[tor-commits] [onionoo/master] Use a lock file to prevent concurrent executions.

[karsten@xxxxxxxxxxxxxx]

commit 92f50e1eae8765d54d4163be0a61f40b15837689
Author: Karsten Loesing <karsten.loesing@xxxxxxx>
Date:   Wed Sep 11 16:47:15 2013 +0200

    Use a lock file to prevent concurrent executions.
---
 src/org/torproject/onionoo/LockFile.java |   46 ++++++++++++++++++++++++++++++
 src/org/torproject/onionoo/Main.java     |   18 ++++++++++++
 2 files changed, 64 insertions(+)

diff --git a/src/org/torproject/onionoo/LockFile.java b/src/org/torproject/onionoo/LockFile.java
new file mode 100644
index 0000000..aad7076
--- /dev/null
+++ b/src/org/torproject/onionoo/LockFile.java
@@ -0,0 +1,46 @@
+/* Copyright 2013 The Tor Project
+ * See LICENSE for licensing information */
+package org.torproject.onionoo;
+
+import java.io.BufferedWriter;
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+
+public class LockFile {
+
+  private File lockFile;
+
+  public LockFile(File lockFile) {
+    this.lockFile = lockFile;
+  }
+
+  public boolean acquireLock() {
+    try {
+      if (this.lockFile.exists()) {
+        return false;
+      }
+      if (this.lockFile.getParentFile() != null) {
+        this.lockFile.getParentFile().mkdirs();
+      }
+      BufferedWriter bw = new BufferedWriter(new FileWriter(
+          this.lockFile));
+      bw.append("" + System.currentTimeMillis() + "\n");
+      bw.close();
+      return true;
+    } catch (IOException e) {
+      System.err.println("Caught exception while trying to acquire "
+          + "lock!");
+      e.printStackTrace();
+      return false;
+    }
+  }
+
+  public boolean releaseLock() {
+    if (this.lockFile.exists()) {
+      this.lockFile.delete();
+    }
+    return !this.lockFile.exists();
+  }
+}
+
diff --git a/src/org/torproject/onionoo/Main.java b/src/org/torproject/onionoo/Main.java
index 0d29ab5..9d9852b 100644
--- a/src/org/torproject/onionoo/Main.java
+++ b/src/org/torproject/onionoo/Main.java
@@ -11,6 +11,16 @@ public class Main {
   public static void main(String[] args) {
 
     printStatus("Initializing.");
+
+    LockFile lf = new LockFile(new File("lock"));
+    if (lf.acquireLock()) {
+      printStatusTime("Acquired lock");
+    } else {
+      printStatusTime("Could not acquire lock.  Is Onionoo already "
+          + "running?  Terminating");
+      return;
+    }
+
     DescriptorSource dso = new DescriptorSource(new File("in"),
         new File("status"));
     printStatusTime("Initialized descriptor source");
@@ -122,6 +132,14 @@ public class Main {
     printStatistics("Reverse domain name resolver",
         rdnr.getStatsString());
 
+    printStatus("Releasing lock.");
+    if (lf.releaseLock()) {
+      printStatusTime("Released lock");
+    } else {
+      printStatusTime("Could not release lock.  The next execution "
+          + "may not start as expected");
+    }
+
     printStatus("Terminating.");
   }
 

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