Channel API Endpoint

Channels are a core mechanism for managing app updates in Capgo. In self-hosted mode, you need to implement channel endpoints to handle device assignments, channel queries, and channel management operations.

Understanding Channels

Channels allow you to:

• Control update distribution: Assign different app versions to different user groups
• A/B testing: Test new features with specific user segments
• Staged rollouts: Gradually deploy updates to minimize risk
• Environment separation: Separate development, staging, and production updates

Configuration

Configure the channel endpoint URL in your capacitor.config.json:

{
  "plugins": {
    "CapacitorUpdater": {
      "channelUrl": "https://myserver.com/api/channel_self"
    }
  }
}

Channel Operations

The plugin performs different channel operations that your endpoint needs to handle:

1. List Compatible Channels (GET Request)

When the plugin calls listChannels(), it sends a GET request to retrieve all channels that are compatible with the device. This returns channels that match the device’s environment (dev/prod, emulator/real device) and allow either public access or self-assignment.

Request Format

// GET /api/channel_self
// Headers:
{
  "Content-Type": "application/json"
}

// Query parameters:
interface ListChannelsRequest {
  app_id: string
  platform: "ios" | "android"
  is_emulator: boolean
  is_prod: boolean
  key_id?: string
}

Response Format

[
  {
    "id": 1,
    "name": "production",
    "public": true,
    "allow_self_set": false
  },
  {
    "id": 2,
    "name": "beta",
    "public": false,
    "allow_self_set": true
  }
]

Understanding Channel Types

The response includes two important flags for each channel:

• public: true: This is a default channel. Devices cannot self-assign to it using setChannel(). Instead, if a device removes its channel assignment (using unsetChannel()), it will automatically receive updates from this public channel if it matches the device’s conditions.

• allow_self_set: true: This is a self-assignable channel. Devices can explicitly assign themselves to this channel using setChannel(). This is useful for beta testing, A/B testing, or allowing users to opt-in to specific update tracks.

Note

A channel can be either public OR allow_self_set, but typically not both. Public channels serve as the default fallback, while self-assignable channels require explicit opt-in.

2. Get Channel (PUT Request)

When the plugin calls getChannel(), it sends a PUT request to retrieve the device’s current channel assignment.

Request Format

// PUT /api/channel_self
// Headers:
{
  "Content-Type": "application/json"
}

// Body:
interface GetChannelRequest {
  device_id: string
  app_id: string
  platform: "ios" | "android"
  plugin_version: string
  version_build: string
  version_code: string
  version_name: string
  is_emulator: boolean
  is_prod: boolean
  defaultChannel?: string
  channel?: string  // For newer plugin versions, contains local channel override
}

Response Format

{
  "status": "ok",
  "channel": "production",
  "allowSet": true,
  "message": "",
  "error": ""
}

3. Set Channel (POST Request)

When the plugin calls setChannel(), it sends a POST request to assign the device to a specific channel.

Request Format

// POST /api/channel_self
interface SetChannelRequest {
  device_id: string
  app_id: string
  channel: string
  platform: "ios" | "android"
  plugin_version: string
  version_build: string
  version_code: string
  version_name: string
  is_emulator: boolean
  is_prod: boolean
}

Response Format

{
  "status": "ok",
  "message": "Device assigned to channel successfully",
  "error": ""
}

Error Cases

When a device tries to assign itself to a public channel (one with public: true), your endpoint should return an error:

{
  "status": "error",
  "error": "public_channel_self_set_not_allowed",
  "message": "This channel is public and does not allow device self-assignment. Unset the channel and the device will automatically use the public channel."
}

When a device tries to assign itself to a channel that doesn’t allow self-assignment:

{
  "status": "error",
  "error": "channel_self_set_not_allowed",
  "message": "This channel does not allow devices to self associate"
}

4. Unset Channel (DELETE Request)

When the plugin calls unsetChannel(), it sends a DELETE request to remove the device’s channel assignment.

