feature: the tfvars store keeps Terraform modules, their instances and the instances' variable files in PostgreSQL.

2026-10-28 23:58:54 +01:00
13 changed files with 667 additions and 8 deletions
@@ -95,3 +95,26 @@ object can be written one after the other. The kind stays the store's, not a fie
 Consequences: A key of `config.json` holding a dot cannot be the key of a store. A single key
 reads and writes as before, so applications of one-key stores need no change. The application
 checks the object of a path, such as the keys it allows in it, itself.
+
+## ADR-5: Terraform modules, instances and their variable files are tables shared through the toolkit
+
+Status: Accepted
+
+Context: Cloud Platform deploys many instances of many Terraform modules, and each module's
+configurator, a separate application, edits the variables of its instances. Both have to read
+and write the same modules, instances and variable files, with the same versions, so that a
+write from an outdated read is refused whichever application made it.
+
+Decision: The toolkit holds the tables and their functions and procedures,
+`server/sql/tfvars_store.sql`, and `createTfvarsStore`, which both applications use with their own
+`pg` pool. An instance names the schema of its state, unique among instances. A variable file is
+a row of its instance, its object as `jsonb` with the one it replaced. The version of an
+instance's files is the name and the SHA-256 of each file's text, `tfvarsText` of its object, in
+name order; a write locks the table, compares the version and writes in one transaction. A change
+the tables refuse is an `HttpError` with the status the routes answer. `pg` is an optional peer
+dependency, as the applications that do not use the store do not need it.
+
+Consequences: Every application of the store works on the same rows and refuses the same
+conflicts, and changes of the tables reach them with a release of the toolkit. The objects' keys
+are in `jsonb`'s order. The store is tested against a real PostgreSQL server, which the release
+workflow does not have, so `npm test` runs on the developer's machine.
@@ -1,5 +1,18 @@
 # Changelog

+## 0.4.0
+
+feature: the tfvars store keeps Terraform modules, their instances and the instances' variable files in PostgreSQL.
+
+- `createTfvarsStore(pool)`: the tables `tf_modules`, `tf_instances` and `tf_variable_files`,
+  created at the first use, with `modules` (`list`, `put`, `delete`), `instances` (`list`,
+  `create`, `delete`) and `variables(module, instance)` (`read`, `write`, `remove`), whose writes
+  take the version read and answer `false` when the files changed since.
+- `versionOf`, `tfvarsText`, and the types `TfModule`, `TfInstance` and `TfvarsFileStatus` with
+  the patterns of their names, also exported from `/web`.
+- `pg` is an optional peer dependency, for the store.
+- `npm test` tests the store against a scratch database of the server the `PG*` variables name.
+
 ## 0.3.0

 feature: the key of a credential store may be a path of keys, so stores of several kinds share one object of config.json.
@@ -64,6 +64,7 @@ code; `vite` for the Vite helpers.
 | `readJsonObject(path, options)` | a JSON object file and its version, the SHA-256 of its bytes; optionally `{}` for a missing file |
 | `encryptionKey()`, `encrypt(text, key)`, `decrypt(encrypted, key)` | the key of the secrets and AES-256-GCM encryption; see [Credential store](#credential-store) |
 | `CredentialStore`, `credentialProblems`, `credentialValues`, `registerCredentialRoutes`, `POSTGRESQL_KIND` | the credential store; see [Credential store](#credential-store) |
+| `createTfvarsStore`, `versionOf`, `tfvarsText`, `TfModule`, `TfInstance`, `TfvarsFileStatus`, `TF_NAME_PATTERN`, `TFVARS_FILE_PATTERN`, `STATE_SCHEMA_PATTERN` | the Terraform modules, their instances and their variable files in PostgreSQL; see [Tfvars store](#tfvars-store) |

 ## sk-react-toolkit/web

@@ -79,6 +80,7 @@ code; `vite` for the Vite helpers.
 | `RowDialog`, `useValidation` | a dialog that edits a value validated by the server as it changes, and the validation hook |
 | `createBrowserSettings(keys, event)` | switches kept in localStorage and followed across tabs |
 | `CredentialsButton` | the dialog of a credential store; see [Credential store](#credential-store) |
+| `TfModule`, `TfInstance`, `TfvarsFileStatus`, `TF_NAME_PATTERN`, `TFVARS_FILE_PATTERN`, `STATE_SCHEMA_PATTERN` | the types and name patterns of the [Tfvars store](#tfvars-store) |

 ## sk-react-toolkit/vite

@@ -159,11 +161,43 @@ them; a tab with a problem has a red label. A secret shows only whether it is ke
 replaces it and Remove drops it. Save writes each store that changed, each write with the version
 the previous one answers.

