Load Balancer quickstart

Enable Load Balancer on a connector, add a second address with a weight, and take one address out of rotation.

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This guide instructs you through spreading the requests of your first connector across two origin servers with Load Balancer.

  • Enable Load Balancer on the connector, and add a second address with a weight for each address.
  • Send repeated requests through your workload and see answers from both servers.
  • Take one address out of rotation, and see every request reach the other one.

Four parts make the chain, listed in the order this guide uses them:

  1. The connector from the Connectors quickstart gets Load Balancer and the Round Robin method.
  2. The addresses of the connector become two: httpbin.org, with a weight of 2, and httpbingo.org, with a weight of 1.
  3. The rule that sends every request under /anything to the connector stays as it is.
  4. The workload that serves your application receives the requests. Its deployment needs no change.

Both servers are public services that answer a request for /anything/get with a JSON copy of that request. Each one identifies itself in the server response header, so the response shows which address answered. To use your own servers, replace both hostnames with servers that hold the same content.

The prerequisites and the three stages show the steps of one interface at a time. Select yours:

Prerequisites

  • The result of the Connectors quickstart: the connector my-connector, and a rule that sends every request under /anything to it.
  • The workload domain of the workload that serves the application, of the form <id>.map.azionedge.net. This guide writes it as <workload-domain>.
  • curl, to send the requests to the workload domain.
  • The Azion CLI on your machine, authorized with a personal token.
  • The ID of the connector.
  • A personal token for the Authorization header.
  • The ID of the connector.

Enable Load Balancer and add an address

A connector holds one address until Load Balancer is on. With Load Balancer on, it holds up to 15 addresses, and a balancing method chooses one for each request. Round Robin takes the addresses in turn. For the bounds, refer to Connectors limits.

Each address carries a weight from 1 to 100, and a higher weight allocates more traffic to that address. The weight shapes the share of requests, not an exact split. Each address also carries a server role. Both addresses in this guide are Primary. A Backup address receives requests only when every primary address fails, and the IP Hash method refuses it. For more information, refer to Server role.

Every address of a connector receives the same Host header and the same transport protocol. Two changes to the connection options make one setting work for both servers:

  • The Host header becomes ${host}, the host the client requested, instead of httpbin.org. A fixed httpbin.org would send httpbingo.org a Host header that names a different server.
  • The connector reaches both servers over HTTP. Over HTTPS, httpbingo.org accepts only connections for its own name.

To enable Load Balancer with the Azion CLI, put the whole connector in a JSON file. The update command needs the full body, with every field the connector keeps. Save this body as connector.json:

JSON
01{
02 "name": "my-connector",
03 "active": true,
04 "type": "http",
05 "attributes": {
06 "addresses": [
07 {
08 "address": "httpbin.org",
09 "modules": { "load_balancer": { "server_role": "primary", "weight": 2 } }
10 },
11 {
12 "address": "httpbingo.org",
13 "modules": { "load_balancer": { "server_role": "primary", "weight": 1 } }
14 }
15 ],
16 "connection_options": {
17 "transport_policy": "force_http",
18 "host": "${host}"
19 },
20 "modules": {
21 "load_balancer": { "enabled": true, "config": { "method": "round_robin" } }
22 }
23 }
24}

modules.load_balancer on each address holds its role and weight. modules.load_balancer under attributes turns Load Balancer on, and config must carry at least one key.

Update the connector from the file. Replace <connector-id> with the ID of your connector. The command needs --type even though the file names the type:

azion update connector --connector-id <connector-id> --type http --file connector.json

The output confirms the update:

Updated Connector with ID <connector-id>

The connector has Load Balancer on and two active addresses. The settings that config leaves out take the API defaults: max_retries 0, connection_timeout 60, and read_write_timeout 120.

To enable Load Balancer with the API, send a PATCH request to the connector. Replace <connector-id> with the ID of your connector, and [TOKEN VALUE] with your personal token:

Shell
01curl --request PATCH \
02 --url https://api.azion.com/v4/workspace/connectors/<connector-id> \
03 --header 'Accept: application/json' \
04 --header 'Authorization: Token [TOKEN VALUE]' \
05 --header 'Content-Type: application/json' \
06 --data {
07 "attributes": {
08 "addresses": [
09 {
10 "address": "httpbin.org",
11 "modules": { "load_balancer": { "server_role": "primary", "weight": 2 } }
12 },
13 {
14 "address": "httpbingo.org",
15 "modules": { "load_balancer": { "server_role": "primary", "weight": 1 } }
16 }
17 ],
18 "connection_options": {
19 "transport_policy": "force_http",
20 "host": "${host}"
21 },
22 "modules": {
23 "load_balancer": { "enabled": true, "config": { "method": "round_robin" } }
24 }
25 }
26}

addresses replaces the list of addresses, and modules.load_balancer on each one holds its role and weight. modules.load_balancer under attributes turns Load Balancer on, and config must carry at least one key. A PATCH keeps the connection options the body leaves out.

The API answers with 202 and "state": "pending". The connector has Load Balancer on and two active addresses. The settings that config leaves out take the API defaults: max_retries 0, connection_timeout 60, and read_write_timeout 120.

