I am stucked with http-kit async behavior when it comes to write to an sqlite table.
The i/o to the database depends on whether I send the code to a boot
repl or run it as a boot
script. The i/o proceed only in the repl case. What am I missing? Here 's my code:
#!/usr/bin/env boot
(defn deps [new-deps]
(boot.core/merge-env! :dependencies new-deps))
(deps '[
[http-kit "2.2.0"]
[org.clojure/core.async "0.2.395"]
[org.clojure/java.jdbc "0.7.0-alpha1"]
[org.xerial/sqlite-jdbc "3.16.1"]
[org.slf4j/slf4j-nop "1.7.22"]
])
(require
'[org.httpkit.client :as http]
'[clojure.java.jdbc :as jdbc]
)
(def db-spec
{:classname "org.sqlite.JDBC"
:subprotocol "sqlite"
:subname "sqlite.db"})
;(jdbc/db-do-commands
;db-spec
;(jdbc/create-table-ddl "test" [[:msg :text]]))
(def ins! (partial jdbc/insert! db-spec "test"))
(http/get "http://locahost" {} (fn [_] (ins! {:msg "repl"})))
(defn -main []
(println (System/getProperty "user.dir"))
(http/get "http://locahost" {} (fn [_] (ins! {:msg "exec"}))))
Thanks
The issue with the script not working from command line is that http-kit asynchronous callbacks are handled by daemon threads and the only non-daemon thread is the main thread running your script.
When your -main
function ends after submitting HTTP request to http-kit for async processing, the main thread terminates and causes that the JVM shutdowns before daemon threads processing your async callback get a chance to run.
You can check that by adding a sleep expression in the end of -main
function to see that your callback is executed:
(defn -main []
(println (System/getProperty "user.dir"))
(http/get "http://locahost" {} (fn [_] (ins! {:msg "exec"})))
(Thread/sleep 60000))
The best way to make sure that the -main
function will wait for the result to be processed is to keep the promise returned by http/get
call. The promise eventually will contain the result produced by your callback function:
(let [result-promise (http/get "https://www.google.com" {} (fn [_] "Result"))]
@result-promise)
@result-promise
is a reader macro/shortcut for (deref result-promise)
.
The full form might be better when you would like to not block indefinitely - just call deref
with timeout-ms and timeout-value arguments:
(deref result-promise 5000 "Didn't get response in 5 seconds. Giving up")