Sadly, we don't use node extensively at my work (yet anyway), however, I wanted to write a small "watcher" app in Node that would preform some very basic health checks on the local server and if a problem is detected I want this watcher app to restart the associated service.
For example, I want to check Apache every 5 minutes to ensure HTTP is available. If not, I'd like the app to restart httpd as well as the application server process and send an alert. I just can't find anything on the internets' that discusses restarting OS level services using Node... but with all the posts on "how to daemonize Node" I could have missed something in the clutter.
Any help/direction would be appreciated.
My particular setup:
OS: Cent OS 6.3
Node: v0.10.19
As Brad pointed out, http://nodejs.org/api/child_process.html was indeed the answer.
In short:
var exec = require( 'child_process' ).exec
exec( 'service httpd stop', function( error, stdout, stderr ){ } );
But please read the docs. :)
Related
The problem is exactly what the title says, I am not able to connect to mongo db server. I don't know where the problem is. Whether its with starting the server of something else. According to the code that I have written I should get the output 'Connected Successfully'. but I am not getting any output
const mongodb=require('mongodb')
const MongoClient=mongodb.MongoClient
const connectionURL='mongodb://127.0.0.1:27017'
const databaseName='task-manager'
MongoClient.connect(connectionURL,{useNewUrlParser:true},(error,client)=>{
if(error){
return console.log('Unable to connect to database')
}
console.log('Connected Successfully')
})
I have attached the related screenshots.
enter image description here
enter image description here
Please help and thank you in advance
I tried searching for things in the documentation but could not find anything. I am expecting console.log statement to work in the nodejs code that I have written.
I can see from the logs that the server is listening at 127.0.0.1:27017. However, are you sure that it is reachable?
Some other software might be blocking the access, as described in a similar question here.
You can confirm by running curl http://127.0.0.1:27017 from a console terminal, if you are on Linux or Mac, or from a PowerShell window on Windows. Some other software might be blocking the access, as described in a similar question here.
If you get a message like below, your server is fine...
user#server ~]$ curl http://127.0.0.1:27017
It looks like you are trying to access MongoDB over HTTP on the native driver port.
user#server ~]$
The second step would be to ensure that you have the right/updated driver. I see from your screenshot that your server runs MongoDB 6.0.2, which is pretty recent.
You need at least driver v4.8 as per the MongoDB/node driver compatibility list.
Then, I would suggest to try running first a piece of code that it is confirmed working well, alongside the supported driver version.
e.g. You can try theses examples, directly from the MongoDB code-samples: https://mongodb.github.io/node-mongodb-native/api-generated/mongoclient.html
I'm running a NodeJS app inside a docker container inside a container-optimized-OS GCE instance.
I need this instance to shutdown an self-delete upon its task completion. Only the NodeJS app is aware of the task completion.
I used to achieve this behavior by setting up this as a startup-script:
node ./dist/app.js
echo "node script execution finished. Deleting this instance"
export NAME=$(curl -X GET http://metadata.google.internal/computeMetadata/v1/instance/name -H 'Metadata-Flavor: Google')
export ZONE=$(curl -X GET http://metadata.google.internal/computeMetadata/v1/instance/zone -H 'Metadata-Flavor: Google')
gcloud compute instance-groups managed delete-instances my-group --instances=$NAME --zone=$ZONE
I've also used similar setups with additional logic based on the NodeJS app exit code.
How do I do it now?
There are two problems:
I don't know how to pass NodeJS exit event (preferably with exit code) up to the startup-script. How do I do that?
Container-optimized-OS GCE instance lacks gcloud. Is there different way of shutting down an instance?
Google Cloud's Healthcheck seems too troublesome and not universal. My app is not a web-server, I prefer not to install express or something else just for sake of handling health checks.
Right now my startup-script ends with docker run ... command. Maybe I should write the shutdown command after that and somehow make docker exit on NodeJS exit?
