我使用以下代码将我的.net客户端（基于CQL）连接到3个节点的Cassandra集群。我获取数据（来自RabbitMQ）30条记录/秒，它们可以顺利存储在cassandra中，最多可存储800-900行。但在那之后我得到了这个例外。任何人都可以告诉我，为避免此异常，我可以做出哪些优化/更改。我无法在任何地方找到解决此问题的具体方法。
错误： ERROR ErrorLog - error in Cassandra GetCWCRow Function Connection :None of the hosts tried for query are available (tried: X.X.X.201:9042, X.X.X.200:9042, X.X.X.X:9042)
代码：
using Cassandra;
using Consumer;
using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
namespace RabbitMqCarWaleUserTracking
{
class DataAccessCassandra
{
public bool InsertCookieLogData(string cwc, string page_uri)
{
try
{
Logs.WriteInfoLog("Cassandra InsertCookieLogData a Function called");
Cluster cluster = Cluster.Builder().AddContactPoints(ConfigurationManager.AppSettings["cassandraCluster"].ToString().Split(',')).Build();
ISession session = cluster.Connect(ConfigurationManager.AppSettings["cassandraKeySpace"].ToString());
string pageCategory = string.Empty;
try
{
if ((Regex.IsMatch(page_uri, "/newcars/upcomingcars", RegexOptions.IgnoreCase)))
{
pageCategory = "upcomingCars";
}
else
if ((Regex.IsMatch(page_uri, "/newcars/dealers/newCarDealerShowroom", RegexOptions.IgnoreCase)) || (Regex.IsMatch(page_uri, "/newcars/dealers/listnewcardealersbycity", RegexOptions.IgnoreCase)
|| (Regex.IsMatch(page_uri, "/newcars/dealers/dealerdetails", RegexOptions.IgnoreCase))))
{
pageCategory = "newcarsDealers";
}
else
if ((Regex.IsMatch(page_uri, "/offers", RegexOptions.IgnoreCase)) || (Regex.IsMatch(page_uri, "/alloffers", RegexOptions.IgnoreCase)))
{
pageCategory = "offers";
}
else
if ((Regex.IsMatch(page_uri, "/dealer/testdrive", RegexOptions.IgnoreCase)))
{
pageCategory = "dealerTestDrive";
}
if (pageCategory != string.Empty)
{
Row result = session.Execute("select logdate from pageWiseCookieLog where cwc ='" + cwc + "' and page_uri ='" + pageCategory + "' and logdate= '" + DateTime.Today.ToString("yyyy-MM-dd") + "'").FirstOrDefault();
if (result == null)
{
session.Execute("insert into pageWiseCookieLog (cwc, page_uri, logdate) values ('" + cwc + "' , '" + pageCategory + "' , '" + DateTime.Now.ToString("yyyy-MM-dd") + "' )");
session.Execute("insert into pageWiseCookieLogByld (cwc, page_uri, logdate) values ('" + cwc + "' , '" + pageCategory + "' , '" + DateTime.Now.ToString("yyyy-MM-dd") + "' )");
session.Dispose();
cluster.Dispose();
return true;
}
}
else
{
//don't want to store the data for rest of the page category but need to return true
session.Dispose();
cluster.Dispose();
return true;
}
}
catch (Exception ex)
{
string subject = string.Concat(ex.Source, " : ", Environment.MachineName);
Logs.WriteErrorLog("error in Cassandra InsertCookieLogData function with cwc :" + cwc + "error is :" + ex.Message);
SendMail.HandleException(ex, subject);
session.Dispose();
cluster.Dispose();
}
}
catch (Exception ex)
{
string subject = string.Concat(ex.Source, " : ", Environment.MachineName);
Logs.WriteErrorLog("error in Cassandra InsertCookieLogData function connection :" + ex.Message);
SendMail.HandleException(ex, subject);
}
return false;
}
public string GetCWCRow(string cwc, int index, string mobileId)
{
try
{
Logs.WriteInfoLog("Cassandra GetCWCRow Function called");
Cluster cluster = Cluster.Builder().AddContactPoints(ConfigurationManager.AppSettings["cassandraCluster"].ToString().Split(',')).Build();
ISession session = cluster.Connect(ConfigurationManager.AppSettings["cassandraKeySpace"].ToString());
try
{
Row result = session.Execute("select cur_visit_id from usertracking where cwc ='" + cwc + "'").FirstOrDefault();
if (result != null)
{
session.Dispose();
cluster.Dispose();
return result[0].ToString();
