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Posted to commits@helix.apache.org by jx...@apache.org on 2023/01/05 19:48:24 UTC
svn commit: r1906412 [3/35] - in /helix/site-content: ./ 0.9.9-docs/ 0.9.9-docs/css/ 0.9.9-docs/images/ 0.9.9-docs/js/ 0.9.9-docs/recipes/ 0.9.9-docs/releasenotes/ 1.0.2-docs/ 1.0.2-docs/css/ 1.0.2-docs/images/ 1.0.2-docs/js/ 1.0.2-docs/recipes/ 1.0.2-...
Modified: helix/site-content/0.9.9-docs/auto_exit_maintenance.html
URL: http://svn.apache.org/viewvc/helix/site-content/0.9.9-docs/auto_exit_maintenance.html?rev=1906412&r1=1906411&r2=1906412&view=diff
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--- helix/site-content/0.9.9-docs/auto_exit_maintenance.html (original)
+++ helix/site-content/0.9.9-docs/auto_exit_maintenance.html Thu Jan 5 19:48:20 2023
@@ -1,13 +1,8 @@
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+ Rendered using Maven Reflow Skin 1.0.0 (http://andriusvelykis.github.com/reflow-maven-skin)
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- <a href="http://helix.apache.org/" id="bannerLeft"><img src="../images/helix-logo.jpg" alt='"''"' /></a>
- <p class="lead">A cluster management framework for partitioned and replicated distributed resources</p>
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<li>Auto-exit of Maintenance Mode</li>
- <li class="publishDate version-date pull-right">Last Published: 2022-10-19</li>
+ <li class="publishDate version-date pull-right">Last Published: 2022-04-15</li>
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-<div class="page-header">
- <h1>Auto-exit of Maintenance Mode</h1>
-</div>
-<section>
- <h2 id="Introduction">Introduction</h2>
- <p>Auto-exit of maintenance mode is a feature addition to Helix. It concerns a feature that allows clusters to switch out of maintenance mode automatically to save operational costs and to improve availability.</p>
-</section>
-<section>
- <h2 id="Background">Background</h2>
- <section>
- <h3 id="Maintenance_Mode">Maintenance Mode</h3>
- <p>The maintenance mode in Helix refers to a Helix cluster state where the Helix Controller will not trigger any type of rebalance. In short, if a cluster is in maintenance, the Controller will not bootstrap any new partitions. However, this does not mean that there won't be any (upward) state transitions. For example, partitions missing a top-state (e.g. <b>MASTER/LEADER</b>) replica will get a state transition in order to fill in the void for a top-state replica.</p>
- <section>
- <h4 id="Possible_Scenarios">Possible Scenarios</h4>
- <p>There are two possible conditions under which a cluster will go into maintenance mode automatically.</p>
- <ol style="list-style-type: decimal">
- <li>There are more offline/disabled instances than ClusterConfig's <b>MAX_OFFLINE_INSTANCES_ALLOWED</b>.</li>
- <li>There exist instances that have more partitions than ClusterConfig's <b>MAX_PARTITIONS_PER_INSTANCE</b>.</li>
- </ol>
- <p>Difficulty in Manually Exiting Maintenance Mode</p>
- <p>Although maintenance mode has been designed to prevent a large-scale reshuffling of replicas when there are intermittent, transient Participant connection issues. When in maintenance, no new partitions will be bootstrapped, which will block many native operations such as creation of stores/DBs. Currently, in order to unblock, an operator must manually disable maintenance mode via Helix REST API. Since it's difficult to predict when temporary disconnects will happen, it has been a challenge to address them in a prompt manner.</p>
- </section>
- </section>
-</section>
-<section>
- <h2 id="Problem_Statement">Problem Statement</h2>
- <p>Currently, once clusters enter maintenance mode automatically, exiting must be done manually. This is an added human effort. We want a feature to automate this to reduce downtime and increase availability.</p>
-</section>
-<section>
- <h2 id="Architecture.2FImplementation">Architecture/Implementation</h2>
- <section>
- <h3 id="Maintenance_Recovery_Threshold">Maintenance Recovery Threshold</h3>
- <p>Recall that there are two cases in which a cluster may enter maintenance mode automatically:</p>
- <blockquote>
- <ol style="list-style-type: decimal">
- <li>There are more offline/disabled instances than ClusterConfig's MAX_OFFLINE_INSTANCES_ALLOWED.</li>
- <li>There exist instances that have more partitions than ClusterConfig's MAX_PARTITIONS_PER_INSTANCE.</li>
- </ol>
- </blockquote>
- <p>It is important to note that we are mainly concerned with Case 1. Case 2 is meant to be a sanity check against Helix's CRUSH-ed rebalance algorithm, and this has little to do with the original motivation behind cluster maintenance mode. So, although we will <i>still</i> check against Case 2 when determining whether it is safe to exit maintenance mode, we will only address Case 1 in this section.</p>
- <p>With that said, it is not hard to imagine a cluster in production experiencing a flip-flop behavior around the exact value of <b>ClusterConfig's MAX_OFFLINE_INSTANCES_ALLOWED</b> field. Such behavior is undesirable and may defeat the purpose of using this feature. To mitigate it in design is to have a separate, <i>more strict</i> threshold for recovering out of maintenance mode. We therefore propose to add a new field, <b>MAINTENANCE_RECOVERY_THRESHOLD</b>. <b>MAINTENANCE_RECOVERY_THRESHOLD</b> will be defined by the user and hold a more conservative value than <b>MAX_OFFLINE_INSTANCES_ALLOWED</b> to allow for some wiggle room in deciding what value is enough to call a cluster â<i>sufficiently recovered</i>â. Additionally, we will also give users the flexibility to <i>âopt-outâ</i> of the auto-exit feature by treating a <b>MAINTENANCE_RECOVERY_THRESHOLD</b> value of -1 as a disable signal.</p>
- <p>In short,</p>
- <ul>
- <li>If NumOfflineDisabledInstances < NUM_OFFLINE_INSTANCES_FOR_AUTO_EXIT, exit maintenance mode</li>
- <li>NUM_OFFLINE_INSTANCES_FOR_AUTO_EXIT <= MAX_OFFLINE_INSTANCES_ALLOWED</li>
- <li>NUM_OFFLINE_INSTANCES_FOR_AUTO_EXIT < 0 or not set â Opt-out of auto-exiting of maintenance mode</li>
- </ul>
