azure-appconfiguration-ts

# Azure App Configuration SDK for TypeScript

Centralized configuration management with feature flags and dynamic refresh.

## Installation

```bash
# Low-level CRUD SDK
npm install @azure/app-configuration @azure/identity

# High-level provider (recommended for apps)
npm install @azure/app-configuration-provider @azure/identity

# Feature flag management
npm install @microsoft/feature-management
```

## Environment Variables

```bash
AZURE_APPCONFIG_ENDPOINT=https://<your-resource>.azconfig.io
# OR
AZURE_APPCONFIG_CONNECTION_STRING=Endpoint=https://...;Id=...;Secret=...
```

## Authentication

```typescript
import { AppConfigurationClient } from "@azure/app-configuration";
import { DefaultAzureCredential } from "@azure/identity";

// DefaultAzureCredential (recommended)
const client = new AppConfigurationClient(
  process.env.AZURE_APPCONFIG_ENDPOINT!,
  new DefaultAzureCredential()
);

// Connection string
const client2 = new AppConfigurationClient(
  process.env.AZURE_APPCONFIG_CONNECTION_STRING!
);
```

## CRUD Operations

### Create/Update Settings

```typescript
// Add new (fails if exists)
await client.addConfigurationSetting({
  key: "app:settings:message",
  value: "Hello World",
  label: "production",
  contentType: "text/plain",
  tags: { environment: "prod" },
});

// Set (create or update)
await client.setConfigurationSetting({
  key: "app:settings:message",
  value: "Updated value",
  label: "production",
});

// Update with optimistic concurrency
const existing = await client.getConfigurationSetting({ key: "myKey" });
existing.value = "new value";
await client.setConfigurationSetting(existing, { onlyIfUnchanged: true });
```

### Read Settings

```typescript
// Get single setting
const setting = await client.getConfigurationSetting({
  key: "app:settings:message",
  label: "production",  // optional
});
console.log(setting.value);

// List with filters
const settings = client.listConfigurationSettings({
  keyFilter: "app:*",
  labelFilter: "production",
});

for await (const setting of settings) {
  console.log(`${setting.key}: ${setting.value}`);
}
```

### Delete Settings

```typescript
await client.deleteConfigurationSetting({
  key: "app:settings:message",
  label: "production",
});
```

### Lock/Unlock (Read-Only)

```typescript
// Lock
await client.setReadOnly({ key: "myKey", label: "prod" }, true);

// Unlock
await client.setReadOnly({ key: "myKey", label: "prod" }, false);
```

## App Configuration Provider

### Load Configuration

```typescript
import { load } from "@azure/app-configuration-provider";
import { DefaultAzureCredential } from "@azure/identity";

const appConfig = await load(
  process.env.AZURE_APPCONFIG_ENDPOINT!,
  new DefaultAzureCredential(),
  {
    selectors: [
      { keyFilter: "app:*", labelFilter: "production" },
    ],
    trimKeyPrefixes: ["app:"],
  }
);

// Map-style access
const value = appConfig.get("settings:message");

// Object-style access
const config = appConfig.constructConfigurationObject({ separator: ":" });
console.log(config.settings.message);
```

### Dynamic Refresh

```typescript
const appConfig = await load(endpoint, credential, {
  selectors: [{ keyFilter: "app:*" }],
  refreshOptions: {
    enabled: true,
    refreshIntervalInMs: 30_000,  // 30 seconds
  },
});

// Trigger refresh (non-blocking)
appConfig.refresh();

// Listen for refresh events
const disposer = appConfig.onRefresh(() => {
  console.log("Configuration refreshed!");
});

// Express middleware pattern
app.use((req, res, next) => {
  appConfig.refresh();
  next();
});
```

### Key Vault References

```typescript
const appConfig = await load(endpoint, credential, {
  selectors: [{ keyFilter: "app:*" }],
  keyVaultOptions: {
    credential: new DefaultAzureCredential(),
    secretRefreshIntervalInMs: 7200_000,  // 2 hours
  },
});

// Secrets are automatically resolved
const dbPassword = appConfig.get("database:password");
```