}
}
catch (Exception ex)
{
string subject = string.Concat(ex.Source, " : ", Environment.MachineName);
Logs.WriteErrorLog("error in Cassandra GetCWCRow function with cwc :" + cwc + "error is :" + ex.Message);
SendMail.HandleException(ex, subject);
session.Dispose();
cluster.Dispose();
}
}
catch (Exception ex)
{
string subject = string.Concat(ex.Source, " : ", Environment.MachineName);
Logs.WriteErrorLog("error in Cassandra GetCWCRow Function Connection :" + ex.Message);
SendMail.HandleException(ex, subject);
}
return string.Empty;
}
public bool InsertCWCRecords(string cwv, Cut_Case caseType, int index, string mobileId)
{
try
{
Logs.WriteInfoLog("Cassandra InsertCWCRecords function called for case:" + caseType);
Cluster cluster = Cluster.Builder().AddContactPoints(ConfigurationManager.AppSettings["cassandraCluster"].ToString().Split(',')).Build();
ISession session = cluster.Connect(ConfigurationManager.AppSettings["cassandraKeySpace"].ToString());
try
{
bool _isProcessed = false;
string visitCount = "";
string[] leadParameters = cwv.Split('.');
string cwc = leadParameters[0];
string visitId = leadParameters[1];
string visitStartTime = leadParameters[2];
string visitPrevPageTime = leadParameters[3];
string visitLastPageTime = leadParameters[4];
if (leadParameters.Length == 6)
{
visitCount = leadParameters[5];
}
string TOT_TIME_SPENT = (Convert.ToInt64(visitLastPageTime) - Convert.ToInt64(visitPrevPageTime)).ToString();
if ((int)caseType == 1) //to enter new cwc data in summary table
{
session.Execute("insert into usertracking (cwc, cur_visit_id, cur_visit_last_ts, tot_page_view, tot_time_spent, tot_visit_count, cur_visit_datetime) values ('" + cwc + "' , '" + visitId + "' ," + visitStartTime + "," + "1" + "," + TOT_TIME_SPENT + "," + "1" + ", '" + DateTime.Today.ToString("yyyy-MM-dd") + "' )");
_isProcessed = true;
}
if ((int)caseType == 2) //if cwc exits and visit id is same
{
Row result = session.Execute("select tot_page_view, tot_time_spent from usertracking where cwc ='" + cwc + "'").FirstOrDefault();
int page_cnt_val = int.Parse(result[0].ToString()) + 1;
Int64 time_spt_val = Int64.Parse(result[1].ToString()) + Convert.ToInt64(visitLastPageTime) - Convert.ToInt64(visitPrevPageTime);
session.Execute("update usertracking SET cur_visit_last_ts = " + visitLastPageTime + ", tot_page_view = " + page_cnt_val + ", tot_time_spent = " + time_spt_val + " WHERE cwc = '" + cwc.Trim() + "'");
_isProcessed = true;
}
if ((int)caseType == 3) //if cwc exits ans visit id is different
{
Row result = session.Execute("select tot_page_view, tot_time_spent, tot_visit_count, cur_visit_last_ts, cur_visit_datetime from usertracking where cwc = '" + cwc + "'").First();
int page_cnt_val = int.Parse(result[0].ToString()) + 1;
Int64 time_spt_val = Int64.Parse(result[1].ToString()) + Convert.ToInt64(visitLastPageTime) - Convert.ToInt64(visitPrevPageTime);
int visit_val = int.Parse(result[2].ToString()) + 1;
Int64 prev_visit_ts_val = Int64.Parse(result[3].ToString());
String prev_visit_datetime_val = Convert.ToDateTime(result[4].ToString()).ToString("yyyy-MM-dd");
session.Execute("update usertracking SET cur_visit_id = '" + visitId + "' , tot_visit_count= " + visit_val
+ " , prev_visit_last_ts= " + prev_visit_ts_val + ", prev_visit_datetime = '" + prev_visit_datetime_val
+ "' , cur_visit_last_ts = " + visitLastPageTime
+ ", tot_page_view = " + page_cnt_val + ", tot_time_spent = " + time_spt_val
+ ", cur_visit_datetime='" + DateTime.Today.ToString("yyyy-MM-dd")
+ "' WHERE cwc = '" + cwc.Trim() + "'");
_isProcessed = true;
}
session.Dispose();
cluster.Dispose();
