I am using MongoDB with java. I need a way to check if MongoDB is running (to prevent exceptoins later). I tried it with this code:
mongoClient = new MongoClient();
try {
mongoClient.getAddress();
mongoRunning = true;
} catch (Throwable e){
log.warn("no db connected");
return;
}
I know throwable is bad but it is not working neither with exception nor with Throwable. I see (the catch block is not entered!):
[INFO ] 2018-11-10 22:33:26.209 [cluster-ClusterId{value='5be74e9f7170312fd4eb1ffe', description='null'}-127.0.0.1:27017] cluster - Exception in monitor thread while connecting to server 127.0.0.1:27017
com.mongodb.MongoSocketOpenException: Exception opening socket
at com.mongodb.internal.connection.SocketStream.open(SocketStream.java:67) ~[mongo-java-driver-3.8.2.jar:?]
at com.mongodb.internal.connection.InternalStreamConnection.open(InternalStreamConnection.java:126) ~[mongo-java-driver-3.8.2.jar:?]
at com.mongodb.internal.connection.DefaultServerMonitor$ServerMonitorRunnable.run(DefaultServerMonitor.java:117) [mongo-java-driver-3.8.2.jar:?]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_102]
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method) ~[?:1.8.0_102]
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85) ~[?:1.8.0_102]
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[?:1.8.0_102]
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[?:1.8.0_102]
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[?:1.8.0_102]
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172) ~[?:1.8.0_102]
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[?:1.8.0_102]
at java.net.Socket.connect(Socket.java:589) ~[?:1.8.0_102]
at com.mongodb.internal.connection.SocketStreamHelper.initialize(SocketStreamHelper.java:64) ~[mongo-java-driver-3.8.2.jar:?]
at com.mongodb.internal.connection.SocketStream.open(SocketStream.java:62) ~[mongo-java-driver-3.8.2.jar:?]
... 3 more
And my program terminates. An i thought i know java :-(. But i also tried:
mongoClient.listDatabases();
This behaves also odd: mongoRunning is set to true and an exception is thrown asynchronously.
I need a way to check the connection once. Is this possible without any exception and in a synchronous way?
MongoClient represents a connection pool. It manages the connections, and everything happening in its threads.
I think it is wrong to ask question "if MongoDB is running". Suppose you have a tool or instrument to check if it is running, and you receive no exception at the time of checking, but right after you checked MongoDB is crashed, what would you do. I.e. it is wrong to attempt such check, instead one should focus to write application in reliable way with proper error handling at the time of queries.
Additionally, you may look at ConnectionPoolSettings which has getMaxWaitQueueSize, by default its 500 queries before it starts throwing exceptions. If that is what causes problems to you, you may try to reduce this to lesser value, to start receiving exceptions earlier.
Related
I'm the new to redis, I start the server about this tutorial. And it work. Then I use write the code using java to connect redis, then it's ok, like this:
Jedis jedis = new Jedis("localhost");
System.out.println("Connection to server sucessfully");
//store data in redis list
jedis.lpush("tutorial-list", "Redis");
jedis.lpush("tutorial-list", "Mongodb");
jedis.lpush("tutorial-list", "Mysql");
But, when I use multithread to push the redis, it will throw the exception "read time out":
Exception in thread "main" java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601) at
org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoader.java:58)
Caused by: redis.clients.jedis.exceptions.JedisConnectionException:
java.net.SocketTimeoutException: Read timed out at
redis.clients.util.RedisInputStream.ensureFill(RedisInputStream.java:201)
at
redis.clients.util.RedisInputStream.readByte(RedisInputStream.java:40)
at redis.clients.jedis.Protocol.process(Protocol.java:141) at
redis.clients.jedis.Protocol.read(Protocol.java:205) at
redis.clients.jedis.Connection.readProtocolWithCheckingBroken(Connection.java:297)
at
redis.clients.jedis.Connection.getBinaryMultiBulkReply(Connection.java:233)
at redis.clients.jedis.Jedis.keys(Jedis.java:185) at
org.v11.redis_mongo_task.UpdateApp.jobDetail(UpdateApp.java:23) at
org.v11.redis_mongo_task.UpdateApp.main(UpdateApp.java:42) ... 5 more
Caused by: java.net.SocketTimeoutException: Read timed out at
java.net.SocketInputStream.socketRead0(Native Method) at
java.net.SocketInputStream.read(SocketInputStream.java:150) at
java.net.SocketInputStream.read(SocketInputStream.java:121) at
java.net.SocketInputStream.read(SocketInputStream.java:107) at
redis.clients.util.RedisInputStream.ensureFill(RedisInputStream.java:195)
... 13 more
What happened for redis? why it can work in single thread?
