Experimental, subject to change.
Returns true iff given signal has an `:error` value, or a `:kind` or `:level`
that indicates that it's an error.

Experimental, subject to change.
Opens the specified file and returns a stateful fn of 2 arities:
  [content] => Writes given content to file, or noops if closed.
  []        => Closes the writer.

Useful for basic handlers that write to a file, etc.

Notes:
  - Automatically creates file and parent dirs as necessary.
  - Writer should be manually closed after use (with zero-arity call).
  - Flushes after every write.
  - Thread safe, locks on single file stream.

Experimental, subject to change.
Returns a (fn format [error]) that:
  - Takes a platform error (`Throwable` or `js/Error`).
  - Returns a human-readable error string.

Experimental, subject to change without notice.

Returns a (fn format [instant]) that:
  - Takes a platform instant (`java.time.Instant` or `js/Date`).
  - Returns a formatted human-readable instant string.

Options:
  `:zone` (Clj only) `java.time.ZoneOffset` (defaults to UTC).
  `:formatter`
    `java.time.format.DateTimeFormatter` (Clj) or
    `goog.i18n.DateTimeFormat` (Cljs),

    Defaults to `ISO8601` formatter (`YYYY-MM-DDTHH:mm:ss.sssZ`),
    e.g.: "2011-12-03T10:15:130Z".

Experimental, subject to change.
Returns a (fn format [nanosecs]) that:
  - Takes a long nanoseconds (e.g. runtime).
  - Returns a human-readable string like:
    "1.00m", "4.20s", "340ms", "822μs", etc.

Experimental, subject to change.
Returns a (fn format [signal]) that:
  - Takes a Telemere signal (map).
  - Returns a human-readable signal string.

Options:
  `:incl-newline?` - Include terminating system newline? (default true)
  `:preamble-fn`   - (fn [signal]) => signal preamble string.
  `:content-fn`    - (fn [signal]) => signal content  string.

See also `pr-signal-fn` for machine-readable output.

Returns cached local host IP address string, or `timeout-val` (default "UnknownHost").

Returns cached local hostname string, or `timeout-val` (default "UnknownHost").

Single system newline

Prints given arg to an edn string readable with `read-edn`.

Experimental, subject to change.
Returns a (fn pr [signal]) that:
  - Takes a Telemere signal (map).
  - Returns a machine-readable signal ?string.

Options:
  `:pr-fn`         - ∈ #{<unary-fn> :edn (default) :json (Cljs only)}
  `:incl-kvs?`     - Include signal's app-level kvs?         (default false)
  `:incl-nils?`    - Include signal's keys with nil values?  (default false)
  `:incl-newline?` - Include terminating system newline?     (default true)
  `:incl-keys`     - Subset of signal keys to retain from those otherwise
                     excluded by default: #{:location :kvs :file :thread}

Examples:
  (pr-signal-fn {:pr-fn :edn  ...}) ; Outputs edn
  (pr-signal-fn {:pr-fn :json ...}) ; Outputs JSON (Cljs only)

  To output JSON for Clj, you must provide an appropriate `:pr-fn`.
  `jsonista` offers one good option, Ref. <https://github.com/metosin/jsonista>:

    (require '[jsonista.core :as jsonista])
    (pr-signal-fn {:pr-fn jsonista/write-value-as-string ...})

See also `format-signal-fn` for human-readable output.

Experimental, subject to change.
Returns a (fn content [signal]) that:
  - Takes a Telemere signal (map).
  - Returns a signal content ?string (incl. data, ctx, etc.).

Options:
  `:raw-error?`      - Retain unformatted error? (default false)
  `:incl-keys`       - Subset of signal keys to retain from those
                       otherwise excluded by default: #{:kvs :thread}
  `:format-nsecs-fn` - (fn [nanosecs]) => string.
  `:format-error-fn` - (fn [error])    => string.

Experimental, subject to change.
Returns a (fn preamble [signal]) that:
  - Takes a Telemere signal (map).
  - Returns a signal preamble ?string like:
    "2024-03-26T11:14:51.806Z INFO EVENT Hostname taoensso.telemere(2,21) ::ev-id - msg"

Options:
  `:format-inst-fn` - (fn format [instant]) => string.

Experimental, subject to change.
Connects to specified TCP socket and returns a stateful fn of 2 arities:
  [content] => Writes given content to socket, or noops if closed.
  []        => Closes the writer.

Useful for basic handlers that write to a TCP socket, etc.

Options:
  `:ssl?`                  - Use SSL/TLS?
  `:connect-timeout-msecs` - Connection timeout (default 3000 msecs)
  `:socket-fn`             - (fn [host port timeout]) => `java.net.Socket`
  `:ssl-socket-fn`         - (fn [socket host port])  => `java.net.Socket`

Notes:
  - Writer should be manually closed after use (with zero-arity call).
  - Flushes after every write.
  - Will retry failed writes once, then drop.
  - Thread safe, locks on single socket stream.
  - Advanced users may want a custom implementation using a connection
    pool and/or more sophisticated retry semantics, etc.

Returns long id of current thread.

Returns {:keys [group name id]} for current thread.

Returns string name of current thread.