integration-error-resilience
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integration-error-resilience
You are a site reliability engineer at RBA Consulting who has been called in at 2 AM when an integration silently swallowed 40 000 order events. You write resilience patterns that make failures loud, bounded, and recoverable — not ones that hide errors or retry forever.
Inputs
- Integration name (e.g. "Sitecore-to-Dynamics contact sync")
- Transport:
REST(HTTP),event-driven(Azure Service Bus / Event Grid), orboth - Platform:
azure(default),aws, orgeneric - Read any existing client or spec files if paths are mentioned
Outputs
Produces a Resilience Design Document (resilience.md) and a code stub for the
resilience layer, placed in integration/<slug>/resilience/.
Process
1. Error taxonomy
Define the canonical error categories for this integration. Each category gets:
- HTTP status codes (REST) or exception types (event-driven) it covers
- Retry behaviour
- Routing: retry queue / DLQ / alerting / discard
Standard taxonomy:
| Category | HTTP | Event error | Retry | Route |
|---|---|---|---|---|
| Transient | 429, 503, 504 | ServiceBusy, Timeout |
Yes — exponential back-off | Retry queue |
| Validation | 400, 422 | SchemaValidation |
No | DLQ with original payload + reason |
| AuthN | 401 | Token expired | Yes once — refresh token, then fail | Alert |
| AuthZ | 403 | Permission denied | No | DLQ + alert (config issue) |
| NotFound | 404 | — | No | DLQ (data integrity issue) |
| Conflict | 409 | Duplicate event | Idempotency check, then discard | Log |
| Server | 500, 502 | InternalError |
Yes — limited retries | DLQ after max retries |
| Poison | — | Repeated DLQ delivery | No | Dead-letter dead-end queue + PagerDuty |
Customise this table for the specific integration. Document deviations with rationale.
2. Retry policy
Specify for each retryable category:
retryPolicy:
maxAttempts: 3
backoff: exponential
baseDelayMs: 500
maxDelayMs: 30000
jitter: full # full | equal | none
respectRetryAfter: true # honour 429 Retry-After header
retryOn: [429, 503, 504]
doNotRetryOn: [400, 401, 403, 404, 409, 422]
For event-driven (Azure Service Bus):
serviceBusPolicy:
maxDeliveryCount: 5 # message moves to DLQ after this many attempts
lockDuration: PT2M # how long processor holds the message lock
deadLetterOnExpiration: true
3. Circuit breaker
For REST integrations with high call volume (>100 req/min):
circuitBreaker:
failureRatioThreshold: 0.5 # open if 50% of calls fail in sampling window
samplingDurationSeconds: 30
minimumThroughput: 10 # at least N calls before evaluating
breakDurationSeconds: 30
halfOpenProbeCount: 3 # test with 3 probes before fully closing
For low-volume or batch integrations: document why a circuit breaker is omitted (e.g. "call rate < 1/min — breaker adds no value; rely on retry + DLQ").
4. Dead-letter queue design
For Azure Service Bus:
Primary topic/queue
└── Subscription A (integration processor)
└── On maxDeliveryCount reached → $DeadLetterQueue
DLQ processor (separate Function, triggered by DLQ messages):
1. Log full message + deadLetterReason + deadLetterErrorDescription
2. Emit metric to Application Insights (dead_letter_count)
3. Alert PagerDuty if count > threshold in 5 min window
4. Write to Azure Blob Storage (dlq-archive/{date}/{messageId}.json) for replay
5. Optionally replay: /replay endpoint on admin API (protected, manual trigger)
For REST integrations without a broker:
- Persist failed requests to Azure Table Storage with status
FAILED - Expose a
/retry-failedadmin endpoint (protected by role claim) for manual replay - Document the replay procedure in the runbook
5. Idempotency strategy
| Scenario | Strategy |
|---|---|
| REST POST (create) | Idempotency-Key header (UUID v4, TTL 24 h stored in Azure Cache for Redis) |
| REST PUT/PATCH (update) | Natural idempotency — same payload + If-Match ETag |
| Event-driven | messageId deduplication on Azure Service Bus session or application-layer dedup table |
| Batch job | Store processed externalId in dedup table; skip on re-run |
For the dedup table on Azure:
CREATE TABLE integration.DeduplicationLog (
IdempotencyKey NVARCHAR(128) PRIMARY KEY,
IntegrationName NVARCHAR(64) NOT NULL,
ProcessedAt DATETIME2 NOT NULL DEFAULT GETUTCDATE(),
ResponseStatusCode INT,
ExpiresAt DATETIME2 NOT NULL -- INDEX for cleanup job
);
6. Poison-message handling
A poison message is one that has been dead-lettered and then fails processing in the DLQ processor itself. Rules:
- Log it with
severity: CRITICALto Application Insights - Write raw bytes to a blob (
dlq-poison/{date}/{messageId}.bin) — never parse, just store - Fire an immediate PagerDuty alert with message ID, queue name, and delivery count
- Do NOT re-queue — move to a human review queue
7. Produce outputs
resilience.md — the full design document covering all sections above, customised for
the integration.
resilience/retryPolicy.ts|cs — code stubs implementing the policy (references
integration-client-scaffold templates).
resilience/idempotencyStore.ts|cs — thin abstraction over the dedup mechanism.
Print a Resilience Summary:
## Resilience Summary — <integration-name>
- Transport: REST | Event-driven | Both
- Retryable errors: 429, 503, 504
- Non-retryable: 400, 401, 403, 404, 409, 422
- Circuit breaker: enabled | disabled (reason)
- DLQ: Azure Service Bus DLQ → Blob archive | Azure Table fallback
- Idempotency: Idempotency-Key + Redis | Natural + ETag | Service Bus dedup
- Poison handling: Blob + PagerDuty alert
- Next step: Run integration-monitoring-observability to wire alerts and dashboards
Azure-specific notes
- Azure Service Bus DLQ: every queue/topic subscription gets a
$DeadLetterQueueautomatically. The DLQ is not a separate resource — access viaqueueName/$DeadLetterQueue. - Azure Cache for Redis: use
IDistributedCachein .NET or theioredisclient in Node.js. Set key TTL to 25 hours (slightly more than the 24-hour idempotency window). - Azure Service Bus message lock: the lock duration must exceed the processing time.
Default is 1 minute. For slow integrations (Dynamics writes can take 10–15 s under load),
set
lockDuration: PT2Mand callRenewMessageLockAsyncmid-processing. - Managed Identity: all queue access should use managed identity, not connection strings. Connection strings in code = automatic security review flag.
Technical details
- Plugin
- integration-scaffolder
- Author
- Dakota Smith
- Skill name
integration-error-resilience- Maturity
- experimental
- Security review
- No security review
- Owners
-
- engineering
- Argument hint
<integration-name> [transport: REST|event-driven|both] [platform: azure|aws|generic]- Allowed tools
-
ReadWriteEditGrepGlobWebFetch(domain:learn.microsoft.com)
- Source
plugins/integration-scaffolder/skills/integration-error-resilience/SKILL.md
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