cap-ui-telemetry
UI5 FESR (frontend performance) + client-error capture for SAP CAP (Node.js), forwarded to SAP Cloud Logging via cds.log.
Built for landscapes that run SAP Cloud Logging but have no Cloud ALM — official FESR targets CALM RUM, which has nowhere to land without it. This plugin uses Cloud Logging as a primary sink for both signals instead: UI5's piggybacked FESR headers, and client-side JS errors.
Features
- FESR capture — reads the
SAP-Perf-FESRec / SAP-Perf-FESRec-opt headers UI5 piggybacks onto the next backend request after each completed interaction (when sap-ui-fesr=true), parses them, and emits one structured cds.log('ui-fesr') record per interaction.
- Client-error ingestion — a CDS REST service (
POST <path>/errors) accepts batches of client errors and emits one cds.log('ui-error') record per entry.
- Cloud-Logging-ready by construction — automatically extends
cds.env.log.cls_custom_fields so every field (app name, step name, durations, error message, ...) lands as a flat, filterable/aggregatable field, not buried in free text.
- No database — pure logging, nothing persisted by this plugin.
- Zero backend wiring — install it and it's active; the only integration work is on the frontend (three copy-paste snippets, see below).
- Optional user attribution on demand —
cds.context.user.id gets attached to a record once you raise that logger's verbosity (DEBUG=ui-fesr / DEBUG=ui-error), config-gated and off by default in normal operation.
Requirements
@sap/cds >= 8.0 (Node.js)- A UI5 app (any version with
sap/ui/performance/trace/FESR and sap/base/Log — i.e., any reasonably recent UI5)
- SAP Cloud Logging bound to your CAP app for the custom fields to be indexed (works locally without it too — see Cloud Logging notes)
Install
npm add cap-ui-telemetry
That's it for the backend — no code changes required. CAP auto-discovers the plugin via cds-plugin.js.
Setup
Backend: nothing to do. On next cds watch / cds-serve you'll see:
[ui-telemetry] - active (FESR → cds.log('ui-fesr'), errors → POST /service/telemetry/errors → cds.log('ui-error'))
Frontend: copy three files from ui5-snippets/ into your app and wire them up — see INTEGRATION.md for numbered, verifiable steps (written so a coding agent can follow them unattended). npx cds add ui-telemetry automates the bootstrap flag + file-copy part of this (see INTEGRATION.md's Shortcut section). Summary:
bootstrap-fesr.html — add data-sap-ui-fesr="true" to your bootstrap tag.fesr-enrichment.js — optional, enriches FESR records with "which app is open" for shells hosting multiple apps.ErrorReporter.js — captures sap/base/Log errors/warnings, uncaught exceptions, and unhandled promise rejections, and POSTs them (batched, CSRF-protected, rate-limited) to the backend. Pass appName (a static string, or a resolver function for shells) so ui-error records correlate with the same app identity as ui-fesr records.
Configuration reference
Set under a top-level cds['ui-telemetry'] key (package.json, .cdsrc.json, or any CAP profile) — not under cds.requires, since nothing ever cds.connect.to's this plugin.
| Key | Default | Description |
|---|
enabled | true | Master switch. false disables everything (FESR middleware, errors service, custom-fields merge). |
fesr.enabled | true | Enable/disable FESR header capture independently. |
fesr.logger | 'ui-fesr' | cds.log(...) category for FESR records. |
fesr.sampling | 1.0 | Fraction of interactions to log (0–1). Useful to cut volume in production (e.g. 0.25). |
errors.enabled | true | Enable/disable the client-error ingestion service independently. |
errors.logger | 'ui-error' | cds.log(...) category for client-error records. |
errors.path | '/service/telemetry' | Service base path — action is served at <path>/errors. Change this if /service/* is already taken. |
errors.maxBatchSize | 50 | Reject (400) a batch with more entries than this. |
errors.maxMessageLength | 2048 | Truncate message beyond this length (never rejects). |
errors.maxStackLength | 8192 | Truncate stackTrace beyond this length (never rejects). |
customFields.extend | true | Auto-merge this plugin's fields into cds.env.log.cls_custom_fields. Set false to manage that list yourself. |
logUserOn | 'debug' | One of 'debug' | 'info' | 'warn' | 'error' | 'never' — attach cds.context.user.id to a record once that logger's configured verbosity reaches this threshold (e.g. DEBUG=ui-fesr). 'never' fully opts out. See Log record reference. |
Example: sample 25% of FESR records and silence errors reporting in production only:
{
"cds": {
"ui-telemetry": {
"fesr": { "sampling": 1.0 },
"[production]": { "fesr": { "sampling": 0.25 } }
}
}
}
Example: relax auth on the errors endpoint for a fully anonymous UI (not recommended unless the route is otherwise protected):
using { TelemetryService } from 'cap-ui-telemetry/lib/telemetry-service';
annotate TelemetryService with @requires: 'any';
Log record reference
Every field listed here is registered in cds.env.log.cls_custom_fields (see Cloud Logging notes for why that matters). Numeric fields are emitted as actual numbers, not strings — required for percentile/avg aggregations.