If you think the Healthcheck is the way to go, what would be the lightest setup for a health check given that my app is not a web-server?
Try to have your app trigger a Cloud Function when the app finishes the job
Cloud function can then have script to delete your VM. See sample script below
https://medium.com/google-cloud/start-stop-compute-engine-instance-from-cloud-function-bf9ae5199609
I decided to post this question because, I have ran out of debugging ideas, just ideas are golden since I know it can be difficult to help debugging a virtual instance through here (debugging code is hard enough jaja). Anyway, I have created a virtual machine in Compute engine , I created a logs file that I populate, for example, with this command in a python script, let's call it logging.py:
import logging
logging.basicConfig(filename= 'app.log' , level = logging.INFO , format = ' %(asctime)s - %(name) - %(levelname)s - %(message)s')
logging.info('Some message ' + str(type(variable)))
everytime I use python3 logging.py , the app.log is effectively populated. ( Logging.py and app.log are in the same directory the /home/username/ folder )
I want stackdriver to show this log in the logging viewer everytime it's written, so , I installed the stackdriver agent as follows, in the virtual machine command line:
$ curl -sSO https://dl.google.com/cloudagents/install-logging-agent.sh
$ sudo bash install-logging-agent.sh
No errors that I see are delivered here, in fact, you can see here the messages obtained
Messags on the stackdriver viewer:
After this, I proceed to create a .conf file that I create in /etc/google-fluentd/config.d/app.conf
with this parameters
<source>
type tail
format none
path /home/username/app.log
pos_file /var/lib/google-fluentd/pos/app.pos
read_from_head true
tag whatever-tag
</source>
After that is created, I launch sudo service google-fluentd restart.
Aftert I execute, python3 logging.py , no logs are added to stack drivers logging viewer.
So, where might Have I gone wrong?
Things I have tried/checked:
-Have more than 13 gygabytes of RAM available
-If I run logger "some message" on the command line, I effectively add a log with "some message" to the log viewer
-If I run
ps ax | grep fluentd
I obtain :
3033 ? Sl 0:09 /opt/google-fluentd/embedded/bin/ruby /usr/sbin/google-fluentd --log /var/log/google-fluentd/google-fluentd.log --no-supervisor
3309 pts/0 S+ 0:00 grep --color=auto fluentd
-Both my user, and the service account I use, have logger admin permission in IAM roles.
-This is the documentation I have based myself on:
https://cloud.google.com/logging/docs/agent/troubleshooting?hl=es-419
https://cloud.google.com/logging/docs/reference/v2/rest/v2/entries/list?hl=es-419
https://cloud.google.com/logging/docs/agent/configuration?hl=es-419
https://medium.com/google-cloud/how-to-log-your-application-on-google-compute-engine-6600d81e70e3
https://cloud.google.com/logging/docs/agent/installation
-If I run sudo service google-fluentd status , the agent appears active.
-My instance hass access, to all the apis. It's an n1-standard-4 (4 vCPUs, 15 GB of memory) using ubuntu linux 18:04
So, what else can I check to debug this? I'm out of ideas here , hope I'm not being an idiot here :(
Based on my understanding, I think that you looking for the following fluentd resource types:
generic_node
“A generic node identifies a machine or other computational resource for which no more specific resource type is applicable. The label values must uniquely identify the node.”
generic_task
“A generic task identifies an application process for which no more specific resource is applicable, such as a process scheduled by a custom orchestration system. The label values must uniquely identify the task.”
The source of my information has been found here
This document explain how to send logs from your application in different ways:
Cloud Logging API
Cloud Logging Agent
Generic fluentd
As you mentioned having installed fluentd, let me provide more focused documentation about Cloud Logging Agent. I also found some python Client Library documentation that you may be interested.
Finally, I found a nginx/apache use-case guide that you may use as reference.
