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" | "electron"
  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" | "electron"
  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" | "electron"
  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" | "electron"
  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" | "electron"
  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"
    }
  }

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

  // 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
  electron: boolean         // Allow updates to Electron apps

  // 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, android, or electron)
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' | 'electron',
  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,
  electron 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.

Keep going from Channel API Endpoint

If you are using Channel API Endpoint to plan channel routing and staged rollout, connect it with Using @capgo/capacitor-updater for the native capability in Using @capgo/capacitor-updater, Channels for the implementation detail in Channels, Channels for the implementation detail in Channels, Channels for the implementation detail in Channels, and Beta Testing Solution for the product workflow in Beta Testing Solution.