Client-Side Append

appendLog Implementation

// executionStore.ts
appendLog: (entry: LogEntry) => set(state => {
    // Idempotency check — skip if logId already in array
    if (state.logs.some(l => l.logId === entry.logId)) {
        return state;  // Return unchanged state — no re-render triggered
    }

    return {
        logs: [...state.logs, entry]
    };
}),

// Batch append (called for historical loads and large SignalR batches)
appendLogs: (entries: LogEntry[]) => set(state => {
    const existingIds = new Set(state.logs.map(l => l.logId));
    const newEntries  = entries.filter(e => !existingIds.has(e.logId));

    if (newEntries.length === 0) return state;  // No change

    return {
        logs: [...state.logs, ...newEntries]
    };
})

SignalR Handler

// useExecutionSignalR.ts — called on every NodeLogEmitted event
connection.on('NodeLogEmitted', (payload: { entries: LogEntry[] }) => {
    useExecutionStore.getState().appendLogs(payload.entries);
    // Batch append — more efficient than calling appendLog N times
});

Why Idempotency Matters

Three scenarios can cause the same log entry to arrive twice on the client: