Send traces to an OTLP backend

For operators — anyone running a Temper deployment who wants distributed traces to arrive
in an OTLP/HTTP-compatible backend (Grafana Cloud, Honeycomb, Dash0, Axiom, …).

Outcome

By the end of this playbook your Temper deployment will export OpenTelemetry traces to a
backend of your choice, and you will have verified that spans appear there after a request. You
will know which environment variables to set, which to avoid, and how to turn export off without
a redeploy.

Prerequisites

A running Temper deployment. If you do not have one, see
self-hosting Temper.

An OTLP/HTTP-compatible backend with an ingest URL and auth credentials ready. Any
backend that accepts OTLP/HTTP on the public internet works.

The telemetry concept. Read telemetry to understand the
export model (direct POST, no collector) and the trace structure before configuring the
destination.

Configure the OTLP exporter

Configuration is entirely spec-standard OpenTelemetry environment variables. No
Temper-specific variable, and no vendor name, appears in the code.

Variable	Purpose
`OTEL_EXPORTER_OTLP_ENDPOINT`	Where spans go — the base, to which the SDK appends `/v1/traces`. Use this one. Must be `https`: plaintext `http` is accepted only for `localhost`, `127.0.0.0/8` and `[::1]`, because the headers below carry your vendor credential. Any other `http` endpoint, or one that does not parse, turns export off with a warning naming the variable; the process keeps serving.
`OTEL_EXPORTER_OTLP_TRACES_ENDPOINT`	The trace endpoint verbatim — nothing is appended. Copying a vendor's base URL into this variable POSTs to `/` and 404s. Avoid unless you need the verbatim form.
`OTEL_EXPORTER_OTLP_HEADERS`	`key=value,key=value`. This is where vendor auth lives — which is what makes the setup vendor-agnostic.
`OTEL_SERVICE_NAME`	Which deployable this is — for the Node hops. Rust functions name themselves in code (`temper-api` / `temper-mcp` / `temper-internal`), which the SDK ranks above this variable. On a project that also runs Node lambdas, set this to name the Node half. On a Rust-only project, leave it unset.
`OTEL_TRACES_SAMPLER`, `OTEL_TRACES_SAMPLER_ARG`	Sampling.
`OTEL_SDK_DISABLED`	Turn the exporter off without a deploy. Only the literal value `true` (case-insensitive) disables export; `1` and `yes` deliberately do not.

Compression is supported via OTEL_EXPORTER_OTLP_COMPRESSION=gzip.

Vendor examples

Grafana Cloud

Honeycomb

Set the variables on Vercel

Each running site is an independent Vercel project, and each Rust surface is a separate
function within it. Environment variables are per project, so all functions in one project
share them.

Redeploy after adding the variables.

service.name for the Rust functions is set in code, not by OTEL_SERVICE_NAME. A
project that runs both Rust functions and Node lambdas cannot name both halves distinctly
from one env var. Each Rust binary claims its own name in code, and the OTel SDK ranks that
code-set value above OTEL_SERVICE_NAME. Set OTEL_SERVICE_NAME to whatever the Node
half should be called; it does not touch the Rust spans.

Tracing the CLI

The temper binary can export too, but it needs a second switch:

Variable	Purpose
`TEMPER_CLI_TRACE`	`true` (case-insensitive; nothing else counts) lets the CLI export. Off by default.

Both this and an OTLP endpoint are required. The extra switch exists because
OTEL_EXPORTER_OTLP_ENDPOINT is often already exported in a developer's shell for an unrelated
project, and the CLI should not start shipping vault activity to a collector configured for
something else.

Verify

After the deployment finishes, confirm traces arrive.

Send a request

Hit any endpoint:

curl https://<instance>/api/health

Or run a CLI command that talks to your instance (with TEMPER_CLI_TRACE=true and an OTLP
endpoint set):

temper resource list

Check the backend

Open your vendor's trace explorer and filter by service.name — temper-api, temper-mcp, or
temper-internal for the Rust surfaces. A root span should appear within seconds.

If nothing arrives:

Confirm the endpoint is the base, not the verbatim traces URL.
OTEL_EXPORTER_OTLP_ENDPOINT gets /v1/traces appended; OTEL_EXPORTER_OTLP_TRACES_ENDPOINT
does not. A 404 in the vendor's ingest logs usually means the wrong variable was set.

Look for an "OTLP endpoint refused" warning. The endpoint is plaintext http to a
host other than this machine (or does not parse), so export was turned off rather than send
the vendor credential in the clear. Switch it to https.

Confirm OTEL_SDK_DISABLED is not true. It is off by default; 1 and yes do not
disable export.

Check deployment logs for the flush-budget warning. A warn reading "span flush
exceeded its budget; spans may be lost" means the endpoint is reachable but slow — spans are
being dropped at the 500ms ceiling.

Remember RUST_LOG=off is not a kill switch. It silences logs but still exports spans.
If you intended to stop export, use OTEL_SDK_DISABLED=true or unset the endpoint.

Confirm export is off when unset

With no OTEL_* variables set, Temper logs to stdout and exports nothing. This is the default
for local development, CI, and any unconfigured process — "unset" means "off," not "export to
localhost."

Send traces to an OTLP backend

Outcome#

Prerequisites#

Configure the OTLP exporter#

Vendor examples#

Set the variables on Vercel#

Tracing the CLI#

Verify#

Send a request#

Check the backend#

Confirm export is off when unset#

Further reading#