According to this answer, a single Jedis instance is not threadsafe. You will have to use JedisPool for multithreading. You can read here on how use it and here to set the max connections and what will happen if those connections are all occupied.
I'm posting links since two of them are SO answers an they should get the credit and one is from github official repo, so if anything gets updated it should be reflected here too.
Below is a simple code snippet that shows how to connect to a VoltDB server.
ClientConfig clientConfig = new ClientConfig();
Client client = ClientFactory.createClient(clientConfig);
String server = "192.168.43.32";
client.createConnection(server);
Based on my experiments, if the server is down or just not connectable from network layer, it will take about 75 seconds to get the response.
SEVERE: Failed to connect to 192.168.43.32, in 75,359 ms
java.net.ConnectException: Operation timed out
at sun.nio.ch.Net.connect0(Native Method)
at sun.nio.ch.Net.connect(Net.java:458)
at sun.nio.ch.Net.connect(Net.java:450)
at sun.nio.ch.SocketChannelImpl.connect(SocketChannelImpl.java:648)
at java.nio.channels.SocketChannel.open(SocketChannel.java:189)
at org.voltdb.client.ConnectionUtil.getAuthenticatedConnection(ConnectionUtil.java:154)
at org.voltdb.client.ConnectionUtil.getAuthenticatedConnection(ConnectionUtil.java:142)
at org.voltdb.client.ConnectionUtil.getAuthenticatedConnection(ConnectionUtil.java:134)
at org.voltdb.client.Distributer.createConnectionWithHashedCredentials(Distributer.java:878)
at org.voltdb.client.ClientImpl.createConnectionWithHashedCredentials(ClientImpl.java:189)
at org.voltdb.client.ClientImpl.createConnection(ClientImpl.java:682)
at src.java.tutorial.voltdb.integration.ConnectionTest.main(ConnectionTest.java:27)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:140)
Is there any ways to set the time out time, so the application needs not to wait for such a long time. A successful connection normally takes just tens of milliseconds, so I think if the connection cannot be established within 1000 milliseconds, something is definitely wrong already.
I have tried the setting of below
clientConfig.setConnectionResponseTimeout(1000);
In this case, it has no effects at all. So I guess it is not for this purpose.
Normally when the database is down and your client tries to connect it will get an immediate Connection refused exception, for example:
Exception in thread "main" java.net.ConnectException: Connection refused
at sun.nio.ch.Net.connect0(Native Method)
at sun.nio.ch.Net.connect(Net.java:364)
at sun.nio.ch.Net.connect(Net.java:356)
at sun.nio.ch.SocketChannelImpl.connect(SocketChannelImpl.java:623)
at java.nio.channels.SocketChannel.open(SocketChannel.java:184)
at org.voltdb.client.ConnectionUtil.getAuthenticatedConnection(ConnectionUtil.java:165)
at org.voltdb.client.ConnectionUtil.getAuthenticatedConnection(ConnectionUtil.java:153)
at org.voltdb.client.ConnectionUtil.getAuthenticatedConnection(ConnectionUtil.java:145)
at org.voltdb.client.Distributer.createConnectionWithHashedCredentials(Distributer.java:890)
at org.voltdb.client.ClientImpl.createConnectionWithHashedCredentials(ClientImpl.java:191)
at org.voltdb.client.ClientImpl.createConnection(ClientImpl.java:684)
at benchmark.Benchmark.<init>(Benchmark.java:17)
at benchmark.Benchmark.main(Benchmark.java:78)
In general, a "java.net.ConnectException: Connection timed out" can occur if there is a firewall that prevents the client from receiving any sort of response, or there could be other causes. The first thing to check might be if you have any firewall or network settings that would prevent access to port 21212 (the default VoltDB database connection port).
