[demo] some fixes, README added

demo/README.md

+# haskell-bee demo
+
+## DB setup
+
+This is a simple demo of pgmq-based workers.
+
+First, you need a postgresql database:
+```shell
+podman run --rm -p 5432:5432 -e POSTGRES_PASSWORD=postgres -e POSTGRES_DB=postgres postgres
+```
+Next, you can configure postgres access via an env variable:
+```shell
+export POSTGRES_CONN="host=localhost port=5432 dbname=postgres user=postgres password=postgres"
+```
+
+## Command-line
+
+To run the command-line and see available options:
+```shell
+cabal v2-run demo -- -h
+```
+
+You need to spawn the worker first:
+```shell
+cabal v2-run demo -- worker
+```
+
+Now you can send tasks to the worker (from another terminal):
+```shell
+cabal v2-run demo -- echo "hello"
+cabal v2-run demo -- error "oops!"
+cabal v2-run demo -- wait 10
+cabal v2-run demo -- quit
+```
+
+## About killing with `Ctrl-C`
+
+`haskell-bee` implements possibility of a graceful shutdown of the worker.
+
+Depending on the `resendWhenWorkerKilled` property in the task
+metadata, the currently running task will be either killed and
+discarded or killed and resent to the broker.
+
+One often kills command-line programs with `Ctrl-C`. Hence, a small
+wrapper is needed around `initWorker` to support such graceful
+shutdown:
+```haskell
+initWorker "default" _ga_queue $ \a _state -> do
+  let tid = asyncThreadId a
+  _ <- installHandler keyboardSignal (Catch (throwTo tid W.KillWorkerSafely)) Nothing
+  
+  wait a
+```

demo/app/App/Types.hs

@@ -20,7 +20,10 @@ data Program =
 
 programParser :: ParserInfo Program
 programParser = info
-  ( ( Program <$> global <*> commandParser ) <**> helper ) mempty
+  ( ( Program <$> global <*> commandParser ) <**> helper )
+  ( fullDesc
+   <> header "haskell-bee demo"
+   <> progDesc "Simple demonstration of worker capabilities" )
 
 data GlobalArgs =
   GlobalArgs { _ga_queue :: B.Queue }
@@ -45,14 +48,14 @@ data Command
 
 commandParser :: Parser Command
 commandParser = subparser
-    ( command "worker" (info (worker <**> helper) mempty )
-   <> command "queue-size" (info (queueSize <**> helper) mempty )
+    ( command "worker" (info (worker <**> helper) (progDesc "run worker") )
+   <> command "queue-size" (info (queueSize <**> helper) (progDesc "show queue size") )
 
    -- tasks
-   <> command "echo" (info (echo <**> helper) mempty )
-   <> command "error" (info (error' <**> helper) mempty )
-   <> command "quit" (info (quit <**> helper) mempty )
-   <> command "wait" (info (wait <**> helper) mempty )
+   <> command "echo" (info (echo <**> helper) (progDesc "echo task") )
+   <> command "error" (info (error' <**> helper) (progDesc "error task") )
+   <> command "quit" (info (quit <**> helper) (progDesc "quit task") )
+   <> command "wait" (info (wait <**> helper) (progDesc "wait task") )
     )
 
 data WorkerArgs =

demo/cabal.project

@@ -2,9 +2,10 @@ with-compiler: ghc-9.4.8
 
 packages:
         ./
-        ../        
+        ../haskell-bee
+        ../haskell-bee-pgmq
 
 source-repository-package
     type: git
     location: https://gitlab.iscpif.fr/gargantext/haskell-pgmq
-    tag: 0591a643d8ba1776af4fac56c1e4ff5fc3e98bb3
+    tag: 1dd92f0aa8e9f8096064e5656c336e562680f4e3

demo/haskell-bee-demo.cabal

@@ -65,6 +65,7 @@ library
                     , aeson >= 2.1 && < 2.3
                     , async >= 2.2 && < 2.3
                     , haskell-bee
+                    , haskell-bee-pgmq
                     , postgresql-simple >= 0.7.0 && < 0.8
                     , safe-exceptions >= 0.1.7 && < 0.2
                     , text >= 2.0 && < 2.2