- </section>
- <section>
- <h3 id="Additional_Fields_in_MaintenanceSignal">Additional Fields in MaintenanceSignal</h3>
- <p>Currently, Helix stores the maintenance signal in /{CLUSTER_NAME}/CONTROLLER/MAINTENANCE. A sample maintenance signal ZNode will look like the following:</p>
- <div class="source">
- <pre><code class="language-json">{
- "id" : "maintenance",
- "simpleFields" : {
- "REASON" : "Offline Instances count 5 greater than allowed count 4. Stop rebalance and put the cluster CLUSTER_TestClusterInMaintenanceModeWhenReachingOfflineInstancesLimit into maintenance mode.",
- "TRIGGERED_BY" : "CONTROLLER",
- "TIMESTAMP" : "12312838831***",
- // The following are sample user-defined fields from the REST call payload //
- "id" : "hulee",
- "jira" : "HELIX-123",
- "cluster" : "testCluster"
- },
- "listFields" : {
- },
- "mapFields" : {
- }
-}
-</code></pre>
- </div>
- <p>A simpleField will be newly added (notice the â<b>TRIGGERED_BY</b>â field) to denote whether the current maintenance signal has been generated automatically by the Controller. There will initially be <b>two</b> possible entries for this field:</p>
- <ul>
- <li><b>CONTROLLER</b></li>
- <li><b>USER</b></li>
- </ul>
- <p>Also, the TIMESTAMP field will be added so that the value could be retrieved via REST.</p>
- <p>In addition, we will allow addition of custom fields in simpleFields. See the example above. Users will be able to add these fields by using the REST endpoints that will be provided when <b>enabling</b> the maintenance mode. Note that when disabling maintenance mode, these fields will no longer be available because disabling maintenance mode will remove the maintenance signal altogether.</p>
- </section>
- <section>
- <h3 id="Recording_Maintenance_History">Recording Maintenance History</h3>
- <p>Currently, Helix maintains the controller history in the /{clusterName}/CONTROLLER/HISTORY ZNode. We plan to add a history for maintenance mode. This way, users will be able to access the history in ZooKeeper directly, or utilize the REST endpoint for viewing. The format will be in a human-readable format like the following (this is how Helix maintains the Controller leader history):</p>
- <div class="source">
- <pre><code class="language-java">long currentTime = System.currentTimeMillis();
-DateFormat df = new SimpleDateFormat("yyyy-MM-dd-HH:mm:ss");
-df.setTimeZone(TimeZone.getTimeZone("UTC"));
-String dateTime = df.format(new Date(currentTime));
-</code></pre>
- </div>
- <p>Note that Helix only records <i>10 most recent</i> changes in the HISTORY ZNode. We will follow a similar protocol for persisting maintenance mode-related history. Note that <b>all changes around maintenance mode will be recorded</b> (both entering and exiting of the mode).</p>
- </section>
- <section>
- <h3 id="Backward_Compatibility">Backward Compatibility</h3>
- <p>Old versions of Helix Controllers will not refer to the newly-added fields, in which case they will simply lack the auto-exit functionality.</p>
- </section>
- <section>
- <h3 id="Asynchronous_Processing">Asynchronous Processing</h3>
- <p>Note that in order for a cluster to exit maintenance mode, the Controller must check against <i>all conditions</i> that are outlined above. That is, it needs to make sure <b>1) the total count of offline/disabled instances is less than the threshold and that 2) there are no instances with more partitions than the threshold</b>. Checking against Condition 2 requires traversing all resources' states, which could be costly in clusters of large scale. From this, we potentially risk adding a significant latency to the pipeline, which is undesirable because it could cause problems regarding availability (for example, longer pipeline runs may exacerbate the rate at which ZooKeeper Event Callbacks accumulate. Helix currently deals with a large number of ZK Event Callbacks by re-booting the Controller, which could nick Helix's as well as applications' availability numbers).</p>
- <p>For this reason, we will make the checks happen asynchronously. Additional tweak may be required to ensure that the maintenance signal is cached appropriately through each run of the pipeline to avoid the race condition.</p>
- </section>
- <section>
- <h3 id="Periodic_Check_on_Cluster_Recovery_Status">Periodic Check on Cluster Recovery Status</h3>
- <p>Auto-exit is inherently triggered as part of Helix's rebalance pipeline; that is, if there is no rebalance triggered, there wouldn't be any auto-exits triggered either. In theory, this is a non-issue because whether a cluster goes into or recovers out of maintenance mode is determined by changes around LiveInstances, and a LiveInstance change is an event that triggers Helix's rebalance pipeline.</p>
- <p>Regardless, there has been anecdotal reports where such events seemed to have been âswallowedâ or âdisappearedâ - if that is true for any reason (mostly a ZK callback queue issue), one way to mitigate it is to enable periodically-triggered rebalances. Note that this is actually a feature <i>already supported</i> by Helix.</p>
- </section>
-</section>
-<section>
- <h2 id="How_to_Use_the_Auto-Exit_Feature">How to Use the Auto-Exit Feature</h2>
- <section>
- <h3 id="Why_Use_Auto-Exit">Why Use Auto-Exit</h3>
- <p>Helix is used to manage resources in distributed clusters; therefore, it inevitably gets to have hundreds of instances. With so many clusters and traffic to the ZooKeeper, Helix's metadata store, there are cases in which some Participants in the cluster experience transient connection failure, which may cause Helix to respond to each little change that happens to the cluster. For users of stateful systems, this may be undesirable, so they opt to set a config for entering maintenance mode automatically. Maintenance mode is a temporary mode that the cluster can enter in order to ensure that there are no bootstrapping state transitions on instances.</p>