For some reason, if I change the directory to which both the .conf file points, and the directory where the logg is to /var/logs/ , being the final path as /var/logs/app.logs, it does work correctly. Possibly there is a configuration issue, causing the logging agent to only capture logs in specific predetermined folders, or a permissions issue that stops it from working if the log is in the username directory.
I found this solution, however, by chance(random testing basically.
). Did not find anything in the main articles that are supposed to teach me how to configure the logging agent, that could point me in the right direction, being those articles this ones,
https://cloud.google.com/logging/docs/agent/troubleshooting?hl=es-419 https://cloud.google.com/logging/docs/reference/v2/rest/v2/entries/list?hl=es-419 https://cloud.google.com/logging/docs/agent/configuration?hl=es-419 https://medium.com/google-cloud/how-to-log-your-application-on-google-compute-engine-6600d81e70e3 https://cloud.google.com/logging/docs/agent/installation
If I needed it to work in my username directory, it's not clear just by checking this articles how to do it,what configuration file I would need to change or where to start, so I recommend to google to improve that aspect of the docs.
This documentation you have sent https://docs.fluentd.org/quickstart is pretty interesting, maybe I can find the explanation there, thank you for your help.
I have a standalone scheduling service set to execute some logic every 1 hour, I want to start this service with forever right after sails start and I am not sure what's the best way to do that.
// services/Scheduler.js
sails.load(function() {
setInterval( logicFn , config.schedulingInterval);
});
Sails can execute bootstrap logic in the config.bootstrap module and I'll be using the forever-monitor node module \
var forever = require('forever-monitor'),
scheduler = new (forever.Monitor)( schedulerPath, {
max: 20,
silent: true,
args: []
});
module.exports.bootstrap = function(cb) {
scheduler.start();
cb();
};
What if the service failed and restarted for whatever reason would it have access to all waterline models again, how to ensure it works as intended every time?
as brittonjb said in comments, a simple solution is to use the cron module for scheduling.
You can specify a function for it to call at whatever interval you wish; this function could be defined within /config/bootstrap.js or it could be defined somewhere else (e.g. mail.dailyReminders() if you have a mail service with a dailyReminders method);
Please please please, always share your sails.js version number! This is really important for people googling questions/answers!
There are many ways to go about doing this. However, for those that want the "sails.js" way, there are hooks for newer sails.js versions.
See this issue thread in github, specifically, after the issue gets closed some very helpful solutions get provided by some users. The latest is shared by "scott-wyatt", commented on Dec 28, 2014:
https://github.com/balderdashy/sails/issues/2092
I'm trying to set up a robust memcached configuration for a nodejs app with the node-memcached driver, but it does not seem to use the specified failover servers when one server dies.
My local experiment goes as follows:
shell
memcached -p 11212
node
MC = require('memcached')
c = new MC('localhost:11211', //this process does not exist
{failOverServers: ['localhost:11212']})
c.get('foo', console.log) //this will eventually time out
c.get('foo', console.log) //repeat 5 or 6 times to exceed the retries number
//wait until all the connection errors appear in the console
//at this point, the failover server should be in use
c.get('foo', console.log) //this still times out :(
Any ideas of what might we be doing wrong?
It seems that the failover feature is somewhat buggy in node-memcached.
To enable failover you must set the remove options:
c = new MC('localhost:11211', //this process does not exist
{failOverServers: ['localhost:11212'],
remove : true})
Unfortunately, this is not going to work because of the following error:
[depricated] HashRing#replaceServer is removed.
[depricated] the API has no replacement
That is, when trying to replace a dead server with a replacement from the failover list, node-memcached outputs a deprecation error from the HashRing library (which, in turn, is maintained by the same author of node-memcached). IMHO, feel free to open a bug :-)
This is come when your nodejs server not getting any session id from memcached
Please check properly in php.ini file you are setting properly or not for memcached
session.save = 'memcache'
session.path = 'tcp://localhost:11212'