I have a requirements to record all incoming and outgoing traffic to my application loadbalancer. I have a tool from F5 (install in EC2) to receive the traffic and process and perform actions (So I can setup ELB+ASG for this). However I want the traffic should go to the web server (Apache+PHP), so that my application also will work well.
I know GuardDuty and VPC flow logs are some alternate. But there are some limitation (It didn't capture all events comes to EC2 instance). Hence I need to rely some third party tools such as F5, checkpoint.
Regards
Senthil
Related
Our infrastructure is composed by
1 F5 load balancer
3 nodes
We have an application which uses websockets, so when a user goes to our site, it opens a websocket to the balancer which it connects to the first available node, and it works as expected.
Our truobles arrives with maintenance tasks, when we have to update our software, we need to turn offline 1 node at a time, deploy the new release and then turn it on again. Doing this task, the balancer drops the open websocket connections to the node and the clients retries to connect after few seconds to the first available nodes, creating an inconvenience for the client because he could miss a signal (or more).
How we can keep the connection between the client and the balancer, changing the backend websocket server? Is the load balancer enough to achieve our goal or we need to change our infrastructure?
To avoid this kind of problems I recommend to read about the Azure SignalR. With this you don't need to thing about stuff like load balancer, redis backplane and other infrastructures that you possibly need to a WebSockets connection.
Basically the clients will not connected to your node directly but redirected to Azure SignalR. You can read more about it here: https://learn.microsoft.com/en-us/azure/azure-signalr/signalr-overview
Since it is important to your application to maintain the connection, I don't see how any other way to archive no connection drop to your nodes, since you need to shut them down.
It's important to understand that the F5 is a full TCP proxy. This means that the F5 is the server to the client and the client to the server. If you are using the websockets protocol then you must apply a websockets profile to the F5 Virtual Server in order for the websockets application to be handled properly by the Load Balancer.
Details of the websockets profile can be found here: https://support.f5.com/csp/article/K14754
If a websockets and an HTTP profile are applied to the Virtual Server - meaning that you have websockets and web traffic using the same port and LB nodes - then the F5 will allow the websockets traffic as passthrough. Also keep in mind that if this is an HTTPS virtual sever that you will need to ensure a client and server side HTTPS profile (SSL offload) are applied to the Virtual Server.
While there are a variety of ways that you can fiddle with load balancers to minimize the downtime caused by a software upgrade, none of them solve the problem, which is that your application-layer protocol seems to not tolerate some small network outages.
Even if you have a perfect load balancer and your software deploys cause zero downtime, the customer's computer may be on flaky wifi which causes a network dropout for half a second - or going over ethernet and someone reconfigures some routing on their LAN, etc.
I'd suggest having your server maintain a queue of messages for clients (up to some size/time limit) so that when a client drops a connection - whether it be due to load balancers/upgrades - or any other reason, it can continue without disruption.
In server-side load balancing, the clients call an intermediate server, which then decides which instance of the actual server (or microservice) to call.
In client-side load balancing also, the clients call an intermediate server (the API gateway - Zuul for instance, configured with a load-balancer - Ribbon for instance and a naming server - Eureka for instance), which then decides which instance of the microservice to call.
Unless we include the API gateway as part of the client, the client still doesn't know the IP address of the exact server to which it should send the request. Seems to me, to be a lot like server-side load-balancing. Is there something I'm missing?
(Including the API gateway as part of client seems weird, since its usually deployed on a different server from the client)
In Client Side load balancing, the Client is doing the heavy lifting of discovery and connection to the origin server. The client may reference a lookup (Eureka, Consul, maybe DDNS), to discover what the end destination is and the registry will dole out a valid origin. The communication is direct, client to server without a middle man.
In Server Side load balancing, the client is dumb, and makes a call to a predetermined address (usually DNS or static IP). That device then either proxies (TCP or protocol level) the connection to the origin server based on either a lookup, heartbeat, etc.
I've seen benefits in client side routing in that as long as you have IP connectivity between client and server, the work of the infrastructure is trivial to add new services, locations, products, apps, etc. As long as the new server can "register" with the registry, and the client has IP access to the server, it just works and IT does not have to be involved in rolling out your new service.
