I'm new to load balancer and Sticky Session. My understanding of Sticky session is that all request of one instance will be served via only one service( please correct me if I'm wrong).
I have a requirement to test the working of sticky session with load balancer. After some finding on google I have come across with a plan which is sending multiple request(using JMeter) to Load Balancer with more than one instance and to trace the IP address that is responding for each instance( which should be unique).
Please help me by validating the above plan or suggest me if any other ways is there to test.
Thank you with Regards,
Manikandan
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I wrote a Jmeter test (that uses different user credentials) to load test a web app which has a load balancer and all it forwards the requests to a single node. How can I solve this?
I used the DNS Cache manager but that did not work.
Are there any other tools which I could use? (I looked into AWS Load testing but that too won't work because all the containers would get the same set of user credentials and when parallel tests are run they would fail.)
It depends on the load balancing mechanism used in your load balancer, it might be the case it's looking into the source IP address and forwarding requests from the same IP to the same backend node. You can try using multiple IP addresses (or aliases) and see whether it makes the difference. See IP Spoofing With JMeter: How to Simulate Requests from Different IP Addresses article for more details.
Also adding DNS Cache Manager might be not sufficient, you can try configurign a custom DNS resolver, i.e. 1.1.1.1 as the DNS server so each thread would resolve the underlying IP address on its own
We are using 2 servers and have setup load balancer to redirect the trafic. Both servers are Compute engines.
We are also using websocket (socket.io) to keep the connection between users (online and offline status). When connection is established between users, it gets disconnected after few seconds. We concluded that it is load balancer configuration issue as if we use single server (without load balancer), connection remains alive until user goes offline.
We need help here if we need to do anything extra in load balancer configurations to work it smoothly with websocket.
Using ip addresses, not domain name (if that makes any difference)
I do have architecture of a Load balancer followed by two Web Application server and Database, I am hitting thousands of HTTP requests to the server from Jmeter distributed testing environment.
At the time of getting response back, few request does not get response back from the server.
I checked Database logs, 100 % requests were responded.
Checked with Web Application servers access logs, 100 % requests were responded.
Can Load balancer cause the damage traversing these pending responses to the respective clients?
Every time different different request are getting stuck.
Thanks in Advance!!
If you suspect load balancer, look at 3 typical causes first:
Server takes longer to respond than load balancer is waiting
Client has shorter timeout than it takes for server to respond.
Port/thread/connection exhaustion on load balancer, or other LB configuration problems
In all three cases, I suggest looking at the load balancer logs. Since you didn't specify which LB you are using, I cannot say exactly how the log looks, but typically LB log gives you option to see:
How long it took for a request to be sent to a web server and for the response from the web server to return to load balancer. You can them compare those numbers to timeouts configured for load balancer and the client (problem 1 and 2).
How long it took for a request from the client to be processed by LB and how long LB took to respond to a client. If it takes long, then something is not right with load balancer (problem 3)
And then of course if you have any errors on load balancer, they may just explain what's going on.
If you cannot review logs for load balancer, I suggest changing your JMeter test temporarily to target servers behind load balancer directly. You can even configure your script to evenly distribute load between all servers (for example by using multiple thread groups). That would allow you to isolate the problem, and get more information on what's going on.
This is a general question based on how web sessions work across multiple servers, my knowledge around web sessions is not very deep but afaik a web session is typically stored directly in memory of the running web server application so when a request comes in it doesn't have to make database requests to fetch the session data. If a popular website needs multiple servers to handle the level of traffic it is receiving, when a request comes in I assume that it could get directed to any of the servers by some load balancer, but how does the server handling that request get the associated session data if the previous request was handled by a different server? do multi server sites require special session handling infrastructure, or do the load balancers know some how to route requests from the same client to the same server?
This question on ServerFault is the same as this question. with a good answer. in overview there are 3 common methods:
Session information stored in cookies only
Load balancer always directs user to the same machine
Shared backend database or key/value store.
See link for more indepth details of each.
What is the difference between session affinity and sticky session in context of load balancing servers?
I've seen those terms used interchangeably, but there are different ways of implementing it:
Send a cookie on the first response and then look for it on subsequent ones. The cookie says which real server to send to.
Bad if you have to support cookie-less browsers
Partition based on the requester's IP address.
Bad if it isn't static or if many come in through the same proxy.
If you authenticate users, partition based on user name (it has to be an HTTP supported authentication mode to do this).
Don't require state.
Let clients hit any server (send state to the client and have them send it back)
This is not a sticky session, it's a way to avoid having to do it.
I would suspect that sticky might refer to the cookie way, and that affinity might refer to #2 and #3 in some contexts, but that's not how I have seen it used (or use it myself)
As I've always heard the terms used in a load-balancing scenario, they are interchangeable. Both mean that once a session is started, the same server serves all requests for that session.
Sticky session means that when a request comes into a site from a client all further requests go to the same server initial client request accessed. I believe that session affinity is a synonym for sticky session.
They are the same.
Both mean that when coming in to the load balancer, the request will be directed to the server that served the first request (and has the session).
Sticky session means to route the requests of particular session to the same physical machine who served the first request for that session.
This article clarifies the question for me and discusses other types of load balancer persistence.
Dave's Thoughts: Load balancer persistence (sticky sessions)
difference is explained in this article:
https://www.haproxy.com/blog/load-balancing-affinity-persistence-sticky-sessions-what-you-need-to-know/
Main part from this link:
Affinity: this is when we use an information from a layer below the application layer to maintain a client request to a single server. Client's IP address is used in this case. IP address may change during same session and then connection may switch to different server.
Persistence: this is when we use Application layer information to stick a client to a single server. In this case, loadbalancer inject some cookie in response and use same cookie in subsequent request to route to same server.
sticky session: a sticky session is a session maintained by persistence
The main advantage of the persistence over affinity is that it’s much more accurate, but sometimes, Persistence is not doable(when client dont allow cookies like cookie less browser), so we must rely on affinity.
Using persistence, we mean that we’re 100% sure that a user will get redirected to a single server.
Using affinity, we mean that the user may be redirected to the same server…
They are Synonyms.
No Difference At all
Sticky Session / Session Affinity:
Affinity/Stickiness/Contact between user session and, the server to which user request is sent is retained.