- <p>However, no bootstrapping state transitions could mean that some operations such as addition of resources would be halted, which causes periods of unavailability. It was the cluster operator's responsibility to determine whether the given cluster has sufficiently recovered enough to exit maintenance mode. The auto-exit feature removes such overhead.</p>
- </section>
- <section>
- <h3 id="Guide">Guide</h3>
- <p>First, we encourage all users of this feature to understand Helix's workflow below:</p>
- <p><img src="./images/auto-exit-maintenance.jpg" alt="Intro"></p>
- <p>In order to use this feature, you'd need to set the following config parameters in your cluster's ClusterConfig.</p>
- <section>
- <h4 id="Auto-enter_maintenance_mode">Auto-enter maintenance mode</h4>
- <p><b>MAX_OFFLINE_INSTANCES_ALLOWED</b>: the number of offline and disabled instances allowed before the cluster automatically enters maintenance mode.</p>
- <p><b>MAX_PARTITIONS_PER_INSTANCE</b>: the number of partitions on any given instance, where, if any instance in the cluster happens to have more partitions than this number, the cluster automatically enters maintenance mode</p>
- </section>
- <section>
- <h4 id="Auto-exit_maintenance_mode">Auto-exit maintenance mode</h4>
- <p><b>NUM_OFFLINE_INSTANCES_FOR_AUTO_EXIT</b>: set this value to allow your cluster to auto-exit when the number of offline and disabled instances are at this value. Note that this value must be less than MAX_OFFLINE_INSTANCES_ALLOWED (Read the design above on why). Note that the appropriate value for this is dependent on the characteristics of the cluster. In general, start with 1, meaning that the cluster will only auto-exit maintenance mode when it is down to 1 offline or disable instance, and increase the value as you increase tolerance.</p>
- <p>Note that the cluster will auto-exit only if it has <i>automatically</i> entered maintenance mode previously.</p>
- </section>
- </section>
-</section>
-<section>
- <h2 id="FAQ">FAQ</h2>
- <section>
- <section>
- <h4 id="How_is_this_related_to_DelayedAutoRebalancer.3F">How is this related to <b>DelayedAutoRebalancer</b>?</h4>
- <ul>
- <li>If you are using DelayedAutoRebalancer for your clusters, this auto-exit feature would still work as expected. Fundamentally, DelayedAutoRebalancer and maintenance mode are mutually independent. That is, under maintenance mode, Helix uses a different rebalancing strategy. Once the cluster auto-exits maintenance mode, it will go back to whichever rebalancing mode it was on previously.</li>
- <li>Delayed Partition Movement is a feature in Helix's FULL-AUTO rebalancer.</li>
- <li>The rebalance delay will work at the instance level and entering/exiting maintenance mode will not affect the time at which the delay-counting started.</li>
- </ul>
- </section>
- <section>
- <h4 id="How_do_I_know_what_the_appropriate_value_is_for_MAINTENANCE_RECOVERY_THRESHOLD.3F">How do I know what the appropriate value is for <b><b>MAINTENANCE_RECOVERY_THRESHOLD</b></b>?</h4>
- <ul>
- <li>As a framework, we cannot provide the right value for this threshold. It should depend on the nature of the application and the risk tolerance thereof. Familiarize yourself with the rules outlined above and start with a low value (for example, 0) and increase your tolerance.</li>
- </ul>
- </section>
- </section>
-</section>
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-
+
<div class="container subfooter">
<div class="row">
<div class="span12">
<p class="pull-right"><a href="#">Back to top</a></p>
<p class="copyright">Copyright ©2022 <a href="https://www.apache.org/">The Apache Software Foundation</a>. All Rights Reserved.</p>
- <p><a href="https://github.com/olamy/reflow-maven-skin" title="Reflow Maven skin">Reflow Maven skin</a> maintained by <a href="https://twitter.com/olamy" target="_blank" title="Olivier Lamy">Olivier Lamy</a>.</p>
- <div class="row span16"><div>Apache Helix, Apache, the Apache feather logo, and the Apache Helix project logos are trademarks of The Apache Software Foundation.
- All other marks mentioned may be trademarks or registered trademarks of their respective owners.</div>
- <a href="https://helix.apache.org/0.9.9-docs/privacy-policy.html">Privacy Policy</a>
- </div>
- </div>
+ <p><a href="http://github.com/andriusvelykis/reflow-maven-skin" title="Reflow Maven skin">Reflow Maven skin</a> by <a href="http://andrius.velykis.lt" target="_blank" title="Andrius Velykis">Andrius Velykis</a>.</p>
+ </div>
</div>
</div>
<!-- Le javascript
================================================== -->
<!-- Placed at the end of the document so the pages load faster -->
- <script src="./js/jquery.min.js"></script>
- <script src="./js/bootstrap.min.js"></script>
- <script src="./js/lightbox.min.js"></script>
- <script src="./js/reflow-scroll.js"></script>
+ <!-- Fallback jQuery loading from Google CDN:
+ http://stackoverflow.com/questions/1014203/best-way-to-use-googles-hosted-jquery-but-fall-back-to-my-hosted-library-on-go -->
+ <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
+ <script type="text/javascript">
+ if (typeof jQuery == 'undefined')
+ {
+ document.write(unescape("%3Cscript src='./js/jquery-1.8.3.min.js' type='text/javascript'%3E%3C/script%3E"));
+ }
+ </script>
+
+ <script src="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.2.2/js/bootstrap.min.js"></script>
+ <script src="./js/lightbox.js"></script>
+ <script src="./js/jquery.smooth-scroll.min.js"></script>
+ <!-- back button support for smooth scroll -->
+ <script src="./js/jquery.ba-bbq.min.js"></script>
<script src="./js/reflow-skin.js"></script>
-
+
</body>
</html>
\ No newline at end of file
Modified: helix/site-content/0.9.9-docs/css/lightbox.css
URL: http://svn.apache.org/viewvc/helix/site-content/0.9.9-docs/css/lightbox.css?rev=1906412&r1=1906411&r2=1906412&view=diff
==============================================================================
--- helix/site-content/0.9.9-docs/css/lightbox.css (original)
+++ helix/site-content/0.9.9-docs/css/lightbox.css Thu Jan 5 19:48:20 2023
@@ -1,45 +1,37 @@
-/* Preload images */
-body:after {
- content: url(../img/close.png) url(../img/loading.gif) url(../img/prev.png) url(../img/next.png);
