Writing Resource and Data Source

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Writing Resource and Data Source

Last updated: 2023-05-29 18:05:06
Resources and data sources are basic extensible datasets in Terraform that allow you to manage resources.
Writing Resources
A resource describes a class of resource entities allowing for CRUD operations, typically CVM instances, disks, databases, TKE clusters, and COS buckets.
This document takes the CVM instance with the following simple configuration as an example:
Name: my-cvm
AZ: Guangzhou Zone 4
Model: SA2.MEDUIM2
Image: TencentOS Server 3.2 (Final)
Network: vpc-xxxxxxxx
Subnet: subnet-xxxxyyyy
Billing mode: Pay-as-you-go
Whether a public IP is assigned: Yes
Public network bandwidth: 10 Mbps
 You can use the high-level configuration syntax HCL for description. Below is the sample code:
resource "tencentcloud_instance" "cvm1" {
  instance_name              = "my-cvm"
  availability_zone          = "ap-guangzhou-4"
  instance_type              = "SA2.MEDIUM2"
  instance_charge_type       = "POSTPAID_BY_HOUR"
  image_id                   = "img-9qrfy1xt"
  allocate_public_ip         = true
  internet_max_bandwidth_out = 10
}
When you run the terraform apply command for the first time, the declared resource will initiate the creation process. After the creation, if you modify the configuration in the code and run terraform apply again, the update process will be initiated. Running the terraform destroy command will initiate the termination process.
Writing resource code
To make the above HCL code effective, you need to register at TencentCloud Provider, find the Provider/ResourceMap field in tencentcloud/provider.go, add the tencentcloud_instance resource structure, and define the parameter schema based on HCL. Below is the sample code:
package tencentcloud
﻿
import (
  "github.com/hashicorp/terraform-plugin-sdk/helper/schema"
  "github.com/hashicorp/terraform-plugin-sdk/terraform"
)
﻿
func Provider() *schema.Provider {
  return &schema.Provider{
    ResourcesMap: map[string]*schema.Resource{
      "tencentcloud_xxx": { /* Other declared resources */ },
      "tencentcloud_yyy": { /* Other declared resources */ },
      "tencentcloud_instance": {
        Schema: map[string]*schema.Schema{
          "instance_name": {
            Optional: true, // Optional field
            Type:     schema.TypeString, // Field type
            Description: "Instance Name.",
          },
          "availability_zone": {
            Required: true, // Required field
            Type:     schema.TypeString,
            ForceNew: true, // If this field is modified and the modification is submitted, the resource will be terminated and recreated, as the server instance cannot switch the AZ.
            Description: "Instance available zone.",
          },
          "instance_type": {
            Optional: true,
            Type:     schema.TypeString,
            Description: "Instance Type.",
          },
          "instance_charge_type": {
            Optional: true,
            Type:     schema.TypeString,
            Description: "Instance charge type.",
          },
          "image_id": {
            Required: true,
            Type:     schema.TypeString,
            Description: "Instance OS image Id.",
          },
          "allocate_public_ip": {
            Optional: true,
            Type:     schema.TypeBool, // Boolean type
            Description: "Specify whether to allocate public IP.",
          },
          "internet_max_bandwidth_out": {
            Optional: true,
            Type:     schema.TypeInt, // Integer type
            Description: "Specify maximum bandwith.",
          },
        },
      },
    },
  }
}
After declaring the resource and parameter schema, you also need to define the CRUD logic triggered by apply, plan, or destroy in Terraform. The SDK for Terraform (v1) defines four CRUD methods:
Create, which is called if terraform apply is run for creation.
Read, which is called if terraform plan / import is run for remote state sync.
Update, which is called if terraform apply is run for update.
Delete, which is called if terraform destroy is run.
 Add the four methods to the schema.Resource structure. Below is the sample code:
package tencentcloud
﻿
import (
  "github.com/hashicorp/terraform-plugin-sdk/helper/schema"
  "github.com/hashicorp/terraform-plugin-sdk/terraform"
)
﻿
func Provider() *schema.Provider {
  return &schema.Provider{
    ResourcesMap: map[string]*schema.Resource{
      "tencentcloud_xxx": { /* Other declared resources */ },
      "tencentcloud_yyy": { /* Other declared resources */ },
      "tencentcloud_instance": {
        Create: resourceTencentCloudInstanceCreate,
        Read:   resourceTencentCloudInstanceRead,
        Update: resourceTencentCloudInstanceUpdate,
        Delete: resourceTencentCloudInstanceDelete,
        Schema: map[string]*schema.Schema{
          // The declaration written above (omitted)
        },
      },
    },
  }
}
﻿
func resourceTencentCloudInstanceCreate (d *schema.ResouceData, m interface{}) error {
  instanceName := d.Get("instance_name").(string)
  instanceType := d.Get("instance_type").(string)
  // ...
  
  // Run `terraform apply` for resource creation
  instanceId := createInstance(&param{
    Name: &instanceName,
    Type: &instanceType,
    // ...
  })
  
  // Set a unique ID for the created resource
  d.SetId(instanceId)
﻿
  // Sync the remote state again after resource creation for consistency check
  return resourceTencentCloudInstanceRead(d, m)
}
﻿
func resourceTencentCloudInstanceRead (d *schema.ResouceData, m interface{}) error {
  // Run `terraform plan` after resource creation/update
  
  instanceId := d.Id() // The ID set in `Create`
  instanceInfo := getInstance(instanceId)
  
  d.Set("instance_name", instanceInfo.Name)
  d.Set("instance_type", instanceInfo.Type)
  
  return nil
}
﻿
func resourceTencentCloudInstanceUpdate (d *schema.ResouceData, m interface{}) error {
  // Run `terraform apply` to update existing resources
  
  updateParam := &param{}
  
  // Check whether fields are updated, and if not, update them in combinations
  if d.HasChange("instance_name") {
    name := d.Get("instance_name").(string)
    updateParam.Name = &name
  }
  
  if d.HasChange("instance_type") {
    insType := d.Get("instance_type").(string)
    updateParam.Type = &insType
  }
  // ...
  updateInstance(d.Id(), updateParam)
  
  // Sync the remote state again after resource creation for consistency check
  return resourceTencentCloudInstanceRead(d, m)
}
﻿
func resourceTencentCloudInstanceDelete (d *schema.ResouceData, m interface{}) error {
  // Run `terraform destroy`
  destroyInstance(d.Id())
  
  return nil
}
 As you can see, the values of the HCL fields can be obtained by referencing the d.Get parameter. d.Set can write back (sync) these values. In addition, after each resource is created, you need to call d.SetId to set the unique resource index by which the specific resource instance can be located.
After the main logic structure is set up, the four functions can be called after Terraform runs plan apply destroy. Then, you can initiate TencentCloud API calls to manipulate resources.
CVM has the following CRUD APIs:
﻿RunInstances: Purchases an instance.
﻿DescribeInstances: Queries the list of instances.
﻿ModifyInstancesAttribute: Modifies an instance attribute.
﻿TerminateInstances: Returns an instance.
 You can pass in the parameters obtained from HCL to the required parameters of the CVM API for call initiation. Below is the sample code:
package main
﻿
import (
  cvm "github.com/tencentcloud/tencentcloud-sdk-go/tencentcloud/cvm/v20170312"
)
﻿
func resourceTencentCloudInstanceCreate(d *schema.ResourceData, meta interface{}) error {
  // Read the values of the fields from HCL
  instanceName       := d.Get("instance_name").(string)
  instanceType       := d.Get("instance_type").(string)
  imageId            := d.Get("image_id").(string)
  instanceChargeType := d.Get("instance_charge_type").(string)
  zone               := d.Get("availability_zone").(string)
  allocatePublicIp   := d.Get("allocate_public_ip").(bool)
  internetBandWith   := int64(d.Get("internet_max_bandwidth_out").(int))
  
  client, _ := cvm.NewClient(credential, "ap-guangzhou")
  request := cvm.NewRunInstancesRequest()
  // Create the parameters required by CVM in combinations
  request.InstanceName       = &instanceName
  request.InstanceType       = &instanceType
  request.ImageId            = &imageId
  request.InstanceChargeType = &instanceChargeType
  request.Placement          = &cvm.Placement {
    Zone: &zone,
  }
  request.InternetAccessible = &cvm.InternetAccessible {
    InternetMaxBandwidthOut: &internetBandWith,
    PublicIpAssigned:        &allocatePublicIp,
  }
    
  // Initiate the call
  id, err := client.RunInstances(request)
  if err != nil{
    return err
  }
  
  // Set the ID returned by the creation as the resource ID
  d.SetId(id)
  
  // Write back the state
  return resourceTencentCloudInstanceRead(d, meta)
}
 After implementing Create, implement Read, Update, and Delete:
package main
﻿
import (
  cvm "github.com/tencentcloud/tencentcloud-sdk-go/tencentcloud/cvm/v20170312"
)
﻿
func resourceTencentCloudInstanceRead(d *schema.ResourceData, meta interface{}) error {
  // The ID set in `Create` or obtained during import
  id := d.Id()
  
  client, _ := cvm.NewClient(credential, "ap-guangzhou")
  request, _ := cvm.NewDescribeInstancesRequest()
  request.InstanceIds = []*string{&id}
  response, err := client.DescribeInstances(request)
  if err != nil{
    return err
  }
  if len(response.Response.InstanceSet) == 0 {
    return fmt.Errorf("instance %s not exists.", id)
  }
  instance := response.Response.InstanceSet[0]
  
  d.Set("instance_name", instance.InstanceName)
  d.Set("instance_type", instance.InstanceType)
  // `d.Set` writes back fields such as `image_id`, `instance_charge_type`, and `availability_zone` (omitted).
  
  return nil
}
﻿
func resourceTencentCloudInstanceUpdate(d *schema.ResourceData, meta interface{}) error {
  id := d.Id()
  client, _ := cvm.NewClient(credential, "ap-guangzhou")
  request, _ := cvm.NewModifyInstancesAttributeRequest()
  request.InstanceIds = []*string{&id}
﻿
  // Check whether the fields are changed and add the parameters
  if d.HasChange("instance_name") {
    name := d.Get("instance_name").(string)
    request.InstanceName = &name
  }
  
  // Process other `HasChange` fields (omitted)
  
  _, err := client.ModifyInstanceAttribute(request)
  if err != nil{
    return err
  }
  