Request Format

// DELETE /api/channel_self
interface UnsetChannelRequest {
  device_id: string
  app_id: string
  platform: "ios" | "android"
  plugin_version: string
  version_build: string
  version_code: string
  version_name: string
}

Implementation Example

Here’s a JavaScript example of how to implement the channel endpoint:

interface ChannelRequest {
  device_id: string
  app_id: string
  channel?: string
  platform: "ios" | "android"
  plugin_version: string
  version_build: string
  version_code: string
  version_name: string
}

interface ChannelResponse {
  status: "ok" | "error"
  channel?: string
  allowSet?: boolean
  message?: string
  error?: string
}

export const handler = async (event) => {
  const method = event.httpMethod || event.method
  const body = JSON.parse(event.body || '{}') as ChannelRequest

  const { device_id, app_id, channel, platform } = body

  try {
    switch (method) {
      case 'GET':
        return await getDeviceChannel(device_id, app_id)

      case 'POST':
        return await setDeviceChannel(device_id, app_id, channel!, platform)

      case 'DELETE':
        return await unsetDeviceChannel(device_id, app_id)

      default:
        return {
          status: "error",
          error: "Method not allowed"
        }
    }
  } catch (error) {
    return {
      status: "error",
      error: error.message
    }
  }
}

async function getDeviceChannel(deviceId: string, appId: string): Promise<ChannelResponse> {
  // Query your database for device channel assignment
  const assignment = await database.getDeviceChannel(deviceId, appId)

  if (assignment) {
    return {
      status: "ok",
      channel: assignment.channel,
      allowSet: assignment.allowSelfAssign
    }
  }

  // Return default channel if no assignment found
  return {
    status: "ok",
    channel: "production", // Your default channel
    allowSet: true
  }
}

async function setDeviceChannel(
  deviceId: string,
  appId: string,
  channel: string,
  platform: string
): Promise<ChannelResponse> {
  // Validate channel exists and allows self-assignment
  const channelConfig = await database.getChannelConfig(channel, appId)

  if (!channelConfig) {
    return {
      status: "error",
      error: "Channel not found"
    }
  }

  if (!channelConfig.allowDeviceSelfSet) {
    return {
      status: "error",
      error: "Channel does not allow self-assignment"
    }
  }

  // Check platform restrictions
  if (platform === "ios" && !channelConfig.ios) {
    return {
      status: "error",
      error: "Channel not available for iOS"
    }
  }

  if (platform === "android" && !channelConfig.android) {
    return {
      status: "error",
      error: "Channel not available for Android"
    }
  }

  // Save the assignment
  await database.setDeviceChannel(deviceId, appId, channel)

  return {
    status: "ok",
    message: "Device assigned to channel successfully"
  }
}

async function unsetDeviceChannel(deviceId: string, appId: string): Promise<ChannelResponse> {
  // Remove device channel assignment
  await database.removeDeviceChannel(deviceId, appId)

  return {
    status: "ok",
    message: "Device channel assignment removed"
  }
}

Channel Configuration

Your channel system should support these configuration options:

interface ChannelConfig {
  name: string
  appId: string

  // Platform targeting
  ios: boolean              // Allow updates to iOS devices
  android: boolean          // Allow updates to Android devices

  // Device type restrictions
  allow_emulator: boolean   // Allow updates on emulator/simulator devices
  allow_device: boolean     // Allow updates on real/physical devices

  // Build type restrictions
  allow_dev: boolean        // Allow updates on development builds (is_prod=false)
  allow_prod: boolean       // Allow updates on production builds (is_prod=true)

  // Channel assignment
  public: boolean           // Default channel - devices fall back to this when no override
  allowDeviceSelfSet: boolean  // Allow devices to self-assign via setChannel()

  // Update policies
  disableAutoUpdate: "major" | "minor" | "version_number" | "none"
  disableAutoUpdateUnderNative: boolean
}

Device Filtering Logic

When listing compatible channels (GET request), you should filter channels based on these conditions:

