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/*-
* Copyright (C) 2011, 2018 Oracle and/or its affiliates. All rights reserved.
*
* This file was distributed by Oracle as part of a version of Oracle NoSQL
* Database made available at:
*
* http://www.oracle.com/technetwork/database/database-technologies/nosqldb/downloads/index.html
*
* Please see the LICENSE file included in the top-level directory of the
* appropriate version of Oracle NoSQL Database for a copy of the license and
* additional information.
*/
package oracle.kv;
import java.io.Serializable;
/**
* Describes how requests may be limited so that one or more nodes with long
* service times don't end up consuming all available threads in the KVS
* client.
*
* @see KVStoreConfig#setRequestLimit
* @see RequestLimitException
*/
public class RequestLimitConfig implements Serializable {
private static final long serialVersionUID = 1;
/**
* The default maximum number of active requests.
*/
public static final int DEFAULT_MAX_ACTIVE_REQUESTS = 100;
/**
* The default threshold for activating request limiting, as a percentage
* of the requested maximum active requests.
*/
public static final int DEFAULT_REQUEST_THRESHOLD_PERCENT = 90;
/**
* The default limit on the number of requests, as a percentage of
* the requested maximum active requests.
*/
public static final int DEFAULT_NODE_LIMIT_PERCENT = 80;
/**
* The maximum number of active requests permitted by the KV client
*/
private final int maxActiveRequests;
/**
* The threshold at which request limiting is activated.
*/
private final int requestThresholdPercent;
/**
* The above threshold expressed as a number of requests.
*/
private final int requestThreshold;
/**
* The limit that must not be exceeded once the above threshold has been
* crossed.
*/
private final int nodeLimitPercent;
/**
* The above limit expressed as a number of requests.
*/
private final int nodeLimit;
private static final RequestLimitConfig defaultRequestLimitConfig =
new RequestLimitConfig(DEFAULT_MAX_ACTIVE_REQUESTS,
DEFAULT_REQUEST_THRESHOLD_PERCENT,
DEFAULT_NODE_LIMIT_PERCENT);
/**
* Creates a request limiting configuration.
*
* The request limiting mechanism is only activated when the number of
* active requests exceeds the threshold specified by the parameter
* requestThresholdPercent. Both the threshold and limit
* parameters below are expressed as a percentage of
* maxActiveRequests.
*
* When the mechanism is active the number of active requests to a node is
* not allowed to exceed nodeRequestLimitPercent. Any new
* requests that would exceed this limit are rejected and a
* RequestLimitException is thrown.
*
* For example, consider a configuration with maxActiveRequests=10,
* requestThresholdPercent=80 and nodeLimitPercent=50. If 8 requests are
* already active at the client, and a 9th request is received that would
* be directed at a node which already has 5 active requests, it would
* result in a RequestLimitException being thrown. If only
* 7 requests were active at the client, the 8th request would be directed
* at the node with 5 active requests and the request would be processed
* normally.
*
* @param maxActiveRequests the maximum number of active requests permitted
* by the KV client. This number is typically derived from the maximum
* number of threads that the client has set aside for processing requests.
* The default is 100. Note that the KVStore does not actually enforce this
* maximum directly. It only uses this parameter as the basis for
* calculating the requests limits to be enforced at a node.
*
* @param requestThresholdPercent the threshold computed as a percentage of
* maxActiveRequests at which requests are limited. The
* default is 90.
*
* @param nodeLimitPercent determines the maximum number of active requests
* that can be associated with a node when the request limiting mechanism
* is active. The default is 80.
*
* @throws IllegalArgumentException if any argument is 0 or less, if {@code
* requestThresholdPercent} is greater than 100, or if {@code
* nodeLimitPercent} is greater than {@code requestThresholdPercent}
*/
public RequestLimitConfig(int maxActiveRequests,
int requestThresholdPercent,
int nodeLimitPercent) {
if (maxActiveRequests <= 0) {
throw new IllegalArgumentException("maxActiveRequests: " +
maxActiveRequests +
" must be positive");
}
this.maxActiveRequests = maxActiveRequests;
if (requestThresholdPercent <= 0) {
throw new IllegalArgumentException(
"requestThresholdPercent: " + requestThresholdPercent +
" must be positive");
} else if (requestThresholdPercent > 100) {
throw new IllegalArgumentException("requestThresholdPercent: " +
requestThresholdPercent +
" cannot exceed 100");
}
this.requestThresholdPercent = requestThresholdPercent;
requestThreshold =
(int) (maxActiveRequests * (requestThresholdPercent / 100.0));
if (nodeLimitPercent <= 0) {
throw new IllegalArgumentException(
"nodeLimitPercent: " + nodeLimitPercent +
" must be positive");
} else if (nodeLimitPercent > requestThresholdPercent) {
String msg = "nodeLimitPercent: " + nodeLimitPercent +
" cannot exceed requestThresholdPercent: " +
requestThresholdPercent;
throw new IllegalArgumentException(msg);
}
this.nodeLimitPercent = nodeLimitPercent;
nodeLimit = (int) (maxActiveRequests * (nodeLimitPercent / 100.0));
}
/**
* Returns the maximum number of active requests permitted by the KVS
* client.
*
* The default value is 100.
*/
public int getMaxActiveRequests() {
return maxActiveRequests;
}
/**
* Returns the percentage used to compute the active request threshold
* above which the request limiting mechanism is activated.
*
* The default value is 90.
*/
public int getRequestThresholdPercent() {
return requestThresholdPercent;
}
/**
* Returns the threshold number of requests above which the request
* limiting mechanism is activated.
*/
public int getRequestThreshold() {
return requestThreshold;
}
/**
* Returns the percentage used to compute the maximum number of requests
* that may be active at a node.
*
* The default value is 80.
*/
public int getNodeLimitPercent() {
return nodeLimitPercent;
}
/**
* Returns the maximum number of requests that may be active at a node.
*/
public int getNodeLimit() {
return nodeLimit;
}
@Override
public String toString() {
return String.format("maxActiveRequests=%d," +
" requestThresholdPercent=%d%%," +
" nodeLimitPercent=%d%%",
maxActiveRequests,
requestThresholdPercent,
nodeLimitPercent);
}
/**
* Returns an instance that uses the default values.
*/
public static RequestLimitConfig getDefault() {
return defaultRequestLimitConfig;
}
}