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A heavy, dull sound such as that made by thick pieces of metal striking together.

Talking to Postgres via sockets. At this point in time, I'm just experimenting with Clojure; learning core.async.

Clojure CI

Running The Tests

You need to have a Postgres (13) Database up and running.

docker compose up -d

Now you can run the tests with

clj -X:test


(ns scratch.client
   [clojure.core.async :as async]
   [com.clunk.core :as clunk]))

(def cfg {:username "jimmy"
          :password "banana"
          :database "world"
          :debug true})

We can now create a client, and connect to the postgres instance:

(def client (clunk/client cfg))

(clunk/connect client)

We will see a bunch of received messages:

{:type :AuthenticationMD5, :salt #object["[B" 0x5ea94109 "[B@5ea94109"]}
{:type :AuthenticationOk}
{:type :ParameterStatus, :param "application_name", :status ""}
{:type :ParameterStatus, :param "client_encoding", :status "UTF8"}
{:type :ParameterStatus, :param "DateStyle", :status "ISO, MDY"}
{:type :ParameterStatus, :param "integer_datetimes", :status "on"}
{:type :ParameterStatus, :param "IntervalStyle", :status "postgres"}
{:type :ParameterStatus, :param "is_superuser", :status "on"}
{:type :ParameterStatus, :param "server_encoding", :status "UTF8"}
{:type :ParameterStatus, :param "server_version", :status "13.4 (Debian 13.4-1.pgdg100+1)"}
{:type :ParameterStatus, :param "session_authorization", :status "jimmy"}
{:type :ParameterStatus, :param "standard_conforming_strings", :status "on"}
{:type :ParameterStatus, :param "TimeZone", :status "Etc/UTC"}
{:type :BackendKeyData, :id 239, :key 2031531424}
{:type :ReadyForQuery, :status 73}

Finally we can define and run a query. The <query! macro is shorthand for an async take on the channel returned from clunk/query. It must be run inside a go block.

(def qs "SELECT name, region, population FROM country ORDER BY name LIMIT 10;")

  (when-let [recv (clunk/<query! client qs)]
    (println recv)

The above async loop prints out the following:

{:name Afghanistan, :region Southern and Central Asia, :population 22720000}
{:name Albania, :region Southern Europe, :population 3401200}
{:name Algeria, :region Northern Africa, :population 31471000}
{:name American Samoa, :region Polynesia, :population 68000}
{:name Andorra, :region Southern Europe, :population 78000}
{:name Angola, :region Central Africa, :population 12878000}
{:name Anguilla, :region Caribbean, :population 8000}
{:name Antarctica, :region Antarctica, :population 0}
{:name Antigua and Barbuda, :region Caribbean, :population 68000}
{:name Argentina, :region South America, :population 37032000}

And lastly, close the client:

(clunk/close client)

Rough Todo / Help needed

  • Build out CLJS test suite
  • Figure out a good way to provide async query results
  • Fix core.async channel closing issues
  • Flush out frontend/backend message parsers
  • Deploy to Clojars
  • Deploy to npm

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Duane Bester & Duane
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