# Langfuse Data Handling - Implementation Details

## Export Trace Data via API

```typescript
import { Langfuse } from "langfuse";
import fs from "fs/promises";

async function exportTraces(options: { fromDate: Date; toDate: Date; format: "json" | "csv"; includeInputs: boolean }) {
  const langfuse = new Langfuse();
  let page = 1;
  const allTraces: any[] = [];

  while (true) {
    const response = await langfuse.fetchTraces({ fromTimestamp: options.fromDate, toTimestamp: options.toDate, limit: 100, page });
    if (response.data.length === 0) break;

    for (const trace of response.data) {
      allTraces.push({
        id: trace.id, name: trace.name, timestamp: trace.timestamp,
        userId: trace.userId, sessionId: trace.sessionId,
        ...(options.includeInputs && { input: trace.input }),
      });
    }
    page++;
    await new Promise((r) => setTimeout(r, 100));
  }

  const filename = `langfuse-export-${options.fromDate.toISOString().split("T")[0]}`;
  if (options.format === "json") {
    await fs.writeFile(`${filename}.json`, JSON.stringify(allTraces, null, 2));
  } else {
    await fs.writeFile(`${filename}.csv`, convertToCSV(allTraces));
  }
  return { filename, count: allTraces.length };
}
```

## Data Retention Policy

```typescript
const DEFAULT_POLICY = {
  defaultRetentionDays: 90,
  traceRetentionDays: 90,
  generationRetentionDays: 30,
  scoreRetentionDays: 365,
  piiRetentionDays: 30,
};

async function applyRetentionPolicy(policy = DEFAULT_POLICY) {
  const langfuse = new Langfuse();
  const cutoffDate = new Date();
  cutoffDate.setDate(cutoffDate.getDate() - policy.traceRetentionDays);

  const oldTraces = await langfuse.fetchTraces({ toTimestamp: cutoffDate, limit: 1000 });
  console.log(`Found ${oldTraces.data.length} traces older than ${policy.traceRetentionDays} days`);
  // For self-hosted: delete via DB. For cloud: configure in dashboard.
}
```

## GDPR Data Subject Requests

```typescript
async function handleDataAccessRequest(userId: string) {
  const langfuse = new Langfuse();
  const traces = await langfuse.fetchTraces({ userId, limit: 10000 });
  return {
    requestType: "GDPR Data Access",
    userId,
    data: { traces: traces.data.map(t => ({ id: t.id, timestamp: t.timestamp, name: t.name })), totalTraces: traces.data.length },
  };
}

async function handleDataDeletionRequest(userId: string) {
  const langfuse = new Langfuse();
  const traces = await langfuse.fetchTraces({ userId, limit: 10000 });
  // For self-hosted: delete from DB. For cloud: submit deletion request.
  return { requestType: "GDPR Deletion", userId, tracesMarkedForDeletion: traces.data.length, status: "pending" };
}
```

## Data Anonymization

```typescript
function anonymizeTrace(trace: any, config = { hashUserId: true, removeInputs: false, removeMetadataFields: ["email", "name", "phone"] }) {
  const anonymized = { ...trace };
  if (config.hashUserId && anonymized.userId) {
    anonymized.userId = crypto.createHash("sha256").update(anonymized.userId).digest("hex").slice(0, 16);
  }
  if (config.removeInputs) anonymized.input = "[REDACTED]";
  if (anonymized.metadata) {
    for (const field of config.removeMetadataFields) delete anonymized.metadata[field];
  }
  return anonymized;
}
```

## Audit Trail

```typescript
class AuditLogger {
  private events: AuditEvent[] = [];

  log(event: Omit<AuditEvent, "timestamp">) {
    const auditEvent = { ...event, timestamp: new Date() };
    this.events.push(auditEvent);
    this.persist(auditEvent);
  }

  private async persist(event: AuditEvent) {
    await fs.appendFile("audit.log", JSON.stringify(event) + "\n");
  }

  async query(options: { from?: Date; actor?: string; action?: string }) {
    const content = await fs.readFile("audit.log", "utf-8");
    let events = content.split("\n").filter(Boolean).map(line => JSON.parse(line));
    if (options.from) events = events.filter(e => new Date(e.timestamp) >= options.from!);
    if (options.actor) events = events.filter(e => e.actor === options.actor);
    return events;
  }
}
```

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