This script can act as a middleman between Sentry's webhook system and Mattermost's Incoming Webhooks

sentry_mattermost_webhook.php

<?php
$json = json_decode(file_get_contents('php://input'), true);

if ($json['action'] !== 'created'){ die('Only create actions are alerted'); }
$error = $json['data']['issue'];

if ($error['project']['id'] == 1){ die('Ignore internal errors.'); }
if (empty($error['shortId'])){ die('No shortId passed'); }

// Set channel and username
$response['username'] = 'Sentry';
$response['response_type'] = 'in_channel';

$attachment = [];
$attachment['fallback'] = 'Error reported by Sentry: ' . $error['id'];
$attachment['author_name'] = strtoupper($error['project']['name']) . ' - ' . $error['shortId'];
$attachment['author_icon'] = 'ICON_HERE';
$attachment['author_link'] = 'PATH_TO_YOUR_ORG_HERE' . $error['id'];
$attachment['text'] = $error['title'] . ' @ ' . $error['culprit'];

$fields = [
        'Function' => $error['metadata']['function'],
        'File' => $error['metadata']['filename']
];

// Generate fields
foreach ($fields as $label => $value){
        $field = [
                'short' => true,
                'title' => $label,
                'value' => $value
        ];
        $attachment['fields'][] = $field;
}

$response['attachments'][] = $attachment;
$response = json_encode($response);

$ch = curl_init('YOUR_MATTERMOST_WEBHOOK');
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $response);
curl_setopt( $ch, CURLOPT_HTTPHEADER, array('Content-Type:application/json'));
echo curl_exec($ch);

Thanks, @dkmonaghan for the headstart. Unfortunately still not able to make progress. If you can please go through the details below. I suspect, some basic mistake I may be making. When an issue is created in Sentry, if I go and check the integration dashboard I can see 2 entries there. first one return with success while the second one fails with internal error. Appreciate it if you can help me out with this

My Webhook script looks likes as below

• My Script is accessible from outside
• My Mattermost incoming webhook URL is OK and tested by providing same to my GitLab instance and it is able to successfully able to communicate with matter most

My Sentry Integration looks like this

1. Page 1:
   

2. Page 2:
   

3. Page 3:
   

4. Page 4:
   

My Alert Configuration in Sentry is as below

1. Page 1:
   
2. Page 2:
   

If the server is returning a 500 error that means there's a problem with the script. Can you provide log output from your webserver showing PHP error logs?

Thanks @dkmonaghan . php curl was missing in the system hence the issue. this is resolved now. Thanks once again for the nice neat solution for Sentry - Mattermost integration

@dkmonaghan Thanks for the idea and the inspiration! Based on this, I created a Sentry - Google Chat webhook connection: https://gist.github.com/Benjaminhu/90471b8f4fc51305a8212223996c4994

For anybody that stumbled upon this and doesn't want to spin a PHP server, we implemented the same with a 2-step flow in N8N (same field mapping as the PHP which is quite elegant)

I've uploaded screenshots of the N8N config.

The result: