JMAP Migration and Portability Extensions

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Table of Contents

1. Introduction

Every server-side software has its own quirks. For example, a JMAP server might only have partially implemented the JMAP standard or design decisions might have been taken that let the server deviate from what is actually required by [RFC8620]. Servers might also have unintended bugs or have certain restrictions that are not sufficiently reflected by their list of supported server capabilities.¶

JMAP as a protocol for data migration and portability targets a large variety of pre-existing systems. Especially legacy systems often come with a lot of constraints that may prohibit them from fully complying with the JMAP standard. Interoperable clients that aim to have a successful structured data exchange with such "unique" servers need to handle these quirks with workarounds on the client-side. Clients only want to apply special workarounds in situations where they are truly necessary. This is typically done by identifying which server-side software they are communicating with.¶

JMAP does not provide a standardized way to retrieve an identifier of the product that is residing on the server side. Due to the lack of standardization clients are left to identify misbehaving servers by error-prone means. Examples are checking against a list of known URLs or checking known unique responses, typically only sent by certain products. This makes identifying products time-consuming and brittle.¶

Related functionality in other standards are the PRODID property in iCalendar [RFC5545] and vCard [RFC6350], which allows identifying the product that produced the files. ManageSieve [RFC5804] and JMAP Sieve [I-D.ietf-jmap-sieve] define an implementation property, which allows identifying the Sieve implementation.¶

Additionally, server-side logs are very valuable to analyze issues a client may run into. Usually, logs are either stored locally on the instances or sent to a dedicated logging server. However, data migrations often take place in constrained environments under which access to server-side logs is limited. JMAP can be leveraged to supply log messages along-side the usual data exchange. This also removes the need to operate a separate logging infrastructure or have dedicated channels for log messages.¶

{
  "capabilities": {
    "urn:ietf:params:jmap:core:backendinfo": {
      "apiBackend": {
        "name": "OpenXPort/Horde",
        "version": "1.0.0"
      },
      "product": {
        "name": "Horde Webmailer",
        "version": "1.0.0"
      },
      "environment": {
        "name": "PHP",
        "version": "5.5"
      }
    }
  },
    ...
}

2. Structured Data Exchange Extension

The Response object as well as all "problem details" objects will be extended via:¶

• logs: LogLine[] (optional) An array of log lines that were created while processing the request.¶

A LogLine object has the following properties:¶

• level: String The log level of the log message. MUST be one of the eight levels defined in RFC5424: debug, info, notice, warning, error, critical, alert or emergency.¶
• message: String The log message¶
• timestamp: UTCDate The date the log message was logged.¶
• class: String|null The name of the class that is currently logging.¶
• file: String|null The file that initiated the log line.¶
• line: String|null The exact line in the file where the log function is being called.¶

An example list of logs sent alongside a response to Core/echo would look like:¶

{
  "logs" : [
    {
      "file" : "Logger.php",
      "level" : "info",
      "line" : 32,
      "message" : "Array Logger has been successfully initialized",
      "timestamp" : "2022-01-18T10:26:56+01:00"
    },
    {
      "file" : "ErrorHandler.php",
      "level" : "warning",
      "line" : 52,
      "message" : "fopen(bridge.php):
        failed to open stream: No such file or directory",
      "timestamp" : "2022-01-18T10:26:56+01:00"
    },
    ...
  ],
  "methodResponses" : [
    [
      "Core/echo",
      ...

3. Security considerations

All security considerations of JMAP [RFC8620] apply to this specification.¶

Log messages might contain sensitive user data as well as detailed information about the system on which an API server has been installed. Appropriate measures must be taken to restrict access to JMAP Debug to trusted parties only.¶

4. IANA considerations

5. Acknowledgements

Bron Gondwana, Neil Jenkins, Alexey Melnikov, Ken Murchison, Robert Stepanek and the JMAP working group at the IETF.¶

Authors' Addresses