1. Platform check: Channel must allow the device’s platform (ios or android)
2. Device type check:
   • If is_emulator=true: Channel must have allow_emulator=true
   • If is_emulator=false: Channel must have allow_device=true
3. Build type check:
   • If is_prod=true: Channel must have allow_prod=true
   • If is_prod=false: Channel must have allow_dev=true
4. Visibility check: Channel must be either public=true OR allow_device_self_set=true

// Example filtering logic
function getCompatibleChannels(
  platform: 'ios' | 'android',
  isEmulator: boolean,
  isProd: boolean,
  channels: ChannelConfig[]
): ChannelConfig[] {
  return channels.filter(channel => {
    // Platform check
    if (!channel[platform]) return false

    // Device type check
    if (isEmulator && !channel.allow_emulator) return false
    if (!isEmulator && !channel.allow_device) return false

    // Build type check
    if (isProd && !channel.allow_prod) return false
    if (!isProd && !channel.allow_dev) return false

    // Must be accessible (public or self-assignable)
    if (!channel.public && !channel.allowDeviceSelfSet) return false

    return true
  })
}

Database Schema Example

You’ll need to store channel configurations and device assignments:

-- Channels table
CREATE TABLE channels (
  id SERIAL PRIMARY KEY,
  name VARCHAR(255) NOT NULL,
  app_id VARCHAR(255) NOT NULL,

  -- Platform targeting
  ios BOOLEAN DEFAULT true,
  android BOOLEAN DEFAULT true,

  -- Device type restrictions
  allow_emulator BOOLEAN DEFAULT true,   -- Allow emulator/simulator devices
  allow_device BOOLEAN DEFAULT true,     -- Allow real/physical devices

  -- Build type restrictions
  allow_dev BOOLEAN DEFAULT true,        -- Allow development builds
  allow_prod BOOLEAN DEFAULT true,       -- Allow production builds

  -- Channel assignment
  public BOOLEAN DEFAULT false,          -- Default channel (fallback)
  allow_device_self_set BOOLEAN DEFAULT false,  -- Allow self-assignment

  -- Update policies
  disable_auto_update VARCHAR(50) DEFAULT 'none',
  disable_auto_update_under_native BOOLEAN DEFAULT false,

  created_at TIMESTAMP DEFAULT NOW(),
  UNIQUE(name, app_id)
);

-- Device channel assignments table
CREATE TABLE device_channels (
  id SERIAL PRIMARY KEY,
  device_id VARCHAR(255) NOT NULL,
  app_id VARCHAR(255) NOT NULL,
  channel_name VARCHAR(255) NOT NULL,
  assigned_at TIMESTAMP DEFAULT NOW(),
  UNIQUE(device_id, app_id)
);

Error Handling

Handle common error scenarios:

// Channel not found
{
  "status": "error",
  "error": "Channel 'beta' not found"
}

// Self-assignment not allowed
{
  "status": "error",
  "error": "Channel does not allow device self-assignment"
}

// Platform not supported
{
  "status": "error",
  "error": "Channel not available for this platform"
}

// Invalid request
{
  "status": "error",
  "error": "Missing required field: device_id"
}

Best Practices

1. Security: Validate all channel assignments against your business rules
2. Logging: Log all channel operations for auditing and debugging
3. Performance: Cache channel configurations to reduce database queries
4. Validation: Verify device_id and app_id authenticity
5. Rate Limiting: Implement rate limiting to prevent abuse

Integration with Updates

Channel assignments work together with your Update API Endpoint. When a device requests an update, check its channel assignment to determine which version to serve:

async function getUpdateForDevice(deviceId: string, appId: string) {
  // Get device's channel assignment
  const channelAssignment = await getDeviceChannel(deviceId, appId)
  const channel = channelAssignment.channel || 'production'

  // Get the version assigned to this channel
  const channelVersion = await getChannelVersion(channel, appId)

  return {
    version: channelVersion.version,
    url: channelVersion.url,
    checksum: channelVersion.checksum
  }
}

This creates a complete self-hosted channel management system that gives you full control over how updates are distributed to your users.