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Fix a race condition in the simian groups connector. When requests were 

too slow they would circumvent the cache (piling up on the network service
and making the problem even worse). This condition happens frequently
during permission checks.
xassetservice
Mic Bowman 2012-02-13 19:38:22 -08:00
parent 4589ce61bc
commit a9e8bd59a3
1 changed files with 64 additions and 9 deletions
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71
OpenSim/Region/OptionalModules/Avatar/XmlRpcGroups/SimianGroupsServicesConnectorModule.cs
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@ -30,6 +30,7 @@ using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Reflection;
using System.Threading;
using Nwc.XmlRpc;
@ -167,6 +168,8 @@ namespace OpenSim.Region.OptionalModules.Avatar.XmlRpcGroups
private bool m_debugEnabled = false;
private Dictionary<string, bool> m_pendingRequests = new Dictionary<string,bool>();
private ExpiringCache<string, OSDMap> m_memoryCache;
private int m_cacheTimeout = 30;
@ -1348,6 +1351,7 @@ namespace OpenSim.Region.OptionalModules.Avatar.XmlRpcGroups
// Immediately forward the request if the cache is disabled.
if (m_cacheTimeout == 0)
{
m_log.WarnFormat("[SIMIAN GROUPS CONNECTOR]: cache is disabled");
return WebUtil.PostToService(m_groupsServerURI, requestArgs);
}
@ -1355,6 +1359,8 @@ namespace OpenSim.Region.OptionalModules.Avatar.XmlRpcGroups
if (requestArgs["RequestMethod"] == "RemoveGeneric"
|| requestArgs["RequestMethod"] == "AddGeneric")
{
m_log.WarnFormat("[SIMIAN GROUPS CONNECTOR]: clearing generics cache");
// Any and all updates cause the cache to clear
m_memoryCache.Clear();
@ -1366,19 +1372,68 @@ namespace OpenSim.Region.OptionalModules.Avatar.XmlRpcGroups
// Create the cache key for the request and see if we have it cached
string CacheKey = WebUtil.BuildQueryString(requestArgs);
OSDMap response = null;
if (!m_memoryCache.TryGetValue(CacheKey, out response))
{
// if it wasn't in the cache, pass the request to the Simian Grid Services
response = WebUtil.PostToService(m_groupsServerURI, requestArgs);
// and cache the response
m_memoryCache.AddOrUpdate(CacheKey, response, TimeSpan.FromSeconds(m_cacheTimeout));
// This code uses a leader/follower pattern. On a cache miss, the request is added
// to a queue; the first thread to add it to the queue completes the request while
// follow on threads busy wait for the results, this situation seems to happen
// often when checking permissions
while (true)
{
OSDMap response = null;
bool firstRequest = false;
lock (m_memoryCache)
{
if (m_memoryCache.TryGetValue(CacheKey, out response))
return response;
if (! m_pendingRequests.ContainsKey(CacheKey))
{
m_pendingRequests.Add(CacheKey,true);
firstRequest = true;
}
}
if (firstRequest)
{
// if it wasn't in the cache, pass the request to the Simian Grid Services
try
{
response = WebUtil.PostToService(m_groupsServerURI, requestArgs);
}
catch (Exception e)
{
m_log.InfoFormat("[SIMIAN GROUPS CONNECTOR] request failed {0}",CacheKey);
}
// and cache the response
lock (m_memoryCache)
{
m_memoryCache.AddOrUpdate(CacheKey, response, TimeSpan.FromSeconds(m_cacheTimeout));
m_pendingRequests.Remove(CacheKey);
}
// return cached response
return response;
}
Thread.Sleep(50); // waiting for a web request to complete, 50msecs is reasonable
}
// if (!m_memoryCache.TryGetValue(CacheKey, out response))
// {
// m_log.WarnFormat("[SIMIAN GROUPS CONNECTOR]: query not in the cache");
// Util.PrintCallStack();
// // if it wasn't in the cache, pass the request to the Simian Grid Services
// response = WebUtil.PostToService(m_groupsServerURI, requestArgs);
// // and cache the response
// m_memoryCache.AddOrUpdate(CacheKey, response, TimeSpan.FromSeconds(m_cacheTimeout));
// }
// // return cached response
// return response;
}
#endregion
}