ui-fesr records
| Field | Type | Source (SAP-Perf-FESRec[-opt] position) |
|---|
rootContextId | string | mandatory #0 |
fesrTransactionId | string | mandatory #1 |
clientNavigationTime | number (ms) | mandatory #2 |
clientRoundTripTime | number (ms) | mandatory #3 |
interactionDuration | number (ms) | mandatory #4 — UI5's Time To Interactive |
completedRoundTrips | number | mandatory #5 |
passportAction | string | mandatory #6 — <trigger>_<event>_<stepCounter> |
networkTime | number (ms) | mandatory #7 |
requestTime | number (ms) | mandatory #8 |
clientOS | string | mandatory #9 |
appName | string | optional #0 (UI5's appNameShort) |
stepName | string | optional #1 |
clientModel | string | optional #3 — browser + version |
bytesSent / bytesReceived | number | optional #4/#5 |
clientProcessingTime | number (ms) | optional #8 |
compressed | boolean | optional #9 |
busyDuration | number (ms) | optional #14 |
interactionType | number | optional #15 — 0 n/a, 1 app start, 2 follow-up step, 3 unknown |
clientDevice | number | optional #16 — 0 unknown, 1 combi, 2 desktop, 3 phone, 4 tablet |
legacyDuration | number (ms) | optional #17 |
interactionStartTime | string | optional #18 — digits-only ISO timestamp |
appNameLong | string | optional #19 |
fesrDirty | boolean | present only if any numeric field carried UI5's own "-1 = dirty" marker |
user | string | cds.context.user.id, only when logUserOn's threshold is met |
ui-error records
| Field | Type | Notes |
|---|
errorLevel | 'error' | 'warn' | 'info' | mapped from the client's level ('error'→error, 'warning'→warn, anything else→info) |
errorMessage | string | truncated to errors.maxMessageLength |
stackTrace | string | truncated to errors.maxStackLength |
errorSource | string | 'ui5-log' | 'window-error' | 'unhandledrejection' |
appName | string | shared name with ui-fesr records — correlate errors to performance by app |
componentName | string | UI5 log component, when available |
clientUrl | string | page URL at the time of the error |
clientUserAgent | string | navigator.userAgent |
clientTimestamp | string | client-supplied ISO timestamp |
user | string | cds.context.user.id, only when logUserOn's threshold is met |
Cloud Logging notes
cls_custom_fields is not an indexing switch — OpenSearch (Cloud Logging's backing store) dynamically indexes any top-level JSON field regardless. What it actually gates is whether an object argument passed to a log call (cds.log(id).info(msg, {...})) gets flattened into top-level fields at all, or falls through as an unstructured, util.inspect-style blob inside msg.
That gate is all-or-nothing per object: if even one key in the object isn't registered, the entire object degrades to text — not "some fields indexed, some not." That's why this plugin auto-registers every field it ever emits (customFields.extend, on by default) — and why, if you ever see plugin fields showing up inside msg instead of as their own JSON properties, the first thing to check is whether customFields.extend got turned off, or whether cls_custom_fields was replaced (not merged) by some other config.
Useful OpenSearch queries once records are flowing:
logger: "ui-fesr" AND appName: "your-app-id" — all performance records for one app- p95/avg of
interactionDuration, faceted by appName + stepName — per-app, per-action performance dashboards
logger: "ui-error" AND errorLevel: "error" — error rate, faceted by appNamerootContextId: "<id>" or fesrTransactionId: "<id>" — exact-match trace correlation across records
Locally, without a Cloud Logging binding, the plain-text formatter is used and none of this matters — log lines are just readable text, no config needed.
Development and testing
npm install
npm run build # tsc → dist/
npm test # build + jest --runInBand (unit + integration, test/app workspace)
test/unit — pure logic: FESR header parsing, custom-fields merge mechanics, client-error sanitization, user-attachment gating, CSN model injection.test/integration — boots the test/app sample CAP project (via @cap-js/cds-test) and exercises the FESR middleware and the errors service end to end over real HTTP.
License
Apache-2.0
