Mickael Bailly created JAMES-2658:
-------------------------------------
Summary: Generic mailet to call an external microservice, and add
extra information to a tag
Key: JAMES-2658
URL: https://issues.apache.org/jira/browse/JAMES-2658
Project: James Server
Issue Type: Wish
Reporter: Mickael Bailly
Hello team. This is a Request For Comments for a feature, to be able to add
extra information to an email on delivery to a local mailbox.
h2. Principle
the mailet calls a remote webservice, with a pre-specified payload. It gets
back, either an error, or another specific payload. This payload can instruct
the James server to add informations to the email. The first case, that we
handle here, is to add extra headers.
h2. Implementation
OK, I'll try to map the mailet syntax, but I'll make mistakes, it's to
illustrate the principle.
James configuration:
{{<mailet match="..." class="AddExtraInfos"
endpoint="https://server.com/api/infos"; />}}
Seeing this, the mailer issues a POST on {{https://server.com/api/infos}} with
the following payload structure:
{{{}}
{{ "messageId" : "messageId",}}
{{ "from" : {}}
{{ "address" : "[email protected]",}}
{{ "personal" : "first_name last_name"}}
{{ },}}
{{ "to" : [ {}}
{{ "address" : "[email protected]",}}
{{ "personal" : "first_name last_name of to1"}}
{{ } ],}}
{{ "cc" : [ {}}
{{ "address" : "[email protected]",}}
{{ "personal" : null}}
{{ }, {}}
{{ "address" : "[email protected]",}}
{{ "personal" : "first_name last_name of cc2"}}
{{ }, {}}
{{ "address" : "[email protected]",}}
{{ "personal" : "first_name last_name of cc3"}}
{{ } ],}}
{{ "bcc" : [ ],}}
{{ "Received" : "Mon, 28 Jan 2019 07:56:43 +0000",}}
{{ "Date" : "Mon, 28 Jan 2019 07:56:43 +0000",}}
{{ "in-Reply-To" : "messageId_in_reply_to",}}
{{ "subject" : "IMPORTANT: Testing The Priority Inbox",}}
{{ "body" : "\nDear, \n\n this a test of the priority inbox\n
regards,\nfirst_name last_name\nDirector Tester",}}
{{ "attachments" : [{}}
{{ "file_size" : "243534",}}
{{ "content_name" : "presentation.pdf",}}
{{ "content_type" : "APPLICATION/PDF"}}
{{ }, {}}
{{ "file_size": "243534",}}
{{ "content_name" : "APPLICATION/PDF",}}
{{ "content_type" : "performance.pdf"}}
{{ }],}}
{{ "emailFolder" : "INBOX",}}
{{ "user" : "first_name last_name of to1",}}
{{ "alternativeAddress" : [ "[email protected]", "[email protected]"
],}}
{{ "X-Spam-Flag" : "NO"}}
{{}}}
Worth noting: all those attributes are JSON formatting of an email contents,
EXCEPT:
* emailFolder : the destination folder of the email
* user & alternativeAddress : the user the email is delivered to
This mailet expects a specific format for the response. Here is a proposal:
1/ "bypass" (do nothing)
{}
2/ "add headers"
{
"addHeaders": [
\{name: "X-INFO1", value: "some header value"}
\{name: "X-INFO1-SCORE", value: "0.4"}
]
}
h3. Handling failure
The mailet may support a specific attribute to allow the behaviour in case of
failure.
{{<mailet match="..." class="AddExtraInfos"
endpoint="https://server.com/api/infos"; on-failure="ignore" />}}
h3. Configuring retries
The mailet may support a retry parameter, allowing to retry x times before
"really" failing. The additional, optional retry delay parameter could set the
time, in seconds, to wait between each retry.
{{<mailet match="..." class="AddExtraInfos"
endpoint="https://server.com/api/infos"; on-failure="ignore" retry="5"
retry-delay="0.5" />}}
h3. Setting blocking behaviour
Some processing may not require an immediate response, and may allow further
processing of the mailet chain. Here, either the "blocking" or the "async"
attribute, I can't choose, may be used.
{{<mailet match="..." class="AddExtraInfos"
endpoint="https://server.com/api/infos"; on-failure="ignore" retry="5"
retry-delay="0.5" blocking="false" />}}
or, as a second proposal
{{<mailet match="..." class="AddExtraInfos"
endpoint="https://server.com/api/infos"; on-failure="ignore" retry="5"
retry-delay="0.5" async="true" />}}
h2. Things I don't know
* Where to send email on failure, if the "on-failure" attribute is not
"ignore".
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