[Pki-devel] [PATCH] 0134 Block reads during reload of LDAP-based profiles
Fraser Tweedale
ftweedal at redhat.com
Wed Sep 14 12:14:41 UTC 2016
Hi team,
The attached patch fixes (yet another) race condition in
LDAPProfileSubsystem.
https://fedorahosted.org/pki/ticket/2453
Additional context: https://fedorahosted.org/freeipa/ticket/6274
Thanks,
Fraser
-------------- next part --------------
From 24a5ad6f84387055468e0125df90fea6635da484 Mon Sep 17 00:00:00 2001
From: Fraser Tweedale <ftweedal at redhat.com>
Date: Wed, 14 Sep 2016 19:39:36 +1000
Subject: [PATCH] Block reads during reload of LDAP-based profiles
LDAP disconnect (e.g. due to DS restart) causes LDAPProfileSubsystem
to drop all its profiles and reload them. If a profile is read
during this time, e.g. to issue a certificate, it might not have
been reloaded thus causing the operation to fail.
Introduce the AsyncLoader class which allows a consumer to await the
completion of a (re)load, if one is happening. Update the
getProfile and getProfileIds method to use it.
The existing 'initialLoadDone' CountDownLatch for blocking
LDAPProfileSubsystem init until the inital load of profiles is
completed was subsumed by AsyncLoader.
Fixes: https://fedorahosted.org/pki/ticket/2453
---
.../src/com/netscape/certsrv/util/AsyncLoader.java | 86 ++++++++++++++++++++++
.../cmscore/profile/LDAPProfileSubsystem.java | 59 ++++++++++-----
2 files changed, 127 insertions(+), 18 deletions(-)
create mode 100644 base/common/src/com/netscape/certsrv/util/AsyncLoader.java
diff --git a/base/common/src/com/netscape/certsrv/util/AsyncLoader.java b/base/common/src/com/netscape/certsrv/util/AsyncLoader.java
new file mode 100644
index 0000000000000000000000000000000000000000..39f8efd3272607ed6ac219b1b42bf9a4cb076a80
--- /dev/null
+++ b/base/common/src/com/netscape/certsrv/util/AsyncLoader.java
@@ -0,0 +1,86 @@
+// --- BEGIN COPYRIGHT BLOCK ---
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; version 2 of the License.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program; if not, write to the Free Software Foundation, Inc.,
+// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+//
+// (C) 2016 Red Hat, Inc.
+// All rights reserved.
+// --- END COPYRIGHT BLOCK ---
+
+package com.netscape.certsrv.util;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.locks.ReentrantLock;
+
+/** A locking mechanism for loading or reloading an initially
+ * unknown number of items.
+ *
+ * The "producer" is the thread that loads items, informing the
+ * Loader when each item is loaded and how many items there are
+ * (when that fact becomes known).
+ *
+ * Other threads can await the completion of a (re)loading
+ * process.
+ */
+public class AsyncLoader {
+ private CountDownLatch producerInitialised = new CountDownLatch(1);
+ private ReentrantLock loadingLock = new ReentrantLock();
+ private Integer numItems = null;
+ private int numItemsLoaded = 0;
+
+ /**
+ * Acquire the lock as a producer.
+ */
+ public void startLoading() {
+ numItems = null;
+ numItemsLoaded = 0;
+ loadingLock.lock();
+ producerInitialised.countDown();
+ }
+
+ /**
+ * Increment the number of items loaded by 1. If the number
+ * of items is known and that many items have been loaded,
+ * unlock the loader.
+ */
+ public void increment() {
+ numItemsLoaded += 1;
+ checkLoadDone();
+ }
+
+ /**
+ * Set the number of items. If the number of items already
+ * loaded is equal to or greater than the number, unlock the
+ * loader.
+ */
+ public void setNumItems(Integer n) {
+ numItems = n;
+ checkLoadDone();
+ }
+
+ private void checkLoadDone() {
+ if (numItems != null && numItemsLoaded >= numItems) {
+ while (loadingLock.isHeldByCurrentThread())
+ loadingLock.unlock();
+ }
+ }
+
+ public void awaitLoadDone() throws InterruptedException {
+ /* A consumer may await upon the Loader immediately after
+ * starting the producer. To ensure that the producer
+ * has time to acquire the lock, we use a CountDownLatch.
