Shift traffic between two origins by weight

You shift requests from one origin to another in steps, with the weights of the addresses of a Load Balancer connector, from Azion Console, the API, or the Azion CLI. To keep a standby out of traffic until the primary fails instead, refer to Add a backup origin to a connector.

Under Round Robin, each address receives a share of the requests in proportion to its weight, a whole number from 1 to 100. The weight sets a proportion, not an exact split: each data center balances on its own, so the share an address receives varies around the one its weight asks for. A weight cannot be 0, so an origin leaves the rotation through its Active switch, not through its weight.

mermaid

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02flowchart TD

03 Pool["Both origins on the connector, weighted"] --> Hold["Hold the current weights"]

04 Hold --> Errors{"New errors on the new origin?"}

05 Errors -->|"yes"| Back["Turn the new origin's address off"]

06 Errors -->|"no"| Share{"Does the new origin carry the share you want?"}

07 Share -->|"no"| Raise["Raise the new origin's weight"]

08 Raise --> Hold

09 Share -->|"yes"| Cut["Turn the old origin's address off"]

Both origins sit on one connector as Primary addresses, and the new origin starts with a small weight.
Hold each set of weights until the new origin has served enough requests to show its errors.
When new errors appear, turn the new origin’s address off to roll back.
When no new error appears, raise the new origin’s weight, and hold again.
When the new origin carries the share you want, turn the old origin’s address off to cut over.

Prerequisites

A connector of type http that reaches the current origin, and a rule whose Set Connector behavior sends requests to it. To create both, refer to Connectors quickstart.
A new origin that holds the same application as the current one. Every address of a connector receives the same Host header, so both origins must answer for the same name.
Access to Azion Console, for the Console procedure. Refer to Access Azion Console.
A personal token and the ID of the connector, for the API procedure.
The Azion CLI installed and authorized, and the ID of the connector, for the CLI procedure.

The examples use old-origin.example.com for the current origin and new-origin.example.com for the new one. Replace them with yours.

Put both origins on the connector

The connector gets Load Balancer with Round Robin, and the new origin joins as a second Primary address. A weight of 9 on the current origin and 1 on the new one sends about one request in ten to the new origin. A connector holds up to 15 addresses with Load Balancer on.

Host takes a name both origins answer for, such as ${host}, which sends the host the client requested. A literal name of the current origin would reach the new origin under a name it may not answer for. The examples set Max Retries, Connection Timeout, and Read/Write Timeout to 3, 30, and 60, the values the Console fills in. The API and the CLI give a key the body leaves out 0, 60, and 120.

To put both origins on the connector in Azion Console:

Open the connector

Access Azion Console > Connectors, and select the connector of the current origin.

Send a host both origins answer for

In Host, enter ${host}.

Turn on Load Balancer

In Modules, turn on Load Balancer. The form fills in Max Retries, Connection Timeout, and Read/Write Timeout.

Select Round Robin

In Load Balancer Configuration, set Method to Round Robin.

Weight the current origin

Under Address Management, on old-origin.example.com, set Server Role to Primary and enter 9 in Weight.

Select Add Address

Enter the new origin

In the new Address, enter new-origin.example.com, without a protocol or a port.

Weight the new origin

Set Server Role to Primary and enter 1 in Weight.

Select Save

The Console shows Connector has been updated.

To put both origins on the connector with the API, send a PATCH request. addresses replaces the list of addresses, so the body carries the current origin as well:

Shell

01curl --request PATCH \

02 --url https://api.azion.com/v4/workspace/connectors/<connector-id> \

03 --header 'Accept: application/json' \

04 --header 'Authorization: Token <personal-token>' \

05 --header 'Content-Type: application/json' \

06 --data {

07 "attributes": {

08 "addresses": [

09 {

10 "address": "old-origin.example.com",

11 "modules": { "load_balancer": { "server_role": "primary", "weight": 9 } }

12 },

13 {

14 "address": "new-origin.example.com",

15 "modules": { "load_balancer": { "server_role": "primary", "weight": 1 } }

16 }

17 ],

18 "connection_options": { "host": "${host}" },

19 "modules": {

20 "load_balancer": {

21 "enabled": true,

22 "config": { "method": "round_robin", "max_retries": 3, "connection_timeout": 30, "read_write_timeout": 60 }

23 }

24 }

25 }

26}

The API answers 202 with "state": "pending". A PATCH keeps the connection options the body leaves out.

The update command takes the whole connector from a file, with every field the connector keeps. To read the current settings of the connector:

azion describe connector --connector-id <connector-id> --format json

The command prints the full object. On a connector of type http, attributes holds addresses, connection_options, and modules.

