Auto Generated Tanstack Query Patterns

Key points:

• refetchInterval receives query object with state.data and state.dataUpdateCount
• Return false to stop polling based on data condition
• Exponential formula: baseDelay * multiplier ** attemptCount
• Always cap max delay with Math.min()

Conditional Query Enabling

Use enabled flag to control when queries run:

// From DigestTrigger.tsx
const { data, error } = useQuery({
  queryKey: ["execution-status", executionArn],
  queryFn: async () => { /* ... */ },
  enabled: !!executionArn && pollingEnabled, // Double condition
  refetchInterval: isPollingEnabled ? 10000 : false,
});

Pattern:

• !!variable ensures boolean for truthy check
• Combine multiple conditions with &&
• Use separate state for polling control (pollingEnabled)
• Set refetchInterval: false when disabled

Status-Based Polling Termination

Stop polling in useEffect when terminal status reached:

// From DigestTrigger.tsx
useEffect(() => {
  if (executionStatus?.status === "SUCCEEDED") {
    setPollingEnabled(false);
    toast.success("Digest generation completed successfully!");
    setExecutionArn(null);
  } else if (executionStatus?.status === "FAILED") {
    setPollingEnabled(false);
    toast.error("Digest generation failed. Check logs for details.");
    setExecutionArn(null);
  } else if (executionStatus?.status === "ABORTED") {
    setPollingEnabled(false);
    toast.error("Digest generation was aborted.");
    setExecutionArn(null);
  }
}, [executionStatus?.status]);

Always:

• Handle terminal statuses: SUCCEEDED, FAILED, ABORTED
• Disable polling first
• Show toast notification
• Clear execution tracking state
• Don't update state in refetchInterval (causes render issues)

Timeout Cleanup Pattern

Add hard timeout to prevent infinite polling:

// From DigestTrigger.tsx
useEffect(() => {
  if (executionArn && pollingEnabled) {
    const timeout = setTimeout(() => {
      toast.warning(
        "Execution status check timed out. The process may still be running in the background."
      );
      setPollingEnabled(false);
      setExecutionArn(null);
    }, 5 * 60 * 1000); // 5 minutes

    return () => clearTimeout(timeout);
  }
}, [executionArn, pollingEnabled]);

Pattern:

• Set timeout only when polling active
• Return cleanup function
• Clear both polling flag and tracking state
• Inform user process may still run

Error Handling with useEffect

Handle query errors separately from success:

// From DigestTrigger.tsx
const { data, error: statusError } = useQuery({
  queryKey: ["execution-status", executionArn],
  queryFn: async () => {
    if (!res.ok) {
      const errorData = await res.json().catch(() => ({}));
      throw new Error(errorData.error || "Failed to fetch execution status");
    }
    return res.json();
  },
  retry: 3,
});

useEffect(() => {
  if (statusError) {
    console.error("Error polling execution status:", statusError);
    toast.error("Unable to check execution status. The process may still be running.");
    setPollingEnabled(false);
    setExecutionArn(null);
  }
}, [statusError]);

Pattern:

• Name error with descriptive suffix: statusError, fetchError
• Log to console for debugging
• Show user-friendly toast
• Clean up polling state
• .catch(() => ({})) for safe JSON parsing

Mutation Pattern with Toast Notifications

Use onSuccess and onError callbacks:

// From DigestTrigger.tsx
const triggerMutation = useMutation({
  mutationFn: async (options: {
    cleanup: boolean;
    useStepFunctions: boolean;
    historicalMode: boolean;
    dateRange?: { start: string; end: string };
  }) => {
    const res = await fetch("/api/digest/trigger", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify(options),
    });

    if (!res.ok) {
      const error = await res.json();
      throw new Error(error.message || "Failed to trigger digest");
    }

    return res.json();
  },
  onSuccess: (data) => {
    if (data.executionArn) {
      setExecutionArn(data.executionArn);
      setPollingEnabled(true);
      toast.success(`Step Functions pipeline started! Execution: ${data.executionName}`);
    } else {
      toast.success(
        cleanup ? "Cleanup digest generation started!" : "Weekly digest generation started!"
      );
    }
  },
  onError: () => {
    toast.error("Failed to trigger digest generation");
  },
});

// Trigger with typed options
const handleTrigger = () => {
  triggerMutation.mutate({
    cleanup,
    useStepFunctions,
    historicalMode,
    ...(historicalMode && startDate && endDate && {
      dateRange: { start: startDate, end: endDate },
    }),
  });
};

Pattern:

• Type mutationFn parameter for safety
• Throw errors in mutationFn to trigger onError
• Handle conditional response data in onSuccess
• Start polling in onSuccess if needed
• Use ternary for context-specific messages

Query Key Patterns

Structure query keys for proper caching:

// Simple key
queryKey: ["executions"]

// Key with parameter
queryKey: ["execution-status", executionArn]

Rules:

• First element: resource type (string)
• Second element: identifier (string, number, null)
• More specific keys for dependent queries
• Include all variables that affect query result

Simple Polling Pattern

For lists that need regular updates:

// From frontend/components/dashboard/ExecutionHistory.tsx
const [isPollingEnabled, setIsPollingEnabled] = useState(true);

const { data, isLoading, refetch } = useQuery({
  queryKey: ["executions"],
  queryFn: async () => {
    const res = await fetch("/api/stepfunctions/executions?maxResults=10");
    if (!res.ok) throw new Error("Failed to fetch executions");
    return res.json();
  },
  refetchInterval: isPollingEnabled ? 10000 : false, // 10s fixed interval
});

// Cleanup on unmount
useEffect(() => {
  return () => {
    setIsPollingEnabled(false);
  };
}, []);

Pattern:

• Fixed interval for list queries (10s typical)
• State-controlled polling enable/disable
• Cleanup in unmount effect
• Provide manual refetch for user control

Loading States

Use mutation and query states for UI:

// Button disabled during mutation or polling
<Button
  disabled={triggerMutation.isPending || !!executionArn}
  onClick={handleTrigger}
>
  {triggerMutation.isPending || executionArn ? (
    <>
      <Loader2 className="animate-spin" />
      Processing...
    </>
  ) : (
    <>
      <Play />
      Generate Digest
    </>
  )}
</Button>

// Show loading state for initial fetch
if (isLoading) {
  return <Loader2 className="animate-spin" />;
}

States to check:

• isPending - Mutation in flight
• isLoading - Initial query load
• isSuccess - Mutation succeeded (don't use for queries)
• Custom state - Async operations like polling

Key Files

• frontend/components/dashboard/DigestTrigger.tsx - Complex polling with exponential backoff
• frontend/components/dashboard/ExecutionHistory.tsx - Simple list polling
• Uses sonner for toast notifications

Avoid

• Don't update state in refetchInterval callback (causes render issues)
• Don't poll without timeout protection
• Don't forget cleanup on unmount
• Don't hardcode error messages (extract from API response)
• Don't use query.state.data without null checks
• Don't mix isLoading and isPending (use correct one for context)