Taoensso open source [**API**][cljdoc docs] | [**Wiki**][GitHub wiki] | [Latest releases](#latest-releases) | [Slack channel][] # Telemere logo ### Structured telemetry library for Clojure/Script **Telemere** is a next-generation replacement for [Timbre](https://www.taoensso.com/timbre). It handles **structured and traditional logging**, **tracing**, and **basic performance monitoring** with a simple unified API. It helps enable Clojure/Script systems that are **observable**, **robust**, and **debuggable** - and it represents the refinement and culmination of ideas brewing over 12+ years in [Timbre](https://www.taoensso.com/timbre), [Tufte](https://www.taoensso.com/tufte), [Truss](https://www.taoensso.com/truss), etc. > [Terminology] *Telemetry* derives from the Greek *tele* (remote) and *metron* (measure). It refers to the collection of *in situ* (in position) data, for transmission to other systems for monitoring/analysis. *Logs* are the most common form of software telemetry. So think of telemetry as the *superset of logging-like activities* that help monitor and understand (software) systems. ## Latest release/s - `2024-05-23` `v1.0.0-beta13`: [release info](../../releases/tag/v1.0.0-beta13) (for early adopters/feedback) [![Main tests][Main tests SVG]][Main tests URL] [![Graal tests][Graal tests SVG]][Graal tests URL] See [here][GitHub releases] for earlier releases. ## Why Telemere? #### Ergonomics - Elegant, lightweight API that's **easy to use**, **easy to configure**, and **deeply flexible**. - **Sensible defaults** to make getting started **fast and easy**. - Extensive **beginner-oriented** [documentation][GitHub wiki], [docstrings](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso), and error messages. #### Interop - 1st-class **out-the-box interop** with [SLF4J v2](https://www.slf4j.org/), [clojure.tools.logging](https://github.com/clojure/tools.logging), [OpenTelemetry](https://opentelemetry.io/), and [Tufte](https://www.taoensso.com/tufte). - Included [shim](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere.timbre) for easy/gradual [migration from Timbre](../../wiki/5-Migrating). - Extensive set of [handlers](../../wiki/4-Handlers#included-handlers) included out-the-box. #### Scaling - Hyper-optimized and **blazing fast**, see [benchmarks](#benchmarks). - An API that **scales comfortably** from the smallest disposable code, to the most massive and complex real-world production environments. - Auto [handler stats](https://cljdoc.org/d/com.taoensso/telemere/1.0.0-beta13/api/taoensso.telemere#get-handlers-stats) for debugging performance and other issues at scale. #### Flexibility - Config via plain **Clojure vals and fns** for easy customization, composition, and REPL debugging. - Unmatched [environmental config](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#help:environmental-config) support: JVM properties, environment variables, or classpath resources. Per platform, or cross-platform. - Unmatched [filtering](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#help:filters) support: by namespace, id pattern, level, level by namespace pattern, etc. At runtime and compile-time. - Fully [configurable](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#help:handler-dispatch-options) **a/sync dispatch support**: blocking, dropping, sliding, etc. - Turn-key **sampling**, **rate-limiting**, and **back-pressure monitoring** with sensible defaults. ## Video demo See for intro and basic usage: Telemere demo video ## Quick examples ```clojure (require '[taoensso.telemere :as t]) (t/log! {:id ::my-id, :data {:x1 :x2}} "My message") %> ;; 2024-04-11T10:54:57.202869Z INFO LOG Schrebermann.local examples(56,1) ::my-id - My message ;; data: {:x1 :x2} (t/log! "This will send a `:log` signal to the Clj/s console") (t/log! :info "This will do the same, but only when the current level is >= `:info`") ;; Easily construct messages (let [x "constructed"] (t/log! :info ["Here's a" x "message!"])) ;; Attach an id (t/log! {:level :info, :id ::my-id} "This signal has an id") ;; Attach arb user data (t/log! {:level :info, :data {:x :y}} "This signal has structured data") ;; Capture for debug/testing (t/with-signal (t/log! "This will be captured")) ;; => {:keys [location level id data msg_ ...]} ;; `:let` bindings available to `:data` and message, only paid for ;; when allowed by minimum level and other filtering criteria (t/log! {:level :info :let [expensive-metric1 (last (for [x (range 100), y (range 100)] (* x y)))] :data {:metric1 expensive-metric1}} ["Message with metric value:" expensive-metric1]) ;; With sampling 50% and 1/sec rate limiting (t/log! {:sample-rate 0.5 :rate-limit {"1 per sec" [1 1000]}} "This signal will be sampled and rate limited") ;;; A quick taste of filtering... (t/set-ns-filter! {:disallow "taoensso.*" :allow "taoensso.sente.*"}) ; Set namespace filter (t/set-id-filter! {:allow #{::my-particular-id "my-app/*"}}) ; Set id filter (t/set-min-level! :warn) ; Set minimum level (t/set-min-level! :log :debug) ; Set minimul level for `:log` signals ;; Set minimum level for `:event` signals originating in the "taoensso.sente.*" ns (t/set-min-level! :event "taoensso.sente.*" :warn) ``` See [examples.cljc](https://github.com/taoensso/telemere/blob/master/examples.cljc) for more REPL-ready snippets. ## API overview See relevant docstrings (links below) for usage info- ### Creating signals | Name | Signal kind | Main arg | Optional arg | Returns | | :---------------------------------------------------------------------------------------------------------- | :---------- | :------- | :------------- | :--------------------------- | | [`log!`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#log!) | `:log` | `msg` | `opts`/`level` | Signal allowed? | | [`event!`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#event!) | `:event` | `id` | `opts`/`level` | Signal allowed? | | [`error!`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#error!) | `:error` | `error` | `opts`/`id` | Given error | | [`trace!`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#trace!) | `:trace` | `form` | `opts`/`id` | Form result | | [`spy!`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#spy!) | `:spy` | `form` | `opts`/`level` | Form result | | [`catch->error!`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#catch-%3Eerror!) | `:error` | `form` | `opts`/`id` | Form value or given fallback | | [`signal!`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#signal!) | `` | `opts` | - | Depends on opts | ### Internal help Help is available without leaving your IDE: | Var | Help with | | :---------------------------------------------------------------------------------------------------------------------------------------- | :------------------------------------------------------------------------ | | [`help:signal-creators`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#help:signal-creators) | Creating signals | | [`help:signal-options`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#help:signal-options) | Signal options | | [`help:signal-content`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#help:signal-content) | Signal content (map given to middleware/handlers) | | [`help:filters`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#help:filters) | Signal and handler filters | | [`help:handlers`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#help:handlers) | Signal handlers | | [`help:handler-dispatch-options`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#help:handler-dispatch-options) | Signal handler dispatch options | | [`help:environmental-config`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#help:environmental-config) | Config via JVM properties, environment variables, or classpath resources. | ### Included handlers See linked docstrings below for features and usage: | Name | Platform | Output target | Output format | | :------------------------------------------------------------------------------------------------------------------------------------------------------- | :------- | :------------------------------------------------------------------------------------------------------------- | :--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | [`handler:console`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#handler:console) | Clj | `*out*` or `*err*` | [edn/JSON](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#pr-signal-fn) or [human-readable](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#format-signal-fn) | | [`handler:console`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#handler:console) | Cljs | Browser console | [edn/JSON](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#pr-signal-fn) or [human-readable](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#format-signal-fn) | | [`handler:console-raw`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#handler:console-raw) | Cljs | Browser console | Raw signals for [cljs-devtools](https://github.com/binaryage/cljs-devtools), etc. | | [`handler:file`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#handler:file) | Clj | File/s on disk | [edn/JSON](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#pr-signal-fn) or [human-readable](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#format-signal-fn) | | [`handler:open-telemetry-logger`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere.open-telemetry#handler:open-telemetry-logger) | Clj | [OpenTelemetry](https://opentelemetry.io/) [Java client](https://github.com/open-telemetry/opentelemetry-java) | [LogRecord](https://opentelemetry.io/docs/specs/otel/logs/data-model/) | | [`handler:postal`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere.postal#handler:postal) | Clj | Email (via [postal](https://github.com/drewr/postal)) | [edn/JSON](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#pr-signal-fn) or [human-readable](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#format-signal-fn) | | [`handler:slack`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere.slack#handler:slack) | Clj | [Slack](https://slack.com/) (via [clj-slack](https://github.com/julienXX/clj-slack)) | [edn/JSON](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#pr-signal-fn) or [human-readable](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#format-signal-fn) | | [`handler:tcp-socket`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere.sockets#handler:tcp-socket) | Clj | TCP socket | [edn/JSON](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#pr-signal-fn) or [human-readable](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#format-signal-fn) | | [`handler:udp-socket`](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere.sockets#handler:udp-socket) | Clj | UDP socket | [edn/JSON](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#pr-signal-fn) or [human-readable](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#format-signal-fn) | See [here](../../wiki/4-Handlers) for more/upcoming handlers, community handlers, info on **writing your own handlers**, etc. ## Documentation - [Wiki][GitHub wiki] (getting started, usage, etc.) - API reference: [cljdoc][cljdoc docs] or [Codox][Codox docs] - Support: [Slack channel][] or [GitHub issues][] - [General observability tips](../../wiki/7-Tips) (advice on building and maintaining observable Clojure/Script systems, and getting the most out of Telemere) ## Benchmarks Telemere is **highly optimized** and offers terrific performance at any scale: | Compile-time filtering? | Runtime filtering? | Time? | Trace? | nsecs | | :---------------------: | :----------------: | :---: | :----: | ----: | | ✓ (elide) | - | - | - | 0 | | - | ✓ | - | - | 200 | | - | ✓ | ✓ | - | 280 | | - | ✓ | ✓ | ✓ | 650 | Measurements: - Are **~nanoseconds per signal call** (= milliseconds per 1e6 calls) - Exclude [handler runtime](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#get-handlers-stats) (which depends on handler/s, is usually async) - Taken on a 2020 Macbook Pro M1, running OpenJDK 21 **Tip**: Telemere offers extensive [filtering](https://cljdoc.org/d/com.taoensso/telemere/CURRENT/api/taoensso.telemere#help:filters) support - including dead-easy per-signal and per-handler **sampling** and **rate-limiting**. Use these to ensure that you're not capturing useless/low-value information in production. See [here](../../wiki/7-Tips) for more tips! ## Funding You can [help support][sponsor] continued work on this project, thank you!! 🙏 ## License Copyright © 2023-2024 [Peter Taoussanis][]. Licensed under [EPL 1.0](LICENSE.txt) (same as Clojure). [GitHub releases]: ../../releases [GitHub issues]: ../../issues [GitHub wiki]: ../../wiki [Slack channel]: https://www.taoensso.com/telemere/slack [Peter Taoussanis]: https://www.taoensso.com [sponsor]: https://www.taoensso.com/sponsor [Codox docs]: https://taoensso.github.io/telemere/ [cljdoc docs]: https://cljdoc.org/d/com.taoensso/telemere/ [Clojars SVG]: https://img.shields.io/clojars/v/com.taoensso/telemere.svg [Clojars URL]: https://clojars.org/com.taoensso/telemere [Main tests SVG]: https://github.com/taoensso/telemere/actions/workflows/main-tests.yml/badge.svg [Main tests URL]: https://github.com/taoensso/telemere/actions/workflows/main-tests.yml [Graal tests SVG]: https://github.com/taoensso/telemere/actions/workflows/graal-tests.yml/badge.svg [Graal tests URL]: https://github.com/taoensso/telemere/actions/workflows/graal-tests.yml