+## Tfvars store
+
+The tfvars store keeps Terraform modules, their instances and the variable files of each
+instance in PostgreSQL, for Cloud Platform, which deploys the instances, and the configurators,
+which edit their variables. `createTfvarsStore(pool)` takes a `pg` pool and applies
+`server/sql/tfvars_store.sql` at its first use, in the schema of the connection's search path:
+
+| Table | Rows |
+| --- | --- |
+| `tf_modules` | `name`, `root`, the folder of the Terraform code, `description` and `configurator_url` |
+| `tf_instances` | `module`, `name` and `state_schema`, the schema of the instance's state in the pg backend, unique, and `created` |
+| `tf_variable_files` | `module`, `instance`, `name` (`*.tfvars.json`), `content` and `previous`, the object it replaced, as `jsonb`, and `updated` |
+
+Names of modules and instances are `TF_NAME_PATTERN`, of variable files `TFVARS_FILE_PATTERN`,
+of state schemas `STATE_SCHEMA_PATTERN`.
+
+- `modules.list()`, `modules.put(module)`, which creates or changes, and `modules.delete(name)`.
+- `instances.list(module)`, `instances.create(module, name, stateSchema)` and
+  `instances.delete(module, name)`, which deletes its variable files too.
+- `variables(module, instance)`: `read()` answers the files, their sizes and times and the
+  version, `versionOf` the files, the name and the SHA-256 of each in name order. `write(version,
+  contents)` writes files given by name as JSON text and `remove(version, name)` deletes one; both
+  lock the table, compare the version and change in one transaction, and answer `false`, changing
+  nothing, when the files changed since the version.
+
+A change the tables refuse throws `HttpError`: 409 for a name or a state schema in use and for a
+module that has instances, 404 for a module or an instance that does not exist, 400 for a name or
+a content the tables do not accept. The content of a file is the object as `jsonb` keeps it,
+written by `tfvarsText`, so the order of object keys is `jsonb`'s; arrays keep theirs.
+
 ## Development

 `npm install` installs the peer dependencies as development dependencies; `npm run typecheck`
-and `npm run lint` check the code. `npm run build` (`build.mjs`) builds the published package in
-`dist/`: the code compiled to JavaScript with its declarations, README.md, CHANGELOG.md and a
+and `npm run lint` check the code. `npm test` tests the tfvars store in a scratch database it
+creates and drops on the PostgreSQL server the `PG*` variables name, connected to through the
+database `postgres`. `npm run build` (`build.mjs`) builds the published package in
+`dist/`: the code compiled to JavaScript with its declarations, the SQL of the server, README.md, CHANGELOG.md and a
 `package.json` whose exports name the compiled files.

 ## Releases
@@ -1,10 +1,11 @@
 #!/usr/bin/env node

 // Builds the published package in dist/: the toolkit compiled to JavaScript with its declarations, the declaration of
-// the font plugin's virtual module, README.md, CHANGELOG.md and a package.json whose exports name the compiled files.
+// the font plugin's virtual module, the SQL of the server, README.md, CHANGELOG.md and a package.json whose exports
+// name the compiled files.

 import { spawnSync } from 'node:child_process';
-import { copyFileSync, readdirSync, readFileSync, rmSync, writeFileSync } from 'node:fs';
+import { copyFileSync, cpSync, readdirSync, readFileSync, rmSync, writeFileSync } from 'node:fs';
 import { join } from 'node:path';

 const ROOT = import.meta.dirname;
@@ -34,6 +35,9 @@ copyFileSync(join(ROOT, 'web', 'virtual-font.d.ts'), join(DIST, 'web', 'virtual-
 const renderApp = join(DIST, 'web', 'renderApp.d.ts');
 writeFileSync(renderApp, `/// <reference path="./virtual-font.d.ts" />\n${readFileSync(renderApp, 'utf8')}`);

+// The tfvars store reads its SQL next to the compiled module.
+cpSync(join(ROOT, 'server', 'sql'), join(DIST, 'server', 'sql'), { recursive: true });
+
 for (const file of ['README.md', 'CHANGELOG.md']) copyFileSync(join(ROOT, file), join(DIST, file));

