Skip to content

Schema by Example

This guide walks you through building schemas from simple to complex, using real-world examples at each step.

🤖 AI-Generated Content

This documentation was generated with AI assistance and is still being audited. Some, or potentially a lot, of this information may be inaccurate. Learn more.

Starting Simple: A Basic Resource

Let's build a simple file resource:

Step 1: Just a Name

Python
1
2
3
4
5
6
7
from pyvider.schema import s_resource, a_str

@classmethod
def get_schema(cls):
    return s_resource({
        "path": a_str(required=True, description="File path"),
    })

Terraform:

Terraform
1
2
3
resource "local_file" "example" {
  path = "/tmp/hello.txt"
}

Step 2: Add Optional Content

Python
1
2
3
4
5
6
@classmethod
def get_schema(cls):
    return s_resource({
        "path": a_str(required=True, description="File path"),
        "content": a_str(default="", description="File content"),
    })

Terraform:

Terraform
1
2
3
4
resource "local_file" "example" {
  path    = "/tmp/hello.txt"
  content = "Hello, World!"
}

Step 3: Add Computed ID

Python
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
@classmethod
def get_schema(cls):
    return s_resource({
        # Inputs
        "path": a_str(required=True, description="File path"),
        "content": a_str(default="", description="File content"),

        # Outputs
        "id": a_str(computed=True, description="File ID"),
    })

Terraform:

Terraform
1
2
3
4
5
6
7
8
resource "local_file" "example" {
  path    = "/tmp/hello.txt"
  content = "Hello, World!"
}

output "file_id" {
  value = local_file.example.id
}

Adding Complexity: Collections

Lists of Strings

Python
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
from pyvider.schema import s_resource, a_str, a_list

@classmethod
def get_schema(cls):
    return s_resource({
        "name": a_str(required=True, description="Server name"),
        "tags": a_list(
            a_str(),
            default=[],
            description="Resource tags"
        ),
    })

Terraform:

Terraform
1
2
3
4
resource "mycloud_server" "web" {
  name = "web-server"
  tags = ["production", "web", "public"]
}

Maps of Strings

Python
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
from pyvider.schema import a_map

@classmethod
def get_schema(cls):
    return s_resource({
        "name": a_str(required=True, description="Server name"),
        "labels": a_map(
            a_str(),
            default={},
            description="Key-value labels"
        ),
    })

Terraform:

Terraform
1
2
3
4
5
6
7
8
resource "mycloud_server" "web" {
  name = "web-server"
  labels = {
    environment = "production"
    team        = "platform"
    cost_center = "engineering"
  }
}

Lists of Numbers

Python
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
from pyvider.schema import a_num

@classmethod
def get_schema(cls):
    return s_resource({
        "name": a_str(required=True, description="Firewall rule name"),
        "ports": a_list(
            a_num(),
            default=[],
            description="Allowed ports"
        ),
    })

Terraform:

Terraform
1
2
3
4
resource "mycloud_firewall_rule" "web" {
  name  = "web-ports"
  ports = [80, 443, 8080]
}

Next Level: Nested Objects

Simple Nested Object

Python
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
from pyvider.schema import a_obj, a_bool

@classmethod
def get_schema(cls):
    return s_resource({
        "name": a_str(required=True, description="Server name"),
        "database": a_obj({
            "host": a_str(required=True, description="Database host"),
            "port": a_num(default=5432, description="Database port"),
            "ssl": a_bool(default=True, description="Enable SSL"),
        }, description="Database connection configuration"),
    })

Terraform:

Terraform
1
2
3
4
5
6
7
8
9
resource "mycloud_app" "api" {
  name = "api-server"

  database = {
    host = "db.example.com"
    port = 5432
    ssl  = true
  }
}

List of Objects

Python
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
@classmethod
def get_schema(cls):
    return s_resource({
        "name": a_str(required=True, description="Load balancer name"),
        "endpoints": a_list(
            a_obj({
                "url": a_str(required=True, description="Endpoint URL"),
                "weight": a_num(default=100, description="Traffic weight"),
                "healthy": a_bool(default=True, description="Health status"),
            }),
            default=[],
            description="Backend endpoints"
        ),
    })

