | |
| } | |
| return metadata, nil | |
| } | |
| func getDockerId() (string, error) { | |
| file, err := os.Open("/proc/self/cgroup") | |
| if err != nil { | |
| fmt.Println("Could not open /proc/self/cgroup, using hostname instead as container id") | |
| return os.Hostname() | |
| } | |
| defer file.Close() | |
| reader := bufio.NewReader(file) | |
| for { | |
| // Example: "2:cpu:/docker/93c562c426414f53582c9830a30bdb54d85642956e18115dd59bc9f435ae5644" | |
| line, err := reader.ReadString('\n') | |
| if err != nil { | |
| break | |
| } | |
| components := strings.Split(line, ":") | |
| if len(components) == 3 { | |
| return strings.TrimRight(path.Base(components[2]), "\n"), nil | |
| } | |
| } | |
| return "", fmt.Errorf("Failed to find Docker ID in /proc/self/group") | |
| } | |
| func main() { | |
| metasession := session.Must(session.NewSession()) | |
| ec2metadataSvc := ec2metadata.New(metasession) | |
| region, err := ec2metadataSvc.Region() | |
| check(err) | |
| sess, err := session.NewSession(aws.NewConfig().WithRegion(region)) | |
| check(err) | |
| // Create the AWS clients | |
| ecsSvc := ecs.New(sess) | |
| // find our task in the ECS agent metadata | |
| dockerId, err := getDockerId() | |
| check(err) | |
| agentMetadata, err := ecsAgentMetadata() | |
| check(err) | |
| if agentMetadata.Cluster == "" { | |
| log.Panic(fmt.Errorf("Could not find ECS cluster for docker container '%s'", dockerId)) | |
| } | |
| agentTaskMetadata, err := ecsAgentTaskMetadata() | |
| check(err) | |
| taskArn := "" | |
| for _, task := range agentTaskMetadata.Tasks { | |
| for _, container := range task.Containers { | |
| if strings.HasPrefix(container.DockerId, dockerId) { | |
| taskArn = task.Arn | |
| break | |
| } | |
| } | |
| } | |
| if taskArn == "" { | |
| log.Panic(fmt.Errorf("Could not find ECS task for docker container '%s' on cluster '%s'", dockerId, agentMetadata.Cluster)) | |
| } | |
| tasks, err := ecsSvc.DescribeTasks(&ecs.DescribeTasksInput{ | |
| Cluster: aws.String(agentMetadata.Cluster), | |
| Tasks: []*string{aws.String(taskArn)}, | |
| }) | |
| check(err) | |
| for _, task := range tasks.Tasks { | |
| for _, container := range task.Containers { | |
| for _, binding := range container.NetworkBindings { | |
| if binding.ContainerPort != nil && binding.HostPort != nil { | |
| log.Println("Found host port: ", *binding.HostPort) | |
| return | |
| } | |
| } | |
| } | |
| } | |
| } |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment