pods: ops value in describe

doc/pods.md

@@ -121,7 +121,8 @@ The pod should reply to this request with a message in the vein of:
 {"format" "json"
  "namespaces"
  [{"name" "pod.lispyclouds.sqlite"
-   "vars" [{"name" "execute!"}]}]}
+   "vars" [{"name" "execute!"}]}]
+ "ops" {"shutdown" {}}}
 ```
 
 In this reply, the pod declares that payloads will be encoded and decoded using
@@ -133,6 +134,12 @@ this message from the pod's stdout.
 
 Upon receiving this message, babashka creates these namespaces and vars.
 
+The optional `ops` value communicates which ops the pod supports, beyond
+`describe` and `invoke`. It is a map of op names and option maps. In the above
+example the pod declares that it supports the `shutdown` op. Since the
+`shutdown` op does not need any additional options right now, the value is an
+empty map.
+
 As a babashka user, you can load the pod with:
 
 ``` clojure
@@ -180,7 +187,8 @@ Now you know most there is to know about the pod protocol!
 
 #### shutdown
 
-When babashka is about to exit, it sends a `{"op" "shutdown"}` message and waits
+When babashka is about to exit, it sends an `{"op" "shutdown"}` message, if the
+pod has declared that it supports it in the `describe` response. Then it waits
 for the pod process to end. This gives the pod a chance to clean up resources
 before it exits.
 

examples/pods/pod-babashka-filewatcher/src/main.rs

@@ -105,10 +105,6 @@ fn handle_incoming(val: bc::Value) {
                 _ => panic!(var)
             };
         },
-        "shutdown" => {
-            // TODO: clean up stuff?
-            std::process::exit(0);
-        }
         _ => panic!(op)
     }
 }

examples/pods/pod-babashka-hsqldb/src/pod/babashka/hsqldb.clj

@@ -33,7 +33,8 @@
           (case op
             :describe (do (write {"format" "edn"
                                   "namespaces" [{"name" "pod.babashka.hsqldb"
-                                                 "vars" [{"name" "execute!"}]}]})
+                                                 "vars" [{"name" "execute!"}]}]
+                                  "ops" {"shutdown" {}}})
                           (recur))
             :invoke (let [var (-> (get message "var")
                                   read-string

examples/pods/pod-lispyclouds-sqlite/pod-lispyclouds-sqlite.py

@@ -56,8 +56,6 @@ def main():
 
             conn.commit()
             conn.close()
-        elif op == "shutdown":
-            sys.exit(0)
 
 if __name__ == "__main__":
     main()

sci

@@ -1 +1 @@
-Subproject commit 806cf61eeff31869727e205a8f1a7021a0ea5b49
+Subproject commit c55a1ef672c82a06f540e91c138d5689b679e02d

src/babashka/impl/pods.clj

@@ -108,21 +108,25 @@
          stdin (.getOutputStream p)
          stdout (.getInputStream p)
          stdout (java.io.PushbackInputStream. stdout)
-         _ (add-shutdown-hook!
-            (fn []
-              (write stdin {"op" "shutdown"
-                            "id" (next-id)})
-              (.waitFor p)))
          _ (write stdin {"op" "describe"
                          "id" (next-id)})
          reply (read stdout)
          format (-> (get reply "format") bytes->string keyword)
+         ops (some->> (get reply "ops") keys (map keyword) set)
          pod {:process p
               :pod-spec pod-spec
               :stdin stdin
               :stdout stdout
               :chans (atom {})
-              :format format}
+              :format format
+              :ops ops}
+         _ (add-shutdown-hook!
+            (fn []
+              (if (contains? ops :shutdown)
+                (do (write stdin {"op" "shutdown"
+                                  "id" (next-id)})
+                    (.waitFor p))
+                (.destroy p))))
          pod-namespaces (get reply "namespaces")
          vars-fn (fn [ns-name-str vars]
                    (reduce

test-resources/pod.clj

@@ -60,7 +60,8 @@
                                               {"name" "assoc"}
                                               {"name" "error"}
                                               {"name" "print"}
-                                              {"name" "print-err"}]}]})
+                                              {"name" "print-err"}]}]
+                                    "ops" {"shutdown" {}}})
                             (recur))
               :invoke (let [var (-> (get message "var")
                                     read-string