PouchDb <-> CouchDb Replicate - couchdb

I have a problem with replicate when I turn off network and after few seconds turn on network.
After turn on network I must wait on replicate sync between 3-5 minutes:
On the prod env thi can be problematic.
Any ideas ?

Okay, sorry for image.
I was read about replication in pouchdb and using retry option
My code:
this.service.synch().then((data) => {
this.lottieSpashScreen.hide();
}).catch((err) => {
console.log('no network or couch not respond')
this.lottieSpashScreen.hide();
});
In service:
synch() {
let optionsToAndFrom = {
live: true,
retry: true,
continuous: true
};
this.db.replicate.to(this.remote, optionsToAndFrom)
return this.db.replicate.from(this.remote)
.on('complete', (info) => {
this.db.replicate.from(this.remote, optionsToAndFrom)
})
.on('error', (info) => {
console.log('error')
})}
Sometimes if a device is disconnected a long of time , replication stop and I have to restart app.
ON the network I can see that stalled on request is over four minutes
Edit: In browser everything working okay, without problem.
Problem is on device with android
EDIT :
When I started App and network not connect I can see in log :
net::ERR_INTERNET_DISCONNECTED
And thats great.
But when I started app and network connect and after few seconds disconnected I can see only in network that request is in pending status without error. When I turn on network after about minutes this request exectued but when I network off after about five minutes this request is in pending without changes status.

Related

How do i resolve this Mongo Server Selection Error

Am quiet new to backend and database. I have a solution currently using mongodb. It was working fine till yesterday when i starting having the connect ETIMEDOUT 13.37.254.237:27017 error. Nothing was changed in the URI path or tampered with. It just started and i have not been able to sort it out.
is there any help available please?
I have created another cluster and its working well. But my initial cluster that has datas which are live from clients is not connecting still.
My connection code
I have used these connections code but it has not worked. It was connecting fine all through yesterday but today without tampering with the code, couldn't connect to my mongodb
mongoose.connect(process.env.MONGO_URI,{ useNewUrlParser: true, useUnifiedTopology: true });
const connectDB = async () => {
try {
const conn = await mongoose.connect(process.env.MONGO_URL);
console.log(`MongoDB Connected: ${conn.connection.host}`);
} catch (error) {
console.log(error);
process.exit(1);
}
};
my mongoose connection and the timedout error
Whenever you connect to Mongodb using IPs that keep updating from your system causes this kind of issues.
also this can be due to your network connection. So i will advice you to:
To allow connection from any IP address(but must ensure your URI is not made known to the public to avoid attack/ access from unwanted users.)
2.Check your network status(data)
3. Run the mongo URI on your atlas

Connection to Redis instance closed every couple of minutes

I'm running a node.js on Google Cloud that uses a redis caching server. It was running fine for a couple of months but it suddenly started throwing connection errors and occasionally stops responding.
The app is running in the standard environment and connects to the VM that is running the Redis instance via a VPC connector. I suspect it is a networking issue because the issue doesn't seem to appear when I run the Node.js app from my own computer (connected to the same Redis server) or when the app is run in a flex environment and connects to the subnetwork directly. However, I'd prefer the app to run in the standard environment because as far as I know that's the only way to force the traffic over https.
When I monitor via Redis-cli the server just doesn't receive any commands when the connection has failed.
Time out in redis.conf is set to 0
Redis version: 5.0.5
Here's the Redis code. I don't think it is the issue though, it was running without issue a couple of weeks ago.
const redis = require('redis')
const redisOptions = {
host: process.env.REDIS_IP,
port: process.env.REDIS_PORT,
password: process.env.REDIS_PASS,
enable_offline_queue: false,
}
const client = redis.createClient(redisOptions.host, redisOptions.port)
// Log any errors
client.on('error', function(error) {
console.log('Error:')
console.log(error)
})
module.exports = client
These errors regularly show up in the Google App engine log. When they occur commands sent to Redis do not show up in in the logs.
A 2019-08-31T12:42:27.162834Z { Error: Redis connection to 10.128.15.197:6379 failed - read ETIMEDOUT "
A 2019-08-31T12:42:27.162868Z at TCP.onStreamRead (internal/stream_base_commons.js:111:27) errno: 'ETIMEDOUT', code: 'ETIMEDOUT', syscall: 'read' }
I see same issue many times with different databases. You already found the issue. Number of opened connections - is limited and costly resource. Try to use following pattern (it is just an example):
// Inside your db module
function dbCall(userFunc) {
const client = anyDb.createClient(host, port, ...);
userFunc(client, () => { client.quit(); /* client.close() or whatever */ }
}
// Usage
dbCall((client, done) => {
client.doSomethingWithCallback(..., () => {
// user code
done();
});
});
dbCall((client, done) => {
client.doSomePromise(...)
.finally(done);
});