To enable Load Balancer in Azion Console:

Open the Connectors page

Access Azion Console > Connectors.

Open your connector

Select my-connector, the connector from the Connectors quickstart.

Send the requested host in the Host header

In Host, enter ${host}.

Connect to the servers over HTTP

In Transport Protocol Policy, select Force HTTP.

Turn on Load Balancer

In Modules, turn on Load Balancer.

Select the balancing method

In Load Balancer Configuration, set Method to Round Robin.

Set the first address

Under Address Management, on httpbin.org, set Server Role to Primary and enter 2 in Weight.

Select Add Address
Enter the second address

In the new Address, enter httpbingo.org, without a protocol or a port.

Set the second address

Set Server Role to Primary and enter 1 in Weight.

Select Save

The Console shows Connector has been updated. The connector has Load Balancer on and two active addresses.

Confirm both addresses answer

The check is the same whichever interface changed the connector. In the commands, replace <workload-domain> with the workload domain of your workload.

A connector change takes several minutes to reach Azion’s distributed infrastructure, and data centers apply it at different times. Until then, some requests still reach httpbin.org alone, and some can return a 502 error page. Repeat the requests until both servers answer. For more information, refer to Propagation.

Send a request for a path under /anything, and print the response headers with the body:

curl -s -D - https://<workload-domain>/anything/get

Send the same request several times. An answer from httpbin.org carries this server header:

Text
01HTTP/2 200
02…
03server: gunicorn/19.9.0
04…

An answer from httpbingo.org carries this one:

Text
01HTTP/2 200
02…
03server: Fly/<version>
04via: 1.1 fly.io, 1.1 fly.io
05…

Both servers answer for the same path, so the connector spreads requests across both addresses.

The answers come in no fixed order. Each data center balances on its own, so a run of requests can favor one address, and the share varies from run to run. For more information, refer to Load Balancer.

Take an address out of rotation

An address with Active off stays on the connector and receives no requests. Use it to take a server out before maintenance, without deleting the address. This stage takes httpbingo.org out.

To take the address out with the Azion CLI, edit the connector.json you saved. Add "active": false to the httpbingo.org address:

JSON
01{
02 "name": "my-connector",
03 "active": true,
04 "type": "http",
05 "attributes": {
06 "addresses": [
07 {
08 "address": "httpbin.org",
09 "modules": { "load_balancer": { "server_role": "primary", "weight": 2 } }
10 },
11 {
12 "address": "httpbingo.org",
13 "active": false,
14 "modules": { "load_balancer": { "server_role": "primary", "weight": 1 } }
15 }
16 ],
17 "connection_options": {
18 "transport_policy": "force_http",
19 "host": "${host}"
20 },
21 "modules": {
22 "load_balancer": { "enabled": true, "config": { "method": "round_robin" } }
23 }
24 }
25}

Update the connector from the file:

azion update connector --connector-id <connector-id> --type http --file connector.json

The output confirms the update:

Updated Connector with ID <connector-id>

The address httpbingo.org is inactive, and it keeps its role and weight.

To take the address out with the API, send a PATCH request with both addresses, and "active": false on httpbingo.org:

Shell
01curl --request PATCH \
02 --url https://api.azion.com/v4/workspace/connectors/<connector-id> \
03 --header 'Accept: application/json' \
04 --header 'Authorization: Token [TOKEN VALUE]' \
05 --header 'Content-Type: application/json' \
06 --data {
07 "attributes": {
08 "addresses": [
09 {
10 "address": "httpbin.org",
11 "modules": { "load_balancer": { "server_role": "primary", "weight": 2 } }
12 },
13 {
14 "address": "httpbingo.org",
15 "active": false,
16 "modules": { "load_balancer": { "server_role": "primary", "weight": 1 } }
17 }
18 ]
19 }
20}

The body lists every address the connector keeps, because addresses replaces the list. The API answers with 202 and "state": "pending". The address httpbingo.org is inactive, and it keeps its role and weight.

To take the address out in Azion Console:

Open your connector

Access Azion Console > Connectors, and select my-connector.

Turn off the second address

Under Address Management, on httpbingo.org, turn off Active.

Select Save

The Console shows Connector has been updated. The address httpbingo.org is inactive.

The change reaches data centers at different times, as when you added the address. For several minutes, some requests still reach httpbingo.org. Send this request several times:

curl -s -D - https://<workload-domain>/anything/get

Once every data center holds the change, every answer carries the httpbin.org header:

Text
01HTTP/2 200
02…
03server: gunicorn/19.9.0
04…

No answer carries the Fly header. The connector sends every request to the active address, and httpbingo.org stays on the connector with its role and weight.

Next steps

Balancing methodsCompare Round Robin, Least Connections, and IP Hash, and see how weight and server role shape the choice.Balance traffic across multiple originsPlan primary and backup servers for an application that must keep answering through an outage.Connectors limitsThe bounds on addresses, weight, retries, and timeouts with Load Balancer on.Connector settingsEvery Load Balancer field, with its default in the API and in the Console.