Qpid Proton C API  0.18.1
Delivery

A message transfer. More...

Macros

#define PN_RECEIVED
 The PN_RECEIVED delivery state is a non terminal state indicating how much (if any) message data has been received for a delivery.
 
#define PN_ACCEPTED
 The PN_ACCEPTED delivery state is a terminal state indicating that the delivery was successfully processed. More...
 
#define PN_REJECTED
 The PN_REJECTED delivery state is a terminal state indicating that the delivery could not be processed due to some error condition. More...
 
#define PN_RELEASED
 The PN_RELEASED delivery state is a terminal state indicating that the delivery is being returned to the sender. More...
 
#define PN_MODIFIED
 The PN_MODIFIED delivery state is a terminal state indicating that the delivery is being returned to the sender and should be annotated by the sender prior to further delivery attempts. More...
 

Typedefs

typedef pn_bytes_t pn_delivery_tag_t
 An AMQP delivery tag.
 
typedef struct pn_disposition_t pn_disposition_t
 A delivery state. More...
 
typedef struct pn_delivery_t pn_delivery_t
 An AMQP Delivery object. More...
 

Functions

pn_delivery_tag_t pn_dtag (const char *bytes, size_t size)
 Construct a delivery tag. More...
 
pn_delivery_tpn_delivery (pn_link_t *link, pn_delivery_tag_t tag)
 Create a delivery on a link. More...
 
void * pn_delivery_get_context (pn_delivery_t *delivery)
 Deprecated - Use pn_delivery_attachments(). More...
 
void pn_delivery_set_context (pn_delivery_t *delivery, void *context)
 Deprecated - Use pn_delivery_attachments(). More...
 
pn_record_t * pn_delivery_attachments (pn_delivery_t *delivery)
 Get the attachments that are associated with a delivery object. More...
 
pn_delivery_tag_t pn_delivery_tag (pn_delivery_t *delivery)
 Get the tag for a delivery object. More...
 
pn_link_tpn_delivery_link (pn_delivery_t *delivery)
 Get the parent link for a delivery object. More...
 
pn_disposition_tpn_delivery_local (pn_delivery_t *delivery)
 Get the local disposition for a delivery. More...
 
uint64_t pn_delivery_local_state (pn_delivery_t *delivery)
 Get the local disposition state for a delivery. More...
 
pn_disposition_tpn_delivery_remote (pn_delivery_t *delivery)
 Get the remote disposition for a delivery. More...
 
uint64_t pn_delivery_remote_state (pn_delivery_t *delivery)
 Get the remote disposition state for a delivery. More...
 
bool pn_delivery_settled (pn_delivery_t *delivery)
 Check if a delivery is remotely settled. More...
 
size_t pn_delivery_pending (pn_delivery_t *delivery)
 Get the amount of pending message data for a delivery. More...
 
bool pn_delivery_partial (pn_delivery_t *delivery)
 Check if a delivery only has partial message data. More...
 
bool pn_delivery_aborted (pn_delivery_t *delivery)
 Check if a received delivery has been aborted. More...
 
bool pn_delivery_writable (pn_delivery_t *delivery)
 Check if a delivery is writable. More...
 
bool pn_delivery_readable (pn_delivery_t *delivery)
 Check if a delivery is readable. More...
 
bool pn_delivery_updated (pn_delivery_t *delivery)
 Check if a delivery is updated. More...
 
void pn_delivery_update (pn_delivery_t *delivery, uint64_t state)
 Update the disposition of a delivery. More...
 
void pn_delivery_clear (pn_delivery_t *delivery)
 Clear the updated flag for a delivery. More...
 
bool pn_delivery_current (pn_delivery_t *delivery)
 Return true if delivery is the current delivery for its link. More...
 
void pn_delivery_abort (pn_delivery_t *delivery)
 Abort a delivery being sent. More...
 
void pn_delivery_settle (pn_delivery_t *delivery)
 Settle a delivery. More...
 
void pn_delivery_dump (pn_delivery_t *delivery)
 Utility function for printing details of a delivery. More...
 
bool pn_delivery_buffered (pn_delivery_t *delivery)
 Check if a delivery is buffered. More...
 
pn_delivery_tpn_work_head (pn_connection_t *connection)
 Extracts the first delivery on the connection that has pending operations. More...
 
pn_delivery_tpn_work_next (pn_delivery_t *delivery)
 Get the next delivery on the connection that needs has pending operations. More...
 
uint64_t pn_disposition_type (pn_disposition_t *disposition)
 Get the type of a disposition. More...
 
const char * pn_disposition_type_name (uint64_t disposition_type)
 Name of a disposition type for logging and debugging: "received", "accepted" etc.
 
