Put the tenant on every log line and trace

How to do it

Set the tenant once per request or job in the logger's context, so each line inherits it. In OpenTelemetry, add it as a span attribute and as baggage, so calls to other services carry it. Use the internal ID, not the company name, since logs are kept longer than many records, as Keep personal data out of logs explains. With the field, you can answer a customer's incident question from logs alone, and spot the tenant behind a slow minute. It also feeds Find and contain noisy neighbours. Write the logs as Log structured events says.

Examples

JavaScript example

app.use((req, res, next) => {
  req.log = logger.child({ tenant_id: req.tenant.id });
  trace.getActiveSpan()?.setAttribute('tenant.id', String(req.tenant.id));
  next();
});

Python example

import structlog
from opentelemetry import trace

@app.middleware("http")
async def bind_tenant(request, call_next):
    structlog.contextvars.bind_contextvars(tenant_id=request.state.tenant.id)
    trace.get_current_span().set_attribute("tenant.id", str(request.state.tenant.id))
    return await call_next(request)

How to check

Take one hour of logs from production. Every line from a signed-in request or a tenant job has a tenant_id field. A test request as tenant A produces a trace whose spans all carry tenant A's ID.

Sources

• OpenTelemetry baggage

Related rules

• OPS-9 Keep personal data out of logs in Operations and observability
• DAT-73 Find and contain noisy neighbours in Data and databases
• OPS-6 Log structured events in Operations and observability