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See the logs for one request

Use this guide when you have found a slow or failed request and want to read what the code printed while it handled it, or when you have an error log and want to see the whole request around it.

How logs and traces are linked

Section titled “How logs and traces are linked”

A log belongs to a request when it carries that request’s trace ID and span ID, in the trace_id and span_id fields. OpenTelemetry SDKs and logging bridges add them for you when a log is written inside an active span. Logs without them can still be searched, but FuseScope cannot tie them to a trace.

From a trace to its logs

Section titled “From a trace to its logs”

  1. Open the trace. From the Traces explorer, a service page or an exception, open the trace of the request you care about.

  2. Pick a span. In the Waterfall, click the span you want to look at, for example the service’s entry span or the one that failed. Span details opens on the right.

  3. Open the Logs tab. It lists the logs written while that span ran, and other logs of the same trace around them for context, newest first. The stripe on each row is the log’s severity. Click a log to open it in the Logs explorer, in a new tab.

  4. Search further. Click Open in Logs Explorer. The Logs explorer opens with a filter on the trace ID, where you can add filters, change the columns or save the view.

A HotROD /dispatch trace with the frontend span selected and the Logs tab open: five frontend logs of the request, from “HTTP GET /dispatch?customer=123 started” to “HTTP GET /dispatch completed 200”, with a red “failed to fetch driver location: redis timeout” in between, and Open in Logs Explorer at the bottom.

From a log to its trace

Section titled “From a log to its trace”

  1. Find the log. Open Logs in the sidebar and search, for example:

    severity_text ILIKE 'error' AND service.name = 'frontend'

    ILIKE ignores case, so it matches ERROR, Error and error. You can also hover ERROR in the Severity Text filter and click Only, which matches every spelling of the level.

  2. Open it. Click the log. Log details shows its service, severity, trace ID and span ID.

  3. Open the trace. Click View trace at the top of the panel. The trace opens in a new tab with the log’s span selected. The trace ID under TRACE ID is a link to the trace too.

Log details for a frontend ERROR log, “failed to fetch driver location: redis timeout”, with View trace at the top and the trace ID and span ID in the highlighted fields.

If View trace is missing, the log has no trace_id; see How logs and traces are linked.

Search by trace ID

Section titled “Search by trace ID”

If you already have a trace ID, from a support ticket or an error page, search for it directly:

In the Logs explorer:

trace_id = '434bfdb4aeb5d5a3e198d3535b5b586f'

Expected result

Section titled “Expected result”

You see the request’s spans and its log lines side by side, in time order, and can move between them in one click.

Section titled “Related”