 const source = JSON.parse(readFileSync(join(ROOT, 'package.json'), 'utf8'));
@@ -1,12 +1,12 @@
 {
  "name": "@koszewscy/sk-react-toolkit",
-  "version": "0.3.0",
+  "version": "0.4.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "@koszewscy/sk-react-toolkit",
-      "version": "0.3.0",
+      "version": "0.4.0",
      "devDependencies": {
        "@emotion/react": "^11.14.0",
        "@emotion/styled": "^11.14.1",
@@ -14,10 +14,12 @@
        "@mui/icons-material": "^9.5.0",
        "@mui/material": "^9.5.0",
        "@types/node": "^26.6.5",
+        "@types/pg": "^8.23.1",
        "@types/react": "^19.3.0",
        "@types/react-dom": "^19.3.0",
        "fastify": "^5.12.7",
        "oxlint": "^1.89.0",
+        "pg": "^8.23.1",
        "react": "^19.3.1",
        "react-dom": "^19.3.1",
        "typescript": "^7.0.2",
@@ -33,6 +35,7 @@
        "@mui/icons-material": "^9.5.0",
        "@mui/material": "^9.5.0",
        "fastify": "^5.12.7",
+        "pg": "^8.23.1",
        "react": "^19.3.1",
        "react-dom": "^19.3.1",
        "vite": "^8.3.5"
@@ -56,6 +59,9 @@
        "fastify": {
          "optional": true
        },
+        "pg": {
+          "optional": true
+        },
        "react": {
          "optional": true
        },
@@ -1539,6 +1545,18 @@
      "dev": true,
      "license": "MIT"
    },
+    "node_modules/@types/pg": {
+      "version": "8.23.1",
+      "resolved": "https://registry.npmjs.org/@types/pg/-/pg-8.23.1.tgz",
+      "integrity": "sha512-fKVHpikPdg4GKks3JuLEhvwSyvwzF23hnabPy6DD8ljVbC7+6J5dQzdv4arV6jqq57djnMgs1HKBxX4P8aBI3A==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@types/node": "*",
+        "pg-protocol": "*",
+        "pg-types": "^2.2.0"
+      }
+    },
    "node_modules/@types/prop-types": {
      "version": "15.7.15",
      "resolved": "https://registry.npmjs.org/@types/prop-types/-/prop-types-15.7.15.tgz",
@@ -3131,6 +3149,103 @@
        "node": ">=8"
      }
    },
+    "node_modules/pg": {
+      "version": "8.23.1",
+      "resolved": "https://registry.npmjs.org/pg/-/pg-8.23.1.tgz",
+      "integrity": "sha512-aL96AHANtWjPLDOLqnhx+ngp9+UK7ETEU8VJrDCGvsSSi/mGLcWYsS6Herg7lmaBJe4uwrfqsa7gTEFaSizDoQ==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "pg-connection-string": "^2.14.1",
+        "pg-pool": "^3.14.0",
+        "pg-protocol": "^1.16.1",
+        "pg-types": "2.2.0",
+        "pgpass": "1.0.5"
+      },
+      "engines": {
+        "node": ">= 16.0.0"
+      },
+      "optionalDependencies": {
+        "pg-cloudflare": "^1.4.1"
+      },
+      "peerDependencies": {
+        "pg-native": ">=3.0.1"
+      },
+      "peerDependenciesMeta": {
+        "pg-native": {
+          "optional": true
+        }
+      }
+    },
+    "node_modules/pg-cloudflare": {
+      "version": "1.4.1",
+      "resolved": "https://registry.npmjs.org/pg-cloudflare/-/pg-cloudflare-1.4.1.tgz",
+      "integrity": "sha512-6PQbsFWZcp9EmJEwy5cGQ2La+AMWpP46lgbb8X+U/XsHIUweYDNCpeuKck5RxL2MdVFi7krbbEi5nX4Zh7JhrQ==",
+      "dev": true,
+      "license": "MIT",
+      "optional": true
+    },
+    "node_modules/pg-connection-string": {
+      "version": "2.14.1",
+      "resolved": "https://registry.npmjs.org/pg-connection-string/-/pg-connection-string-2.14.1.tgz",
+      "integrity": "sha512-qR3kGNPBLpCNtz0evbKA0Y/MRFXwSSdT+pTJvYp/bXTcReZbvX1kzF0IyTc1QnxqF7AZbOeBhNL8R5mYQZV/MA==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/pg-int8": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/pg-int8/-/pg-int8-1.0.1.tgz",
+      "integrity": "sha512-WCtabS6t3c8SkpDBUlb1kjOs7l66xsGdKpIPZsg4wR+B3+u9UAum2odSsF9tnvxg80h4ZxLWMy4pRjOsFIqQpw==",
+      "dev": true,
+      "license": "ISC",
+      "engines": {
+        "node": ">=4.0.0"
+      }
+    },
+    "node_modules/pg-pool": {
+      "version": "3.14.0",
+      "resolved": "https://registry.npmjs.org/pg-pool/-/pg-pool-3.14.0.tgz",
+      "integrity": "sha512-gKtPkFdQPU3DksooVLi9LsjZxrsBUZIpa+7aVx+LV5pNh0KzP4Zleud2po+ConrxbuXGBJ6Hfer6hdgpIBpBaw==",
+      "dev": true,
+      "license": "MIT",
+      "peerDependencies": {
+        "pg": ">=8.0"
+      }
+    },
+    "node_modules/pg-protocol": {
+      "version": "1.16.1",
+      "resolved": "https://registry.npmjs.org/pg-protocol/-/pg-protocol-1.16.1.tgz",
+      "integrity": "sha512-p9VOFMiHB/ZbJATetbg+99PxssTVSQRnyuPSQ67mN1+1KBOjZaZ83ZQzltnxPhJwSsC3nwVjJ10DVJlerbFzLg==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/pg-types": {
+      "version": "2.2.0",
+      "resolved": "https://registry.npmjs.org/pg-types/-/pg-types-2.2.0.tgz",
+      "integrity": "sha512-qTAAlrEsl8s4OiEQY69wDvcMIdQN6wdz5ojQiOy6YRMuynxenON0O5oCpJI6lshc6scgAY8qvJ2On/p+CXY0GA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "pg-int8": "1.0.1",
+        "postgres-array": "~2.0.0",
+        "postgres-bytea": "~1.0.0",
+        "postgres-date": "~1.0.4",
+        "postgres-interval": "^1.1.0"
