Configure mirroring-based back-to-origin

When you send a request to KS3 to access an object that does not exist in KS3, KS3 sends a request to the origin address to retrieve the object if back-to-origin rules are configured, and returns the object to you. For a large object such as an image or a video, KS3 requests part of its data from the origin address and returns it to you, reducing your waiting time. Meanwhile, the object is saved to KS3.

Note:

1. You can use the mirroring-based back-to-origin service to obtain an object of up to 50 GB in size.

2. You can configure up to 20 back-to-origin rules.

3. The data pulled to KS3 is stored in Standard storage by default.

4. You cannot use the object name setting feature of KS3 to change the names of objects pulled to KS3.

5. You must contact Kingsoft Cloud business staff or submit a ticket to apply for using the mirroring-based back-to-origin service before you start configuration in the console.

Configure mirroring-based back-to-origin

1. Log in to the KS3 console and click Bucket in the left navigation pane. On the page that appears, click the name of the target bucket.

2. Click Bucket Settings. Then, click the Mirror tab. The Mirroring Back-to-Origin tab appears by default.

3. Click Add Rule. In the Add Rule panel, configure the parameters described in the following table.

Example of setting an HTTP header transmission rule: Allow: Select Transmit Specified HTTP Header and enter response-content-type. Deny: Select Prohibit Transmission of Specified HTTP Header and enter If-Modified-Since. Set up: Set the specified HTTP header c-header to 111.

Based on the preceding configurations, assume that the request you send to KS3 contains the following HTTP headers:

GET /object
host : bucketname. ks3-cn-beijing.ksyuncs.com
response-content-type :String
If-Modified-Since : Fri, 26 Dec 2014 06:48:46 GMT
c-header : ccc

After mirroring-based back-to-origin is triggered, the request that KS3 sends to the origin server contains the following headers:

GET /object
host : source.com
response-content-type :String
c-header : 111 

Note:

You cannot configure transmission rules for the following HTTP headers:

Headers starting with the following prefixes:

• x-kss-

• x-ks3-

All standard HTTP headers, for example:

• content-length

• authorization2

• authorization

• range

• date

The rule priority is as follows: Set up > Deny > Allow. For example, assume that the following three rules are configured for the x-age header: allow x-age to be transmitted to the origin server, prohibit x-age from being transmitted to the origin server, and set x-age to 1. In this case, the x-age header with a value of 1 is transmitted to the origin server.

4. Click OK.

Edit mirroring-based back-to-origin rules

1. Log in to the KS3 console and click Bucket in the left navigation pane. On the Bucket list page, click the name of the target bucket.

2. Click Bucket Settings. Then, click the Mirror tab. The Mirroring Back-to-Origin tab appears by default.

3. Find the back-to-origin rule that you want to edit and click Edit in the Action column.

4. In the panel that appears, edit the rule.

Delete mirroring-based back-to-origin rules

1. Log in to the KS3 console and click Bucket in the left navigation pane. On the Bucket list page, click the name of the target bucket.

2. Click Bucket Settings. Then, click the Mirror tab. The Mirroring Back-to-Origin tab appears by default.

3. Find the back-to-origin rule that you want to delete and click Delete in the Action column.

4. In the message that appears, click OK.

Adjust the sequence of back-to-origin rules

You can move up or down the back-to-origin rules to adjust their sequence. KS3 determines the matching priority of the rules based on their sequence. If Rule 1 is matched, Rule 2 will not be matched. However, if the origin server in Rule 1 is unavailable, KS3 will send a request to the standby origin server in Rule 2. You can configure up to 20 rules. Therefore, a maximum of 19 standby origin servers are available.

1. Log in to the KS3 console and click Bucket in the left navigation pane. On the Bucket list page, click the name of the target bucket.

2. Click Bucket Settings. Then, click the Mirror tab. The Mirroring Back-to-Origin tab appears by default.

3. Find the target back-to-origin rule and click Move Up or Move Down in the Action column.

Example of matching multiple rules:

Assume that multiple rules with the same or partially overlapping back-to-origin conditions are configured:

Rule 1: Access test.com when the 404 error is returned for all objects.

Rule 2: Access 141.0.0.12 when the 404 error is returned for all objects.

Rule 3: Access back.com when the 404 error is returned for objects with the name prefix 333.

Processing of KS3:

1. KS3 matches the request against Rule 1. If data can be properly pulled from test.com, KS3 no longer matches the request against Rule 2.

2. KS3 matches the request against Rule 1. However, test.com is unavailable when the back-to-origin service of KS3 attempts to access it. Then, KS3 attempts to access 141.0.0.12 configured in Rule 2.

3. If 141.0.0.12 configured in Rule 2 is also unavailable and the object name prefix is 333, KS3 continues to access back.com in Rule 3. If the object name prefix is not 333, KS3 returns the 404 error to you.