How do I enable Blocked Connection Notifications extension in RabbitMQ

I am trying to use the blocked and unblocked channel events using Nodejs module amqplib on RabbitMQ. My understanding is RabbitMQ will send a connection blocked command to the producers if the system resources have reached an "alarm" state. My intention is to utilize this to determine if the producer should proceed in creating a job, or to respond to with a "try again later".
amqplib docs: http://www.squaremobius.net/amqp.node/channel_api.html#model_events
Here are the versions of software I am using:
RabbitMQ 3.6.6, Erlang R16B03
NodeJS 6.9.2
amqplib ^0.5.1 (node module)
Ubuntu 14.04
Things I have tried
My nodejs code:
var amqp = require('amqplib');
amqp.connect('amqp://localhost').then((connection) => {
return connection.createChannel();
}).then((channel) => {
channel.on('blocked', (reason) => {
console.log(`Channel is blocked for ${reason}`);
});
channel.on('unblocked', () => {
console.log('Channel has been unblocked.');
});
return channel.assertQueue('myQueue', {
durable : true,
// This doesn't seem to do anything
arguments : {
"connection.blocked" : true
}
}).then(() => {
channel.sendToQueue('myQueue', new Buffer('some message'), {
persistent : true
});
});
});
I understand that this particular feature is an extension to the AMQP protocol and needs to be enabled/declared. I'm not very familiar with the erlang config syntax. Using an example config, I built a config that looks something like:
[{rabbit, [
{"server-properties", [
{"compatibilities", {
{ "connection.blocked", true }
}}
]}
As per the docs here: https://www.rabbitmq.com/consumer-cancel.html#capabilities
"To receive these notifications, the client must present a
capabilities table in its client-properties in which there is a key
connection.blocked and a boolean value true. See the capabilities
section for further details on this. Our supported clients indicate
this capability by default and provide a way to register handlers for
the connection.blocked and connection.unblocked methods."
And then restarted the server using service rabbitmq-server restart.
This does not crash the server, but the events do not fire either. I'm expecting that the connection should become block in the event that system resources are low. The RabbitMQ docs has a link for more info on Capabilities but the link is dead, and I'm not sure what else to try.
blocked and unblocked are on connection not on channel.
In your example: connection.on('blocked', console.log) and connection.on('unblocked', () => console.log('unblocked')).
To test it just run: rabbitmqctl set_vm_memory_high_watermark 0.000001 and send a new message to your queue.
compatibilities are enabled by default, and amqplib informs server about connection.blocked. Nothing should be done here.

strange mongodb behavior when connecting to invalid host/port combination

I use node.js, mongodb, mongoose 2.3 for my app.
I have following code:
console.log(config);
db = mongoose.connect(
config[MONGO_HOST_CONFIG],
config[MONGO_ACCOUNTS_DB_CONFIG],
config[MONGO_PORT_CONFIG],
function(err) {
if (err) throw err;
}
);
Config looks like:
{ 'mongo.host': 'google.com',
'mongo.port': '27',
'mongo.accounts.db': 'accounts',
'mongo.sessions.db': 'sessions' }
It times out after some time. Question: How do I find out the timeout interval?
If I change HOST to: example.com: It fails immediately which is good.
If I change host to aruunt.com, it never times out and goes into wait state. The connection is also not established. aruunt.com is some random domain owned by me.
What is the issue here?
Default driver is never to timeout or whatever is the os default timeout (I think it's 30 min on linux bot not completely sure). You can tweak it yourself as the link above show. But don't set it to small or you'll continuously get timeouts and reconnects

Does mongoDB have reconnect issues or am i doing it wrong?