+      },
+      "engines": {
+        "node": ">=4"
+      }
+    },
+    "node_modules/pgpass": {
+      "version": "1.0.5",
+      "resolved": "https://registry.npmjs.org/pgpass/-/pgpass-1.0.5.tgz",
+      "integrity": "sha512-FdW9r/jQZhSeohs1Z3sI1yxFQNFvMcnmfuj4WBMUTxOrAyLMaTcE1aAMBiTlbMNaXvBCQuVi0R7hd8udDSP7ug==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "split2": "^4.1.0"
+      }
+    },
    "node_modules/picocolors": {
      "version": "1.1.1",
      "resolved": "https://registry.npmjs.org/picocolors/-/picocolors-1.1.1.tgz",
@@ -3220,6 +3335,49 @@
        "node": "^10 || ^12 || >=14"
      }
    },
+    "node_modules/postgres-array": {
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/postgres-array/-/postgres-array-2.0.0.tgz",
+      "integrity": "sha512-VpZrUqU5A69eQyW2c5CA1jtLecCsN2U/bD6VilrFDWq5+5UIEVO7nazS3TEcHf1zuPYO/sqGvUvW62g86RXZuA==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=4"
+      }
+    },
+    "node_modules/postgres-bytea": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/postgres-bytea/-/postgres-bytea-1.0.1.tgz",
+      "integrity": "sha512-5+5HqXnsZPE65IJZSMkZtURARZelel2oXUEO8rH83VS/hxH5vv1uHquPg5wZs8yMAfdv971IU+kcPUczi7NVBQ==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=0.10.0"
+      }
+    },
+    "node_modules/postgres-date": {
+      "version": "1.0.7",
+      "resolved": "https://registry.npmjs.org/postgres-date/-/postgres-date-1.0.7.tgz",
+      "integrity": "sha512-suDmjLVQg78nMK2UZ454hAG+OAW+HQPZ6n++TNDUX+L0+uUlLywnoxJKDou51Zm+zTCjrCl0Nq6J9C5hP9vK/Q==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=0.10.0"
+      }
+    },
+    "node_modules/postgres-interval": {
+      "version": "1.2.0",
+      "resolved": "https://registry.npmjs.org/postgres-interval/-/postgres-interval-1.2.0.tgz",
+      "integrity": "sha512-9ZhXKM/rw350N1ovuWHbGxnGh/SNJ4cnxHiM0rxE4VN41wsg8P8zWn9hv/buK00RP4WvlOyr/RBDiptyxVbkZQ==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "xtend": "^4.0.0"
+      },
+      "engines": {
+        "node": ">=0.10.0"
+      }
+    },
    "node_modules/process-warning": {
      "version": "5.1.1",
      "resolved": "https://registry.npmjs.org/process-warning/-/process-warning-5.1.1.tgz",
@@ -3744,6 +3902,16 @@
          "optional": true
        }
      }
+    },
+    "node_modules/xtend": {
+      "version": "4.0.2",
+      "resolved": "https://registry.npmjs.org/xtend/-/xtend-4.0.2.tgz",
+      "integrity": "sha512-LKYU1iAXJXUgAXn9URjiu+MWhyUXHsvfp7mcuYm9dSUKK0/CjtrUwFAxD82/mCWbtLsGjFIad0wIsod4zrTAEQ==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=0.4"
+      }
    }
  }
 }
@@ -1,6 +1,6 @@
 {
  "name": "@koszewscy/sk-react-toolkit",
-  "version": "0.3.0",
+  "version": "0.4.0",
  "description": "Shared code of the React and Fastify web applications: web components, server helpers and the Vite font plugin.",
  "private": true,
  "type": "module",
@@ -19,6 +19,7 @@
  "scripts": {
    "typecheck": "tsc -p tsconfig.json",
    "lint": "oxlint",
+    "test": "node --test server/tfvarsStore.test.ts",
    "build": "node build.mjs"
  },
  "peerDependencies": {
@@ -28,6 +29,7 @@
    "@mui/icons-material": "^9.5.0",
    "@mui/material": "^9.5.0",
    "fastify": "^5.12.7",
+    "pg": "^8.23.1",
    "react": "^19.3.1",
    "react-dom": "^19.3.1",
    "vite": "^8.3.5"
@@ -35,6 +37,7 @@
  "peerDependenciesMeta": {
    "@fastify/static": { "optional": true },
    "fastify": { "optional": true },
+    "pg": { "optional": true },
    "vite": { "optional": true },
    "@emotion/react": { "optional": true },
    "@emotion/styled": { "optional": true },
@@ -50,10 +53,12 @@
    "@mui/icons-material": "^9.5.0",
    "@mui/material": "^9.5.0",
    "@types/node": "^26.6.5",
+    "@types/pg": "^8.23.1",
    "@types/react": "^19.3.0",
    "@types/react-dom": "^19.3.0",
    "fastify": "^5.12.7",
    "oxlint": "^1.89.0",
+    "pg": "^8.23.1",
    "react": "^19.3.1",
    "react-dom": "^19.3.1",
    "typescript": "^7.0.2",
@@ -4,3 +4,6 @@ export { HttpError, errorHandler, notFoundHandler, strict } from './http.ts'
 export { QUIET, createLog, fail, timestampsOn, type Log } from './log.ts'
 export { exitOnSignals, gitVersion, readJsonObject } from './process.ts'
 export { decrypt, encrypt, encryptionKey } from './secrets.ts'
+export type { TfInstance, TfModule, TfvarsFileStatus } from '../shared/tfvars.ts'
+export { STATE_SCHEMA_PATTERN, TFVARS_FILE_PATTERN, TF_NAME_PATTERN } from '../shared/tfvars.ts'
+export { createTfvarsStore, tfvarsText, versionOf, type InstanceVariables, type TfvarsDocument, type TfvarsFile, type TfvarsStore } from './tfvarsStore.ts'
@@ -0,0 +1,117 @@
+-- The store of Terraform modules, their instances and the instances' variable files: the tables tf_modules,
+-- tf_instances and tf_variable_files, and the functions and procedures the store calls. The store applies the file on