The drawback is it makes the client a little more heavy, it does require IP access direct from client to server, and may be confusing for traditional IT folks and auditors. Each client needs to be aware of the registry and have code to make calls (or use a sidecar/sidekick).
I've seen it in practice where a group started to transition their apps to a Docker environment, and they were able to run their Docker based apps along side their non-docker versions at the same time w/o having to get IT involved and do a lot of experimentation and testing quickly and autonomously.
If you have autonomous teams, are highly advanced on the devops spectrum, and have a lot of trust with your teams, Client Side routing and load balancing may be a good experience for you.
I have two different service fabric applications. Both are stateless web api models. I do have a situation that from service 1 inside application 1, I need to invoke service 2 which is part of application 2. I am deploying both applications in the same cluster. Can someone advise the best practice here. What could be best way to communicate. Please provide some sample as well.
Fabric Transport (aka Service Remoting) is the sdk built-in communication model. Compared to communication over HTTP or WCF it does a little more, especially on the client side of the communication.
When it comes to communicating with Service Fabric services (or really, any distributed systems service) your communication should take into account that the connection could be fail to established on an initial try, or be interrupted mid communication and that you really shouldn't build your solution to expect it to always work flawlessly. The reason for this is in the nature of how Service Fabric at any time can decide to move primaries from a node to another node, the nodes themselves can go down and the services can crash. Nothing strange about he great thing with Service Fabric is that it does a lot of the heavy lifting for you when it comes to maintaining your services and nodes over time.
So, in terms of communication this means that a client needs to be able to do three things (for it to truly work in a distributed environment);
resolve the address to the service (figure out which node it is on, which port it is listening on, which partition id and replica to target and so on)
connect to the service, package and send requests and then recieve and unpack responses
retry the resolve and connect if the communication fails
Fabric Transport does all this when you are using the Service Remoting clients (like ServiceProxy) and service side listeners.
Thats the good part with Fabric Transport, you get all that out of the box and most of the time you don't have to change the default setup either. The bad part is that it only works for communication inside the cluster, i.e. you cannot communicate from the outside to a service running in the cluster using Fabric Transport. For that you need HTTP or WCF.
HTTP(s) and WCF (over HTTP(s)) communication allow you to build your own clients and handle the communication yourself. There are a number of samples on how you can do the resolve, connect and retry for HTTP clients, this one for instance
According to Microsoft there are three built-in communication options. It's up to you to decide which one works best for you. I'm personally using service remoting which is easy to quickly set up. It also allows you to exception handling in your client service.
Is that called "clustering" of servers? When a web request is sent, does it go through the main server, and if the main server can't handle the extra load, then it forwards it to the secondary servers that can handle the load? Also, is one "server" that's up and running the application called an "instance"?
[...] Is that called "clustering" of servers?
Clustering is indeed using transparently multiple nodes that are seen as a unique entity: the cluster. Clustering allows you to scale: you can spread your load on all the nodes and, if you need more power, you can add more nodes (short version). Clustering allows you to be fault tolerant: if one node (physical or logical) goes down, other nodes can still process requests and your service remains available (short version).
When a web request is sent, does it go through the main server, and if the main server can't handle the extra load, then it forwards it to the secondary servers that can handle the load?
In general, this is the job of a dedicated component called a "load balancer" (hardware, software) that can use many algorithms to balance the request: round-robin, FIFO, LIFO, load based...
In the case of EC2, you previously had to load balance with round-robin DNS and/or HA Proxy. See Introduction to Software Load Balancing with Amazon EC2. But for some time now, Amazon has launched load balancing and auto-scaling (beta) as part of their EC2 offerings. See Elastic Load Balancing.
Also, is one "server" that's up and running the application called an "instance"?
Actually, an instance can be many things (depending of who's speaking): a machine, a virtual machine, a server (software) up and running, etc.
In the case of EC2, you might want to read Amazon EC2 Instance Types.
Here is a real example:
This specific configuration is hosted at RackSpace in their Managed Colo group.
