I have the following use case that I would appreciate any input on. I have a Docker Swarm running with Traefik pointed to it for ingress and routing. Currently I have it as a single service that is defined to have 6 replicas of the same image, so works out to be two containers each on three nodes.
The containers basically host a GraphQL server and my requirement is that depending on which client the request is coming from, it always goes to the same specific container (ie replica). So as an example say I have user1 and user2 at client1 and user3 and user4 at client2, if user1 makes a request and it goes to replica1, then if user2 makes a request it MUST go to replica1 as well. So basically, I could take a numeric hash on the client id (client1) and mod 6 it and decide which replica it goes to and in that way make sure any subsequent calls from any user in that client id goes to the same replica. Additionally, that information of what client the call is coming from is coded in a JWT token that the user sends in their request.
Any idea how I would go about changing my Docker Swarm to implement this? My best guess is to change the swarm to not be 6 replicas and instead define each container as a separate service with its own port. Then I could potentially point Traefik to nginx or something similar which would then receive the request, grab the JWT, decode it to find the client id, take a hash and then internally route it to the appropriate node:port combination.
But I feel like there must be a more elegant and simpler way of doing this. Maybe Traefik could facilitate this directly somehow or Docker Swarm has some configuration that I don't know about, that could be used. Any ideas?
Edit: Just to clarify my usecase, not just looking for the same user to always go to the same container but the same type of user to always go to the same container
For this kind of routing you need to setup Traefik for Sticky Sessions
This is a Traefik middleware that adds a cookie to responses that is used in subsequent requests to route to the same service.
Related
We have a multiservice architecture consisting of HAProxy front end ( we can change this to another proxy if required), a mongodb database, and multiple instances of a backend app running under Docker Swarm.
Once an initial request is routed to an instance ( container ) of the backend app we would like all future requests from mobile clients to be routed to the same instance. The backend app uses TCP sockets to communicate with a VoIP PBX.
Ideally we would like to control the number of instances of the backend app using the replicas key in the docker-compose file. However if a container died and was recreated we would require mobile clients continue routing to the same container. The reason for this is each container is holding state info.
Is this possible with Docker swarm? We are thinking each instance of the backend app when created gets an identifier which is then used to do some sort of path based routing.
HAproxy has what you need. This article explains all.
As a conclusion of the article, you may choose from two solutions:
IP source affinity to server and Application layer persistence. The latter solution is stronger/better than the first but it requires cookies.
Here is an extras from the article:
IP source affinity to server
An easy way to maintain affinity between a user and a server is to use user’s IP address: this is called Source IP affinity.
There are a lot of issues doing that and I’m not going to detail them right now (TODO++: an other article to write).
The only thing you have to know is that source IP affinity is the latest method to use when you want to “stick” a user to a server.
Well, it’s true that it will solve our issue as long as the user use a single IP address or he never change his IP address during the session.
Application layer persistence
Since a web application server has to identify each users individually, to avoid serving content from a user to an other one, we may use this information, or at least try to reproduce the same behavior in the load-balancer to maintain persistence between a user and a server.
The information we’ll use is the Session Cookie, either set by the load-balancer itself or using one set up by the application server.
What is the difference between Persistence and Affinity
Affinity: this is when we use an information from a layer below the application layer to maintain a client request to a single server
Persistence: this is when we use Application layer information to stick a client to a single 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, 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…
Affinity configuration in HAProxy / Aloha load-balancer
The configuration below shows how to do affinity within HAProxy, based on client IP information:
frontend ft_web
bind 0.0.0.0:80
default_backend bk_web
backend bk_web
balance source
hash-type consistent # optional
server s1 192.168.10.11:80 check
server s2 192.168.10.21:80 check
Session cookie setup by the Load-Balancer
The configuration below shows how to configure HAProxy / Aloha load balancer to inject a cookie in the client browser:
frontend ft_web
bind 0.0.0.0:80
default_backend bk_web
backend bk_web
balance roundrobin
cookie SERVERID insert indirect nocache
server s1 192.168.10.11:80 check cookie s1
server s2 192.168.10.21:80 check cookie s2
I'm currently developing a Wolkenkit application which is run on my local machine.
I want to upload a file from the Wolkenkit app to the blob server (as documented here).
When sending a POST request from the server to https://local.wolkenkit.io:3001/, Node.js gives me the error ECONNREFUSED.
I've tested the POST-Request with another program and it works there. Any idea why it doesn't work from the wolkenkit application itself?
Thanks!
The Storing files sample you linked to shows code that is to be run in the browser, not in the backend itself. Of course, both should work, but there are a few minor differences you need to watch out for.
Fixing the host name
First, I suppose that local.wolkenkit.io in your case maps to 127.0.0.1, which is the default for wolkenkit. That means that when you try to connect to this domain from within a Docker container, the container does not try to call out to the blog storage container, but it stays within itself. So, the first thing that needs to be fixed is the host name.
Basically, there are two options for this: You can either setup local.wolkenkit.io so that it resolves to the external IP address of your machine. This would work, but is pretty cumbersome. The other option is to directly address the appropriate container that is responsible for blob storage, by its internal name. The internal name is <name-of-your-app>-depot-file. So you need to replace https://local.wolkenkit.io:3001/ by https://<...>-depot-file.wolkenkit.io:3001/.
Fixing the port
Second, the port is wrong. This is because the blob storage service is internally running on port 3000, externally on 3001. So instead of https://<...>-depot-file.wolkenkit.io:3001/ you need to use https://<...>-depot-file.wolkenkit.io:3000/.
Once you have done this you should not get any more errors like ECONNREFUSED, since now the service can be found.
Fixing SSL issues
Third, since you are now connecting to the blob storage service using a different domain name, the SSL certificate doesn't match any more, since it was issued for local.wolkenkit.io. As a result, you will get SSL errors when trying to connect.
The simplest way to get around this is to disable any SSL checks (albeit this is also the most insecure way to handle this!). How to do this depends on the HTTP client module you are using. E.g., in request there is an option called strictSSL that you can set to false.
Of course, what you actually should do is to either use a custom certificate which includes this domain name as well, or to write a function that handles the certificate check and accepts the presented one, especially in this case.
If you do all of this, things should work :-)
PS: I am one of the authors of wolkenkit. Thanks a lot for bringing up this issue, and we will take care of this in the future, to make storing blobs easier.
I am working with a Synology NAS type aDS716+II, DSM 6.1.4-15217 Update 2 on wich runs Docker with a Jira container.
So now what I want to do I'm assinged to get to work is to access Jira's webinterface with let's say jira.synology.local with synology being the servername.
I read a lot about nginx and how it's built in since DSM 6.X but I don't seem to get it to work properly at all.
I can access Jira's webinterface from another machine within the LAN via IP_OF_SYNOLGY:PORT so when setting up a reverse proxy on the server it should be pointing to LOCALHOST:PORT right? I have also tried using the actual IP instead of LOCALHOST but without success.
I can access the interface of Synology itself not only via IP_OF_SYNOLGY:PORT but also via DOMAINNAME.LOCAL if I set the domain name.
I really don't know what I'm missing and I tried everything I could think of. Does someone has experience with this?
If some information is missing, I'll gladly provide it. I'm fairly new to synology I have to admit. Thanks in advance!
So this has gotten zero response but I figured probably someone will have a similar "problem" in the future, so I will answer anyway.
I solved everything, when I setup Active Directory. When installing AD, the DNS-Server will automatically be installed too.
So we have JIRA running in a Docker container (on port, let's say, 12345) and I want to access it via the LAN on jira.domainname.
To do so we need to have installed DSM6.X or higher (for nginx) and the DNS-Server. That's it.
In the DNS-Server you will have to create a new master zone
and apply the following settings, whereas you can freely choose the domain name and Master DNS server must be the IP of your synology station, since it functions as a DNS
Then you want to edit the Resource Record
There you want to add an A Record Resource
and an CNAME Record Resource
So your Resource Records will look like this
Now the last step for setting up the DNS server is to tell it what to do if there is no specific record for a query. So for example if you want to open jira.domainname in your browser, there is a specific record for that and the DNS server knows how to direct it. But if you want to open up for example google.com the DNS server has no information on that and does now know what to do. So what we do now is to to tell the DNS server to forward the request, if it has no records for a request. To do so, enable the forwarders and put in the IP of your gateway/ managed switch as primary and some public DNS server (8.8.8.8 for one of google's DNS server) as secondary.
Please remember that jira.domainname shall always be the domainname you choose and 192.168.0.200 shall always be the IP of your synology station.