Save the connector as connector.json, with both origins and Load Balancer on. Replace name and the other connection_options with the values the command printed:

JSON

01{

02 "name": "<connector-name>",

03 "active": true,

04 "type": "http",

05 "attributes": {

06 "addresses": [

07 {

08 "address": "old-origin.example.com",

09 "modules": { "load_balancer": { "server_role": "primary", "weight": 9 } }

10 },

11 {

12 "address": "new-origin.example.com",

13 "modules": { "load_balancer": { "server_role": "primary", "weight": 1 } }

14 }

15 ],

16 "connection_options": {

17 "dns_resolution": "both",

18 "transport_policy": "preserve",

19 "host": "${host}"

20 },

21 "modules": {

22 "load_balancer": {

23 "enabled": true,

24 "config": { "method": "round_robin", "max_retries": 3, "connection_timeout": 30, "read_write_timeout": 60 }

25 }

26 }

27 }

28}

Update the connector from the file. 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 holds two active addresses and sends about one request in ten to the new origin. A connector change reaches Azion’s distributed infrastructure over several minutes, and until every data center holds it, some requests reach the current origin alone.

Change the weights

Each step changes only the weights. Hold a step long enough for the new origin to serve the requests that expose its faults before you take the next one. Each record of the HTTP Requests data source of Real-Time Events carries Upstream Status and Upstream Addr, the status and the address of the origin that answered, so a filter on the new origin’s address shows its errors.

To change the weights in Azion Console:

Open the connector

Access Azion Console > Connectors, and select the connector.

Set the current origin's weight

Under Address Management, on old-origin.example.com, enter the new weight in Weight, such as 5.

Set the new origin's weight

On new-origin.example.com, enter the new weight in Weight, such as 5.

Select Save

The Console shows Connector has been updated.

To change the weights with the API, send both addresses with their new weights. A PATCH with only addresses keeps the Load Balancer configuration of the connector:

Shell

01curl --request PATCH \

02 --url https://api.azion.com/v4/workspace/connectors/<connector-id> \

03 --header 'Accept: application/json' \

04 --header 'Authorization: Token <personal-token>' \

05 --header 'Content-Type: application/json' \

06 --data {

07 "attributes": {

08 "addresses": [

09 {

10 "address": "old-origin.example.com",

11 "modules": { "load_balancer": { "server_role": "primary", "weight": 5 } }

12 },

13 {

14 "address": "new-origin.example.com",

15 "modules": { "load_balancer": { "server_role": "primary", "weight": 5 } }

16 }

17 ]

18 }

19}

The API answers 202 with "state": "pending". A weight of 0 is refused with 10050, and a weight above 100 with 10068.

To change the weights with the Azion CLI, edit the weight of both addresses in connector.json, such as 5 and 5, and 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 new origin receives the share of the new weights once the change reaches each data center. During the spread, some data centers still apply the previous weights, so judge a step only after it has spread.

Take an origin out of rotation

The Active switch of an address takes it out of rotation without deleting it. The address keeps its ports, role, and weight, so turning it back on restores the step it left. Turning the new origin’s address off rolls back, and turning the current origin’s address off cuts over.

To take the new origin out in Azion Console:

Open the connector

Access Azion Console > Connectors, and select the connector.

Turn the address off

Under Address Management, on new-origin.example.com, turn off Active.

Select Save

The Console shows Connector has been updated. To cut over instead, turn off Active on old-origin.example.com.

To take the new origin out with the API, send both addresses with "active": false on the new one:

Shell

01curl --request PATCH \

02 --url https://api.azion.com/v4/workspace/connectors/<connector-id> \

03 --header 'Accept: application/json' \

04 --header 'Authorization: Token <personal-token>' \

05 --header 'Content-Type: application/json' \

06 --data {

07 "attributes": {

08 "addresses": [

09 {

10 "address": "old-origin.example.com",

11 "modules": { "load_balancer": { "server_role": "primary", "weight": 5 } }

12 },

13 {

14 "address": "new-origin.example.com",

15 "active": false,

16 "modules": { "load_balancer": { "server_role": "primary", "weight": 5 } }

17 }

18 ]

19 }

20}

The API answers 202 with "state": "pending". To cut over instead, move "active": false to the current origin’s address.

To take the new origin out with the Azion CLI, add "active": false to the new-origin.example.com address in connector.json, and 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>

To cut over instead, move "active": false to the current origin’s address.

The address that is off receives no request once every data center holds the change. The change takes several minutes to spread, so keep the origin you turned off answering until no request reaches it.

Next steps

Balancing methodsHow the weight, the method, and active addresses decide where each request goes.Add a backup origin to a connectorKeep the old origin as a standby after the cutover, out of daily traffic.Migrate an application to a new origin without downtimeA weight schedule from one request in a hundred to the cutover, with the checks of each step.Load Balancer quickstartEnable Load Balancer on a first connector and see both addresses answer.