+ */
+ producerInitialised.await();
+ loadingLock.lock();
+ loadingLock.unlock();
+ }
+}
diff --git a/base/server/cmscore/src/com/netscape/cmscore/profile/LDAPProfileSubsystem.java b/base/server/cmscore/src/com/netscape/cmscore/profile/LDAPProfileSubsystem.java
index 6dea1a0d88beaefeea489ea58ad9ad13d2da8bd7..fd5aa64eed8385ad18a307b6addaee6222d9f9cf 100644
--- a/base/server/cmscore/src/com/netscape/cmscore/profile/LDAPProfileSubsystem.java
+++ b/base/server/cmscore/src/com/netscape/cmscore/profile/LDAPProfileSubsystem.java
@@ -20,11 +20,11 @@ package com.netscape.cmscore.profile;
import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.util.Arrays;
+import java.util.Enumeration;
import java.util.Hashtable;
import java.util.LinkedHashMap;
import java.util.TreeMap;
import java.util.TreeSet;
-import java.util.concurrent.CountDownLatch;
import netscape.ldap.LDAPAttribute;
import netscape.ldap.LDAPAttributeSet;
@@ -49,6 +49,7 @@ import com.netscape.certsrv.profile.IProfile;
import com.netscape.certsrv.profile.IProfileSubsystem;
import com.netscape.certsrv.registry.IPluginInfo;
import com.netscape.certsrv.registry.IPluginRegistry;
+import com.netscape.certsrv.util.AsyncLoader;
import com.netscape.cmscore.base.LDAPConfigStore;
import com.netscape.cmsutil.ldap.LDAPUtil;
@@ -71,10 +72,7 @@ public class LDAPProfileSubsystem
/* Set of nsUniqueIds of deleted entries */
private TreeSet<String> deletedNsUniqueIds;
- /* Variables to track initial loading of profiles */
- private Integer initialNumProfiles = null;
- private int numProfilesLoaded = 0;
- private CountDownLatch initialLoadDone = new CountDownLatch(1);
+ private AsyncLoader loader = new AsyncLoader();
/**
* Initializes this subsystem with the given configuration
@@ -118,7 +116,7 @@ public class LDAPProfileSubsystem
monitor = new Thread(this, "profileChangeMonitor");
monitor.start();
try {
- initialLoadDone.await();
+ loader.awaitLoadDone();
} catch (InterruptedException e) {
CMS.debug("LDAPProfileSubsystem: caught InterruptedException "
+ "while waiting for initial load of profiles.");
@@ -126,6 +124,27 @@ public class LDAPProfileSubsystem
CMS.debug("LDAPProfileSubsystem: finished init");
}
+ public IProfile getProfile(String id)
+ throws EProfileException {
+ try {
+ loader.awaitLoadDone();
+ } catch (InterruptedException e) {
+ CMS.debug("LDAPProfileSubsystem.getProfile: caught InterruptedException "
+ + "while waiting for profiles to be loaded.");
+ }
+ return super.getProfile(id);
+ }
+
+ public Enumeration<String> getProfileIds() {
+ try {
+ loader.awaitLoadDone();
+ } catch (InterruptedException e) {
+ CMS.debug("LDAPProfileSubsystem.getProfile: caught InterruptedException "
+ + "while waiting for profiles to be loaded.");
+ }
+ return super.getProfileIds();
+ }
+
/**
* Read the given LDAPEntry into the profile subsystem.
*/
@@ -395,12 +414,6 @@ public class LDAPProfileSubsystem
return "cn=" + id + "," + dn;
}
- private void checkInitialLoadDone() {
- if (initialNumProfiles != null
- && numProfilesLoaded >= initialNumProfiles)
- initialLoadDone.countDown();
- }
-
private void ensureProfilesOU(LDAPConnection conn) throws LDAPException {
try {
conn.search(dn, LDAPConnection.SCOPE_BASE, "(objectclass=*)", null, false);
@@ -431,7 +444,6 @@ public class LDAPProfileSubsystem
CMS.debug("Profile change monitor: starting.");
while (!stopped) {
- forgetAllProfiles();
try {
conn = dbFactory.getConn();
ensureProfilesOU(conn);
@@ -443,16 +455,28 @@ public class LDAPProfileSubsystem
LDAPSearchResults results = conn.search(
dn, LDAPConnection.SCOPE_SUB, "(objectclass=*)",
attrs, false, cons);
+
+ /* Wait until the last possible moment before taking
+ * the load lock and dropping all profiles, so that
+ * we can continue to service requests while LDAP is
+ * down.
+ *
+ * Once we reconnect, we need to forget all profiles
+ * and reload in case some were removed in the
+ * interim.
+ */
+ loader.startLoading();
+ forgetAllProfiles();
+
while (!stopped && results.hasMoreElements()) {
LDAPEntry entry = results.next();
String[] objectClasses =
entry.getAttribute("objectClass").getStringValueArray();
if (Arrays.asList(objectClasses).contains("organizationalUnit")) {
- initialNumProfiles = new Integer(
+ loader.setNumItems(new Integer(
entry.getAttribute("numSubordinates")
- .getStringValueArray()[0]);
- checkInitialLoadDone();
+ .getStringValueArray()[0]));
continue;
}
@@ -486,8 +510,7 @@ public class LDAPProfileSubsystem
} else {
CMS.debug("Profile change monitor: immediate result");
readProfile(entry);
- numProfilesLoaded += 1;
- checkInitialLoadDone();
+ loader.increment();
}
}
} catch (ELdapException e) {
--
2.5.5
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