The ClientConfig setConnectionResponseTimeout() setting is used to cause a live connection to be closed if it hasn't received a response from a procedure call or a ping for the given number of milliseconds, but it is not used for creating a new connection.
I am getting following error when i try to run Oozie workflow using java
IO_ERROR : java.net.ConnectException: Connection timed out: connect
at org.apache.oozie.client.OozieClient.validateWSVersion(OozieClient.java:234)
at org.apache.oozie.client.OozieClient.createURL(OozieClient.java:300)
at org.apache.oozie.client.OozieClient.access$000(OozieClient.java:71)
at org.apache.oozie.client.OozieClient$ClientCallable.call(OozieClient.java:366)
at org.apache.oozie.client.OozieClient.run(OozieClient.java:547)
at oozieDemo.main(oozieDemo.java:27)
Caused by: java.net.ConnectException: Connection timed out: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
Here is my code:
OozieClient wc = new OozieClient("http:xxxxxxx/oozie");
System.out.println(" connection established....." + wc);
Properties conf = wc.createConfiguration();
conf.setProperty(OozieClient.APP_PATH,"hdfs:foo/xxx/workflow.xml");
conf.setProperty("jobTracker", "foo:8021");
conf.setProperty("nameNode","hdfs:xxxx");
conf.setProperty("queueName", "default");
conf.setProperty("appLibLoc","hdfs:/foo/xxx/lib");
String jobId = wc.run(conf);
System.out.println("Workflow job submitted");
So here I can see connection is getting established but unable to run the workflow.
I am new to this. So can't figure it out where exactly it is failing.
Connection timeout means either:
URL is incorrect or down, try pinging it.
Firewall is blocking it.
Default timeout expired.
Your internet access is down, which I'm going to assume isn't the case.
I am working on Java EE JSF application using Hibernate with C3P0 connection pool. I have tried to search anything possible and impossible and tried many things, but couldnt figure this out.
The problem is handling database connection fail, for example when database is shut down. I couldn't find a way how to catch ecfeption which I could use to show error status on user interface. The only thing I could do is see some exceptions in console:
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server. Attempted reconnect 3 times. Giving up.
at sun.reflect.GeneratedConstructorAccessor408.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.Util.getInstance(Util.java:386)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1015)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:989)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:975)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:920)
at com.mysql.jdbc.ConnectionImpl.connectWithRetries(ConnectionImpl.java:2404)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2325)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:834)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
at sun.reflect.GeneratedConstructorAccessor407.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:416)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:347)
at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:146)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:195)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:184)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:200)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1086)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1073)
at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:44)
at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1810)
at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:648)
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.GeneratedConstructorAccessor404.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1129)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:358)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2498)
at com.mysql.jdbc.ConnectionImpl.connectWithRetries(ConnectionImpl.java:2343)
... 18 more
Caused by: java.net.ConnectException: Connection timed out: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:579)
at java.net.Socket.connect(Socket.java:528)
at java.net.Socket.<init>(Socket.java:425)
at java.net.Socket.<init>(Socket.java:241)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:256)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:308)
... 20 more
]]
But I can't catch this, it's just on console and it's not even printed in web browser response (client thread does not receive any exception, it's just hanging while trying to load the page for infinity).
Here is my C3P0 configuration:
c3p0.testConnectionOnCheckout=true
c3p0.idleConnectionTestPeriod=60
c3p0.acquireIncrement=1
c3p0.preferredTestQuery=SELECT 1
c3p0.acquireRetryAttempts=1
My question is: How to handle case of database connection fail in the user-friendly way?
