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Posted to commits@felix.apache.org by fm...@apache.org on 2009/08/31 16:04:33 UTC
svn commit: r809597 -
/felix/trunk/configadmin/src/main/java/org/apache/felix/cm/impl/ConfigurationImpl.java
Author: fmeschbe
Date: Mon Aug 31 14:04:33 2009
New Revision: 809597
URL: http://svn.apache.org/viewvc?rev=809597&view=rev
Log:
FELIX-1545 implement last modification and last update trackers
as simple counters (instead of System.currentTimeMillis()) :
last modification time is incremented whenever
Configuration.update(Dictionary) is called
last update time is set to last modification time after each
update of the Configuration's properties in a ManagedSerive[Factory].
Modified:
felix/trunk/configadmin/src/main/java/org/apache/felix/cm/impl/ConfigurationImpl.java
Modified: felix/trunk/configadmin/src/main/java/org/apache/felix/cm/impl/ConfigurationImpl.java
URL: http://svn.apache.org/viewvc/felix/trunk/configadmin/src/main/java/org/apache/felix/cm/impl/ConfigurationImpl.java?rev=809597&r1=809596&r2=809597&view=diff
==============================================================================
--- felix/trunk/configadmin/src/main/java/org/apache/felix/cm/impl/ConfigurationImpl.java (original)
+++ felix/trunk/configadmin/src/main/java/org/apache/felix/cm/impl/ConfigurationImpl.java Mon Aug 31 14:04:33 2009
@@ -83,6 +83,17 @@
* method (but still sends the CM_UPDATED event).
*
* See also FELIX-1542.
+ *
+ * FELIX-1545 provides further update to the concurrency situation defining
+ * three more failure cases:
+ *
+ * (1) System.currentTimeMillis() may be too coarse graind to protect
+ * against race condition.
+ * (2) ManagedService update sets last update time regardless of whether
+ * configuration was provided or not. This may cause a configuration
+ * update to be lost.
+ * (3) ManagedService update does not respect last update time which
+ * in turn may cause duplicate configuration delivery.
*/
/**
@@ -126,24 +137,19 @@
private volatile boolean isDeleted;
/**
- * Time of last configuration properties update.
- * This is intended to be managed by the {@link #configure(Dictionary)}
- * method when setting the properties field.
- * <p>
- * This field is set to the current time upon construction and every time
- * the {@link #configure(Dictionary)} method sets the {@link #properties}
- * field.
+ * Current configuration modification counter. This field is incremented
+ * each time the {@link #properties} field is set (in the constructor or the
+ * {@link #configure(Dictionary)} method. field.
*/
private volatile long lastModificationTime;
/**
- * Time of last submission of the configuration properties to the (or more)
- * ManagedService[Factory] services this is managed by the update thread
- * and must solely be handled on the Update Thread.
- * <p>
- * This field is initialized to -1 in the constructors and is set to the
- * current time when the configuration properties are supplied to the
- * ManagedService[Factory] in the Update Thread.
+ * Value of the {@link #lastModificationTime} counter at the time the non-
+ * <code>null</code> properties of this configuration have been updated to a
+ * ManagedService[Factory]. This field is initialized to -1 in the
+ * constructors and set to the value of the {@link #lastModificationTime} by
+ * the {@link #setLastUpdatedTime()} method called from the respective task
+ * updating the configuration.
*
* @see #lastModificationTime
*/
@@ -172,10 +178,12 @@
this.factoryPID = factoryPid;
this.isDeleted = false;
- this.properties = null;
- this.lastModificationTime = System.currentTimeMillis();
this.lastUpdatedTime = -1;
+ // first "update"
+ this.properties = null;
+ setLastModificationTime();
+
// this is a new configuration object, store immediately unless
// the new configuration object is created from a factory, in which
// case the configuration is only stored when first updated
@@ -378,39 +386,64 @@
/**
- * Returns the time of the last update of this configuration object. In
- * particular this is the time at which the properties field has been
- * set to new values.
+ * Increments the last modification counter of this configuration to cause
+ * the ManagedService or ManagedServiceFactory subscribed to this
+ * configuration to be updated.
+ * <p>
+ * This method is intended to only be called by the constructor(s) of this
+ * class and the {@link #update(Dictionary)} method to indicate to the
+ * update threads, the configuration is ready for distribution.
* <p>
- * This value may be compared to the {@link #getLastUpdatedTime()} to
- * decide whether to update the ManagedService[Factory] or not.
+ * Setting the properties field and incrementing this counter should be
+ * done synchronized on this instance.
+ */
+ void setLastModificationTime( )
+ {
+ this.lastModificationTime++;
+ }
+
+
+ /**
+ * Returns the modification counter of the last modification of the
+ * properties of this configuration object.
+ * <p>
+ * This value may be compared to the {@link #getLastUpdatedTime()} to decide
+ * whether to update the ManagedService[Factory] or not.
+ * <p>
+ * Getting the properties of this configuration and this counter should be
+ * done synchronized on this instance.
*/
long getLastModificationTime()
{
return lastModificationTime;
}
+
/**
- * Returns the time of the last update of this configuration to the
- * subscribing ManagedService or ManagedServiceFactory. This time may be
- * compared to the {@link #getLastModificationTime()} to decide whether
- * the configuration should be updated or not.
+ * Returns the modification counter of the last update of this configuration
+ * to the subscribing ManagedService or ManagedServiceFactory. This value
+ * may be compared to the {@link #getLastModificationTime()} to decide
+ * whether the configuration should be updated or not.
*/
long getLastUpdatedTime()
{
return lastUpdatedTime;
}
+
/**
- * Sets the time of the last update of this configuration to the
- * ManagedService or ManagedServiceFactory subscribed to this configuration.
+ * Sets the last update time field to the current value of the last
+ * modification time field to indicate the properties of this configuration
+ * have been updated in the ManagedService[Factory].
* <p>
* This method should only be called from the Update Thread after supplying
* the configuration to the ManagedService[Factory].
*/
void setLastUpdatedTime( )
{
- this.lastUpdatedTime = System.currentTimeMillis();
+ synchronized (this) {
+ this.lastUpdatedTime = getLastModificationTime();
+ }
}
/**
@@ -475,7 +508,7 @@
synchronized ( this )
{
this.properties = newProperties;
- this.lastModificationTime = System.currentTimeMillis();
+ setLastModificationTime();
}
}