- display: none;
-}
-
-.lightboxOverlay {
+/* line 6, ../sass/lightbox.sass */
+#lightboxOverlay {
position: absolute;
top: 0;
left: 0;
z-index: 9999;
background-color: black;
- filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=80);
- opacity: 0.8;
+ filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=85);
+ opacity: 0.85;
display: none;
}
-.lightbox {
+/* line 15, ../sass/lightbox.sass */
+#lightbox {
position: absolute;
left: 0;
width: 100%;
z-index: 10000;
text-align: center;
line-height: 0;
+ font-family: "lucida grande", tahoma, verdana, arial, sans-serif;
font-weight: normal;
}
-
-.lightbox .lb-image {
- display: block;
+/* line 24, ../sass/lightbox.sass */
+#lightbox img {
+ width: auto;
height: auto;
- max-width: inherit;
- -webkit-border-radius: 3px;
- -moz-border-radius: 3px;
- -ms-border-radius: 3px;
- -o-border-radius: 3px;
- border-radius: 3px;
}
-
-.lightbox a img {
+/* line 27, ../sass/lightbox.sass */
+#lightbox a img {
border: none;
}
+/* line 30, ../sass/lightbox.sass */
.lb-outerContainer {
position: relative;
background-color: white;
@@ -53,35 +45,30 @@ body:after {
-o-border-radius: 4px;
border-radius: 4px;
}
-
+/* line 38, ../../../../.rvm/gems/ruby-1.9.2-p290/gems/compass-0.12.1/frameworks/compass/stylesheets/compass/utilities/general/_clearfix.scss */
.lb-outerContainer:after {
content: "";
display: table;
clear: both;
}
+/* line 39, ../sass/lightbox.sass */
.lb-container {
- padding: 4px;
+ padding: 10px;
}
+/* line 42, ../sass/lightbox.sass */
.lb-loader {
position: absolute;
- top: 43%;
- left: 0;
+ top: 40%;
+ left: 0%;
height: 25%;
width: 100%;
text-align: center;
line-height: 0;
}
-.lb-cancel {
- display: block;
- width: 32px;
- height: 32px;
- margin: 0 auto;
- background: url(../img/loading.gif) no-repeat;
-}
-
+/* line 51, ../sass/lightbox.sass */
.lb-nav {
position: absolute;
top: 0;
@@ -91,57 +78,48 @@ body:after {
z-index: 10;
}
+/* line 59, ../sass/lightbox.sass */
.lb-container > .nav {
left: 0;
}
+/* line 62, ../sass/lightbox.sass */
.lb-nav a {
outline: none;
- background-image: url('data:image/gif;base64,R0lGODlhAQABAPAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==');
}
+/* line 65, ../sass/lightbox.sass */
.lb-prev, .lb-next {
+ width: 49%;
height: 100%;
- cursor: pointer;
+ background-image: url("data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7");
+ /* Trick IE into showing hover */
display: block;
}
-.lb-nav a.lb-prev {
- width: 34%;
+/* line 72, ../sass/lightbox.sass */
+.lb-prev {
left: 0;
float: left;
- background: url(../img/prev.png) left 48% no-repeat;
- filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=0);
- opacity: 0;
- -webkit-transition: opacity 0.6s;
- -moz-transition: opacity 0.6s;
- -o-transition: opacity 0.6s;
- transition: opacity 0.6s;
-}
-
-.lb-nav a.lb-prev:hover {
- filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=100);
- opacity: 1;
}
-.lb-nav a.lb-next {
- width: 64%;
+/* line 76, ../sass/lightbox.sass */
+.lb-next {
right: 0;
float: right;
- background: url(../img/next.png) right 48% no-repeat;
- filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=0);
- opacity: 0;
- -webkit-transition: opacity 0.6s;
- -moz-transition: opacity 0.6s;
- -o-transition: opacity 0.6s;
- transition: opacity 0.6s;
}
-.lb-nav a.lb-next:hover {
- filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=100);
- opacity: 1;
+/* line 81, ../sass/lightbox.sass */
+.lb-prev:hover {
+ background: url(../images/prev.png) left 48% no-repeat;
+}
+
+/* line 85, ../sass/lightbox.sass */
+.lb-next:hover {
+ background: url(../images/next.png) right 48% no-repeat;
}
+/* line 88, ../sass/lightbox.sass */
.lb-dataContainer {
margin: 0 auto;
padding-top: 5px;
@@ -149,62 +127,55 @@ body:after {
width: 100%;
-moz-border-radius-bottomleft: 4px;
-webkit-border-bottom-left-radius: 4px;
+ -ms-border-bottom-left-radius: 4px;
+ -o-border-bottom-left-radius: 4px;
border-bottom-left-radius: 4px;
-moz-border-radius-bottomright: 4px;
-webkit-border-bottom-right-radius: 4px;
+ -ms-border-bottom-right-radius: 4px;
+ -o-border-bottom-right-radius: 4px;
border-bottom-right-radius: 4px;
}
-
+/* line 38, ../../../../.rvm/gems/ruby-1.9.2-p290/gems/compass-0.12.1/frameworks/compass/stylesheets/compass/utilities/general/_clearfix.scss */
.lb-dataContainer:after {
content: "";
display: table;
clear: both;
}
+/* line 95, ../sass/lightbox.sass */
.lb-data {
- padding: 0 4px;
- color: #ccc;
+ padding: 0 10px;
+ color: #bbbbbb;
}
-
+/* line 98, ../sass/lightbox.sass */
.lb-data .lb-details {
width: 85%;
float: left;
text-align: left;
line-height: 1.1em;
}
-
+/* line 103, ../sass/lightbox.sass */
.lb-data .lb-caption {
font-size: 13px;
font-weight: bold;
line-height: 1em;
}
-
+/* line 107, ../sass/lightbox.sass */
.lb-data .lb-number {
display: block;
clear: left;
padding-bottom: 1em;
- font-size: 12px;
- color: #999999;
+ font-size: 11px;
}
-
+/* line 112, ../sass/lightbox.sass */
.lb-data .lb-close {
- display: block;
+ width: 35px;
float: right;
- width: 30px;
- height: 30px;
- background: url(../img/close.png) top right no-repeat;
- text-align: right;
+ padding-bottom: 0.7em;
outline: none;
- filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=70);
- opacity: 0.7;
- -webkit-transition: opacity 0.2s;
- -moz-transition: opacity 0.2s;
- -o-transition: opacity 0.2s;
- transition: opacity 0.2s;
}
-
+/* line 117, ../sass/lightbox.sass */
.lb-data .lb-close:hover {
cursor: pointer;
- filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=100);
- opacity: 1;
}
\ No newline at end of file
Modified: helix/site-content/0.9.9-docs/css/reflow-skin.css
URL: http://svn.apache.org/viewvc/helix/site-content/0.9.9-docs/css/reflow-skin.css?rev=1906412&r1=1906411&r2=1906412&view=diff
==============================================================================
--- helix/site-content/0.9.9-docs/css/reflow-skin.css (original)
+++ helix/site-content/0.9.9-docs/css/reflow-skin.css Thu Jan 5 19:48:20 2023
@@ -1,6 +1,6 @@
/* Jumps to in-page links (e.g. page.html#foo) do not honor fixed navbar.
Use pseudo element to move them down.
