Is there any limit of concurrent queries that mongodb can run in a second?
I am trying to implement an API that runs 300 queries in each request in mongodb.
So if there are 100 client requests in a second so the number of queries becomes 100 x 300 which is resulting in high latency.
Any clue?
The only limit is the number of conections mongo can have in parallel. Check out net.maxIncomingConnections
The maximum number of simultaneous connections that mongos or mongod will accept. This setting has no effect if it is higher than
your operating system’s configured maximum connection tracking
threshold.
But still you'll need to monitor your system to figure out what's actually happening.
And yes, 300 queries per API request is a bit too much even from networking perspective/requests parsing overhead.
Related
What is the maximum theoretical number of parallel requests that we can squize from single mongodb instance before deciding to shard?
Considering the database and indexes fit in memory and all requests are find() queries fetching single document based on indexed field. The hosting OS is Ubuntu , the data partition is SSD. ulimits are set to max.
In my laptop with simple test on single instance I reach near 40k/sec , after that the avg execution times start to increase significantly, but wondering what can be the upper theoretical limit?
It depends. If your active dataset can fit in the memory - if most of the requests don't need to perform any disk I/O - then you can achieve 24k+ requests pretty easily. If not on a (bigger) single machine, then at least use a replica set cluster with multiple secondaries.
If an active dataset is much larger than the available RAM then you have the same problem as with any other database. The advantage of MongoDB's new engine WiredTiger (since v3.0) is a transparent compression - it can reduce the amount of data and I/O and thus improve performance - even despite the fact that compression adds CPU load.
For more performance it really helps:
if the most accessed documents are small so it takes less time to
load them, transfer them, and less time to deserialize in your app List item
If you use projections in find(), for the same reasons
if you use bulk operations to reduce networking I/O and context switches
Even MongoDB itself has an option to limit the maximum number of incoming connections. It defaults to 64k.
for more information you can refer link
I have one publisher with around 50 subscribers. Not so often (few times a month) a binary file of size 30MB is written to the database. At this point all subscriber are getting this file and I have network bandwidth issues.
Is it possible to limit (in Postgres or OS) the bandwidth used by the logical replication per publisher/subscribers?
Is it possible to limit the bandwidth used during first sync?
At the PostgreSQL level I can suggest trying to reduce max_wal_senders parameter at the sending server (it is 10 by default)
Depending on the latency you can accept, you can limit the number of concurrent sending processes up to 1 process at a time
MongoDB Atlas has rate limit of 100 requests per minute per project but if I host mongodb on my own server then will it have a rate limit or I can make unlimited read/write calls per minute to database. (obviously it is relative to the specifications of server) I am using Node js for making calls with mongoose
No, when you install MongoDB in your own premises, then you don't have any limit. Of course, the system has some MongoDB Limits and Thresholds but I don't think you will hit any of them.
Is throughput the max number of requests a server instance can handle or is it the number of requests that the server instance is currently handling?
Edit: By "currently handling" I mean, the number of requests the server is receiving for a given time interval in recent time. For eg: The server is currently handling 400 reqs every min.
For eg:, I might have a server instance with a lot of hardware which can have high throughput, but I might be only receiving small amount of traffic. What does throughput measure in such a situation. Also, what about the inverse case, i.e if my instance can only handle x requests per min. but is receiving y>>>x requests per min.
If throughput is the max no. of requests a server can handle, how is it measured? Do we do a load/stress test, where we keep increasing the requests per min on the server until it cannot handle them anymore?
No, Throughput is an aggregation that depends on execution time, you can send 1000 requests in the same second and your server won't handle, but when you'll send 1000 requests in an hour and your server will handle it normally.
Throughput is calculated as requests/unit of time. The time is calculated from the start of the first sample to the end of the last sample. This includes any intervals between samples, as it is supposed to represent the load on the server.
The formula is: Throughput = (number of requests) / (total time).
You want to find the number of concurrent users that your server can handle by increasing JMeter threads until server reach his maximum
Throughput is the number of Samplers which JMeter executes within the duration of your test. If you want to see the actual amount of requests which are being sent - consider using i.e. Server Hits Per Second listener (can be installed using JMeter Plugins Manager)
If you see that your server resources consumption doesn't increase as you increase the load in JMeter the reasons are in:
Your application middleware configuration is not suitable for high load (i.e. there is a limit of concurrent sessions and requests are queuing up instead of being processed), check out Web Performance Optimization: Top 3 Server and Client-Side Performance Tips for overall ideas what could be looked at
Your application code doesn't utilize underlying OS resources efficiently, consider using profiler tool to see what's going on under the hood.
JMeter may fail to send requests fast enough, make sure to follow JMeter Best Practices and if JMeter's machine is overloaded - consider going for Distributed Testing
I followed this tutorial and there is configuration connections per host.
What is this?
connectionsPerHost are the amount of physical connections a single Mongo client instance (it's singleton so you usually have one per application) can establish to a mongod/mongos process. At time of writing the java driver will establish this amount of connections eventually even if the actual query throughput is low (in order words you will see the "conn" statistic in mongostat rise until it hits this number per app server).
There is no need to set this higher than 100 in most cases but this setting is one of those "test it and see" things. Do note that you will have to make sure you set this low enough so that the total amount of connections to your server do not exceed
Found here How to configure MongoDB Java driver MongoOptions for production use?