Requests pass through a Cisco Firewall. They are then routed across a Gigabit LAN to a Cisco CSS 11501 Content Services Switch (eg Load Balancer). The Load Balancer matches the incoming content to a content rule, handles the SSL decryption if necessary, and then forwards the traffic to one of several back-end web servers.
Each 5 seconds, the load balancer requests a URL on each webserver. If the webserver fails (two times in a row, IIRC) to respond with the correct value, that server is not sent any traffic until the URL starts responding correctly.
Further behind the webservers is a MySQL master / slave configuration. Connections may be mad to the master (for transactions) or to the slaves for read only requests.
Memcached is installed on each of the webservers, with 1 GB of ram dedicated to caching. Each web application may utilize the cluster of memcache servers to cache all kinds of content.
Deployment is handled using rsync to sync specific directories on a management server out to each webserver. Apache restarts, etc.. are handled through similar scripting over ssh from the management server.
The amount of traffic that can be handled through this configuration is significant. The advantages of easy scaling and easy maintenance are great as well.
For clustering, any web request would be handled by a load balancer, which being updated as to the current loads of the server forming the cluster, sends the request to the least burdened server. As for if it's an instance.....I believe so but I'd wait for confirmation first on that.
You'd' need a very large application to be bothered with thinking about clustering and the "fun" that comes with it software and hardware wise, though. Unless you're looking to start or are already running something big, it wouldn't' be anything to worry about.
Yes, it can be required for clustering. Typically as the load goes up you might find yourself with a frontend server that does url rewriting, https if required and caching with squid say. The requests get passed on to multiple backend servers - probably using cookies to associate a session with a particular backend if necessary. You might have the database on a separate server also.
I should add that there are other reasons why you might need multiple servers, for instance there may be a requirement that the database is not on the frontend server for security reasons
Windows NLB works great and removes computer from the cluster when the computer is dead.
But what happens if the application dies but the server still works fine? How have you solved this issue?
Thanks
By not using NLB.
Hardware load balancers often have configurable "probe" functions to determine if a server is responding to requests. This can be by accessing the real application port/URL, or some specific "healthcheck" URL that returns only if the application is healthy.
Other options on these look at the queue/time taken to respond to requests
Cisco put it like this:
The Cisco CSM continually monitors server and application availability
using a variety of probes, in-band
health monitoring, return code
checking, and the Dynamic Feedback
Protocol (DFP). When a real server or
gateway failure occurs, the Cisco CSM
redirects traffic to a different
location. Servers are added and
removed without disrupting
service—systems easily are scaled up
or down.
(from here: http://www.cisco.com/en/US/products/hw/modules/ps2706/products_data_sheet09186a00800887f3.html#wp1002630)
Presumably with Windows NLB there is some way to programmatically set the weight of nodes? The nodes should self-monitor and if there is some problem (e.g. a particular node is low on disc space), set its weight to zero so it receives no further traffic.
However, this needs to be carefully engineered and have further human monitoring to ensure that you don't end up with a situation where one fault causes the entire cluster to announce itself down.
You can't really hope to deal with a "byzantine general" situation in network load balancing; an appropriately broken node may think it's fine, appear fine, but while being completely unable to do any actual work. The trick is to try to minimise the possibility of these situations happening in production.
There are multiple levels of health check for a network application.
is the server machine up?
is the application (service) running?
is the service accepting network connections?
does the service respond appropriately to a "are you ok" request?
does the service perform real work? (this will also check back-end systems behind the service your are probing)
My experience with NLB may be incomplete, but I'll describe what I know. NLB can do 1 and 2. With custom coding you can add the other levels with varying difficulty. With some network architectures this can be very difficult.
Most hardware load balancers from vendors like Cisco or F5 can be easily configured to do 3 or 4. Level 5 testing still requires custom coding.
We start in the situation where all nodes are part of the cluster but inactive.
We run a custom service monitor which makes a request on the service locally via the external interface. If the response was successful we start the node (allow it to start handling NLB traffic). If the response failed we stop the node from receiving traffic.
All the intermediate steps described by Darron are irrelevant. Did it work or not is the only thing we care about. If the machine is inaccessible then the rest of the NLB cluster will treat it as failed.