So now the DNS server is completely setup. Now we want to take advantage of the built-in reverse proxy (which runs on nginx in the background). To do so we navigate as seen here
and create a new reverse proxy rule
So now that the URL's can point to the same destination (your synology, 192.168.0.200) but on different Port. That comes in very handy for some applications running in docker.
So now if you are running this in an home setup or small office, you probably are working with standard issue commercial router such as for example a FritzBox by AVM. Those are pretty good but beware that some prohibit the so called DNS Rebinding which means that DNS requests pointing to a local IP will be not allowed. Since in this setup the DNS server (your synology) and the destination JIRA (also your synology) are in the same LAN, we have to create an exception. Probably other routers don't suppress those requests, but if so exceptions are necessary.
So the next step, it to tell your Gateway or managed switch that it has to use the newly setup DNS server as the primary DNS server. For FritzBox' you can do so here
put in the IP of your DNS server and an secondary DNS server. This is important as a fallback solution if your DNS server probably stops working at some point.
Now that everything is setup I would recommend to restart the router/ managed switch, synology and the workstation you are working on, to flush all caches. After that you can simply open your browser and type in jira.domainname and JIRA should open up. You can also open a terminal/ cmd and type in nslookup jira.domainname to see if it is being resolved correctly.
I really hope this will help someone at some point and if there are any additional questions, please feel free to comment this or write me directly!
I'm trying to figure out how these all work together, and there are bits and pieces of information all over the internet.
Here's what I (think) I know:
1) When you enter a url into your browser that gets looked up in a domain name server (DNS), and you are sent an IP address.
2) Your computer then follows this IP address to a server somewhere.
3) On the server there are nameservers, which direct you to the specific content you want within the server. -> This step is unclear to me.
4) With this information, your request is received and the server relays site content back to you.
Is this correct? What do I have wrong? I've done a lot of searching over the past week, and the thing I think I'm missing is the big picture explanation of how all these details tie together.
Smaller questions:
a) How does the nameserver know which site I want directions to?
b) How can a site like GoDaddy own urls? Why do I have to pay them yearly fees, and why can't I buy a url outright?
I'm looking for a cohesive explanation of how all this stuff works together. Thanks!
How contents get loaded when I put a URL in a browser ?
Well there some very well docs available on this topic each step has its own logic and algorithms attached with it, here I am giving you a walk through.
Step 1: DNS Lookup : Domain name get converted into IP address, in this process domain name from the URL is used to find IP address of the associated server machine by looking up records on multiple servers called name servers.
Step 2: Service Request : Once the IP address is known, as service request depending on protocol is created in form of packets and sent to the server machine using IP address. In case of a browser normally it will be a HTTP request; in other cases it can be something else.
Step 3: Request handling: Depending on the service request and underlying protocol, request is handled by a software program which lives normally on the server machine whose address was discovered in previous step. As per the logic programmed on the server program it will return a appropriate response in case of HTTP its called HTTP Response.
Step 4: Response handling: In this step the requesting program in your case a browser receives the response as mentioned in the previous step and renders it and display it as per defined in the protocol, in case of HTTP a HTTP body is extracted and rendered, which is written in HTML.
How does the nameserver know which site I want directions to
URL has a very well defined format, using which a browser find out a hostname/domain name which is used in turn to find out the associated IP address; there are different algorithms that name-servers runs to find out the correct server machine IP.
Find more about DNS resolution here.
How can a site like GoDaddy own urls? Why do I have to pay them yearly fees, and why can't I buy a url outright?
Domain name are resources which needed management and regulation which is done ICANN they have something called registries from which registrar(like GoDaddy) get domains and book them for you; the cost you pay is split up between ICANN and registrar.
Registrar does a lot of work for you, eg setup name server provide hosting etc.
Technically you can create you own domain name but it won't be free off course because you will need to create a name server, need to replicate it other servers and that way you can have whatever name you want (has too be unique); a simple way to do that is by editing your local hosts files in linux it is located at /etc/hosts and in windows it is located at C:\Windows\System32\drivers\etc\hosts but its no good on internet, since it won't be accepted by other servers.
(Precise and detailed description of this process would probably take too much space and time to write, I am sure you can google it somewhere). So, although very simplified, you have pretty good picture of what is going on, but some clarifications are needed (again, I will be somewhat imprecise) :
Step 2: Your computer does follow the IP address received in step 1, but the request set to that IP address usually contains one important piece of information called 'Host header', that is the actual name as you typed in your browser.
