iRule Event Order
There is an excellent article on DevCentral regarding iRule order but this focuses on TCP, the event order for an HTTP request is different as you can see below:
Event Order – HTTP Request
1. RULE_INIT
2. CLIENT_ACCEPTED
3. CLIENTSSL_HANDSHAKE
4. CLIENTSSL_CLIENTCERT
5. CLIENT_DATA
6. HTTP_REQUEST | CACHE_REQUEST
7. HTTP_CLASS_FAILED | HTTP_CLASS_SELECTED
8. STREAM_MATCHED
9. HTTP_REQUEST_DATA
10. CLIENT_DATA | HTTP_REQUEST_DATA
11. LB_SELECTED | LB_FAILED
12. STREAM_MATCHED
13. SERVER_CONNECTED (Here is where the backend server is reached)
14. SERVER_SSL_HANDSHAKE
15. HTTP_REQUEST_SEND
16. SERVER_DATA (CACHE_RESPONSE | HTTP_RESPONSE)
17. HTTP_RESPONSE_DATA
Event Order – TCP Connection
1. RULE_INIT
2. CLIENT_ACCEPTED
3. CLIENT_DATA
4. STREAM_MATCHED
5. LB_FAILED | LB_SELECTED
6. SERVER_CONNECTED
7. SERVER_DATA