Terraform:

Terraform
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
resource "mycloud_lb" "main" {
  name = "main-lb"

  endpoints = [
    {
      url    = "https://backend1.example.com"
      weight = 100
    },
    {
      url    = "https://backend2.example.com"
      weight = 50
    }
  ]
}

Advanced: Using Blocks

Single Optional Block

Python
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
from pyvider.schema import b_single

@classmethod
def get_schema(cls):
    return s_resource({
        "name": a_str(required=True, description="Server name"),

        "logging": b_single("logging",
            attributes={
                "enabled": a_bool(default=True, description="Enable logging"),
                "level": a_str(default="INFO", description="Log level"),
                "destination": a_str(required=True, description="Log destination"),
            },
            description="Logging configuration"
        ),
    })

Terraform:

Terraform
1
2
3
4
5
6
7
8
9
resource "mycloud_server" "web" {
  name = "web-server"

  logging {
    enabled     = true
    level       = "DEBUG"
    destination = "cloudwatch"
  }
}

Multiple Repeatable Blocks

Python
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
from pyvider.schema import b_list

@classmethod
def get_schema(cls):
    return s_resource({
        "name": a_str(required=True, description="Security group name"),

        "ingress_rule": b_list("ingress_rule",
            attributes={
                "from_port": a_num(required=True, description="Start port"),
                "to_port": a_num(required=True, description="End port"),
                "protocol": a_str(required=True, description="Protocol"),
                "cidr_blocks": a_list(a_str(), description="CIDR blocks"),
            },
            description="Ingress rules"
        ),
    })

Terraform:

Terraform
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
resource "mycloud_security_group" "web" {
  name = "web-sg"

  ingress_rule {
    from_port   = 80
    to_port     = 80
    protocol    = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }

  ingress_rule {
    from_port   = 443
    to_port     = 443
    protocol    = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }
}

Nested Blocks

Python
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
@classmethod
def get_schema(cls):
    return s_resource({
        "name": a_str(required=True, description="Server name"),

        "monitoring": b_single("monitoring",
            attributes={
                "enabled": a_bool(default=True, description="Enable monitoring"),
                "interval": a_num(default=60, description="Check interval (seconds)"),
            },
            block_types=[
                b_list("alert",
                    attributes={
                        "metric": a_str(required=True, description="Metric to monitor"),
                        "threshold": a_num(required=True, description="Alert threshold"),
                        "email": a_str(required=True, description="Alert email"),
                    },
                    description="Alert rules"
                )
            ],
            description="Monitoring configuration"
        ),
    })

Terraform:

Terraform
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
resource "mycloud_server" "web" {
  name = "web-server"

  monitoring {
    enabled  = true
    interval = 30

    alert {
      metric    = "cpu_utilization"
      threshold = 80
      email     = "[email protected]"
    }

    alert {
      metric    = "memory_utilization"
      threshold = 90
      email     = "[email protected]"
    }
  }
}

Real-World Example: Complete Web Server

Let's build a complete, production-focused web server resource schema:

Python
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
from pyvider.resources import register_resource, BaseResource
from pyvider.resources.context import ResourceContext
from pyvider.schema import (
    s_resource, a_str, a_num, a_bool, a_list, a_map,
    b_single, b_list, PvsSchema
)
import attrs

@attrs.define
class WebServerConfig:
    name: str
    instance_type: str = "t2.micro"
    ami: str | None = None

@attrs.define
class WebServerState:
    id: str
    name: str
    instance_type: str
    ami: str
    public_ip: str
    private_ip: str
    status: str
    created_at: str

@register_resource("web_server")
class WebServer(BaseResource):
    config_class = WebServerConfig
    state_class = WebServerState

    @classmethod
    def get_schema(cls) -> PvsSchema:
        return s_resource({
            # ===== BASIC CONFIGURATION =====
            "name": a_str(
                required=True,
                description="Server name (must be unique)"
            ),
            "instance_type": a_str(
                default="t2.micro",
                description="EC2 instance type"
            ),
            "ami": a_str(
                description="Amazon Machine Image ID (defaults to latest Ubuntu)"
            ),

            # ===== TAGS AND LABELS =====
            "tags": a_list(
                a_str(),
                default=[],
                description="Resource tags for organization"
            ),
            "labels": a_map(
                a_str(),
                default={},
                description="Key-value labels for metadata"
            ),

            # ===== NETWORK CONFIGURATION =====
            "network": b_single("network",
                attributes={
                    "vpc_id": a_str(
                        required=True,
                        description="VPC to launch server in"
                    ),
                    "subnet_id": a_str(
                        required=True,
                        description="Subnet for server placement"
                    ),
                    "public_ip": a_bool(
                        default=True,
                        description="Assign public IP address"
                    ),
                    "security_groups": a_list(
                        a_str(),
                        default=[],
                        description="Security group IDs"
                    ),
                },
                description="Network configuration"
            ),

            # ===== STORAGE CONFIGURATION =====
            "root_volume": b_single("root_volume",
                attributes={
                    "size": a_num(
                        default=20,
                        description="Root volume size in GB"
                    ),
                    "type": a_str(
                        default="gp3",
                        description="Volume type (gp2, gp3, io1, io2)"
                    ),
                    "encrypted": a_bool(
                        default=True,
                        description="Enable encryption"
                    ),
                },
                description="Root volume configuration"
            ),

            "data_volume": b_list("data_volume",
                attributes={
                    "size": a_num(
                        required=True,
                        description="Volume size in GB"
                    ),
                    "type": a_str(
                        default="gp3",
                        description="Volume type"
                    ),
                    "device": a_str(
                        required=True,
                        description="Device name (e.g., /dev/sdb)"
                    ),
                    "mount_point": a_str(
                        description="Mount point (e.g., /data)"
                    ),
                },
                description="Additional data volumes"
            ),

            # ===== APPLICATION CONFIGURATION =====
            "application": b_single("application",
                attributes={
                    "port": a_num(
                        default=8080,
                        description="Application port"
                    ),
                    "protocol": a_str(
                        default="HTTP",
                        description="Protocol (HTTP, HTTPS)"
                    ),
                    "health_check_path": a_str(
                        default="/health",
                        description="Health check endpoint"
                    ),
                },
                block_types=[
                    b_single("ssl",
                        attributes={
                            "cert_arn": a_str(
                                required=True,
                                description="SSL certificate ARN"
                            ),
                            "min_tls_version": a_str(
                                default="TLSv1.2",
                                description="Minimum TLS version"
                            ),
                        },
                        description="SSL/TLS configuration"
                    ),
                    b_list("environment_variable",
                        attributes={
                            "name": a_str(
                                required=True,
                                description="Variable name"
                            ),
                            "value": a_str(
                                required=True,
                                description="Variable value"
                            ),
                            "sensitive": a_bool(
                                default=False,
                                description="Mark as sensitive"
                            ),
                        },
                        description="Environment variables"
                    ),
                ],
                description="Application configuration"
            ),

            # ===== MONITORING & LOGGING =====
            "monitoring": b_single("monitoring",
                attributes={
                    "enabled": a_bool(
                        default=True,
                        description="Enable CloudWatch monitoring"
                    ),
                    "detailed": a_bool(
                        default=False,
                        description="Enable detailed monitoring (1-minute intervals)"
                    ),
                },
                block_types=[
                    b_list("alarm",
                        attributes={
                            "name": a_str(
                                required=True,
                                description="Alarm name"
                            ),
                            "metric": a_str(
                                required=True,
                                description="CloudWatch metric"
                            ),
                            "threshold": a_num(
                                required=True,
                                description="Threshold value"
                            ),
                            "comparison": a_str(
                                default="GreaterThanThreshold",
                                description="Comparison operator"
                            ),
                            "sns_topic": a_str(
                                description="SNS topic ARN for notifications"
                            ),
                        },
                        description="CloudWatch alarms"
                    )
                ],
                description="Monitoring configuration"
            ),

            # ===== COMPUTED OUTPUTS =====
            "id": a_str(
                computed=True,
                description="EC2 instance ID"
            ),
            "public_ip": a_str(
                computed=True,
                description="Public IP address"
            ),
            "private_ip": a_str(
                computed=True,
                description="Private IP address"
            ),
            "status": a_str(
                computed=True,
                description="Instance status (pending, running, stopped, terminated)"
            ),
            "created_at": a_str(
                computed=True,
                description="Creation timestamp"
            ),
        })

    async def _validate_config(self, config: WebServerConfig) -> list[str]:
        errors = []

        # Validate instance type
        valid_types = ["t2.micro", "t2.small", "t2.medium", "t3.micro", "t3.small"]
        if config.instance_type not in valid_types:
            errors.append(f"instance_type must be one of: {', '.join(valid_types)}")

        return errors

    async def read(self, ctx: ResourceContext) -> WebServerState | None:
        if not ctx.state:
            return None
        # Implementation here
        pass

    async def _create_apply(self, ctx: ResourceContext) -> tuple[WebServerState | None, None]:
        if not ctx.config:
            return None, None
        # Implementation here
        pass

    async def _update_apply(self, ctx: ResourceContext) -> tuple[WebServerState | None, None]:
        if not ctx.config or not ctx.state:
            return None, None
        # Implementation here
        pass

    async def _delete_apply(self, ctx: ResourceContext) -> None:
        if not ctx.state:
            return
        # Implementation here
        pass

Complete Terraform Example:

Terraform
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
resource "mycloud_web_server" "production" {
  name          = "prod-web-01"
  instance_type = "t3.small"
  ami           = "ami-0c55b159cbfafe1f0"

  tags = ["production", "web", "critical"]

  labels = {
    environment = "production"
    team        = "platform"
    cost_center = "engineering"
    managed_by  = "terraform"
  }

  network {
    vpc_id          = "vpc-12345"
    subnet_id       = "subnet-67890"
    public_ip       = true
    security_groups = ["sg-web", "sg-ssh"]
  }

  root_volume {
    size      = 30
    type      = "gp3"
    encrypted = true
  }

  data_volume {
    size        = 100
    type        = "gp3"
    device      = "/dev/sdb"
    mount_point = "/var/www"
  }

  data_volume {
    size        = 50
    type        = "gp3"
    device      = "/dev/sdc"
    mount_point = "/var/log"
  }

  application {
    port              = 443
    protocol          = "HTTPS"
    health_check_path = "/api/health"

    ssl {
      cert_arn        = "arn:aws:acm:us-east-1:123456789:certificate/abcd-1234"
      min_tls_version = "TLSv1.3"
    }

    environment_variable {
      name  = "APP_ENV"
      value = "production"
    }

    environment_variable {
      name      = "DATABASE_URL"
      value     = "postgres://db.internal:5432/app"
      sensitive = true
    }
  }

  monitoring {
    enabled  = true
    detailed = true

    alarm {
      name       = "high-cpu"
      metric     = "CPUUtilization"
      threshold  = 80
      comparison = "GreaterThanThreshold"
      sns_topic  = "arn:aws:sns:us-east-1:123456789:alerts"
    }

    alarm {
      name       = "low-disk"
      metric     = "DiskSpaceUtilization"
      threshold  = 90
      comparison = "GreaterThanThreshold"
      sns_topic  = "arn:aws:sns:us-east-1:123456789:alerts"
    }
  }
}

# Use computed outputs
output "server_public_ip" {
  value = mycloud_web_server.production.public_ip
}

output "server_id" {
  value = mycloud_web_server.production.id
}

Key Takeaways

  1. Start Simple - Begin with required attributes, add complexity gradually
  2. Use Defaults - Provide sensible defaults for optional attributes
  3. Organize Logically - Group related attributes into blocks
  4. Validate Early - Add validators to catch errors during planning
  5. Document Thoroughly - Every attribute should have a clear description
  6. Use Appropriate Types - Lists for ordered items, maps for key-value, blocks for nested structures
  7. Mark Computed Fields - Clearly indicate what the provider generates vs what users provide

See Also