In my embedded debezium based CDC application, I want to capture the database connection failures to retry the connection automatically.
Is there a way to capture that the database connection is failed in my program?
Build the EmbeddedEngine using a CompletionCallback.
EmbeddedEngine.CompletionCallback completionCallback = (success, message, error) -> {
//Handle the error.
};
EmbeddedEngine engine = EmbeddedEngine.create()
.using(completionCallback)
...
.build();
Related
I'm using Azure Cosmos DB 4.0 with MongoDB C# Driver 2.10.4.
Most of the times the queries work fine, but I'm getting intermittent errors like this:
MongoDB.Driver.MongoConnectionException: An exception occurred while sending a message to the server.
System.IO.IOException: Unable to write data to the transport connection: An existing connection was forcibly closed by the remote host.
System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host
at System.Net.Sockets.Socket.BeginSend(...
at System.Net.Sockets.NetworkStream.BeginWrite
--- End of inner exception stack trace ---
at System.Net.Sockets.NetworkStream.BeginWrite
at System.Net.Security._SslStream.StartWriting
at System.Net.Security._SslStream.ProcessWrite
at System.Net.Security._SslStream.BeginWrite
When that error happens the call takes 10-25 seconds before failing.
I'm building the MongoClient with new MongoClient(MongoClientSettings.FromConnectionString(cnstr)) and I was using the connectionstring with these arguments ?ssl=true&replicaSet=globaldb&retrywrites=false.
I tried with retryWrites=true (as per Azure Support suggestion) but that didn't help.
I tried different settings and that didn't work either (connect=direct, maxIdleTimeMS=30000, serverSelectionTimeout=5000ms, socketTimeout=10000ms).
What's causing those exceptions?
The fix was to set/force TLS 1.2 (based on this Microsoft document):
//return new MongoClient(connectionString);
var settings = MongoClientSettings.FromConnectionString(connectionString);
settings.SslSettings = new SslSettings()
{
EnabledSslProtocols = System.Security.Authentication.SslProtocols.Tls12
};
return new MongoClient(settings);
Looks like although my connection string had ssl=true, it wasn't enough to work on some servers (the error is intermittent). The same underlying error can usually be fixed by forcing TLS 1.2 so I assumed that in Mongo it could be the same issue - and it really fixed the problem.
Is there anything in the modern PostgreSQL connection protocol that would indicate the server version?
And if not, is there a special low-level request that an endpoint can execute against an open connection to pull the server details that would contain the version?
I'm looking at a possible extension of node-postgres that would automatically provide the server version upon every fresh connection. And I want to know if this is at all possible.
Having to execute SELECT version() upon every new connection and then parsing it is too high-level for the base driver that manages the connection. It should be done on the protocol level.
After a bit of research, I found that PostgreSQL does provide server version during connection, within the start-up message.
And specifically within node-postgres driver, we can make Pool provide a custom Client that handles event parameterStatus on the connection, and exposes the server version:
const {Client, Pool} = require('pg');
class MyClient extends Client {
constructor(config) {
super(config);
this.connection.on('parameterStatus', msg => {
if (msg.parameterName === 'server_version') {
this.version = msg.parameterValue;
}
});
}
}
const cn = {
database: 'my-db',
user: 'postgres',
password: 'bla-bla',
Client: MyClient // here's our custom Client type
};
const pool = new Pool(cn);
pool.connect()
.then(client => {
console.log('Server Version:', client.version);
client.release(true);
})
.catch(console.error);
On my test PC, I use PostgreSQL v11.2, so this test outputs:
Server Version: 11.2
UPDATE - 1
Library pg-promise has been updated to support the same functionality in TypeScript. And you can find a complete example in this ticket.
UPDATE - 2
See example here:
// tests connection and returns Postgres server version,
// if successful; or else rejects with connection error:
async function testConnection() {
const c = await db.connect(); // try to connect
c.done(); // success, release connection
return c.client.serverVersion; // return server version
}
I have been trying to load the SQL script schema into MySQL DB using Vertx.
Though, i am able to load or update any single DB command but unable to load complete schema in one go.
The second challenge faced is that, this might be blocking code for Vertx application. If that is the case, how can it be avoided?
