availability: adds check on DB connection

data-discovery/src/main/java/search/DbObstap.java

@@ -80,6 +80,35 @@ public class DbObstap
    }
 
 
+   public int queryObstapRowCount()
+      throws Exception
+		{
+			LOGGER.fine("trace");
+
+			String theQuery = "SELECT count(*) AS total FROM obscore";
+			LOGGER.fine(theQuery);
+			LOGGER.fine("Connecting to: " + dbConnArgs.uri() + " with user: " + dbConnArgs.userName() );
+
+			int rowCount = -1;
+			try(
+					Connection conn = DriverManager.getConnection(dbConnArgs.uri(), dbConnArgs.userName(), dbConnArgs.password());
+					Statement  st   = conn.createStatement();
+					ResultSet  res  = st.executeQuery(theQuery);)
+			{
+				while (res.next())
+				{
+					rowCount = res.getInt("total");
+				}
+			}
+			catch (SQLException se)
+			{
+				dbError(se);
+				// se.printStackTrace();
+				throw new Exception(se.toString());
+			}
+
+			return rowCount;
+		}
 
 
 	public String[] queryOverlapingPubdid(QueryArgs qArgs)

data-discovery/src/main/java/webapi/VosiServlet.java

@@ -27,24 +27,47 @@ import static java.nio.file.StandardCopyOption.*;
 public class VosiServlet
     extends javax.servlet.http.HttpServlet
 {
-    // for logs and debug
 	String className = this.getClass().getSimpleName();
+	private static final SearchSettings settings = SearchSettings.getInstance("search.properties");
 
-// VOSI
-// String accessURL = null; // FIXME now read from MERGEURL later introduce own param
-// String funcName = "vlkb_cutout"; // FIXME read from config file
 
-	private static final String availStr = 
+	private String availString()
+	{ 
+		boolean available;
+		int obstapRowCount = -1;
+		DbObstap dbObstap;
+		String note;
+		try
+		{
+			synchronized(DbObstap.class)
+			{
+				dbObstap = new DbObstap(settings.dbConnArgs);
+			}
+			obstapRowCount = dbObstap.queryObstapRowCount();
+			available = (obstapRowCount >= 0);
+			note = "Table obstap in " + settings.dbConnArgs.toString() + " has "
+					+ String.valueOf(obstapRowCount)  + " rows";
+		}
+		catch(Exception ex)
+		{
+			note = "Accessing " + settings.dbConnArgs.toString()
+				+ " failed with " + ex.toString();
+			available = false;
+		}
+		String availStr = 
 			"<?xml version=\"1.0\" encoding=\"UTF-8\"?>"
-		+ "<vosi:availability  "
-		+ " xmlns:vosi=\"http://www.ivoa.net/xml/VOSIAvailability/v1.0\">"
-		+ " <vosi:available>true</vosi:available>"
+			+ "<vosi:availability xmlns:vosi=\"http://www.ivoa.net/xml/VOSIAvailability/v1.0\">"
+			+ "<vosi:available> "+ (available ? "true":"false") +" </vosi:available>"
 			+ "<vosi:note> VLKB-SIAv2 "+ Version.asString +" is accepting queries </vosi:note>"
+			+ "<vosi:note> " + note + " </vosi:note>"
 			+ "</vosi:availability>";
 
-	private String capsStr = null;
+		return availStr;
+	}
 
 
+	private String capsStr = null;
+
 	protected void SetCapsStr(String URL, String funcName)
 	{
 		if(URL != null)
@@ -138,7 +161,7 @@ public class VosiServlet
 			}
 			else if(-1 != requestURL.lastIndexOf("/availability"))
 			{
-			writer.println(availStr);	
+				writer.println(availString());	
 			}
 			// error FIXME what to do if none of above given ? e.g. misconfigured web.xml