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The JSON Actor Message Protocol defines a bidirectional messaging protocol using JSON as a payload serialization format. Messages are typed and addressed. Both unidirectional messages and bidirectional queries are supported. JAMP can be sent on messaging framing protocols like WebSockets, HTTP (REST), or STOMP.
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1.
Introduction
2.
Requirements
3.
Protocol Overview
4.
General Requirements
4.1.
Requirements
4.2.
Syntax Notation
4.3.
Terminology
4.4.
Basic Rules
5.
Messages
5.1.
send
5.2.
query
5.3.
reply
5.4.
error-query
5.5.
error
6.
Security Considerations
7.
Normative References
§
Author's Address
§
Intellectual Property and Copyright Statements
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The goal of JAMP is to provide structure for a JSON-based messaging over a WebSockets connection.
JAMP supports:
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This section is non-normative.
A unidirectional message looks as follows:
["send", "jamp+ws://target.example.com/to-actor", "jamp+ws://source.example.com/from-actor", "my_action", ["arg1", "arg2"]]
Bidirectional queries consist of a "query" packet and a corresponding "reply" packet. The query and reply are correlated with a correlation-id, which is a 64-bit integer. The query/reply pair can be used to implement remote procedure calls (RPC)
A service MUST response to a "query" with either a "reply" or a "error_reply" because the client will be waiting for the response.
A query looks as follows:
["query", 12345, "jamp+http://target.example.com/service-actor", "jamp+http://source.example.com/query-actor", "my_action", ["my-arg1", "my-arg2"]]
The corresponding reply looks as follows:
["reply", 12345, "jamp+http://source.example.com/query-actor", "jamp+http://target.example.com/service-actor", "my-result"]
Addresses are strings in this specification, interpreted by the implementation. If the implementation does any routing, it is recommended to use URLs as addresses.
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
An implementation is not compliant if it fails to satisfy one or more of the MUST or REQUIRED level requirements for the protocols it implements. An implementation that satisfies all the MUST or REQUIRED level and all the SHOULD level requirements for its protocols is said to be "unconditionally compliant"; one that satisfies all the MUST level requirements but not all the SHOULD level requirements for its protocols is said to be "conditionally compliant."
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This specification uses the Augmented Backus-Naur Form (ABNF) notation of [RFC5234] (Crocker, D. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF,” January 2008.).
The following core rules are included by reference, as defined in [RFC5234] (Crocker, D. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF,” January 2008.), Appendix B.1: ALPHA (letters), CR (carriage return), CRLF (CR LF), DIGIT (decimal 0-9), OCTET (any 8-bit sequence of data), SP (space), VCHAR (any visible [USASCII] character), and WSP (whitespace).
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This specification the following JAMP
address: An opaque string representing JAMP actor.
payload: A JSON value.
type: A string representing a message type.
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The following basic rules follow the definitions in HTTP [RFC2616] (Fielding, R., Gettys, J., Mogul, J., Mainter, L., Leach, P., and T. Berners-Lee, “Hypertext Transfer Protocol -- HTTP/1.1,” June 1999.).
type = 1* ( ALPHA / DIGIT / "_" / "." )
query_id = 1* DIGIT
string = JSON string
object = JSON object
to-address = string
from-address = string
action-name = string
parameters = parameter-list?
parameter-list = object
/ object ',' parameterlist
reply-object = object
error-object = object
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The following 5 packets are the only message allowed for JAMP: message, query, reply, error_reply, error.
The stream consists of a sequence of messages.
message = send
/ query
/ reply
/ error-reply
/ error
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send is a unidirectional message.
send grammar
send ::= '['
"send" ','
to-address ','
from-address ','
action-name ','
'[' parameters ']'
']'
A unidirectional message looks as follows:
["send", "jamp+ws://target.example.com/to-actor", "jamp+ws://source.example.com/from-actor", "my_action", ["arg1", "arg2"]]
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query is a bidirectional request for a response. A receiver MUST response with either a "reply" or a "error-query"
query grammar
query ::= '['
"query" ','
query_id ','
to-address ','
from-address ','
action-name ','
'[' parameters ']'
']'
Example: A query looks as follows:
["query", 12345, "jamp+http://target.example.com/service-actor", "jamp+ws://source.example.com/query-actor", "my_action", ["arg1", "arg2"]]
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"reply" is a bidirectional response to a query.
reply grammar
reply ::= '['
"reply" ','
query_id ','
to-address ','
from-address ','
reply-object
']'
Example: A reply looks as follows:
["reply", 12345, "jamp+http://source.example.com/client", "jamp+http://source.example.com/service", "my-result"]
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error-query is an error response to a query.
query-error grammar
error_query ::= '['
"error_query" ','
query_id ','
to-address ','
from-address ','
error_object
']'
A error query message looks as follows:
["error_query",
12345,
"jamp+http://source.example.com/client",
"jamp+http://source.example.com/service",
{"type" : "internal-server-error",
"message" : "the server was unable to process the request"}]
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'error' is a general error in response to a message. It can be used to inform a client of service availability.
error grammar
error ::= '['
"error" ','
to-address ','
from-address ','
error-object
']'
An error message looks as follows:
["error",
"jamp+ws://source.example.com/my-actor",
"jamp+ws://target.example.com/my-service",
{"type": "service-not-found",
"message": "'my-service' is an unknown service"}]
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This section is meant to inform application developers and users of security issues related to JAMP. This list is unlikely to be complete.
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| [RFC2616] | Fielding, R., Gettys, J., Mogul, J., Mainter, L., Leach, P., and T. Berners-Lee, “Hypertext Transfer Protocol -- HTTP/1.1,” RFC 2616, June 1999. |
| [RFC3629] | Yergeau, F., “UTF-8, a transformation format of ISO 10646,” STD 63, RFC 3629, November 2003. |
| [RFC5234] | Crocker, D. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF,” STD 68, RFC 5234, January 2008. |
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| Scott Ferguson | |
| Caucho Technology |
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