fix problem with package cache corruption when different processes install the same package at the same time

org.hl7.fhir.utilities/src/main/java/org/hl7/fhir/utilities/cache/PackageCacheManager.java

@@ -35,11 +35,15 @@ import java.io.BufferedOutputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.File;
 import java.io.FileInputStream;
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
+import java.io.RandomAccessFile;
 import java.net.HttpURLConnection;
 import java.net.URL;
 import java.net.URLConnection;
+import java.nio.channels.FileChannel;
+import java.nio.channels.FileLock;
 import java.sql.Timestamp;
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
@@ -186,6 +190,42 @@ public class PackageCacheManager {
     }
   }
 
+  public interface CacheLockFunction<T> {
+    T get() throws IOException;
+  }
+  public class CacheLock {
+
+    private final File lockFile;
+
+    public CacheLock(String name) throws IOException {
+      this.lockFile = new File(cacheFolder, name + ".lock");
+      if (!lockFile.isFile()) {
+        TextFile.stringToFile("", lockFile);
+      }
+    }
+
+    public <T> T doWithLock(CacheLockFunction<T> f) throws FileNotFoundException, IOException {
+      try (FileChannel channel = new RandomAccessFile(lockFile, "rw").getChannel()) {
+        final FileLock fileLock = channel.lock();
+        T result = null;
+        try {
+          result = f.get();
+        } finally {
+          fileLock.release();
+        }
+        try {
+          if (!lockFile.delete()) {
+            lockFile.deleteOnExit();
+          }
+        } catch (Throwable t) {
+          System.out.println("unable to clean up lock file for "+lockFile.getName()+": "+t.getMessage());
+          // nothing
+        }
+        return result;
+      } 
+    }
+  }
+
   public static final String PRIMARY_SERVER = "http://packages.fhir.org";
   public static final String SECONDARY_SERVER = "http://packages2.fhir.org/packages";
 //  private static final String SECONDARY_SERVER = "http://local.fhir.org:960/packages";
@@ -256,6 +296,7 @@ public class PackageCacheManager {
   private void clearCache() throws IOException {
     for (File f : new File(cacheFolder).listFiles()) {
       if (f.isDirectory()) {
+        new CacheLock(f.getName()).doWithLock(() -> {
           Utilities.clearDirectory(f.getAbsolutePath());
           try {
             FileUtils.deleteDirectory(f);
@@ -266,6 +307,8 @@ public class PackageCacheManager {
               // just give up 
             }          
           }
+          return null; // must return something
+        });
       }
       else if (!f.getName().equals("packages.ini"))
         FileUtils.forceDelete(f);
@@ -413,6 +456,7 @@ public class PackageCacheManager {
    * @throws IOException
    */
   public void removePackage(String id, String ver) throws IOException  {
+    new CacheLock(id+"#"+ver).doWithLock(() -> {
       String f = Utilities.path(cacheFolder, id+"#"+ver);
       File ff = new File(f);
       if (ff.exists()) {    
@@ -422,6 +466,8 @@ public class PackageCacheManager {
         ini.save();
         ff.delete();
       }
+      return null;
+    });
   }
 
   /**
@@ -494,7 +540,10 @@ public class PackageCacheManager {
     if (version == null)
       version = npm.version();
 
-    String packRoot = Utilities.path(cacheFolder, id+"#"+version);
+    String v = version;
+    return new CacheLock(id+"#"+version).doWithLock(() -> {
+      NpmPackage pck = null;
+      String packRoot = Utilities.path(cacheFolder, id+"#"+v);
       try {
         Utilities.createDirectory(packRoot);
         Utilities.clearDirectory(packRoot);
@@ -527,30 +576,31 @@ public class PackageCacheManager {
 
         IniFile ini = new IniFile(Utilities.path(cacheFolder, "packages.ini"));
         ini.setTimeStampFormat("yyyyMMddhhmmss");
-      ini.setTimestampProperty("packages", id+"#"+version, Timestamp.from(Instant.now()), null);
+        ini.setTimestampProperty("packages", id+"#"+v, Timestamp.from(Instant.now()), null);
-      ini.setIntegerProperty("package-sizes", id+"#"+version, size, null);
+        ini.setIntegerProperty("package-sizes", id+"#"+v, size, null);
         ini.save();
         if (progress)
           System.out.println(" done.");
 
-      NpmPackage pck = loadPackageInfo(packRoot);
+        pck = loadPackageInfo(packRoot);
-      if (!id.equals(JSONUtil.str(npm.getNpm(), "name")) || !version.equals(JSONUtil.str(npm.getNpm(), "version"))) {
+        if (!id.equals(JSONUtil.str(npm.getNpm(), "name")) || !v.equals(JSONUtil.str(npm.getNpm(), "version"))) {
           if (!id.equals(JSONUtil.str(npm.getNpm(), "name"))) {
             npm.getNpm().addProperty("original-name", JSONUtil.str(npm.getNpm(), "name"));
             npm.getNpm().remove("name");
             npm.getNpm().addProperty("name", id);
           }
-        if (!version.equals(JSONUtil.str(npm.getNpm(), "version"))) {
+          if (!v.equals(JSONUtil.str(npm.getNpm(), "version"))) {
             npm.getNpm().addProperty("original-version", JSONUtil.str(npm.getNpm(), "version"));
             npm.getNpm().remove("version");
-          npm.getNpm().addProperty("version", version);
+            npm.getNpm().addProperty("version", v);
           }
-        TextFile.stringToFile(new GsonBuilder().setPrettyPrinting().create().toJson(npm.getNpm()), Utilities.path(cacheFolder, id+"#"+version, "package", "package.json"), false);
+          TextFile.stringToFile(new GsonBuilder().setPrettyPrinting().create().toJson(npm.getNpm()), Utilities.path(cacheFolder, id+"#"+v, "package", "package.json"), false);
         }
-      return pck;
       } catch (Exception e) {
         try {
           // don't leave a half extracted package behind
+          System.out.println("Clean up package "+packRoot+" because installation failed: "+e.getMessage());
+          e.printStackTrace();
           Utilities.clearDirectory(packRoot);
           new File(packRoot).delete();
         } catch (Exception ei) {
@@ -558,6 +608,8 @@ public class PackageCacheManager {
         }
         throw e;
       }
+      return pck;
+    });    
   }
 
   public String getPackageId(String canonical) throws IOException {