> ## Documentation Index
> Fetch the complete documentation index at: https://elastly.io/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Go SDK

> Price lines with a hard deadline and a fallback, verify webhooks, and sync a connector, from Go.

The `github.com/elastly/elastly-go` module is the supported way to call Elastly from Go. The request and
response types are generated from the same [OpenAPI contract](/docs/api/overview) our servers validate
against, so they cannot drift from the API. On top of that it adds what every integration needs: a price
call that never breaks your quote screen, typed errors, webhook verification, and a connector that
pages, checkpoints, retries, and reports for you.

```bash theme={null}
go get github.com/elastly/elastly-go@latest
```

## Keys and scopes

Create API keys under [Settings → API keys](https://app.elastly.io/settings). Scopes are separate on
purpose: a serving key can never write your catalog, and a connector key can never read prices.

| Scope         | Used for               | SDK surface                           |
| ------------- | ---------------------- | ------------------------------------- |
| **ERP**       | Price serving          | `Prices`                              |
| **Connector** | Ingest and write-backs | `ConnectorClient`, `ConnectorRuntime` |

```go theme={null}
import elastly "github.com/elastly/elastly-go"

client := elastly.NewAPIClient(elastly.NewConfiguration())
ctx := context.WithValue(context.Background(), elastly.ContextAccessToken, "elastly_live_...")

prices := elastly.NewPrices(elastly.NewTransport(client))
```

## The one thing to get right: the decision id

Every priced line comes back with a `PricingDecisionID`. **Store it in your own system, on the quote
line it priced.** When that quote later closes and you send it back to Elastly, the id ties what Elastly
recommended to what your rep actually charged. That difference is what the model learns from.

Skip it and everything still looks like it works: prices serve, quotes ingest, dashboards fill. But the
model learns nothing from your quotes, and nothing tells you. So wire it first:

```go theme={null}
result, err := prices.Get(ctx, line, policy)
if err != nil {
    return err
}

if result.Source == elastly.PriceSourceElastly {
    erp.UpdateQuoteLine(quoteLineID, result.Price.PriceCents, result.Price.PricingDecisionID)
}
```

## Price a line, with a fallback

A price call usually runs inside a rep's quote screen or a checkout render. If Elastly is slow or down,
your system must keep working. The SDK makes that a policy you declare, not code you write:

```go theme={null}
line := elastly.PricesRequestLinesInner{}
line.SetProductSku("VLV-200")
line.SetCustomerExternalId("cust-1042")
line.SetQuantity(25)

policy := elastly.StaticFallback(
    func(line elastly.PricesRequestLinesInner, cause elastly.FailOpenCause) (*elastly.FallbackPrice, error) {
        return &elastly.FallbackPrice{PriceCents: erp.ListPrice(line.GetProductSku()), Currency: "USD"}, nil
    },
    elastly.FailOpenDeadline(800*time.Millisecond),
)

result, err := prices.Get(ctx, line, policy)
if err != nil {
    return err
}

switch result.Source {
case elastly.PriceSourceElastly:
    render(result.Price.PriceCents, result.Price.ReasonSummary)
case elastly.PriceSourceFallback:
    render(result.Fallback.PriceCents) // result.Cause.Reason tells you why
case elastly.PriceSourceUnavailable:
    // no price available
}
```

Under this policy a timeout, a 5xx, a rate limit, a malformed body, or a network failure never returns
an error. The SDK retries where it can, then calls your fallback and returns a result with
`Source == PriceSourceFallback` and the cause attached. If your resolver returns `(nil, nil)`, you get
`PriceSourceUnavailable`, an explicit typed no-answer.

Requests that mean your call is wrong (`invalid_request`, `feature_not_enabled`) always return a typed
error, because a bug in your integration is not an outage to paper over. For batch jobs where a wrong
price is worse than no price, use `ThrowOnFailure`, which returns every failure as an error:

```go theme={null}
results, err := prices.GetMany(ctx, lines, elastly.ThrowOnFailure())
```

`GetMany` prices up to 100 lines in one HTTP call. One unknown SKU fails that line alone, never the
whole batch.

## Typed errors

Every contract error code is an `errors.Is` target, and the full detail lives on `*APIStatusError`:

```go theme={null}
_, err := prices.Get(ctx, line, elastly.ThrowOnFailure())

var apiErr *elastly.APIStatusError
if errors.As(err, &apiErr) {
    fmt.Println(apiErr.Code, apiErr.Status, apiErr.RequestID, apiErr.Param)
}

if errors.Is(err, elastly.ErrorCodeRateLimited) {
    // back off; apiErr.RetryAfter carries the delay
}
if errors.Is(err, context.DeadlineExceeded) {
    // the deadline budget was spent
}
```

Every code is exported as a constant (`ErrorCodeUnknownProduct`, `ErrorCodeNoCostBasis`,
`ErrorCodeMonthlyVolumeExceeded`, and the rest) with its HTTP status via `.HTTPStatus()`. Transport
faults are their own types: `*NetworkError`, `*TimeoutError`, `*MalformedResponseError`.

## Verify a webhook

```go theme={null}
verifier := elastly.NewWebhookVerifier("whsec_...")

event, err := verifier.Verify(rawBody, req.Header.Get("Elastly-Signature"))
if err != nil {
    http.Error(w, "bad signature", http.StatusBadRequest)
    return
}

if data, ok := event.SyncCompleted(); ok {
    fmt.Println(data.Connector, data.Totals)
}
```

`Verify` checks the signature in constant time, rejects anything older than five minutes, and returns a
typed event. It returns a `*SignatureVerificationError` on a bad signature, a replay, or a malformed
body. The four event types are `sync.completed`, `recommendation.created`, `price.written_back`, and
`test.ping`, each with a typed accessor (`SyncCompleted`, `RecommendationCreated`, `PriceWrittenBack`,
`TestPing`).

## What the SDK handles for you

* **Idempotency.** Every mutating call carries a key that stays stable across retries, so a retried
  price call can never double-count against your plan.
* **Retries.** Failed calls back off with full jitter and honor `Retry-After` and `RateLimit-Reset`.
* **A circuit breaker.** After repeated failures it stops hammering Elastly and goes straight to your
  fallback, then probes once to recover.
* **Fail-open telemetry.** Every call that falls open reports itself to Elastly (fire and forget, never
  on your latency path), so an outage that hit your quote screen shows up in your dashboard.

## Build a connector

To push your own ERP or storefront into Elastly, the SDK ships a connector runtime: implement a few
methods that read your data, and `ConnectorRuntime` runs the whole sync, with paging, checkpoints,
retries, and write-back leases handled for you.

<Card title="Build a connector" icon="wrench" href="/docs/sdks/build-a-connector">
  Feed your data in, apply approved prices back, in Go or any other language.
</Card>

## Versioning

The SDK's major version is bound to the API version in the URL. Every `0.x` and `1.x` release talks to
`/api/v1`, so an upgrade within a major is always safe.

The source is on [GitHub](https://github.com/elastly/elastly-go). It is generated, so file an issue
rather than a pull request against generated code.