## Feature Flags

### Create Feature Flag (Low-Level)

```typescript
import {
  featureFlagPrefix,
  featureFlagContentType,
  FeatureFlagValue,
  ConfigurationSetting,
} from "@azure/app-configuration";

const flag: ConfigurationSetting<FeatureFlagValue> = {
  key: `${featureFlagPrefix}Beta`,
  contentType: featureFlagContentType,
  value: {
    id: "Beta",
    enabled: true,
    description: "Beta feature",
    conditions: {
      clientFilters: [
        {
          name: "Microsoft.Targeting",
          parameters: {
            Audience: {
              Users: ["user@example.com"],
              Groups: [{ Name: "beta-testers", RolloutPercentage: 50 }],
              DefaultRolloutPercentage: 0,
            },
          },
        },
      ],
    },
  },
};

await client.addConfigurationSetting(flag);
```

### Load and Evaluate Feature Flags

```typescript
import { load } from "@azure/app-configuration-provider";
import {
  ConfigurationMapFeatureFlagProvider,
  FeatureManager,
} from "@microsoft/feature-management";

const appConfig = await load(endpoint, credential, {
  featureFlagOptions: {
    enabled: true,
    selectors: [{ keyFilter: "*" }],
    refresh: {
      enabled: true,
      refreshIntervalInMs: 30_000,
    },
  },
});

const featureProvider = new ConfigurationMapFeatureFlagProvider(appConfig);
const featureManager = new FeatureManager(featureProvider);

// Simple check
const isEnabled = await featureManager.isEnabled("Beta");

// With targeting context
const isEnabledForUser = await featureManager.isEnabled("Beta", {
  userId: "user@example.com",
  groups: ["beta-testers"],
});
```

## Snapshots

```typescript
// Create snapshot
const snapshot = await client.beginCreateSnapshotAndWait({
  name: "release-v1.0",
  retentionPeriod: 2592000,  // 30 days
  filters: [{ keyFilter: "app:*", labelFilter: "production" }],
});

// Get snapshot
const snap = await client.getSnapshot("release-v1.0");

// List settings in snapshot
const settings = client.listConfigurationSettingsForSnapshot("release-v1.0");
for await (const setting of settings) {
  console.log(`${setting.key}: ${setting.value}`);
}

// Archive/recover
await client.archiveSnapshot("release-v1.0");
await client.recoverSnapshot("release-v1.0");

// Load from snapshot (provider)
const config = await load(endpoint, credential, {
  selectors: [{ snapshotName: "release-v1.0" }],
});
```

## Labels

```typescript
// Create settings with labels
await client.setConfigurationSetting({
  key: "database:host",
  value: "dev-db.example.com",
  label: "development",
});

await client.setConfigurationSetting({
  key: "database:host",
  value: "prod-db.example.com",
  label: "production",
});

// Filter by label
const prodSettings = client.listConfigurationSettings({
  keyFilter: "*",
  labelFilter: "production",
});

// No label (null label)
const noLabelSettings = client.listConfigurationSettings({
  labelFilter: "\0",
});

// List available labels
for await (const label of client.listLabels()) {
  console.log(label.name);
}
```

## Key Types

```typescript
import {
  AppConfigurationClient,
  ConfigurationSetting,
  FeatureFlagValue,
  SecretReferenceValue,
  featureFlagPrefix,
  featureFlagContentType,
  secretReferenceContentType,
  ListConfigurationSettingsOptions,
} from "@azure/app-configuration";

import { load } from "@azure/app-configuration-provider";

import {
  FeatureManager,
  ConfigurationMapFeatureFlagProvider,
} from "@microsoft/feature-management";
```

## Best Practices

1. **Use provider for apps** - `@azure/app-configuration-provider` for runtime config
2. **Use low-level for management** - `@azure/app-configuration` for CRUD operations
3. **Enable refresh** - For dynamic configuration updates
4. **Use labels** - Separate configurations by environment
5. **Use snapshots** - For immutable release configurations
6. **Sentinel pattern** - Use a sentinel key to trigger full refresh
7. **RBAC roles** - `App Configuration Data Reader` for read-only access