Webhooks

Webhooks allow client apps to be notified by HTTP post requests when data changes in PageSeeder. A webhook can be configured to only send requests for certain event types, projects, groups or for server events, so it can be tailored to specific client apps.

Events

The following event types are supported by webhooks:

Admin

• webhook.ping

Group or project events

• comment.created
• comment.modified
• comment.archived
• comment.unarchived
• comment.deleted
• group.deleted, group.archived, group.modified
• groupproperties.modified
• groupfolder.created, groupfolder.deleted groupfolder.modified
• membership.created
• membership.modified
• membership.deleted
• publication.created
• publication.modified
• publication.deleted
• task.updated (changes to any <task> attributes or content).
• workflow.updated (changes to any <workflow> attributes or content).
• uri.created (includes upload).
• uri.modified (includes move, edit, etc. – any time uri/@lastmodified is changed).
• uri.archived
• uri.deleted

Project events

• group.created
• project.deleted, project.archived, project.modified

Server events

• member.created
• member.modified
• member.deleted
• project.created
• server.started (requires PageSeeder v5.99 or higher)

A uri/comment/task move between groups and a group/project rename produces a deleted and possible created (and modified for uri) event with the relevant groups for each.

A task/workflow/URL change produces a separate event for each group, as the content for each group can be different.

Requests

• Webhook POST requests can be in XML or JSON format (shown following).
• Each request contains one or more webevents.
• Each webevent contains zero or more event groups (these are the PageSeeder groups the event affects).
• Each webevent also contains an object in either minimal (private and public IDs only) or basic format depending on the webhook configuration.
• For delete events, the object always has minimal format.

The top level <webhook> element only has an @id attribute and optional @name attribute. See <webevent> element for more details on the request content.

XML format

<webevents>
  <webhook id="123" [name="xyz"] />
  <webevent id="[object id].[nano time]"
            datetime="2012-11-23T22:35:12+10:00"
            type="[object].[action]">
    <event>
      <group id="" name="">
      [<group .../> ...]
    </event>
    <webhook|uri|comment|task|workflow|membership|member|...
             id=""
             [name="[group name]"]
             [docid=""] [path=""]
             [username=""]
             [email=""]
             [...]>
        [...]
    </...>
  </webevent>
  [<webevent ...> ... </webevent> ...]
</webevents>

JSON format

{
  "webhook": {
    "id" : "123", 
    "name" : "xyz"
  },
  "webevents": [
    { 
      "id": "[object id].[nano time]", 
      "datetime": "2012-11-23T22:35:12+10:00", 
      "type": "[object].[action]",
      "event": [
        {"id":"", "name":""}
      ], 
      "webhook|uri|comment|task|...": {
        ...
      }
    },
    ...
  ]
}

Configuration

Webhooks can only be configured by PageSeeder administrators using the Web service API or the user interface by selecting the system administration > OAuth > Webhooks page and following the steps below.

Step 1: Register a client

On the OAuth > Clients page click, the Register new client button. Enter the details required and click Register.

Most of the details are related to OAuth  configuration so that the client app can also connect to PageSeeder and access data.

If a Webhook secret is entered, it is used to sign all POST requests to this client with an HMAC of the request body and sends it in an  X-PS-Signature HTTP header. This is so the app can verify the POST is coming from PageSeeder. Following is an example Java code snippet that could be used to verify the signature:

SecretKeySpec key = new SecretKeySpec(
  webhook_secret.getBytes(StandardCharsets.UTF_8), "AES");
Mac mac = Mac.getInstance("HmacSHA256");
mac.init(key);
String signature = Base64.getEncoder().encodeToString(mac.doFinal(body));

Step 2: Start the client app

When a webhook is registered, it immediately sends a webhook.ping event POST to the URL for the webhook. If the client app replies with HTTP 200 and HTTP header X-PS-Secret set to the same value as was sent in that header on the POST, then the webhook status changes from “pending” to “active”.

