Service Unavailable (service_unavailable)

HTTP 503Horizon RFC 7807 ProblemCode: service_unavailable

Type URI: https://orion.stellarchain.io/horizon-errors/service_unavailable

The request cannot be serviced at this time because a required subsystem is warming up or temporarily unreachable.

Quick Fix & Resolution

Retry the request; HA load balancing automatically routes around unavailable replicas.

Response Payload & SDK Handling

RFC 7807 JSON Response

{
  "type": "https://orion.stellarchain.io/horizon-errors/service_unavailable",
  "title": "Service Unavailable",
  "status": 503,
  "detail": "The request cannot be serviced at this time."
}

TypeScript (@stellar/stellar-sdk)

import { Horizon } from '@stellar/stellar-sdk';

const server = new Horizon.Server('https://pubnet.stellarchain.io');

try {
  const res = await server.ledgers().limit(10).call();
} catch (err: any) {
  const problem = err?.response?.data;
  if (problem?.type === 'https://orion.stellarchain.io/horizon-errors/service_unavailable') {
    console.error('[service_unavailable] HTTP 503:', problem.detail, problem.extras);
  }
}

Go (horizonclient)

client := &horizonclient.Client{
    HorizonURL: "https://pubnet.stellarchain.io",
}
_, err := client.Root()
if hErr := horizonclient.GetError(err); hErr != nil {
    if hErr.Problem.Status == 503 {
        log.Printf("Problem (%s): %s - extras=%v", hErr.Problem.Type, hErr.Problem.Detail, hErr.Problem.Extras)
    }
}

cURL Diagnostic

curl -i -s "https://pubnet.stellarchain.io/" \
  -H "Accept: application/hal+json"

Common Root Causes

• Node is restarting or refreshing its state snapshot.
• Upstream Stellar RPC node is temporarily unreachable.

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