- Taken from https://nicolasgallagher.com/jump-links-and-viewport-positioning/demo/#method-B
+ Taken from http://nicolasgallagher.com/jump-links-and-viewport-positioning/demo/#method-B
*/
h1[id]:before,
h2[id]:before,
@@ -52,20 +52,25 @@ a[name]:before {
width: 1170px;
}
}
-
+@media (min-width: 768px) and (max-width: 979px) {
+ .navbar.affix .container {
+ width: 724px;
+ }
+}
+@media (max-width: 767px) {
+ .navbar.affix {
+ margin-right: -20px;
+ margin-left: -20px;
+ }
+}
@media (max-width: 979px) {
.navbar.affix {
position: static;
- }
-
- /* Give a positive z-index to ToC bar, otherwise the pseudo elements before may overlap and
- make the button unclickable. */
- #toc-bar {
- position: relative;
- z-index:1020;
margin-bottom: 20px;
}
-
+ .navbar.affix .navbar-inner {
+ padding: 5px;
+ }
}
/* Fix for header links - do not color/underline them */
Modified: helix/site-content/0.9.9-docs/dependencies.html
URL: http://svn.apache.org/viewvc/helix/site-content/0.9.9-docs/dependencies.html?rev=1906412&r1=1906411&r2=1906412&view=diff
==============================================================================
--- helix/site-content/0.9.9-docs/dependencies.html (original)
+++ helix/site-content/0.9.9-docs/dependencies.html Thu Jan 5 19:48:20 2023
@@ -7,7 +7,7 @@
<!--
- Generated by Apache Maven Doxia at 2022-12-15 Rendered using Reflow Maven Skin 2.0.0 (https://olamy.github.io/reflow-maven-skin)
+ Generated by Apache Maven Doxia at 2023-01-05 Rendered using Reflow Maven Skin 2.0.0 (https://olamy.github.io/reflow-maven-skin)
-->
<html xml:lang="en" lang="en">
@@ -130,7 +130,7 @@
<li><a href="./" title="Release 0.9.9">Release 0.9.9</a></li>
<li class="divider">/</li>
<li>Project Dependencies</li>
- <li class="publishDate version-date pull-right">Last Published: 2022-12-15</li>
+ <li class="publishDate version-date pull-right">Last Published: 2023-01-05</li>
</ul>
</div>
</header>
@@ -498,14 +498,14 @@
<td align="left"><a class="externalLink" href="https://maven.restlet.talend.com">https://maven.restlet.talend.com</a></td>
<td align="center">Yes</td>
<td align="center">No</td>
- <td align="center">No</td>
+ <td align="center">Yes</td>
</tr>
<tr class="b">
<td align="left">sonatype-nexus-snapshots</td>
<td align="left"><a class="externalLink" href="http://oss.sonatype.org/content/repositories/snapshots">http://oss.sonatype.org/content/repositories/snapshots</a></td>
<td align="center">No</td>
<td align="center">Yes</td>
- <td align="center">Yes</td>
+ <td align="center">No</td>
</tr>
<tr class="a">
<td align="left">apache.snapshots</td>
@@ -522,7 +522,7 @@
<tr class="a">
<th>Artifact</th>
<th>central</th>
- <th>restlet.talend.com</th>
+ <th>sonatype-nexus-snapshots</th>
<th>apache.snapshots</th>
</tr>
<tr class="b">
@@ -594,7 +594,7 @@
<tr class="b">
<th>Total</th>
<th>central</th>
- <th>restlet.talend.com</th>
+ <th>sonatype-nexus-snapshots</th>
<th>apache.snapshots</th>
</tr>
<tr class="a">
@@ -674,7 +674,7 @@
<div class="row">
<div class="span12">
<p class="pull-right"><a href="#">Back to top</a></p>
- <p class="copyright">Copyright ©2022 <a href="http://www.apache.org">Apache Software Foundation</a>. All Rights Reserved.</p>
+ <p class="copyright">Copyright ©2023 <a href="http://www.apache.org">Apache Software Foundation</a>. All Rights Reserved.</p>
<p><a href="https://github.com/olamy/reflow-maven-skin" title="Reflow Maven skin">Reflow Maven skin</a> maintained by <a href="https://twitter.com/olamy" target="_blank" title="Olivier Lamy">Olivier Lamy</a>.</p>
<div class="row span16"><div>Apache Helix, Apache, the Apache feather logo, and the Apache Helix project logos are trademarks of The Apache Software Foundation.
All other marks mentioned may be trademarks or registered trademarks of their respective owners.</div>
Modified: helix/site-content/0.9.9-docs/dependency-info.html
URL: http://svn.apache.org/viewvc/helix/site-content/0.9.9-docs/dependency-info.html?rev=1906412&r1=1906411&r2=1906412&view=diff
==============================================================================
--- helix/site-content/0.9.9-docs/dependency-info.html (original)
+++ helix/site-content/0.9.9-docs/dependency-info.html Thu Jan 5 19:48:20 2023
@@ -7,7 +7,7 @@
<!--
- Generated by Apache Maven Doxia at 2022-12-15 Rendered using Reflow Maven Skin 2.0.0 (https://olamy.github.io/reflow-maven-skin)
+ Generated by Apache Maven Doxia at 2023-01-05 Rendered using Reflow Maven Skin 2.0.0 (https://olamy.github.io/reflow-maven-skin)
-->
<html xml:lang="en" lang="en">
@@ -130,7 +130,7 @@
<li><a href="./" title="Release 0.9.9">Release 0.9.9</a></li>
<li class="divider">/</li>
<li>Dependency Information</li>
- <li class="publishDate version-date pull-right">Last Published: 2022-12-15</li>
+ <li class="publishDate version-date pull-right">Last Published: 2023-01-05</li>
</ul>
</div>
</header>
@@ -263,7 +263,7 @@
<div class="row">
<div class="span12">
<p class="pull-right"><a href="#">Back to top</a></p>
- <p class="copyright">Copyright ©2022 <a href="http://www.apache.org">Apache Software Foundation</a>. All Rights Reserved.</p>
+ <p class="copyright">Copyright ©2023 <a href="http://www.apache.org">Apache Software Foundation</a>. All Rights Reserved.</p>
<p><a href="https://github.com/olamy/reflow-maven-skin" title="Reflow Maven skin">Reflow Maven skin</a> maintained by <a href="https://twitter.com/olamy" target="_blank" title="Olivier Lamy">Olivier Lamy</a>.</p>
<div class="row span16"><div>Apache Helix, Apache, the Apache feather logo, and the Apache Helix project logos are trademarks of The Apache Software Foundation.
All other marks mentioned may be trademarks or registered trademarks of their respective owners.</div>
Modified: helix/site-content/0.9.9-docs/dependency-management.html
URL: http://svn.apache.org/viewvc/helix/site-content/0.9.9-docs/dependency-management.html?rev=1906412&r1=1906411&r2=1906412&view=diff
==============================================================================
--- helix/site-content/0.9.9-docs/dependency-management.html (original)
+++ helix/site-content/0.9.9-docs/dependency-management.html Thu Jan 5 19:48:20 2023
@@ -7,7 +7,7 @@
<!--
- Generated by Apache Maven Doxia at 2022-12-15 Rendered using Reflow Maven Skin 2.0.0 (https://olamy.github.io/reflow-maven-skin)
+ Generated by Apache Maven Doxia at 2023-01-05 Rendered using Reflow Maven Skin 2.0.0 (https://olamy.github.io/reflow-maven-skin)
-->
<html xml:lang="en" lang="en">
@@ -130,7 +130,7 @@
<li><a href="./" title="Release 0.9.9">Release 0.9.9</a></li>
<li class="divider">/</li>
<li>Project Dependency Management</li>
- <li class="publishDate version-date pull-right">Last Published: 2022-12-15</li>
+ <li class="publishDate version-date pull-right">Last Published: 2023-01-05</li>
</ul>
</div>
</header>
@@ -326,7 +326,7 @@
<div class="row">
<div class="span12">
<p class="pull-right"><a href="#">Back to top</a></p>
- <p class="copyright">Copyright ©2022 <a href="http://www.apache.org">Apache Software Foundation</a>. All Rights Reserved.</p>
+ <p class="copyright">Copyright ©2023 <a href="http://www.apache.org">Apache Software Foundation</a>. All Rights Reserved.</p>
<p><a href="https://github.com/olamy/reflow-maven-skin" title="Reflow Maven skin">Reflow Maven skin</a> maintained by <a href="https://twitter.com/olamy" target="_blank" title="Olivier Lamy">Olivier Lamy</a>.</p>
<div class="row span16"><div>Apache Helix, Apache, the Apache feather logo, and the Apache Helix project logos are trademarks of The Apache Software Foundation.