pn_condition_tpn_disposition_condition (pn_disposition_t *disposition)
 Access the condition object associated with a disposition. More...
 
pn_data_tpn_disposition_data (pn_disposition_t *disposition)
 Access the disposition as a raw pn_data_t. More...
 
uint32_t pn_disposition_get_section_number (pn_disposition_t *disposition)
 Get the section number associated with a disposition. More...
 
void pn_disposition_set_section_number (pn_disposition_t *disposition, uint32_t section_number)
 Set the section number associated with a disposition. More...
 
uint64_t pn_disposition_get_section_offset (pn_disposition_t *disposition)
 Get the section offset associated with a disposition. More...
 
void pn_disposition_set_section_offset (pn_disposition_t *disposition, uint64_t section_offset)
 Set the section offset associated with a disposition. More...
 
bool pn_disposition_is_failed (pn_disposition_t *disposition)
 Check if a disposition has the failed flag set. More...
 
void pn_disposition_set_failed (pn_disposition_t *disposition, bool failed)
 Set the failed flag on a disposition. More...
 
bool pn_disposition_is_undeliverable (pn_disposition_t *disposition)
 Check if a disposition has the undeliverable flag set. More...
 
void pn_disposition_set_undeliverable (pn_disposition_t *disposition, bool undeliverable)
 Set the undeliverable flag on a disposition. More...
 
pn_data_tpn_disposition_annotations (pn_disposition_t *disposition)
 Access the annotations associated with a disposition. More...
 

Detailed Description

A message transfer.

Macro Definition Documentation

◆ PN_ACCEPTED

#define PN_ACCEPTED

The PN_ACCEPTED delivery state is a terminal state indicating that the delivery was successfully processed.

Once in this state there will be no further state changes prior to the delivery being settled.

◆ PN_REJECTED

#define PN_REJECTED

The PN_REJECTED delivery state is a terminal state indicating that the delivery could not be processed due to some error condition.

Once in this state there will be no further state changes prior to the delivery being settled.

◆ PN_RELEASED

#define PN_RELEASED

The PN_RELEASED delivery state is a terminal state indicating that the delivery is being returned to the sender.

Once in this state there will be no further state changes prior to the delivery being settled.

◆ PN_MODIFIED

#define PN_MODIFIED

The PN_MODIFIED delivery state is a terminal state indicating that the delivery is being returned to the sender and should be annotated by the sender prior to further delivery attempts.

Once in this state there will be no further state changes prior to the delivery being settled.

Typedef Documentation

◆ pn_disposition_t

A delivery state.

Dispositions record the current state or final outcome of a transfer. Every delivery contains both a local and remote disposition. The local disposition holds the local state of the delivery, and the remote disposition holds the last known remote state of the delivery.

◆ pn_delivery_t

typedef struct pn_delivery_t pn_delivery_t

An AMQP Delivery object.

A pn_delivery_t object encapsulates all of the endpoint state associated with an AMQP Delivery. Every delivery exists within the context of a pn_link_t object.

The AMQP model for settlement is based on the lifecycle of a delivery at an endpoint. At each end of a link, a delivery is created, it exists for some period of time, and finally it is forgotten, aka settled. Note that because this lifecycle happens independently at both the sender and the receiver, there are actually four events of interest in the combined lifecycle of a given delivery:

  • created at sender
  • created at receiver
  • settled at sender
  • settled at receiver

Because the sender and receiver are operating concurrently, these events can occur in a variety of different orders, and the order of these events impacts the types of failures that may occur when transferring a delivery. Eliminating scenarios where the receiver creates the delivery first, we have the following possible sequences of interest:

Sender presettles (aka at-most-once):

  1. created at sender
  2. settled at sender
  3. created at receiver
  4. settled at receiver

In this configuration the sender settles (i.e. forgets about) the delivery before it even reaches the receiver, and if anything should happen to the delivery in-flight, there is no way to recover, hence the "at most once" semantics.

Receiver settles first (aka at-least-once):

  1. created at sender
  2. created at receiver
  3. settled at receiver
  4. settled at sender

In this configuration the receiver settles the delivery first, and the sender settles once it sees the receiver has settled. Should anything happen to the delivery in-flight, the sender can resend, however the receiver may have already forgotten the delivery and so it could interpret the resend as a new delivery, hence the "at least once" semantics.

Receiver settles second (aka exactly-once):

  1. created at sender
  2. created at receiver
  3. settled at sender
  4. settled at receiver

In this configuration the receiver settles only once it has seen that the sender has settled. This provides the sender the option to retransmit, and the receiver has the option to recognize (and discard) duplicates, allowing for exactly once semantics.

