The JMS 2.0 specification adds support for shared subscriptions. QPIDJMS-220 outlines how the Qpid JMS client maps the JMS semantics to AMQP terms. This document outlines how the broker responds to those AMQP performatives.
Connection Open
“SHARED-SUB” capability should be set on offered capabilities.
Link Attach
Assumptions:
- If source is set the address is specified as “exchange/binding” and exchange with name “exchange” exists. If exchange with name “exchange” does not exist the link is refused with error “not found”.
- Link does not exist. for Link reattachment see below.
- Terminus durability : NO means 0, YES means 1 or 2.
- When creating a queue its life time policy will be derived from source expiry policy as follow:
- “link-detach” becomes “delete on no outbound link”
- “session-end” becomes “delete on session end”
- “connection-close” becomes “delete on connection close”
- “never” becomes “permanent"
- SHARED and GLOBAL are derived from Source capabilities if Source is set and from Link capabilities otherwise
Not Null Source | SHARED | GLOBAL | TERMINUS DURABILITY | outcome |
YES | NO | NO | NO | Create a non-durable queue with random name and exclusivity policy “link”. Bind queue to exchange “exchange” using binding key “binding”. Broker replies with attach having capability “topic” on a source and attach offered capability “SHARED-SUB”. |
YES | NO | NO | YES | Create a durable queue with name derived from link name, container id and source durability. Exclusivity policy is set to “link”. Bind queue to exchange. Broker replies with attach having capability “topic” on a source and attach offered capability “SHARED-SUB”. If queue already exists the link should be refused with error “resource locked” |
YES | NO | YES | NO | The same as for SHARED=NO, GLOBAL=NO and DURABLE=NO |
YES | NO | YES | YES | Create a durable queue with name derived from link name, global name space and source durability. Exclusivity policy is set to “link”. Bind queue to exchange. Broker replies with attach having capabilities “topic” and “global” on a source and attach offered capability “SHARED-SUB”. If queue already exists the link should be refused with error “resource locked” |
YES | YES | NO | NO | Create a non-durable queue with name derived from link name (up to “|”), container id and source durability. Exclusivity policy is set to “shared”. Bind queue to exchange. Broker replies with attach having capabilities “topic” and “shared” on a source and attach offered capability “SHARED_SUB”. If queue already exists and filters and/or binding key are not the same as derived from attach source, then:
If existing queue exclusivity policy is not “shared”, then link creation is refused with error “resource locked”. If existing queue lifetime and/or durability are different from expected, then link creation is allowed but the source fields in the reply should be modified accordingly. |
YES | YES | NO | YES | Create a durable queue with name derived from link name (up to “|”), container id and source durability. Exclusivity policy is set to “shared”. Bind queue to exchange. Broker replies with attach having capabilities “topic” and “shared” on a source and attach offered capability “SHARED_SUB”. See above, if queue exists |
YES | YES | YES | NO | Create a non-durable queue with name derived from link name (up to “|”), global namespace and source durability. Exclusivity policy is set to “shared”. Bind queue to exchange. Broker replies with attach having capabilities “topic”, “shared” and “global” on a source and attach offered capability “SHARED_SUB”. See above, if queue exists |
YES | YES | YES | YES | Create a durable queue with name derived from link name (up to “|”), global name space and source durability. Exclusivity policy is set to “shared”. Bind queue to exchange. Broker replies with attach having capabilities “topic”, “shared” and “global” on a source and attach offered capability “SHARED_SUB”. See above, if queue exists |
NO | NO | NO | N/A | Look for queue with name derived from link name, container id and “true” durability. If queue exists and there is no consumer, Attach the link with the Source set. If queue does not exist, refuse the link with error “not found”. |
NO | NO | YES | N/A | Look for queue with name derived from link name, global name space and “true” durability. If queue exists and there is no consumer, Attach the link with the Source set. If queue does not exist, refuse the link with error “not found” |
NO | YES | NO | N/A | Look for queue with name derived from link name (up to “|”), container id and “true” durability. If queue exists and there is no consumer, Attach the link with the Source set. If queue does not exist, refuse the link with error “not found”. |
NO | YES | YES | N/A | Look for queue with name derived from link name (up to “|”), global name space and “true” durability. If queue exists and there is no consumer, Attach the link with the Source set. If queue does not exist, refuse the link with error “not found”. |
Link re-Attach
If link exists and the queue exists see the instructions for the existing queue for SHARED=YES.
If link exists and the queue does not exist, recreate a queue as described in corresponding instructions above.
Link Detach
If the Detach has close=true
- If Link Source has capability "topic" and queue has no consumers, the queue is deleted and the Link is Detached
- If Link Source has capability "topic" and queue has consumers, the Link is detached with error(resource-locked)
- if Link Source does not have capability "topic", the Link is detached
Pseudo Code
The above described behaviour results in the following pseudo code. Where the below differs from the above the above is considered normative:
if Link does not exists
if Source is set
if Source has SHARED capability
subscription_name = Link name up to (excluding) “|”
exclusivity_policy = “SHARED”
else
subscription_name = Link name
exclusivity_policy = “LINK”
if Source has GLOBAL capability
name_space = global name space
else
name_space = name space derived from container-id
queue_name = get_queue_name(
name_space,
subscription_name,
Source Durability)
if queue exists
if has same exclusivity_policy
if different binding key or filter
if no consumer
rebind queue
else
error(resource-locked)
else
error(resource-locked)
else
create_queue(
queue_name
exclusivity_policy,
Source Durability,
Source Expiry Policy)
bind queue
send Attach
else
// name_space and subscription_name are derived as above just from Link capabilities instead of Source capabilities
queue_name = get_queue_name(
name_space,
subscription_name,
TRUE_DURABILITY)
if queue exists
Attach Link with correct Source set
else
error(not-found)
else
queue_name = get_queue_name(
name_space,
subscription_name,
TRUE_DURABILITY)
if queue exists
if has same exclusivity_policy
if different binding key or filter
if no consumer
rebind queue
else
error(resource-locked)
else
error(resource-locked)
else
create_queue(
queue_name
exclusivity_policy,
Source Durability,
Source Expiry Policy)
bind queue
send Attach