You could use the Omnifaces FullAjaxExceptionHandler to display whatever you want for the exception. See the following link to documentation:
http://showcase.omnifaces.org/exceptionhandlers/FullAjaxExceptionHandler
OK, after of few days of work I have constructed a solution.
The problem was that just typical Hibernate session did not throw any exception while using it without database connected. But this piece of code does throw an exception when database not connected (so it can be used as a test):
Properties p = hibernateConnection.getCfg().getProperties();
String url = p.getProperty("hibernate.connection.url");
String user = p.getProperty("hibernate.connection.username");
String password = p.getProperty("hibernate.connection.password");
DriverManager.getConnection(url, user, password).close();
So, simple try-catch can be used. If an exception is caught, connection is dead.
I used this for regular checking of database connection. On application deploy, a TimerTask is scheduled to run every minute. When it catches an exception, it sets a static variable dbAvailable to false (otherwise to true). This variable is being checked on every HTTP client request and if it's true, error 503 is sent back in response.
For scheduling the timer I used ServletContextListener. C3P0 configuration mentioned in the question.
If I set a socket SoTimeout, and read from it. when read time exceed the timeout limit, I'll get an "SocketTimeoutException: Read timed out".
and here is the stack in my case:
java.net.SocketTimeoutException: Read timed out
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:150)
at java.net.SocketInputStream.read(SocketInputStream.java:121)
at java.io.FilterInputStream.read(FilterInputStream.java:133)
at org.apache.hadoop.ipc.Client$Connection$PingInputStream.read(Client.java:277)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:235)
at java.io.BufferedInputStream.read(BufferedInputStream.java:254)
at java.io.DataInputStream.readInt(DataInputStream.java:387)
at org.apache.hadoop.ipc.Client$Connection.receiveResponse(Client.java:527)
at org.apache.hadoop.ipc.Client$Connection.run(Client.java:462)
but here I encountered "IOExcetion: Connection timed out", i don't know how it happened.
Stacks:
java.io.IOException: Connection timed out
at sun.nio.ch.FileDispatcher.read0(Native Method)
at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:21)
at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:198)
at sun.nio.ch.IOUtil.read(IOUtil.java:171)
at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:245)
at org.apache.hadoop.net.SocketInputStream$Reader.performIO(SocketInputStream.java:55)
at org.apache.hadoop.net.SocketIOWithTimeout.doIO(SocketIOWithTimeout.java:142)
at org.apache.hadoop.net.SocketInputStream.read(SocketInputStream.java:155)
at org.apache.hadoop.net.SocketInputStream.read(SocketInputStream.java:128)
at java.io.FilterInputStream.read(FilterInputStream.java:116)
at org.apache.hadoop.ipc.Client$Connection$PingInputStream.read(Client.java:277)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
at java.io.BufferedInputStream.read(BufferedInputStream.java:237)
at java.io.DataInputStream.readInt(DataInputStream.java:370)
at org.apache.hadoop.ipc.Client$Connection.receiveResponse(Client.java:527)
at org.apache.hadoop.ipc.Client$Connection.run(Client.java:462)
Can someone tell me what's the differences between the two exceptions, Thanks.
A connection timeout means you attempted to connect to the remote IP/port pair and failed to do so: it did not answer at all. Another possible error at that stage would be connection refused, in which this pair is available but rejected your connection attempt. Both of these errors appear on the initial setup of a socket. Note that these errors only occur with TCP, since a TCP connection requires the establishment of a session.
When you have a socket read timeout, it means you are connected, but failed to read data in time. Timeouts on sockets are configurable. You may also get a connection reset error, which means you did connect successfully, but the other end decided that after all you're not worth it :p
Simple answer:
In one case (Connection timed out) your application cannot connect to the server in a timely manner. In the other case (Read timed out) the connection can be established but during read the connection times out.
'Connection timed out' after the connect phase means that something has gone seriously wrong with the connection and it must be closed. 'Read timeout' just means that no data arrived within the specified receive timeout period: it isn't fatal.