+-- its first use in the schema its connection's search path names; every statement can run again.
+
+CREATE TABLE IF NOT EXISTS tf_modules (
+  name             text PRIMARY KEY CHECK (name ~ '^[a-z][a-z0-9-]*$'),
+  root             text NOT NULL CHECK (root <> ''),
+  description      text NOT NULL DEFAULT '',
+  configurator_url text
+);
+
+CREATE TABLE IF NOT EXISTS tf_instances (
+  module       text NOT NULL REFERENCES tf_modules (name),
+  name         text NOT NULL CHECK (name ~ '^[a-z][a-z0-9-]*$'),
+  state_schema text NOT NULL UNIQUE CHECK (state_schema ~ '^[a-z_][a-z0-9_]*$'),
+  created      timestamptz NOT NULL DEFAULT now(),
+  PRIMARY KEY (module, name)
+);
+
+CREATE TABLE IF NOT EXISTS tf_variable_files (
+  module   text NOT NULL,
+  instance text NOT NULL,
+  name     text NOT NULL CHECK (name ~ '^[A-Za-z0-9_.-]+\.tfvars\.json$'),
+  content  jsonb NOT NULL CHECK (jsonb_typeof(content) = 'object'),
+  previous jsonb CHECK (jsonb_typeof(previous) = 'object'),
+  updated  timestamptz NOT NULL DEFAULT now(),
+  PRIMARY KEY (module, instance, name),
+  FOREIGN KEY (module, instance) REFERENCES tf_instances (module, name) ON DELETE CASCADE
+);
+
+-- The modules, by name.
+CREATE OR REPLACE FUNCTION tf_modules_list()
+RETURNS TABLE (name text, root text, description text, configurator_url text)
+LANGUAGE sql STABLE
+SET search_path FROM CURRENT
+AS $$
+  SELECT m.name, m.root, m.description, m.configurator_url FROM tf_modules m ORDER BY m.name
+$$;
+
+-- Creates a module, or changes the one of that name.
+CREATE OR REPLACE PROCEDURE tf_module_put(module_name text, module_root text, module_description text, module_configurator_url text)
+LANGUAGE sql
+SET search_path FROM CURRENT
+AS $$
+  INSERT INTO tf_modules (name, root, description, configurator_url)
+  VALUES (module_name, module_root, module_description, module_configurator_url)
+  ON CONFLICT (name) DO UPDATE SET root = excluded.root, description = excluded.description, configurator_url = excluded.configurator_url
+$$;
+
+-- Deletes a module; the foreign key of tf_instances refuses it while the module has instances.
+CREATE OR REPLACE PROCEDURE tf_module_delete(module_name text)
+LANGUAGE sql
+SET search_path FROM CURRENT
+AS $$
+  DELETE FROM tf_modules WHERE name = module_name
+$$;
+
+-- The instances of a module, by name.
+CREATE OR REPLACE FUNCTION tf_instances_list(module_name text)
+RETURNS TABLE (module text, name text, state_schema text, created timestamptz)
+LANGUAGE sql STABLE
+SET search_path FROM CURRENT
+AS $$
+  SELECT i.module, i.name, i.state_schema, i.created FROM tf_instances i WHERE i.module = module_name ORDER BY i.name
+$$;
+
+-- Creates an instance of a module with the schema of its state.
+CREATE OR REPLACE PROCEDURE tf_instance_create(module_name text, instance_name text, instance_state_schema text)
+LANGUAGE sql
+SET search_path FROM CURRENT
+AS $$
+  INSERT INTO tf_instances (module, name, state_schema) VALUES (module_name, instance_name, instance_state_schema)
+$$;
+
+-- Deletes an instance with its variable files.
+CREATE OR REPLACE PROCEDURE tf_instance_delete(module_name text, instance_name text)
+LANGUAGE sql
+SET search_path FROM CURRENT
+AS $$
+  DELETE FROM tf_instances WHERE module = module_name AND name = instance_name
+$$;
+
+-- The variable files of an instance, by name: content, whether the content it replaced is kept, and the time of the
+-- last write.
+CREATE OR REPLACE FUNCTION tf_variable_files_read(module_name text, instance_name text)
+RETURNS TABLE (name text, content jsonb, previous boolean, updated timestamptz)
+LANGUAGE sql STABLE
+SET search_path FROM CURRENT
+AS $$
+  SELECT f.name, f.content, f.previous IS NOT NULL, f.updated FROM tf_variable_files f
+  WHERE f.module = module_name AND f.instance = instance_name ORDER BY f.name
+$$;
+
+-- Keeps other writers out until the end of the transaction, from the comparison of the version to the commit.
+CREATE OR REPLACE PROCEDURE tf_variable_files_lock()
+LANGUAGE sql
+SET search_path FROM CURRENT
+AS $$
+  LOCK TABLE tf_variable_files IN EXCLUSIVE MODE
+$$;
+
+-- Writes a variable file of an instance, keeping the content it replaces as previous.
+CREATE OR REPLACE PROCEDURE tf_variable_file_put(module_name text, instance_name text, file_name text, file_content jsonb)
+LANGUAGE sql
+SET search_path FROM CURRENT
+AS $$
+  INSERT INTO tf_variable_files (module, instance, name, content) VALUES (module_name, instance_name, file_name, file_content)
+  ON CONFLICT (module, instance, name) DO UPDATE SET previous = tf_variable_files.content, content = excluded.content, updated = now()
+$$;
+
+-- Deletes a variable file of an instance.
+CREATE OR REPLACE PROCEDURE tf_variable_file_delete(module_name text, instance_name text, file_name text)
+LANGUAGE sql
+SET search_path FROM CURRENT
+AS $$
+  DELETE FROM tf_variable_files WHERE module = module_name AND instance = instance_name AND name = file_name
