move to rest controller, use isDisconnected() waiter, add configurable PV_READ_TIMEOUT

Author: rerpha

src/main/java/org/phoebus/pvws/EpicsConfiguration.java

@@ -61,6 +61,9 @@ public class EpicsConfiguration {
     @Value("${PV_WRITE_SUPPORT:true}")
     private String pvWriteSupport;
 
+    @Value("${PV_READ_TIMEOUT:5000}")
+    private String pvReadTimeout;
+
     @PostConstruct
     public void init() {
         logger.log(Level.INFO, "===========================================");
@@ -89,6 +92,7 @@ else if (pvDefaultType != null && !pvDefaultType.isEmpty()) {
         System.setProperty("PV_THROTTLE_MS", pvThrottleMs);
         System.setProperty("PV_ARRAY_THROTTLE_MS", pvArrayThrottleMs);
         System.setProperty("PV_WRITE_SUPPORT", pvWriteSupport);
+        System.setProperty("PV_READ_TIMEOUT", pvReadTimeout);
 
         // Configure JCA/CAJ to use environment vars, not java properties or preferences
         System.setProperty("jca.use_env", "true");
@@ -98,6 +102,7 @@ else if (pvDefaultType != null && !pvDefaultType.isEmpty()) {
         logger.log(Level.INFO, "EPICS_CA_MAX_ARRAY_BYTES=" + System.getenv("EPICS_CA_MAX_ARRAY_BYTES"));
         logger.log(Level.INFO, "EPICS_PVA_ADDR_LIST=" + epicsPvaAddrList);
         logger.log(Level.INFO, "EPICS_PVA_AUTO_ADDR_LIST=" + epicsPvaAutoAddrList);
+        logger.log(Level.INFO, "PV_READ_TIMEOUT=" + pvReadTimeout);
 
         logger.log(Level.INFO, "===========================================");
 

src/main/java/org/phoebus/pvws/EpicsWebSocketServerApplication.java

@@ -18,28 +18,20 @@
 
 package org.phoebus.pvws;
 
-import org.epics.vtype.VType;
 import org.phoebus.pv.PV;
 import org.phoebus.pv.PVPool;
 import org.phoebus.pv.RefCountMap;
-import org.phoebus.pvws.ws.Vtype2Json;
 import org.phoebus.pvws.ws.WebSocket;
-import org.phoebus.pvws.ws.WebSocketPV;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.boot.builder.SpringApplicationBuilder;
 import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
 import org.springframework.context.ApplicationContext;
-import org.springframework.http.MediaType;
-import org.springframework.web.bind.annotation.GetMapping;
-import org.springframework.web.bind.annotation.RequestParam;
-import org.springframework.web.bind.annotation.RestController;
 
 
 import java.util.List;
 
 @SpringBootApplication
-@RestController
 public class EpicsWebSocketServerApplication extends SpringBootServletInitializer {
 
     public static void main(String[] args) {
@@ -62,26 +54,4 @@ public static void main(String[] args) {
     protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
         return application.sources(EpicsWebSocketServerApplication.class);
     }
-
-    @GetMapping(value= "/pvget", produces = MediaType.APPLICATION_JSON_VALUE)
-    public String pvget(@RequestParam String name) {
-        final WebSocketPV pv = new WebSocketPV(name, null);
-        String ret;
-        try {
-            int maxAttempts = 100;
-            int retryDelay = 50;
-
-            VType lastValue = null;
-            for (int i = 0; i< maxAttempts; i++) {
-                Thread.sleep(retryDelay);
-                lastValue = pv.get();
-                if (lastValue != null) break;
-            }
-            ret = Vtype2Json.toJson(name, lastValue, null, true, true);
-        } catch (final Exception ex) {
-            ret = String.format("Unable to get PV value for %s - exception %s", name, ex);
-        }
-        pv.dispose();
-        return ret;
-    }
 }

src/main/java/org/phoebus/pvws/controllers/PvwsRestController.java

@@ -22,19 +22,25 @@
 import org.epics.util.array.ListInteger;
 import org.epics.vtype.Array;
 import org.epics.vtype.VType;
+import org.phoebus.core.vtypes.VTypeHelper;
 import org.phoebus.pv.PV;
 import org.phoebus.pv.PVPool;
 import org.phoebus.pv.RefCountMap;
 import org.phoebus.pvws.model.*;
+import org.phoebus.pvws.ws.Vtype2Json;
 import org.phoebus.pvws.ws.WebSocket;
 import org.phoebus.pvws.ws.WebSocketPV;
 import org.phoebus.util.time.TimestampFormats;
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.http.MediaType;
 import org.springframework.web.bind.annotation.*;
 
 import java.time.Instant;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -146,4 +152,30 @@ public InfoData info(@RequestParam(name = "env", defaultValue = "false") boolean
         }
         return infoData;
     }
+
+    @GetMapping(value= "/pvget", produces = MediaType.APPLICATION_JSON_VALUE)
+    public String pvget(@RequestParam String name) {
+        CountDownLatch countDownLatch = new CountDownLatch(1);
+        AtomicReference<VType> value = new AtomicReference<>(null);
+        try {
+            int pvReadTimeout = Integer.parseInt(System.getProperty("PV_READ_TIMEOUT"));
+            PV pv = PVPool.getPV(name);
+            pv.onValueEvent().subscribe(vtype -> {
+                if (!VTypeHelper.isDisconnected(vtype)) {
+                    value.set(pv.read());
+                }
+                countDownLatch.countDown();
+            });
+            countDownLatch.await(pvReadTimeout, TimeUnit.MILLISECONDS);
+            PVPool.releasePV(pv);
+            if(value.get() == null){
+                logger.info("PV " + name + " never connected.");
+                return null;
+            }
+            return Vtype2Json.toJson(name, value.get(), null, true, true);
+        } catch (Exception e) {
+            logger.warning("Exception when reading PV " + name + " Exception: " + e);
+            return null;
+        }
+    }
 }

src/main/java/org/phoebus/pvws/ws/WebSocketPV.java

@@ -169,17 +169,6 @@ public void write(Object new_value) throws Exception
             throw new Exception("PV_WRITE_SUPPORT is disabled");
     }
 
-    /**
-     * Get current value by calling read() on the PV
-     * @return the current value
-     * @throws Exception on error
-     */
-    public VType get() throws Exception
-    {
-        pv = PVPool.getPV(name);
-        return pv.read();
-    }
-
     /** Close PV */
     public void dispose()
     {

src/main/resources/application.properties

@@ -14,3 +14,5 @@ EPICS_PVA_ADDR_LIST=
 EPICS_PVA_AUTO_ADDR_LIST=YES
 EPICS_PVA_BROADCAST_PORT=5076
 EPICS_PVA_NAME_SERVERS=
+
+PV_READ_TIMEOUT=5000