Note that in the last scenario the sender needs some way to know when it is safe to settle. This is where delivery state comes in. In addition to these lifecycle related events surrounding deliveries there is also the notion of a delivery state that can change over the lifetime of a delivery, e.g. it might start out as nothing, transition to PN_RECEIVED and then transition to PN_ACCEPTED. In the first two scenarios the delivery state isn't required, however in final scenario the sender would typically trigger settlement based on seeing the delivery state transition to a terminal state like PN_ACCEPTED or PN_REJECTED.

In practice settlement is controlled by application policy, so there may well be more options here, e.g. a sender might not settle strictly based on what has happened at the receiver, it might also choose to impose some time limit and settle after that period has expired, or it could simply have a sliding window of the last N deliveries and settle the oldest whenever a new one comes along.

Function Documentation

◆ pn_dtag()

pn_delivery_tag_t pn_dtag ( const char *  bytes,
size_t  size 
)

Construct a delivery tag.

Parameters
[in]bytesa pointer to the beginning of the tag
[in]sizethe size of the tag
Returns
the delivery tag

◆ pn_delivery()

pn_delivery_t* pn_delivery ( pn_link_t link,
pn_delivery_tag_t  tag 
)

Create a delivery on a link.

Every delivery object within a link must be supplied with a unique tag. Links maintain a sequence of delivery object in the order that they are created.

Parameters
[in]linka link object
[in]tagthe delivery tag
Returns
a newly created delivery, or NULL if there was an error

◆ pn_delivery_get_context()

void* pn_delivery_get_context ( pn_delivery_t delivery)

Deprecated - Use pn_delivery_attachments().

Get the application context that is associated with a delivery object.

The application context for a delivery may be set using pn_delivery_set_context.

Parameters
[in]deliverythe delivery whose context is to be returned.
Returns
the application context for the delivery object

◆ pn_delivery_set_context()

void pn_delivery_set_context ( pn_delivery_t delivery,
void *  context 
)

Deprecated - Use pn_delivery_attachments().

Set a new application context for a delivery object.

The application context for a delivery object may be retrieved using pn_delivery_get_context.

Parameters
[in]deliverythe delivery object
[in]contextthe application context

◆ pn_delivery_attachments()

pn_record_t* pn_delivery_attachments ( pn_delivery_t delivery)

Get the attachments that are associated with a delivery object.

Parameters
[in]deliverythe delivery whose attachments are to be returned.
Returns
the attachments for the delivery object

◆ pn_delivery_tag()

pn_delivery_tag_t pn_delivery_tag ( pn_delivery_t delivery)

Get the tag for a delivery object.

Parameters
[in]deliverya delivery object
Returns
the delivery tag

◆ pn_delivery_link()

pn_link_t* pn_delivery_link ( pn_delivery_t delivery)

Get the parent link for a delivery object.

Parameters
[in]deliverya delivery object
Returns
the parent link

◆ pn_delivery_local()

pn_disposition_t* pn_delivery_local ( pn_delivery_t delivery)

Get the local disposition for a delivery.

The pointer returned by this object is valid until the delivery is settled.

Parameters
[in]deliverya delivery object
Returns
a pointer to the local disposition

◆ pn_delivery_local_state()

uint64_t pn_delivery_local_state ( pn_delivery_t delivery)

Get the local disposition state for a delivery.

Parameters
[in]deliverya delivery object
Returns
the local disposition state

◆ pn_delivery_remote()

pn_disposition_t* pn_delivery_remote ( pn_delivery_t delivery)

Get the remote disposition for a delivery.

The pointer returned by this object is valid until the delivery is settled.

Parameters
[in]deliverya delivery object
Returns
a pointer to the remote disposition

◆ pn_delivery_remote_state()

uint64_t pn_delivery_remote_state ( pn_delivery_t delivery)

Get the remote disposition state for a delivery.

Parameters
[in]deliverya delivery object
Returns
the remote disposition state

◆ pn_delivery_settled()

bool pn_delivery_settled ( pn_delivery_t delivery)

Check if a delivery is remotely settled.

Parameters
[in]deliverya delivery object
Returns
true if the delivery is settled at the remote endpoint, false otherwise

◆ pn_delivery_pending()

size_t pn_delivery_pending ( pn_delivery_t delivery)

Get the amount of pending message data for a delivery.

Parameters
[in]deliverya delivery object
Returns
the amount of pending message data in bytes

◆ pn_delivery_partial()

bool pn_delivery_partial ( pn_delivery_t delivery)

Check if a delivery only has partial message data.

The receiver can expect more PN_DELIVERY events for this delivery containing the remainder of this message.

Parameters
[in]deliverya delivery object
Returns
true if the delivery only contains part of a message, false otherwise

◆ pn_delivery_aborted()

bool pn_delivery_aborted ( pn_delivery_t delivery)

Check if a received delivery has been aborted.