All other marks mentioned may be trademarks or registered trademarks of their respective owners.</div>
Modified: helix/site-content/0.9.9-docs/design_crushed.html
URL: http://svn.apache.org/viewvc/helix/site-content/0.9.9-docs/design_crushed.html?rev=1906412&r1=1906411&r2=1906412&view=diff
==============================================================================
--- helix/site-content/0.9.9-docs/design_crushed.html (original)
+++ helix/site-content/0.9.9-docs/design_crushed.html Thu Jan 5 19:48:20 2023
@@ -1,13 +1,8 @@
<!DOCTYPE html>
-
-
-
-
-
-
<!--
- Generated by Apache Maven Doxia at 2022-10-19 Rendered using Reflow Maven Skin 2.0.0 (https://olamy.github.io/reflow-maven-skin)
+ Generated by Apache Maven Doxia at 2022-04-15
+ Rendered using Maven Reflow Skin 1.0.0 (http://andriusvelykis.github.com/reflow-maven-skin)
-->
<html xml:lang="en" lang="en">
@@ -18,84 +13,61 @@
<meta name="description" content="" />
<meta http-equiv="content-language" content="en" />
- <link href="./css/bootstrap.min.css" rel="stylesheet" />
- <link href="./css/bootstrap-responsive.min.css" rel="stylesheet" />
+ <link href="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.2.2/css/bootstrap.min.css" rel="stylesheet" />
+ <link href="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.2.2/css/bootstrap-responsive.min.css" rel="stylesheet" />
<link href="./css/docs.css" rel="stylesheet" />
<link href="./css/reflow-skin.css" rel="stylesheet" />
-
-
+
+
<link href="./css/lightbox.css" rel="stylesheet" />
-
+
<link href="./css/site.css" rel="stylesheet" />
<link href="./css/print.css" rel="stylesheet" media="print" />
-
+
<!-- Le HTML5 shim, for IE6-8 support of HTML5 elements -->
<!--[if lt IE 9]>
- <script src="./js/html5.js"></script>
+ <script src="http://html5shim.googlecode.com/svn/trunk/html5.js"></script>
<![endif]-->
+
+ </head>
+ <body class="page-$config.fileId project-$config.projectId" data-spy="scroll" data-offset="60" data-target="#toc-scroll-target">
-
-
-
-
-<!-- Matomo -->
-<script>
- var _paq = window._paq = window._paq || [];
- _paq.push(['disableCookies']);
- _paq.push(['trackPageView']);
- _paq.push(['enableLinkTracking']);
-
- (function() {
- var u="https://analytics.apache.org";
- _paq.push(['setTrackerUrl', u+'/matomo.php']);
- _paq.push(['setSiteId', '15']);
- var d=document, g=d.createElement('script'), s=d.getElementsByTagName('script')[0];
- g.async=true; g.src=u+'/matomo.js'; s.parentNode.insertBefore(g,s);
- })();
-</script>
-<!-- End Matomo Code -->
- </head>
-
- <body class="page-design_crushed project-099-docs" data-spy="scroll" data-offset="60" data-target="#toc-scroll-target">
-
-
<div class="navbar navbar-fixed-top">
<div class="navbar-inner">
<div class="container">
- <a class="btn btn-navbar" data-toggle="collapse" data-target="#top-nav-collapse">
+ <a class="btn btn-navbar" data-toggle="collapse" data-target=".nav-collapse">
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</a>
- <a class="brand" href="..">Apache Helix</a>
- <div class="nav-collapse collapse" id="top-nav-collapse">
+ <div class="nav-collapse">
<ul class="nav pull-right">
- <li ><a href="index.html" title="Helix 0.9.9">Helix 0.9.9</a></li>
- <li class="dropdown">
+ <li class="active"><a href="" title="Helix 0.9.9">Helix 0.9.9 </a></li>
+ <li class="dropdown active">
<a href="#" class="dropdown-toggle" data-toggle="dropdown">Get Helix <b class="caret"></b></a>
<ul class="dropdown-menu">
- <li ><a href="download.html" title="Download">Download</a></li>
- <li ><a href="Building.html" title="Building">Building</a></li>
- <li ><a href="releasenotes/release-0.9.9.html" title="Release Notes">Release Notes</a></li>
+ <li class="active"><a href="" title="Download">Download </a></li>
+ <li class="active"><a href="" title="Building">Building </a></li>
+ <li class="active"><a href="" title="Release Notes">Release Notes </a></li>
</ul>
</li>
- <li class="dropdown">
+ <li class="dropdown active">
<a href="#" class="dropdown-toggle" data-toggle="dropdown">Hands-On <b class="caret"></b></a>
<ul class="dropdown-menu">
- <li ><a href="Quickstart.html" title="Quick Start">Quick Start</a></li>
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+ <li class="active"><a href="" title="Distributed lock manager">Distributed lock manager </a></li>
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@@ -103,36 +75,30 @@
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- <a href="http://helix.apache.org/" id="bannerLeft"><img src="../images/helix-logo.jpg" alt='"''"' /></a>
- <p class="lead">A cluster management framework for partitioned and replicated distributed resources</p>
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- <li class="divider">/</li>
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+ <li><a href="" title="Apache Helix">Apache Helix </a></li>
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+ <li><a href="" title="Release 0.9.9">Release 0.9.9 </a></li>
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<li>CrushED (Crush-based rebalancer with Even Distribution)</li>
- <li class="publishDate version-date pull-right">Last Published: 2022-10-19</li>
+ <li class="publishDate version-date pull-right">Last Published: 2022-04-15</li>
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@@ -141,230 +107,94 @@
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<div class="span12">
<div class="body-content">
-<div class="page-header">
- <h1>CrushED (Crush-based rebalancer with Even Distribution)</h1>
-</div>
-<section>
- <h2 id="Overview">Overview</h2>
- <p>Helix provides AutoRebalanceStrategy which is based on card dealing strategy. This strategy takes the current mapping as an input, and computes new mappings only for the partitions that need to be moved. This provides minimum partition movement, but the mapping is not deterministic, and moreover, fault-zone aware mapping (i.e. rack-aware partitioning) is not possible.</p>
