Starting a Process from Outside of Questetra BPM Suite (Error-handling Chapter)

• Starting a Process from Outside of Questetra BPM Suite (Preparatory Chapter)
• Starting a Process from Outside of Questetra BPM Suite (curl Chapter)
• Starting a Process from Outside of Questetra BPM Suite (Python Chapter)
• Starting a Process from Outside of Questetra BPM Suite (Error-handling Chapter)

An error returned from the API!

You will probably encounter a situation while you are dealing with the Message Start Event (HTTP) API when you might think “I don’t know why, but it doesn’t work”. In this article, I will explain the errors returned by the Message Start Event (HTTP) API.

How to check for errors

Please check the HTTP status code and the error message returned by the API in the event that the Process does not start even though Message Start Event (HTTP) was accessed. You can roughly tell where an error occurred with the HTTP status code, and the API error message points out what needs to be fixed when the client (user) side has a deficiency.

Check the HTTP status code

For curl command

You can display the response header returned from Message Start Event (HTTP) if you use the -i option.

$ curl -i https://example.questetra.net/... 

For example, a response header will be like the following.

HTTP/1.1 200 200
Date: Wed, 16 Jan 2019 05:46:50 GMT
Server: Apache
Pragma: no-cache
Cache-Control: no-store
Expires: Thu, 01 Jan 1970 00:00:00 GMT
X-Q-Access-ID: {SERVER NAME ("example" in the above)}
Content-Type: text/plain;charset=UTF-8
Content-Language: en
Content-Length: 3
Vary: Accept-Encoding
P3P: CP="CAO PSA OUR"

In this case, data transmission was successful as the HTTP status code is 200 (OK), whereas cases with 400s and 500s are errors. In the following cases for example, the HTTP status code 400 (Bad Request) has returned from the Message Start Event (HTTP) API.

HTTP/1.1 400 400
Date: Fri, 18 Jan 2019 07:49:58 GMT
Server: Apache
Pragma: no-cache
Cache-Control: no-store
Expires: Thu, 01 Jan 1970 00:00:00 GMT
X-Q-Access-ID: shichijo-onmae-134
Content-Disposition: inline
Content-Type: text/xml;charset=UTF-8
Content-Language: en
P3P: CP="CAO PSA OUR"
Connection: close
Transfer-Encoding: chunked

<?xml version="1.0" encoding="UTF-8" standalone="yes"?><message-start-event-errors><error><key>q_selects</key><detail>Select more than one.</detail></error></message-start-event-errors>

For the meaning of each HTTP status code, refer to the Major HTTP status code list.

For Python 3 (utilizing Request package)

The code example shown in the Python chapter has been designed so the HTTP status code will be stdout.。

try:
    r = requests.post(url, data=params, files=files) # POST 送信
    r.raise_for_status()
    print('Headers: ')
    print(r.request.headers)
    print('Status Code: {0}'.format(r.status_code))
    print(r.text)
except requests.exceptions.HTTPError as e: # Catching HTTP error
    print('Error')
    print('Status Code: {0}'.format(r.status_code))
    print(r.text)
except requests.exceptions.Timeout as e: # Cathing Timeout
    print('Timeout')

As you see in the code, the Response object that requests.post () returns contains the status code in the instance variable status_code. In the code example, if there is no HTTP error the stdout is as follows.

Headers: 
{'User-Agent': 'python-requests/2.21.0', 'Accept-Encoding': 'gzip, deflate', 'Accept': '*/*', 'Connection': 'keep-alive', 'Content-Length': '72753', 'Content-Type': 'multipart/form-data; boundary=bf3a1ec648ccb798d9a9c6a914d77c81'}
Status Code: 200
151

However, if there is an HTTP error an HTTP Error exception is thrown when Response.raise_for_status () is executed.

Error
Status Code: 400
<?xml version="1.0" encoding="UTF-8" standalone="yes"?><message-start-event-errors><error><key>key</key><detail>Invalid API Key</detail></error></message-start-event-errors>

In the case above, the HTTP status code 400 (Bad Request) is returned from the Message Start Event (HTTP) API. For the meaning of each HTTP status code refer to the following Major HTTP status code list.

Major HTTP status code list

Check the error message

If the HTTP status code indicates 400 then there is something wrong with the data sent by the client (user). Please review and make corrections to the error message returned by the Message Start Event (HTTP) API. Error messages are stored in the response body.

For curl command

In the case of curl commands the response body is stdout by default. For example, as mentioned in the HTTP status code section, the following XML data is displayed. (In order to make it easier to read I have inserted line feeds as appropriate.)

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<message-start-event-errors>
<error>
<key>q_str</key>
<detail>5 or more characters required.</detail>
</error>
<error>
<key>q_selects</key>
<detail>Select more than one.</detail>
</error>
</message-start-event-errors>

Between <key> and </key> is the parameter name which returned the error, and between <detail> and </detail> is the content of the error. In the case above, the following error messages are returned.

• “5 or more characters required.” from “q_str” (String type Data Item)
• “Select more than one.” from “q_selects” (Select type Data Item)

For Python 3 (utilizing Request package)

The response body is stored in the instance variable text of the Requests object. In the code example XML data is displayed by stdout as with the curl command chapter.

Troubleshooting by error message

processModelInfold, nodeNumber – “not found”

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<message-start-event-errors>
<error>
<key>processModelInfoId</key>
<detail>not found</detail>
</error>
</message-start-event-errors>

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<message-start-event-errors>
<error>
<key>nodeNumber</key>
<detail>not found</detail>
</error>
</message-start-event-errors>

The specified App or node does not exist. In the case of processModelInfold it is an App, and nodeNumber for a node. Confirm whether the specified number is wrong.

If nodeNumber returns “not found”, it may be referring to another App because the processModelInfold is incorrect.

nodeNumber – “not start event (HTTP)”

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<message-start-event-errors>
<error>
<key>nodeNumber</key>
<detail>not start event (HTTP)</detail>
</error>
</message-start-event-errors>

The specified node is not a Message Start Event. Confirm that the value of processModelInfold and nodeNumber is correct.

key – “Invalid API key”

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<message-start-event-errors>
<error>
<key>key</key>
<detail>Invalid API Key</detail>
</error>
</message-start-event-errors>

The API key is invalid. Confirm whether the API key is incorrect.

Others

There are various types of error messages. Even so, an error message would specifically instruct the solution, such as for example, “the number of characters must be n characters or more” for a String-type Data Item. If a specific error message is returned, check the contents of the message and the Data Item Settings.