  return resourceTencentCloudInstanceRead(d, meta)
}
﻿
func resourceTencentCloudInstanceDelete(d *schema.ResourceData, meta interface{}) error {
  id := d.Id()
﻿
  client, _ := cvm.NewClient(credential, "ap-guangzhou")
  request, _ := cvm.NewTerminateInstancesRequest()
  request.InstanceIds = []*string{&id}
  _, err := client.TerminateInstances(request)
  if err != nil{
    return err
  }
  return nil
}
 At this point, you have implemented the resource containing the name, field declaration, and CRUD logic in TencentCloud Provider.
Implementing the import logic
After implementing the resource CRUD successfully, you can implement the resource import logic. The command for importing a single resource is in the format of terraform import <type>.<index> <id>, such as:
terraform import tencentcloud_instance.cvm1 ins-abcd1234
As you can see, there is only the ins-abcd1234 input for resource import. As indicated in the implemented Read method, when the ID is specified, you can use the ID to query the detailed configuration of a remote resource and automatically sync the configuration locally. Therefore, you only need to declare Importer in schema.Resource to indicate that the resource can be imported. Further sync will be taken over by Read:
package tencentcloud
﻿
import (
  "github.com/hashicorp/terraform-plugin-sdk/helper/schema"
  "github.com/hashicorp/terraform-plugin-sdk/terraform"
)
﻿
func Provider() *schema.Provider {
  return &schema.Provider{
    ResourcesMap: map[string]*schema.Resource{
      "tencentcloud_xxx": { /* Other declared resources */ },
      "tencentcloud_yyy": { /* Other declared resources */ },
      "tencentcloud_instance": {
        Create: resourceTencentCloudInstanceCreate,
        Read:   resourceTencentCloudInstanceRead,
        Update: resourceTencentCloudInstanceUpdate,
        Delete: resourceTencentCloudInstanceDelete,
        Schema: map[string]*schema.Schema{
          // The declaration written above (omitted)
        },
        // In most cases, you only need to add `schema.ImportStatePassthrough`.
        Importer: &schema.ResourceImporter{
          State: schema.ImportStatePassthrough,
        },
      },
    },
  }
}
Data Source
Data sources represent read-only entities for query only. No matter how many times they are called, existing resources will not be affected, such as CVM instance list, image list, AZ list, database list, parameter template, and audit log. Theoretically, any data that can be found via APIs are data sources. As indicated above, the CVM image is displayed as TencentOS Server 3.2 (Final), but the parameter passed in to the API is its ID img-9qrfy1xt. To get the ID based on the image name, you can use the data source to query and reference the image ID:
data "tencentcloud_images" "fav_os" {
  filters = {
    image_name: "TencentOS Server 3.2",
    image_type: "PUBLIC_IMAGE"
  }
}
﻿
resource "tencentcloud_instance" "cvm1" {
  image_id = data.tencentcloud_images.fav_os.images.0.image_id
}
As shown above, write image_id into the reference of data.tencentcloud_images.fav_os. Then, Terraform will read the data source information first and then calculate the value. Compared to a static method, a data source can effectively organize resources with dependencies.
Writing a data source
A data source is implemented in a similar way to a resource. You need to register at TencentCloud Provider, find the Provider/DataSourceMap field in the source code of tencentcloud/provider.go, add the tencentcloud_images structure (the names of all data sources must end with s), and define the parameter schema based on HCL:
package tencentcloud
﻿
import (
  "github.com/hashicorp/terraform-plugin-sdk/helper/schema"
  "github.com/hashicorp/terraform-plugin-sdk/terraform"
)
﻿
func Provider() *schema.Provider {
  return &schema.Provider{
    DataSourceMap: map[string]*schema.Resource{
      "tencentcloud_xxxs": { /* Other declared data sources */ },
      "tencentcloud_yyys": { /* Other declared data sources */ },
      "tencentcloud_images": {
        Schema: map[string]*schema.Schema{
          "filters": {
            Optional: true,
            Type:     schema.TypeMap, // Specify the `Map` type
            Description: "Query filter",
          },
          // Saves the result in JSON locally
          // TencentCloud Provider requires that every data source should have `result_output_file`.
          "result_output_file": {
            Optional: true,
            Type: schema.TypeString,
            Description: "Used for store as local file.",
          },
          "result": {
            Computed: true, // `Computed` indicates that the field will be updated passively.
            Type:    schema.TypeList,
            Description: "",
            Elem: &schema.Resource{
              Schema: map[string]*schema.Schema{
                "id": {
                  Type: schema.TypeString,
                  Computed: true,
                  Description: "Image Id.",
                },
                "name": {
                  Type: schema.,
                  Computed: true,
                  Description: "Image name.",
                },
              },
            },
          },
        },
      },
    },
  }
}
﻿
Compared to a resource, a data source requires implementing only the Read method:
package tencentcloud
﻿
import (
  "encoding/json"
  "github.com/hashicorp/terraform-plugin-sdk/helper/schema"
  "github.com/hashicorp/terraform-plugin-sdk/terraform"
)
﻿
const ImgNameFilterKey = "image-name"
﻿
func Provider() *schema.Provider {
  return &schema.Provider{
    DataSourceMap: map[string]*schema.Resource{
      "tencentcloud_xxxs": { /* Other declared data sources */ },
      "tencentcloud_yyys": { /* Other declared data sources */ },
      "tencentcloud_images": {
        Schema: map[string]*schema.Schema{ /* Omitted */},
        Read: func(d *schema.ResourceData, meta interface{}) {
          // Declare the `Client` and `request`
          client, _ := cvm.NewClient(credential, "ap-guangzhou")
          request := cvm.NewDescribeImagesRequest()
          
          // Get `Filters` of `Map` type
          filters := d.Get("filters").(map[string]interface{})
          
          // Check `filters["name"]` and add parameters
          if name, ok := filters["name"].(string); ok {
            request.Filters = append(request.Filters, &cvm.Filter{
              Name: &ImgNameFilterKey,
              Values: []*string{&name}
            })
          }
          
          // Initiate the call
          response, err := client.DescribeImages(request)
          if err != nil{
            return err
          }
          
          // Assemble and write the `result` field
          imageSet := response.Response.ImageSet
          result := make([]map[string]interface{}, 0, len(imageSet))
          for i := range imageSet {
            item := imageSet[i]
            result = append(result, map[string]interface{}{
              "id": *item.Id,
              "name": *item.Name,
            })
          }
          d.Set("result", result)
          
          // If `result_output_file` has a definition, write the result into the specified file.
          if v, ok := d.GetOk("result_output_file"); ok {
            writeToFile(v.(string), result)
          }
          return nil
        }
      },
    },
  }
}
﻿
At this point, you have written the tencentcloud_images and can use the data source to query specified OS images.
Writing an Acceptance Test
To ensure that your newly added resource or data source can work properly, you need to write an acceptance test as instructed in Writing Test Case.
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Recent Pages

Writing Resource and Data Source

Writing Resources

Writing resource code

Implementing the import logic

Data Source

Writing a data source

Writing an Acceptance Test

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Recent Pages

Writing Resource and Data Source

Writing Resources

Writing resource code

Implementing the import logic

Data Source

Writing a data source

Writing an Acceptance Test

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