- <p>CRUSH-based partitioning scheme was implemented to provide fault-zone aware mapping and deterministic partition assignment. CrushRebalanceStrategy (and MultiRoundCrushRebalanceStrategy) algorithm uses pseudo-random partition placement to ensure consistent partition distribution. As the number of placed items (i.e partitions) approaches infinity, the distribution will be perfectly uniform. However, with a small number of placed items, especially for resources (i.e. databases) with a small number of partitions, the placement algorithm may result in fairly uneven partition distribution.</p>
- <p>We want to provide a new rebalance strategy that provides a deterministic and fault-zone aware mapping while providing even partition distribution in all cases. In this document, we propose a hybrid algorithm that uses CRUSH, card dealing strategy, and consistent hashing to ensure both even distribution and minimal partition movement (while cluster topology remains the same). We call it CrushED (Crush w/ Even Distribution). Compared to CRUSH, CrushED results in a much more uniform distribution and minimal partition movements as long as topology remains the same, at the cost of additional run time computation.</p>
-</section>
-<section>
- <h2 id="Design">Design</h2>
- <p>In addition to what we already achieved in CrushRebalanceStrategy, we have 2 high level goals :</p>
- <ol style="list-style-type: decimal">
- <li>Even distribution.</li>
- <li>Minimize partition movements when instances go up/down.</li>
- </ol>
- <p>CrushRebalanceStrategy has very small movement count, but the distribution is not optimal. MultiRoundCrushRebalanceStrategy was designed to solve this problem by running CRUSH multiple times on partition assignments that contribute to uneven mapping. However, due to potentially high number of rounds, computation cost is high, we observed significantly more partition movements when the cluster topology is changed.</p>
- <p>Since we have a good base strategy, CrushRebalanceStrategy, we built CrushEDRebalanceStrategy on top of it. Sample mapping of both strategies are as following. Note that blue parts remain unchanged before and after.</p>
- <p>Before (CRUSH)</p>
- <p><img src="images/design/crushed/before-using-crush.png" alt="Before (CRUSH)"></p>
- <p>After (new strategy)</p>
- <p><img src="images/design/crushed/after-using-crushed.png" alt="After (new strategy)"></p>
- <p>Since the problem is NP-hard. We are not expecting the best assignment. A greedy algorithm works good enough.<br> After we tried different designs, we found it's hard to achieve both goals (even distribution and fewer movements) using a single strategy. So we decided to apply a hybrid algorithm that finishes the work step by step.</p>
- <p><b>Step 1, run CRUSH to get a base assignment.</b><br> The base assignment usually contains a certain number of uneven partitions(i.e. extra partitions above perfect distribution), so we need the following steps to re-distribute them.</p>
- <p><b>Step 2, run a card dealing algorithm on the uneven parts.</b><br> Assign extra partitions to under-loaded nodes, using card dealing strategy. This algorithm is conceptually simple. The result ensures that all partitions are assigned to instances with minimum difference. When gauranteeing fault-zone safe assignment, our greedy algorithm may not be able to calculate possible results because of fault-zone conflict.</p>
- <p>Example of assignments after step 2,</p>
- <p><img src="images/design/crushed/example-cluster-partition-dist.png" alt="Example"></p>
- <p><b>Step 3, Shuffle partitions' preference lists.</b><br> State assignments (i.e. Master, Slave, Online, Offline, etc) are made according to preflist, ordered node. When using randomly ordered lists, State assignment is also random, and it may result in uneven state distribution. To resolve this issue, CrushED assigns scores to nodes as it computes pref list, to give all nodes equal chances in appearing at the top of the pref list. This operation results in a much more even state distribution.</p>
- <p>Example of master distribution before step 3,</p>
- <p><img src="images/design/crushed/example-cluster-master-dist.png" alt="Example"></p>
- <p>Example of master distribution after step 3,</p>
- <p><img src="images/design/crushed/example-cluster-master-dist-after.png" alt="Example"></p>
- <p><b>Step 4, re-calculate the assignment for the partitions on temporarily disabled nodes using a consistent hashing algorithm.</b><br> Consistent hashing ensures minimize partition movement.<br> Note that the first 3 steps are using full node list, regardless of disabled or offline nodes. So the assignment will be stable even the algorithm contains random factors such hashCode. Then step 4 ensures all the disabled nodes are handled correctly without causing huge partition movements.</p>
- <p>Pseudocode of above algorithm is as follows :</p>
- <p><b>Pseudo Code</b></p>
- <div class="source">
- <pre><code>// Round 1: Calculate mapping using the base strategy.
-// Note to use all nodes for minimizing the influence of live node changes.
-origPartitionMap = getBaseRebalanceStrategy().computePartitionAssignment(allNodes, clusterData);
-
-// Transform current assignment to instance->partitions map, and get total partitions
-nodeToPartitionMap = convertMap(origPartitionMap);
-
-// Round 2: Rebalance mapping using card dealing algorithm.
-Topology allNodeTopo = new Topology(allNodes, clusterData);
-cardDealer.computeMapping(allNodeTopo, nodeToPartitionMap);
-
-// Since states are assigned according to preference list order, shuffle preference list for even states distribution.
-shufflePreferenceList(nodeToPartitionMap);
-
-// Round 3: Re-mapping the partitions on non-live nodes using consistent hashing for reducing movement.
-// Consistent hashing ensures minimum movements when nodes are disabled unexpectedly.
