Custom body message in riemann email - clojure

Question

I am trying to create a custom message in the body section of email using riemann.
I couldn't append the field dynamically.
Riemann config:
(let [email (mailer
{:host "XXXXX" :port XX :user "XXX" :pass "XXX" :auth "true"
:subject (fn [events] "Team")
:body (fn [events]
(apply str "Hello Team, now the time is" (:timestamp event) "Thank You!"))
:from "xxx#gmail.com"})]
My output:
Hello Team, now the time is Thank You!
My expected output:
Hello Team, now the time is 12:13:45 Thank You!.
My timestamp not getting appended in the :body.

Answer 1

from the docs:
These formatting functions take a sequence of
events and return a string.
so the question is which event in the sequence would you like to get the timestamp from? If you lookup a keyword in a sequence, as opposed to one of the members of that sequence, you will get back nil as a default:
core> (:asdf '(1 2 3))
nil
and if you apply str that into a couple other strings it will have no effect because str will ignore it. Which is where your output is coming from. Here is an analogous example function:
core> (let [body-fn (fn [events]
(apply str "Hello Team, now the time is"
(:timestamp events)
"Thank You!"))]
(body-fn [{:timestamp 42} {:timestamp 43}]))
"Hello Team, now the time isThank You!"
if we choose the timestamp from the first event:
core> (let [body-fn (fn [events]
(apply str "Hello Team, now the time is"
(:timestamp (first events))
"Thank You!"))]
(body-fn [{:timestamp 42} {:timestamp 43}]))
"Hello Team, now the time is42Thank You!"
When alerting through riemann my personal opinion is to wrap the things being alerted into fixed time windows and use the timestamp from the start of that window, though this is primarily because of personal preference.