return _isProcessed;
}
catch (Exception ex)
{
string subject = string.Concat(ex.Source, " : ", Environment.MachineName);
Logs.WriteErrorLog("error in Cassandra InsertCWCRecords function with cwv :" + cwv + "error is :" + ex.Message);
SendMail.HandleException(ex, subject);
session.Dispose();
cluster.Dispose();
return false;
}
}
catch (Exception ex)
{
string subject = string.Concat(ex.Source, " : ", Environment.MachineName);
Logs.WriteErrorLog("error in Cassandra InsertCWCRecords function connection :" + ex.Message);
SendMail.HandleException(ex, subject);
return false;
}
}
public bool UpdateReferrerTimeSpent(string cwc, int referrerCategoryId, double referrerTimeSpent, int index, string mobileId)
{
bool _isUpdated = false;
try
{
Logs.WriteInfoLog("Cassandra UpdateReferrerTimeSpent function called");
Cluster cluster = Cluster.Builder().AddContactPoints(ConfigurationManager.AppSettings["cassandraCluster"].ToString().Split(',')).Build();
ISession session = cluster.Connect("cw");
try
{
Row result = session.Execute("select time_spent_in_sec from userTimeSpentPage WHERE cwc = '" + cwc.Trim() + "' And logdate = '" + DateTime.Today.ToString("yyyy-MM-dd") + "' And page_category_id =" + referrerCategoryId).FirstOrDefault();
if (result != null)
{
if (result[0].ToString().Trim() != string.Empty)
{
Int64 page_time_spent_val = Int64.Parse(result[0].ToString());
Int64 tot_time_spt_val = page_time_spent_val + Int64.Parse(referrerTimeSpent.ToString());
session.Execute("update userTimeSpentPage set time_spent_in_sec= " + tot_time_spt_val + "WHERE cwc = '" + cwc.Trim() + "' And logdate = '" + DateTime.Today.ToString("yyyy-MM-dd") + "' And page_category_id=" + referrerCategoryId);
}
}
else
{
session.Execute("insert into userTimeSpentPage (cwc, page_category_id, time_spent_in_sec, logdate) values ('" + cwc + "' ," + referrerCategoryId + "," + referrerTimeSpent + ", '" + DateTime.Now.ToString("yyyy-MM-dd") + "' )");
}
_isUpdated = true;
session.Dispose();
cluster.Dispose();
return _isUpdated;
}
catch (Exception ex)
{
string subject = string.Concat(ex.Source, " : ", Environment.MachineName);
Logs.WriteErrorLog("error in Cassandra UpdateReferrerTimeSpent function with cwc:" + cwc + "error is :" + ex.Message);
SendMail.HandleException(ex, subject);
session.Dispose();
cluster.Dispose();
return _isUpdated;
}
}
catch (Exception ex)
{
string subject = string.Concat(ex.Source, " : ", Environment.MachineName);
Logs.WriteErrorLog("error in Cassandra UpdateReferrerTimeSpent function connection" + ex.Message);
SendMail.HandleException(ex, subject);
return _isUpdated;
}
}
}
}
编辑问题：
output of netstat -an | awk '/^tcp/ {print $NF}' | sort | uniq -c | sort -rn
On Machine 1 While cassandra running :
773 ESTABLISHED
36 LISTEN
1 CLOSE_WAIT
After cassandra stopped :
274 ESTABLISHED
36 LISTEN
1 CLOSE_WAIT
Machine 2 while cassandra running :
3941 ESTABLISHED
26 LISTEN
7 CLOSE_WAIT
After cassandra stopped :
26 LISTEN
9 ESTABLISHED
On machine 3 while cassandra running :
500 ESTABLISHED
21 LISTEN
After cassandra stopped :
21 LISTEN
13 ESTABLISHED
答案 0 :(得分：2)
由于许多原因，可能会抛出NoHostAvailableException。然而，这完全是关于driver documentation：
中描述的问题由于没有主机而无法执行查询时抛出异常 可用。如果
，则抛出此异常
- 要么没有主持人住 查询时的集群
- 所有已经尝试的主持人 因连接问题而失败
现在为什么会发生这种情况 - 可能有几个原因。
Row result = session.Execute("select cur_visit_id from usertracking where cwc ='" + cwc + "'").FirstOrDefault();。在未来的道路上，您正在为同一个集群密钥cws执行大量更新，由于SSTable的不可变性，它会生成大量版本化数据，从而导致数据检索时间增加，因为集群需要为您的每个请求组合所有这些数据。很难在没有任何表架构的情况下提出建议，逆向工程也无济于事，但我建议以某种方式利用复合主键来加快查找速度。调整JVM，创建会话和集群单例，并在代码中重用它们。看看这是否有帮助。
阅读Cassandra集群日志，重点关注问题发生的时间。查看这些日志中是否有任何线索，例如垃圾收集活动或超时错误。
HTH
罗马