-if (!liveNodes.containsAll(allNodes)) {
- Topology liveNodeTopo = new Topology(liveNodes, clusterData);
- hashPlacement.computeMapping(liveNodeTopo, nodeToPartitionMap);
-}
-
-if (!nodeToPartitionMap.isEmpty()) {
- // Round 2 and 3 is done successfully
- return convertMap(nodeToPartitionMap);
-} else {
- return getBaseRebalanceStrategy().computePartitionAssignment(liveNodes, clusterData);
-}
-</code></pre>
- </div>
- <section>
- <h3 id="Maximum_uneven_partition_assignment_using_CrushED">Maximum uneven partition assignment using CrushED</h3>
- <p>Helix cluster typically manages 1 or more resources (i.e. databases). For each resource, CrushED makes the best effort to ensure the partition count difference is at most 1 across all the instances. Assuming such assignment is possible considering fault-zone configuration, the worst partition distribution happens when all one off partitions are located in one node. So N resources in a cluster can theoretically have their extra partitions in one node, so the node will have N additional partitions in total. Thus, the maximum difference between the most heavily loaded node and the least is <b>the number of resources</b> in a cluster.</p>
- </section>
-</section>
-<section>
- <h2 id="Experiment">Experiment</h2>
- <p>We tested CrushED by simulating real production cluster topology data. And we tested multiple scenarios:</p>
- <ul>
- <li>Distribution based on cluster topology.</li>
- <li>Disabling hosts to simulate hosts down.</li>
- <li>Adding hosts to simulate expansion.</li>
- <li>Rolling upgrade.</li>
- </ul>
- <p>All results show that CrushED generates more uniform global distribution compared with CRUSH.<br> Moreover, partition movements in most scenarios are minimized. When topology changes (i.e. cluster expansion), there can be significantly more partition movements, but we can control the impact by using State Transition Throttling feature.</p>
- <section>
- <h3 id="Partition_Distribution">Partition Distribution</h3>
- <p>Following charts demonstrate the worst cases (min load vs. max load) and STDEVs of partition/master distributions from some sample clusters data.<br> If we measure the improvement by STDEV, CrushED improves the partition distribution evenness by 87% on average compared with CRUSH. And for state assignment (i.e. Mastership assignment) the evenness improvement is 68% on average.</p>
- <p><img src="images/design/crushed/cursh-partition-dist.png" alt="Example"><img src="images/design/crushed/crushed-partition-dist.png" alt="Example"></p>
- <p><img src="images/design/crushed/cursh-master-dist.png" alt="Example"><img src="images/design/crushed/crushed-master-dist.png" alt="Example"></p>
- </section>
- <section>
- <h3 id="Disabling_Nodes">Disabling Nodes</h3>
- <p>When nodes are offline or disabled, CrushED will re-assign the partitions to other live nodes. The algorithm move only the necessary partitions.<br> We simulated disabling nodes, and measured partition movement changes and mastership changes. We also used the expected movement (the partitions/masters count on the disabled nodes) as a baseline to measure extra movements.</p>
- <p>The results show that movement is highly correlated to the number of disabled nodes, and extra movements are minor (in most cases 0 movements).</p>
- <p>Note that <b>Rate</b> in this document is <b>the changed number / total partition or master count</b>.</p>
- <p><img src="images/design/crushed/node-down-partition-move.png" alt="Example"><img src="images/design/crushed/node-down-master-move.png" alt="Example"></p>
- </section>
- <section>
- <h3 id="Rolling_upgrade">Rolling upgrade</h3>
- <p>Rolling upgrade is different from disabling nodes. Since nodes are reset one by one, in this test we assume the difference could be 2 nodes in maximum (for example, upgrading Node A then upgrading Node B).<br> In this case, movements are still minimized. Even in the worst case scenario, extra partition movements and mastership changes are still close to 0%.</p>
- <p>Note that in real production clusters, we can completely avoid partition movements while doing rolling upgrade, by enabling Delayed Rebalancing.</p>
- </section>
- <section>
- <h3 id="Adding_Nodes">Adding Nodes</h3>
- <p>Adding nodes (i.e. cluster expansion) changes topology. CrushED uses card dealing strategy to provide even distribution, so when topology changes, there are a lot of additional partition movements than CRUSH.</p>
- <p>Note that the extra change rate is not correlated with the number of additional nodes. So our recommendation is finishing expansion in one operation so as to do only one partition shuffling.</p>
- </section>
- <section>
- <h3 id="Algorithm_Performance">Algorithm Performance</h3>
- <p>We compared CrushED with CRUSH algorithms using different instance numbers. The tests are executed multiple times and we recorded median computation time.<br> CrushED does not cost much additional computation time for regular rebalancing. In some of the worst cases, 30% more runtime was observed, compared with CRUSH, but it is quicker than MultiRoundCRUSH.</p>
- <p>However, when there are down nodes since CrushED needs to run an additional consistent hashing based re-distribution, the computation time will be much longer. In some cases, we saw more than 3 times compared to CRUSH.</p>
- <p>With some <b>performance improvements</b>, such as using cache to avoid duplicate calculation, we achieved to greatly reduce CrushED's running time. According to our experiment, it is now close to MultiRound CRUSH.</p>
- <p><img src="images/design/crushed/performance.png" alt="Example"></p>
- </section>
-</section>
-<section>
- <h2 id="Conclusion">Conclusion</h2>
- <p>CrushED achieves more uniform distribution compared with CRUSH at the cost of higher rebalance computation and more partition movement when the cluster topology changes.</p>
-</section>
-<section>
- <h2 id="Simple_User_Guide">Simple User Guide</h2>
- <ol style="list-style-type: decimal">
- <li>Ensure the resouce is using FULL_AUTO mode.</li>
- <li>Set rebalance strategy to be âorg.apache.helix.controller.rebalancer.strategy.CrushEdRebalanceStrategyâ.</li>
- <li>Expect more partition movement on topology changes when using the new strategy.</li>
- </ol>
- <p><b>IdeaState SimpleFields Example</b></p>
- <div class="source">
- <pre><code>HELIX_ENABLED : "true"
-IDEAL\_STATE\_MODE : "AUTO_REBALANCE"
-REBALANCE\_MODE : "FULL\_AUTO"
-REBALANCE_STRATEGY : "org.apache.helix.controller.rebalancer.strategy.CrushRebalanceStrategy"
-MIN\_ACTIVE\_REPLICAS : "0"
-NUM_PARTITIONS : "64"
-REBALANCER\_CLASS\_NAME : "org.apache.helix.controller.rebalancer.DelayedAutoRebalancer"
-REPLICAS : "1"
-STATE\_MODEL\_DEF_REF : "LeaderStandby"
-</code></pre>
- </div>
-</section>
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Modified: helix/site-content/0.9.9-docs/distribution-management.html
URL: http://svn.apache.org/viewvc/helix/site-content/0.9.9-docs/distribution-management.html?rev=1906412&r1=1906411&r2=1906412&view=diff
==============================================================================
--- helix/site-content/0.9.9-docs/distribution-management.html (original)
+++ helix/site-content/0.9.9-docs/distribution-management.html Thu Jan 5 19:48:20 2023
@@ -7,7 +7,7 @@
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+ Generated by Apache Maven Doxia at 2023-01-05 Rendered using Reflow Maven Skin 2.0.0 (https://olamy.github.io/reflow-maven-skin)
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@@ -130,7 +130,7 @@
<li><a href="./" title="Release 0.9.9">Release 0.9.9</a></li>
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- <li class="publishDate version-date pull-right">Last Published: 2022-12-15</li>
+ <li class="publishDate version-date pull-right">Last Published: 2023-01-05</li>
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@@ -223,7 +223,7 @@
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