I'm using nodejs and a mongoDB - and I'm having some connection issues.
Well, actually "wake" issues! It connects perfectly well - is super fast and I'm generally happy with the results.
My problem: If i don't use the connection for a while (i say while, because the timeframe varies 5+ mins) it seems to stall. I don't get disconnection events fired - it just hangs.
Eventually i get a response like Error: failed to connect to [ * .mongolab.com: * ] - ( * = masked values)
A quick restart of the app, and the connection's great again. Sometimes, if i don't restart the app, i can refresh and it reconnects happily.
This is why i think it is "wake" issues.
Rough outline of code:
I've not included the code - I don't think it's needed. It works (apart from the connection dropout)
Things to note: There is just the one "connect" - i never close it. I never reopen.
I'm using mongoose, socketio.
/* constants */
var mongoConnect = 'myworkingconnectionstring-includingDBname';
/* includes */
/* settings */
/* Schema */
var db = mongoose.connect(mongoConnect);
/* Socketio */
io.configure(function (){
io.set('authorization', function (handshakeData, callback) {
});
});
io.sockets.on('connection', function (socket) {
});//sockets
io.sockets.on('disconnect', function(socket) {
console.log('socket disconnection')
});
/* The Routing */
app.post('/login', function(req, res){
});
app.get('/invited', function(req, res){
});
app.get('/', function(req, res){
});
app.get('/logout', function(req, res){
});
app.get('/error', function(req, res){
});
server.listen(port);
console.log('Listening on port '+port);
db.connection.on('error', function(err) {
console.log("DB connection Error: "+err);
});
db.connection.on('open', function() {
console.log("DB connected");
});
db.connection.on('close', function(str) {
console.log("DB disconnected: "+str);
});
I have tried various configs here, like opening and closing all the time - I believe though, the general consensus is to do as i am with one open wrapping the lot. ??
I have tried a connection tester, that keeps checking the status of the connection... even though this appears to say everthing's ok - the issue still happens.
I have had this issue from day one. I have always hosted the MongoDB with MongoLab.
The problem appears to be worse on localhost. But i still have the issue on Azure and now nodejit.su.
As it happens everywhere - it must be me, MongoDB, or mongolab.
Incidentally i have had a similar experience with the php driver too. (to confirm this is on nodejs though)
It would be great for some help - even if someone just says "this is normal"
thanks in advance
Rob
UPDATE: Our support article for this topic (essentially a copy of this post) has moved to our connection troubleshooting doc.
There is a known issue that the Azure IaaS network enforces an idle timeout of roughly thirteen minutes (empirically arrived at). We are working with Azure to see if we can't make things more user-friendly, but in the meantime others have had success by configuring their driver options to work around the issue.
Max connection idle time
The most effective workaround we've found in working with Azure and our customers has been to set the max connection idle time below four minutes. The idea is to make the driver recycle idle connections before the firewall forces the issue. For example, one customer, who is using the C# driver, set MongoDefaults.MaxConnectionIdleTime to one minute and it cleared up their issues.
MongoDefaults.MaxConnectionIdleTime = TimeSpan.FromMinutes(1);
The application code itself didn't change, but now behind the scenes the driver aggressively recycles idle connections. The result can be seen in the server logs as well: lots of connection churn during idle periods in the app.
There are more details on this approach in the related mongo-user thread, SocketException using C# driver on azure.
Keepalive
You can also work around the issue by making your connections less idle with some kind of keepalive. This is a little tricky to implement unless your driver supports it out of the box, usually by taking advantage of TCP Keepalive. If you need to roll your own, make sure to grab each idle connection from the pool every couple minutes and issue some simple and cheap command, probably a ping.
Handling disconnects
Disconnects can happen from time to time even without an aggressive firewall setup. Before you get into production you want to be sure to handle them correctly.
First, be sure to enable auto reconnect. How to do so varies from driver to driver, but when the driver detects that an operation failed because the connection was bad turning on auto reconnect tells the driver to attempt to reconnect.
But this doesn't completely solve the problem. You still have the issue of what to do with the failed operation that triggered the reconnect. Auto reconnect doesn't automatically retry failed operations. That would be dangerous, especially for writes. So usually an exception is thrown and the app is asked to handle it. Often retrying reads is a no-brainer. But retrying writes should be carefully considered.
The mongo shell session below demonstrates the issue. The mongo shell by default has auto reconnect enabled. I insert a document in a collection named stuff then find all the documents in that collection. I then set a timer for thirty minutes and tried the same find again. It failed, but the shell automatically reconnected and when I immediately retried my find it worked as expected.
% mongo ds012345.mongolab.com:12345/mydatabase -u *** -p ***
MongoDB shell version: 2.2.2
connecting to: ds012345.mongolab.com:12345/mydatabase
> db.stuff.insert({})
> db.stuff.find()
{ "_id" : ObjectId("50f9b77c27b2e67041fd2245") }
> db.stuff.find()