Here is the code snippet i have been trying to execute:
jdbcClient.getConnection(resConn -> {
if(resConn.succeeded()) {
SQLConnection connection = resConn.result();
connection.execute("<Trying to load the SQL Script schema>", resSchema -> {
connection.close();
if(resSchema.succeeded()) {
async.complete();
} else {
testContext.fail("Failed to load bootstrap schema: " + resSchema.cause().getMessage());
}
});
} else {
testContext.fail("Failed to obtain DB connection for schema write");
}
});
The MySQL JDBC driver does not allow to execute a file as a SQL script. You must parse the script and execute individual commands one by one.
I'm trying to create an alarm system for my application, that will trigger when one of the services (e.g. MongoDB) is not working.
What I'm doing is, once the application is started, I shut down my MongoDB server and try to connect to it, but instead of receiving an error my application just gets stuck into the execution of the method. The server console looks like something is in execution.
My current code (coffeescript) is:
checkMongoService: ()->
mongo = Npm.require 'mongodb'
assert = Npm.require 'assert'
url = 'mongodb://....'
mongo.connect url, (err, db) ->
assert.equal null, err
console.log 'Connected correctly to server'
db.close()
return
I've also been trying by doing a simple
Meteor.users.find().count();
or using MongoInternals with
testConnection = new MongoInternals.RemoteCollectionDriver("mongodb://...);
but still same issue, when mongo is not running no error is thrown and the console stops to work. If then I start Mongo again, it will just return the result (in this case the log 'Connected correctly to server')
Something that I've noticed is if I try with meteor shell to execute testConnection = new MongoInternals.RemoteCollectionDriver("mongodb://...); I get an error "Error: failed to connect to [127.0.0.1:27017]"
TL;DR
Do you might have an idea on how I can check if mongo is reachable or do you know if I'm doing something wrong with the code above?
Try setting the timeouts to be a bit shorter than the default 30 seconds:
mongo.connect(url, {
connectTimeoutMS: 1000,
socketTimeoutMS: 1000,
reconnectTries: 1
}, function(err, db) {...}
(Full set of connection params are here)
Meteor.status().status
from the docs
This method returns the status of the connection between the client and the server. The return value is an object with the following fields:
connected (Boolean)
True if currently connected to the server. If false, changes and method invocations will be queued up until the connection is reestablished.
status (String)
Blockquote
Describes the current reconnection status. The possible values are connected (the connection is up and running), connecting (disconnected and trying to open a new connection), failed (permanently failed to connect; e.g., the client and server support different versions of DDP), waiting (failed to connect and waiting to try to reconnect) and offline (user has disconnected the connection).
https://docs.meteor.com/api/connections.html
I am trying to connect my GWT application to an ldap server using jdbc, but could not make it work so far.
Here is a code sample of my attempt to connect to it:
String ldapConnectString = "jdbc:ldap://SERVERIP:389/dc=SERVERNAME,dc=office,dc=COMPANY,dc=com?SEARCH_SCOPE:=subTreeScope";
java.sql.Connection con;
try {
con = DriverManager.getConnection(ldapConnectString,"cn=USERNAME","PASSWORD");
} catch (SQLException e) {
System.out.println("An error has ocurred!!! Connection failed");
e.printStackTrace();
}
The example I used to write this is: http://myvd.sourceforge.net/bridge.html
When I run the application I get following error message:
java.sql.SQLException: No suitable driver found for jdbc:ldap://SERVERIP:389/dc=SERVERNAME,dc=office,dc=COMPANY,dc=com?SEARCH_SCOPE:=subTreeScope
I would be thankful for any help
Edit:
The code sample I provided is running on server side accessed by RPC. I included 2 jar files in my lib/ directory downloaded from here: http://sourceforge.net/projects/myvd/files/jdbc%20ldap%20bridge/jdbc%20ldap%20bridge%202.1/jdbc-ldap-2.1.zip/download
You generally need to register the JDBC driver before you can connect to the backend.
Try something like
DriverManager.registerDriver(new com.octetstring.jdbcLdap.sql.JdbcLdapDriver());
before setting up the connection.
More general information on ways of registering drivers.