+$$;
@@ -0,0 +1,95 @@
+import assert from 'node:assert/strict'
+import { after, before, test } from 'node:test'
+import pg from 'pg'
+import { HttpError } from './http.ts'
+import { createTfvarsStore, tfvarsText, type TfvarsStore } from './tfvarsStore.ts'
+
+// The tests create a scratch database on the server the PG* variables name, connected to through the database
+// postgres, and drop it at the end.
+const database = `tfvars_store_test_${process.pid}`
+const admin = new pg.Client({ database: 'postgres' })
+let pool: pg.Pool
+let store: TfvarsStore
+
+before(async () => {
+  await admin.connect()
+  await admin.query(`CREATE DATABASE ${database}`)
+  pool = new pg.Pool({ database })
+  store = createTfvarsStore(pool)
+})
+
+after(async () => {
+  await pool?.end()
+  await admin.query(`DROP DATABASE IF EXISTS ${database}`)
+  await admin.end()
+})
+
+const status = async (promise: Promise<unknown>) => {
+  try {
+    await promise
+  } catch (error) {
+    assert.ok(error instanceof HttpError, String(error))
+    return error.statusCode
+  }
+  return 0
+}
+
+test('modules are created, changed, listed and deleted', async () => {
+  await store.modules.put({ name: 'router', root: 'router/terraform', description: 'VPN router', configuratorUrl: null })
+  await store.modules.put({ name: 'router', root: 'router/terraform', description: 'VPN router', configuratorUrl: 'http://localhost:7083/' })
+  await store.modules.put({ name: 'app', root: 'app', description: '', configuratorUrl: null })
+  assert.deepEqual(await store.modules.list(), [
+    { name: 'app', root: 'app', description: '', configuratorUrl: null },
+    { name: 'router', root: 'router/terraform', description: 'VPN router', configuratorUrl: 'http://localhost:7083/' },
+  ])
+  await store.modules.delete('app')
+  assert.deepEqual((await store.modules.list()).map((module) => module.name), ['router'])
+  assert.equal(await status(store.modules.put({ name: 'Bad', root: 'x', description: '', configuratorUrl: null })), 400)
+})
+
+test('instances are created and refused for a missing module or a name in use', async () => {
+  await store.instances.create('router', 'platform', 'terraform_remote_state')
+  await store.instances.create('router', 'test', 'tf_router_test')
+  assert.deepEqual((await store.instances.list('router')).map((instance) => [instance.name, instance.stateSchema]), [
+    ['platform', 'terraform_remote_state'],
+    ['test', 'tf_router_test'],
+  ])
+  assert.equal(await status(store.instances.create('missing', 'x', 'tf_missing_x')), 404)
+  assert.equal(await status(store.instances.create('router', 'test', 'tf_other')), 409)
+  assert.equal(await status(store.instances.create('router', 'other', 'tf_router_test')), 409)
+  assert.equal(await status(store.modules.delete('router')), 409)
+})
+
+test('variable files are written with their version and refused against another version', async () => {
+  const variables = store.variables('router', 'test')
+  const empty = await variables.read()
+  assert.deepEqual(empty.files, [])
+  assert.equal(empty.version, '')
+  assert.equal(await variables.write(empty.version, { 'platform.tfvars.json': tfvarsText({ a: 1 }), 'secrets.tfvars.json': tfvarsText({ s: 'x' }) }), true)
+  const written = await variables.read()
+  assert.deepEqual(written.files.map((file) => [file.name, file.content.toString('utf8')]), [
+    ['platform.tfvars.json', tfvarsText({ a: 1 })],
+    ['secrets.tfvars.json', tfvarsText({ s: 'x' })],
+  ])
+  assert.deepEqual(written.status.map((file) => file.previous), [false, false])
+  assert.equal(await variables.write(empty.version, { 'platform.tfvars.json': tfvarsText({ a: 2 }) }), false)
+  assert.equal(await variables.write(written.version, { 'platform.tfvars.json': tfvarsText({ a: 2 }) }), true)
+  const changed = await variables.read()
+  assert.deepEqual(changed.status.map((file) => file.previous), [true, false])
+  assert.notEqual(changed.version, written.version)
+  assert.equal(await variables.remove(written.version, 'secrets.tfvars.json'), false)
+  assert.equal(await variables.remove(changed.version, 'secrets.tfvars.json'), true)
+  assert.deepEqual((await variables.read()).files.map((file) => file.name), ['platform.tfvars.json'])
+  assert.deepEqual((await store.variables('router', 'platform').read()).files, [])
+  assert.equal(await status(variables.write((await variables.read()).version, { 'notes.json': tfvarsText({}) })), 400)
+  assert.equal(await status(store.variables('router', 'missing').write('', { 'a.tfvars.json': tfvarsText({}) })), 404)
+})
+
+test('an instance is deleted with its variable files, then its module', async () => {
+  await store.instances.delete('router', 'test')
+  await store.instances.delete('router', 'platform')
+  assert.deepEqual(await store.instances.list('router'), [])
+  assert.equal((await pool.query('SELECT count(*)::int AS n FROM tf_variable_files')).rows[0].n, 0)
+  await store.modules.delete('router')
+  assert.deepEqual(await store.modules.list(), [])
+})
@@ -0,0 +1,158 @@
+import { createHash } from 'node:crypto'
+import { readFileSync } from 'node:fs'
+import type { Pool, PoolClient } from 'pg'
+import type { TfInstance, TfModule, TfvarsFileStatus } from '../shared/tfvars.ts'
+import { HttpError } from './http.ts'
+
+/** A variable file of an instance: its name and its content, the object jsonb keeps written as JSON text. */
+export type TfvarsFile = { name: string; content: Buffer }
+
+/** The variable files of an instance, by name, with their version, versionOf the files. */
+export type TfvarsDocument = { files: TfvarsFile[]; status: TfvarsFileStatus[]; version: string }
+
+/** The variable files of one instance. */
+export type InstanceVariables = {
+  read(): Promise<TfvarsDocument>
+  /**
+   * Writes the given files, name and JSON text of an object, when the files are still those of version, keeping each
+   * replaced content as its previous one; answers false, writing nothing, when they changed since.
+   */
+  write(version: string, contents: Record<string, string>): Promise<boolean>
+  /** Deletes the file name when the files are still those of version; answers false, deleting nothing, otherwise. */
+  remove(version: string, name: string): Promise<boolean>
+}
+
+/** The modules, the instances and their variable files in PostgreSQL. */
+export type TfvarsStore = {
+  modules: {
+    list(): Promise<TfModule[]>
+    /** Creates the module, or changes the one of its name. */
+    put(module: TfModule): Promise<void>
+    /** Deletes the module; HttpError 409 while it has instances. */
+    delete(name: string): Promise<void>
+  }
+  instances: {
+    list(module: string): Promise<TfInstance[]>
+    /** HttpError 409 for a name or a state schema in use, 404 for a module that does not exist. */
+    create(module: string, name: string, stateSchema: string): Promise<void>
+    /** Deletes the instance with its variable files. */
+    delete(module: string, name: string): Promise<void>
+  }
+  variables(module: string, instance: string): InstanceVariables
+}
+
+/** The text of a variable file as both stores write it: the object as JSON with two spaces, and a final newline. */
+export function tfvarsText(content: unknown): string {
+  return `${JSON.stringify(content, null, 2)}\n`
+}
+
+/** Identifies the variable files: the name and the SHA-256 of the content of each, in name order. */
+export function versionOf(files: TfvarsFile[]): string {
+  return [...files].sort((a, b) => a.name.localeCompare(b.name))
+    .map((file) => `${file.name}=${createHash('sha256').update(file.content).digest('hex')}`).join(':')
+}
+
+const SQL = new URL('./sql/tfvars_store.sql', import.meta.url)
+
+type FileRow = { name: string; content: object; previous: boolean; updated: Date }
+
+/**
+ * The store of sql/tfvars_store.sql in the database of pool, applied at the first use in the schema of the
+ * connection's search path. A refused change is an HttpError: 409 for a name in use or a module that has instances,
+ * 404 for a module or an instance that does not exist, 400 for a value the tables do not accept.
+ */
+export function createTfvarsStore(pool: Pool): TfvarsStore {
+  let created: Promise<unknown> | null = null
+  const ready = () => (created ??= pool.query(readFileSync(SQL, 'utf8')))
+  const query = async <T extends object>(text: string, values: unknown[]): Promise<T[]> => {
+    await ready()
+    try {
+      return (await pool.query<T>(text, values)).rows
+    } catch (error) {
+      throw refused(error)
+    }
+  }
+  const document = (rows: FileRow[]): TfvarsDocument => {
+    const files = rows.map((row) => ({ name: row.name, content: Buffer.from(tfvarsText(row.content), 'utf8') }))
+    return {
+      files,
+      status: rows.map((row, index) => ({ name: row.name, bytes: files[index].content.length, modified: row.updated.toISOString(), previous: row.previous })),
+      version: versionOf(files),
+    }
+  }
+  /** Runs change in a transaction that holds the lock of the variable files, when they are still those of version. */
+  const locked = async (module: string, instance: string, version: string, change: (client: PoolClient) => Promise<void>) => {
+    await ready()
+    const client = await pool.connect()
+    try {
+      await client.query('BEGIN')
+      await client.query('CALL tf_variable_files_lock()')
+      const { rows } = await client.query<FileRow>('SELECT * FROM tf_variable_files_read($1, $2)', [module, instance])
+      if (document(rows).version !== version) {
+        await client.query('ROLLBACK')
+        return false
+      }
+      await change(client)
+      await client.query('COMMIT')
+      return true
+    } catch (error) {