Fri Jan 18 13:29:28 Socket recv() errno:60 Operation timed out 192.168.1.111:12345
Fri Jan 18 13:29:28 SocketException: remote: 192.168.1.111:12345 error: 9001 socket exception [1] server [192.168.1.111:12345]
Fri Jan 18 13:29:28 DBClientCursor::init call() failed
Fri Jan 18 13:29:28 query failed : mydatabase.stuff {} to: ds012345.mongolab.com:12345
Error: error doing query: failed
Fri Jan 18 13:29:28 trying reconnect to ds012345.mongolab.com:12345
Fri Jan 18 13:29:28 reconnect ds012345.mongolab.com:12345 ok
> db.stuff.find()
{ "_id" : ObjectId("50f9b77c27b2e67041fd2245") }
We're here to help
Of course, if you have any questions please feel free to contact us at support#mongolab.com. We're here to help.
Thanks for all the help guys - I have managed to solve this issue on both localhost and deployed to a live server.
Here is my now working connect code:
var MONGO = {
username: "username",
password: "pa55W0rd!",
server: '******.mongolab.com',
port: '*****',
db: 'dbname',
connectionString: function(){
return 'mongodb://'+this.username+':'+this.password+'#'+this.server+':'+this.port+'/'+this.db;
},
options: {
server:{
auto_reconnect: true,
socketOptions:{
connectTimeoutMS:3600000,
keepAlive:3600000,
socketTimeoutMS:3600000
}
}
}
};
var db = mongoose.createConnection(MONGO.connectionString(), MONGO.options);
db.on('error', function(err) {
console.log("DB connection Error: "+err);
});
db.on('open', function() {
console.log("DB connected");
});
db.on('close', function(str) {
console.log("DB disconnected: "+str);
});
I think the biggest change was to use "createConnection" over "connect" - I had used this before, but maybe the options help now. This article helped a lot http://journal.michaelahlers.org/2012/12/building-with-nodejs-persistence.html
If I'm honest I'm not overly sure on why I have added those options - as mentioned by #jareed, i also found some people having success with "MaxConnectionIdleTime" - but as far as i can see the javascript driver doesn't have this option: this was my attempt at trying to replicate the behavior.
So far so good - hope this helps someone.
UPDATE: 18 April 2013 note, this is a second app with a different setup
Now I thought i had this solved but the problem rose it's ugly head again on another app recently - with the same connection code. Confused!!!
However the set up was slightly different…
This new app was running on a windows box using IISNode. I didn't see this as significant initially.
I read there were possibly some issues with mongo on Azure (#jareed), so I moved the DB to AWS - still the problem persisted.
So i started playing about with that options object again, reading up quite a lot on it. Came to this conclusion:
options: {
server:{
auto_reconnect: true,
poolSize: 10,
socketOptions:{
keepAlive: 1
}
},
db: {
numberOfRetries: 10,
retryMiliSeconds: 1000
}
}
That was a bit more educated that my original options object i state.
However - it's still no good.
Now, for some reason i had to get off that windows box (something to do with a module not compiling on it) - it was easier to move than spend another week trying to get it to work.
So i moved my app to nodejitsu. Low and behold my connection stayed alive! Woo!
So…. what does this mean… I have no idea! What i do know is is those options seem to work on Nodejitsu…. for me.
I believe IISNode uses some kind of "forever" script for keeping the app alive. Now to be fair the app doesn't crash for this to kick in, but i think there must be some kind of "app cycle" that is refreshed constantly - this is how it can do continuous deployment (ftp code up, no need to restart app) - maybe this is a factor; but i'm just guessing now.
Of course all this means now, is this isn't solved. It's still not solved. It's just solved for me in my setup.
A couple of recommendations for people still having this issue:
Make sure you are using the latest mongodb client for node.js. I noticed significant improvements in this area when migrating from v1.2.x to v1.3.10 (the latest as of today)
You can pass an options object to the MongoClient.connect. The following options worked for me when connecting from Azure to MongoLab:
options = {
db: {},
server: {
auto_reconnect: true,
socketOptions: {keepAlive: 1}
},
replSet: {},
mongos: {}
};
MongoClient.connect(dbUrl, options, function(err, dbConn) {
// your code
});
See this other answer in which I describe how to handle the 'close' event which seems to be more reliable. https://stackoverflow.com/a/20690008/446681
Enable the auto_reconnect Server option like this:
var db = mongoose.connect(mongoConnect, {server: {auto_reconnect: true}});
The connection you're opening here is actually a pool of 5 connections (by default) so you're right to just connect and leave it open. My guess is that you intermittently lose connectivity with mongolab and your connections die when that occurs. Hopefully, enabling auto_reconnect resolves that.
Increasing timeouts may help.
"socketTimeoutMS" : How long a send or receive on a socket can take
before timing out.
"wTimeoutMS" : It controls how many milliseconds the server waits for
the write concern to be satisfied.
"connectTimeoutMS" : How long a connection can take to be opened
before timing out in milliseconds.
$m = new MongoClient("mongodb://127.0.0.1:27017",
array("connect"=>TRUE, "connectTimeoutMS"=>10, "socketTimeoutMS"=>10,
"wTimeoutMS"=>10));
$db= $m->mydb;
$coll = $db->testData;
$coll->insert($paramArr);
I had a similar problem being disconnected from MongoDB periodically. Doing two things fixed it:
Make sure your computer never sleeps (that'll kill your network connection).
Bypass your router/firewall (or configure it properly, which I haven't figured out how to do yet).

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