serviceradar-sdk-go

ServiceRadar plugin SDK for Go (TinyGo/WASM).

Overview

This SDK lets you write ServiceRadar plugin checkers in Go without handling low-level WASM host calls. It handles:

• Config decoding from the host
• Result builder for serviceradar.plugin_result.v1
• Logging bridge
• HTTP/TCP/UDP proxy wrappers
• Support for Websockets
• Event emission + alert promotion hints

Install

go get git.carverauto.dev/carverauto/serviceradar-sdk-go

Example

package main

import (
    "context"
    "fmt"
    "git.carverauto.dev/carverauto/serviceradar-sdk-go/sdk"
)

type Config struct {
    URL     string  `json:"url"`
    WarnMS  float64 `json:"warn_ms"`
    CritMS  float64 `json:"crit_ms"`
}

//export run_check
func run_check() {
    _ = sdk.Execute(func() (*sdk.Result, error) {
        var cfg Config

        if err := sdk.LoadConfig(&cfg); err != nil {
            return nil, err
        }

        resp, err := sdk.HTTP.GetContext(context.Background(), cfg.URL)
        if err != nil {
            return nil, fmt.Errorf("http request failed: %w", err)
        }

        latency := float64(resp.Duration.Milliseconds())
        thresholds := sdk.Thresholds(cfg.WarnMS, cfg.CritMS)

        return sdk.NewResult().
            WithSummary(fmt.Sprintf("http %d in %.0fms", resp.Status, latency)).
            WithThresholds(latency, thresholds.Warn, thresholds.Crit).
            WithMetric("latency_ms", latency, "ms", thresholds).
            WithStatCard("Latency", fmt.Sprintf("%.0fms", latency), "success"), nil
    })
}

func main() {}

Examples

• examples/http-check: HTTP latency check with thresholds and events
• examples/tcp-check: TCP connectivity check with optional write/read
• examples/udp-check: UDP send check with bytes-sent metric
• examples/widgets-check: HTTP check demonstrating stat card, table, sparkline, and markdown widgets

API ergonomics

Execute and error handling

Execute accepts a function that returns (*Result, error) and itself returns an error:

err := sdk.Execute(func() (*sdk.Result, error) {
    // ...
    return sdk.Ok("ok"), nil
})
if err != nil {
    // Optional: handle submit/serialize errors (logging is already done by the SDK)
}

If your function returns a non-nil error, the SDK auto-generates a critical result (or upgrades your result to critical) and records the error details in the payload. This keeps the happy path concise while still surfacing failures.

Defaults and zero-value behavior

Defaults are applied at the edge (right before serialization) so Serialize does not mutate the original object:

• SchemaVersion defaults to 1
• Status defaults to UNKNOWN
• Summary defaults to the status string
• ObservedAt defaults to “now” in RFC3339Nano

This means var r sdk.Result is safe; serialization produces a valid payload without altering r.

Fluent builders

Result has both conventional setters (SetSummary, AddMetric, etc.) and fluent builders (WithSummary, WithMetric, etc.) so you can choose style:

return sdk.NewResult().
    WithSummary("all good").
    WithMetric("cpu", 10, "%", nil).
    WithLabel("version", "1.2.3"), nil

Threshold helpers

Use ThresholdSpec for warning/critical thresholds and Thresholds(warn, crit) to build one without helper functions:

thresholds := sdk.Thresholds(50, 100)
res.WithMetric("latency_ms", 10, "ms", thresholds)
res.WithThresholds(10, thresholds.Warn, thresholds.Crit)

Context-aware I/O

Context variants exist for host I/O to match Go expectations:

• HTTP: HTTP.DoContext, HTTP.GetContext, HTTP.PostContext
• TCP: TCPDialContext, (*TCPConn).ReadContext, (*TCPConn).WriteContext
• UDP: UDPSendToContext
• WebSocket: WebSocketDialContext, (*WebSocketConn).SendContext, (*WebSocketConn).RecvContext

These currently check ctx.Err() before the host call (TinyGo/Wasm is synchronous), but give you a stable API if cancellation support is added later.

WebSocket Support

The SDK provides WebSocket client capabilities for plugins that need to communicate with WebSocket servers:

// Dial a WebSocket endpoint
conn, err := sdk.WebSocketDialContext(ctx, "ws://localhost:8080/ws", 10*time.Second)
if err != nil {
    return nil, fmt.Errorf("websocket dial failed: %w", err)
}
defer conn.Close()

// Send a message
if err := conn.SendContext(ctx, []byte(`{"method": "getInfo"}`), 10*time.Second); err != nil {
    return nil, fmt.Errorf("websocket send failed: %w", err)
}

// Read response
buf := make([]byte, 4096)
n, err := conn.RecvContext(ctx, buf, 10*time.Second)
if err != nil {
    return nil, fmt.Errorf("websocket recv failed: %w", err)
}
data := buf[:n]

WebSocket connections are mediated by the host runtime, which enforces:

• Domain allowlists: Only permitted domains can be connected to
• Port restrictions: Only allowed ports can be accessed
• Connection limits: Maximum concurrent connections per plugin

The plugin must have the following capabilities in its manifest:

• websocket_connect: Permission to establish WebSocket connections
• websocket_send: Permission to send messages
• websocket_recv: Permission to receive messages
• websocket_close: Permission to close connections

To include headers (for example Authorization) on the initial WebSocket handshake:

headers := map[string]string{
  "Authorization": "Basic <base64-user-pass>",
}
conn, err := sdk.WebSocketConnectWithHeaders("wss://camera.local/vapix/ws-data-stream?sources=events", headers, 10*time.Second)

Config loading

LoadConfig is an alias of GetConfig for more idiomatic naming in user code:

if err := sdk.LoadConfig(&cfg); err != nil {
    return nil, err
}

Policy input payload helpers (serviceradar.plugin_inputs.v1)

For policy-driven plugin assignments, decode and validate the typed input payload:

var payload sdk.PluginInputsPayload

if err := sdk.LoadConfig(&payload); err != nil {
    return nil, err
}
if err := payload.Validate(); err != nil {
    return nil, err
}

// Iterate all resolved items (devices/interfaces/etc.)
err := payload.EachItem(func(item sdk.PluginInputItem) error {
    // item.Entity: "devices" | "interfaces" | ...
    // item.Item:   map with resolved fields (uid/ip/if_name/etc.)
    return nil
})
if err != nil {
    return nil, err
}

devices := payload.ItemsByEntity("devices")
_ = devices

Helpers also include:

• sdk.ParsePluginInputsJSON([]byte)
• sdk.ParsePluginInputsMap(map[string]any)
• (*PluginInputsPayload).FlattenItems()
• (*PluginInputsPayload).ItemsByEntity(string)
• (*PluginInputsPayload).ItemsByName(string)

Build

# Requires TinyGo
cd examples/http-check

tinygo build -o plugin.wasm -target=wasi ./

Host ABI

The agent imports host functions from the env module:

• get_config
• log
• submit_result
• http_request
• tcp_connect / tcp_read / tcp_write / tcp_close
• udp_sendto
• websocket_connect / websocket_send / websocket_recv / websocket_close
• camera_media_open / camera_media_write / camera_media_heartbeat / camera_media_close

The SDK wraps these functions and exports alloc/dealloc for host memory access.

Event and Alert Hints

The SDK emits optional fields in the result payload to support event promotion:

• events: list of OCSF Event Log Activity objects
• alert_hint: boolean flag for immediate promotion
• condition_id: string used for de-duplication and auto-clear logic

These fields are ignored safely by older control-plane builds.