+      await client.query('ROLLBACK')
+      throw refused(error)
+    } finally {
+      client.release()
+    }
+  }
+  return {
+    modules: {
+      list: async () => (await query<{ name: string; root: string; description: string; configurator_url: string | null }>('SELECT * FROM tf_modules_list()', []))
+        .map((row) => ({ name: row.name, root: row.root, description: row.description, configuratorUrl: row.configurator_url })),
+      async put(module) {
+        await query('CALL tf_module_put($1, $2, $3, $4)', [module.name, module.root, module.description, module.configuratorUrl])
+      },
+      async delete(name) {
+        await query('CALL tf_module_delete($1)', [name])
+      },
+    },
+    instances: {
+      list: async (module) => (await query<{ module: string; name: string; state_schema: string; created: Date }>('SELECT * FROM tf_instances_list($1)', [module]))
+        .map((row) => ({ module: row.module, name: row.name, stateSchema: row.state_schema, created: row.created.toISOString() })),
+      async create(module, name, stateSchema) {
+        await query('CALL tf_instance_create($1, $2, $3)', [module, name, stateSchema])
+      },
+      async delete(module, name) {
+        await query('CALL tf_instance_delete($1, $2)', [module, name])
+      },
+    },
+    variables: (module, instance) => ({
+      read: async () => document(await query<FileRow>('SELECT * FROM tf_variable_files_read($1, $2)', [module, instance])),
+      write: (version, contents) => locked(module, instance, version, async (client) => {
+        for (const [name, text] of Object.entries(contents)) {
+          await client.query('CALL tf_variable_file_put($1, $2, $3, $4::jsonb)', [module, instance, name, text])
+        }
+      }),
+      remove: (version, name) => locked(module, instance, version, async (client) => {
+        await client.query('CALL tf_variable_file_delete($1, $2, $3)', [module, instance, name])
+      }),
+    }),
+  }
+}
+
+/** The HttpError of an error of PostgreSQL that refuses a change, by its SQLSTATE; any other error as it is. */
+function refused(error: unknown): unknown {
+  const { code, constraint, detail } = error as { code?: string; constraint?: string; detail?: string }
+  const reason = detail ?? (error as Error).message
+  switch (code) {
+    case '23505':
+      return new HttpError(409, `The name is in use (${reason}).`)
+    case '23503':
+      if (reason.includes('is still referenced')) {
+        return new HttpError(409, `The module has instances; delete them first (${reason}).`)
+      }
+      return new HttpError(404, `The ${constraint === 'tf_instances_module_fkey' ? 'module' : 'instance'} does not exist (${reason}).`)
+    case '23514':
+    case '22P02':
+      return new HttpError(400, `The value is not allowed (${reason}).`)
+    default:
+      return error
+  }
+}
@@ -0,0 +1,36 @@
+/** A registered Terraform module: a folder of Terraform code, relative to the modules folder of Cloud Platform. */
+export type TfModule = {
+  name: string
+  root: string
+  description: string
+  /** The address of the module's configurator, the application that edits the variables of its instances. */
+  configuratorUrl: string | null
+}
+
+/** A deployment of a module, whose state is kept in the schema stateSchema of the pg backend. */
+export type TfInstance = {
+  module: string
+  name: string
+  stateSchema: string
+  /** ISO 8601. */
+  created: string
+}
+
+/** A variable file of an instance, without its content. */
+export type TfvarsFileStatus = {
+  name: string
+  bytes: number
+  /** ISO 8601, the time of the last write. */
+  modified: string
+  /** Whether the content the last write replaced is kept. */
+  previous: boolean
+}
+
+/** The names of modules and instances: a lower-case letter, then lower-case letters, digits and hyphens. */
+export const TF_NAME_PATTERN = /^[a-z][a-z0-9-]*$/
+
+/** The names of variable files: letters, digits, '_', '.' and '-', ending in .tfvars.json. */
+export const TFVARS_FILE_PATTERN = /^[A-Za-z0-9_.-]+\.tfvars\.json$/
+
+/** The names of pg schemas of a state: a lower-case letter or '_', then lower-case letters, digits and '_'. */
+export const STATE_SCHEMA_PATTERN = /^[a-z_][a-z0-9_]*$/
@@ -6,5 +6,6 @@
    "outDir": "dist",
    "declaration": true,
    "rewriteRelativeImportExtensions": true
-  }
+  },
+  "exclude": ["dist", "**/*.test.ts"]
 }
@@ -1,4 +1,6 @@
 export type { CredentialField, CredentialKind, CredentialProfile, CredentialsDocument } from '../shared/credentials.ts'
+export type { TfInstance, TfModule, TfvarsFileStatus } from '../shared/tfvars.ts'
+export { STATE_SCHEMA_PATTERN, TFVARS_FILE_PATTERN, TF_NAME_PATTERN } from '../shared/tfvars.ts'
 export { ApiError, request, type Validation } from './api.ts'
 export { createBrowserSettings } from './browserSettings.ts'
 export { default as Card } from './Card.tsx'