This confirms that the client wishes to receive webhook POST requests from PageSeeder and helps guard against PageSeeder sending unwanted or SPAM requests. It is similar to the immediate confirmation mechanism described here http://resthooks.org/docs/security/ .

Step 3: Register a webhook

On the OAuth > Webhooks page, click the Register new webhook button. Choose the client, enter a URL plus other details (see following) if required and click Register.

• Support insecure SSL – means that the SSL certificate is not checked when sending requests. This can be useful for development servers but must not be used for production.
• Object type: minimal – means that only private and public IDs are returned for the object (no other content), see <webevent> for more detail on the minimal type.
• Event filters – means the events that are sent to this webhook. Multiple event types can be specified by selecting different event types repeatedly.
• Include server events – means include the following events which are not specific to a project or group: member.created, member.modified, member.deleted, project.created, server.started.

Check the Webhooks page to ensure the status is “active”. Event POST requests are only sent to “active” webhooks.

Troubleshooting

Following are the possible status values for a webhook and the remedies required:

An error is displayed on the Administration dashboard if there are any webhooks with a status of warning, unreachable or error. The status of each webhook is displayed on the Webhooks page. For further detail, view the Recent logs page.

Webhook caches

The following message might appear on the Administration dashboard page:

The webhooks caches were corrupted probably due to an unclean shutdown so unprocessed events before the shutdown will not have been sent (see general logs).

In this case, view the General logs for the day the server was shutdown and look for the following lines in the general log to see if there were any unprocessed events. If any numbers are non-zero or these lines are missing, the client app caches might need to be cleared or updated for the missing events.

There was 0 unprocessed webhook events at shutdown.
There was 0 unprocessed webhook jobs at shutdown.
There was 0 unprocessed failed webhook jobs at shutdown.

The contents of the webhook caches can be viewed on the Server status > Caching page. Click Info next to the webhook-events, webhook-failed-jobs or webhook-jobs cache, then click each entry to see detailed information.

Failed POST requests

Following are the rules used to process failed POST requests to a webhook URL:

• If POST fails with 3xx or 410 error, set webhook status to unreachable and stop sending to that webhook.
• If POST fails with 4xx, 5xx or other error increment, RetryNumber and retry again using exponential backoff after 2retries x 10 seconds (e.g. 10s, 20s, 40s, 80s, ... ~12 hrs for webhookRetries=12). Also, set webhook status to warning.
• If RetryNumber > webhookRetries (see following), set webhook status to unreachable and stop sending to that webhook

Global properties

If there are issues with memory, performance or failure processing, the following global properties can be adjusted to modify the system.

Sample Webhook handler

The following example in Java provides the scaffolding for handling webhook payloads on your client app.

@WebServlet(urlPatterns = "/webhook")
public class WebhookHandler extends HttpServlet {

  @Override
  protected void doPost(HttpServletRequest req, HttpServletResponse res) 
      throws IOException {
    // We're not returning any content
    res.setStatus(HttpServletResponse.SC_NO_CONTENT);

    // If the secret is specified, send it back for pings
    String secret = req.getHeader("X-PS-Secret");
    if (secret != null) {
      res.setHeader("X-PS-Secret", secret);
    }

    // Get the payload
    byte[] payload = req.getInputStream().readAllBytes();

    // If the payload is signed
    String signature = req.getHeader("X-PS-Signature");
    if (signature != null) {
      boolean signatureFailed = false;
      try {
        SecretKeySpec key = new SecretKeySpec("my_secret".getBytes(StandardCharsets.UTF_8), "AES");
        Mac mac = Mac.getInstance("HmacSHA1");
        mac.init(key);
        String signatureCheck = Base64.getEncoder().encodeToString(mac.doFinal(payload));
        if (!signature.equals(signatureCheck)) {
          res.sendError(HttpServletResponse.SC_BAD_REQUEST);
          signatureFailed = true;
        }
      } catch (GeneralSecurityException ex) {
        res.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
        signatureFailed = true;
      }
      if (signatureFailed) return;
    }

    // Handle the data here...
    String data = new String(payload, StandardCharsets.UTF_8);

  }

}