Step 3: There is no nameserver involved here, the software(/hardware) is usually called 'webserver' (for example Apache, IIS, nginx etc...). One webserver can serve one or many different sites. In case there are more than one, webserver will use the 'Host header' to direct you to the specific content you want.
ICAAN 'owns' the domain names, and the registration process involves technical and administrative effort, so you pay registrars to handle that.
This seems to have something to do with the subnet/availability zone, but I'm new to using a VPC and it's eluding me.
VPC: 10.80.0.0/16
subnet: 10.80.1.0/24 (us-east-1b)
subnet: 10.80.2.0/24 (us-east-1a)
All instances are Windows Server 2012.
I have an internet facing ELB created within my VPC (10.80.0.0/16). There is one instance added from AZ us-east-1a, which is on subnet 10.80.2.0/24. The instance is running IIS 7.5, with an app running on port 80 and /health.aspx set up for use as the ELB health check.
Internal traffic on the VPC is flowing normally (unrestricted). I can request health.aspx from this instance from another instance in us-east-1b (10.80.1.0/24). I can also copy files from one instance to another.
Outbound traffic is unrestricted. I can RDP to the instance (when connected to our VPN) and open a browser and request a web page and get it.
The ELB says the instance is healthy and I can see the requests to health.aspx in the IIS logs. Both the ELB and the instance are configured with a security group that allows 80 and 443.
But if I try to request {elb-url}/health.aspx over the open internet the request just times out. Similarly, with an elastic IP associated to the instance, a request to {elastic-ip}/health.aspx times out.
#Chris, thanks for the response...as it happens, I've already worked it out with some help from a friend. I'll post my findings here for posterity (in case anybody else was similarly confused about how ELB works).
This would be more clear with a diagram. But the summary is that in each availability zone, you need to create both a public and a private subnet. When you add availability zones to your ELB, you need to select the public subnet for the zone. This had already been done in us-east-1b before I got to this setup, and I had simply missed this nuance of ELB configuration. So for the new availability zone, I had to do this...
us-east-1c
private subnet 10.1.3.0/24 (using nat instance as default route)
public subnet 10.1.4.0/24 (using internet gateway as default route)
Then my instance goes in the private subnet as expected.
And the lynch pin of this whole thing is (drum roll....)
When I add us-east-1c to my ELB, I have to select the public subnet...10.1.4.0. Otherwise the instances will pass the health check (since the ELB can communicate with any instance within my entire VPC) but the responses from the servers cannot make it back out to the public internet.
This is what is so confusing. And I still don't fully understand it. The instance can make a request for, say, www.google.com. I can RDP to it and open a browser and get the web page. But a request from a host (like my laptop at my house) will die. strange.
PS: another note...make sure you are using enough NAT instance for your load. I think we ran into an issue where our NAT instance simply ran out of ports because too many web servers were trying to route outbound connections to 3rd party APIs through it. Quite honestly, I'm not good enough at this level of network/OS troubleshooting to be sure. But my theory is that our 8 instances of IIS were holding too many connections open to the NAT instance. We were also abusing the NIC on that micro instance. I upped us to two large instances, one per AZ and things smoothed back out. Both NAT instances are humming and we're not seeing the hung processes in IIS anymore.
Debugging this kind of issue is always a challenge. I have a few ideas to suggest based on what you have written (and generally apply to trying to solve this problem) that come from dealing with this a number of times.
Have you checked both the security groups and network ACLs? Bear in mind that all network ACLs need to be specified in both directions, as they are stateless. Also bear in mind that ELBs are a bit unique in this regard. While they are associated with your VPC, they sometimes need extra rules to ensure connectivity. In the past I have debugged this by opening all network ACLs on all ports, then removing these rules until it has stopped working in order to identify where the block was.
Security groups should be checked too. They are stateful but ensure that your load balancer has permissions to be hit from the web.
Have you checked this isn't an application configuration problem? I don't know how IIS comes out of the box but I would check it is setup to respond to all hostnames.
Check the ELB isn't an internal one, as that wouldn't be publically addressable.
You say the ELB is configured with the health check, but it's worth checking you also have the listener setup for port 80? It's in a separate tab on the dashboard and you will need this in addition to the health check for connectivity through the ELB.
Hope one of these tips is useful to you.