An aborted delivery means the sender cannot complete this message and the receiver should discard any data already received. The link remains open for future messages.

You must still call pn_delivery_settle() to free local resources. An aborted delivery consumes a credit, use pn_link_flow() to issue new credit as for a successful delivery.

Calling pn_link_recv() when the current delivery is aborted returns PN_ABORTED.

See also
pn_delivery_abort()
Parameters
[in]deliverya delivery object
Returns
true if the delivery has been aborted, false otherwise

◆ pn_delivery_writable()

bool pn_delivery_writable ( pn_delivery_t delivery)

Check if a delivery is writable.

A delivery is considered writable if it is the current delivery on an outgoing link, and the link has positive credit.

Parameters
[in]deliverya delivery object
Returns
true if the delivery is writable, false otherwise

◆ pn_delivery_readable()

bool pn_delivery_readable ( pn_delivery_t delivery)

Check if a delivery is readable.

A delivery is considered readable if it is the current delivery on an incoming link.

Parameters
[in]deliverya delivery object
Returns
true if the delivery is readable, false otherwise

◆ pn_delivery_updated()

bool pn_delivery_updated ( pn_delivery_t delivery)

Check if a delivery is updated.

A delivery is considered updated whenever the peer communicates a new disposition for the delivery. Once a delivery becomes updated, it will remain so until pn_delivery_clear is called.

Parameters
[in]deliverya delivery object
Returns
true if the delivery is updated, false otherwise

◆ pn_delivery_update()

void pn_delivery_update ( pn_delivery_t delivery,
uint64_t  state 
)

Update the disposition of a delivery.

When update is invoked the updated disposition of the delivery will be communicated to the peer.

Parameters
[in]deliverya delivery object
[in]statethe updated delivery state

◆ pn_delivery_clear()

void pn_delivery_clear ( pn_delivery_t delivery)

Clear the updated flag for a delivery.

See pn_delivery_updated.

Parameters
[in]deliverya delivery object

◆ pn_delivery_current()

bool pn_delivery_current ( pn_delivery_t delivery)

Return true if delivery is the current delivery for its link.

Parameters
[in]deliverya delivery object
Returns
true if delivery is the current delivery for its link.

◆ pn_delivery_abort()

void pn_delivery_abort ( pn_delivery_t delivery)

Abort a delivery being sent.

Aborting means the sender cannot complete this message. It will not send any more data, and data sent so far should be discarded by the receiver. The link remains open for future messages.

If some data has already been sent on the network, an AMQP "aborted" frame will be sent to inform the peer. If no data has yet been sent, the delivery will simply be forgotten.

The delivery will be freed, and cannot be used after the call.

See also
pn_delivery_aborted()
Parameters
[in]deliverya delivery object

◆ pn_delivery_settle()

void pn_delivery_settle ( pn_delivery_t delivery)

Settle a delivery.

A settled delivery can never be used again.

Note
If pn_delivery_current(delivery) is true before the call then pn_link_advance(pn_delivery_link(deliver)) is called automatically.
Parameters
[in]deliverya delivery object

◆ pn_delivery_dump()

void pn_delivery_dump ( pn_delivery_t delivery)

Utility function for printing details of a delivery.

Parameters
[in]deliverya delivery object

◆ pn_delivery_buffered()

bool pn_delivery_buffered ( pn_delivery_t delivery)

Check if a delivery is buffered.

A delivery that is buffered has not yet been written to the wire.

Note that returning false does not imply that a delivery was definitely written to the wire. If false is returned, it is not known whether the delivery was actually written to the wire or not.

Parameters
[in]deliverya delivery object
Returns
true if the delivery is buffered

◆ pn_work_head()

pn_delivery_t* pn_work_head ( pn_connection_t connection)

Extracts the first delivery on the connection that has pending operations.

Retrieves the first delivery on the Connection that has pending operations. A readable delivery indicates message data is waiting to be read. A writable delivery indicates that message data may be sent. An updated delivery indicates that the delivery's disposition has changed. A delivery will never be both readable and writible, but it may be both readable and updated or both writiable and updated.

Parameters
[in]connectionthe connection
Returns
the first delivery object that needs to be serviced, else NULL if none

◆ pn_work_next()

pn_delivery_t* pn_work_next ( pn_delivery_t delivery)

Get the next delivery on the connection that needs has pending operations.

Parameters
[in]deliverythe previous delivery retrieved from either pn_work_head or pn_work_next
Returns
the next delivery that has pending operations, else NULL if none

◆ pn_disposition_type()

uint64_t pn_disposition_type ( pn_disposition_t disposition)

Get the type of a disposition.

Defined values are:

Parameters
[in]dispositiona disposition object
Returns
the type of the disposition

◆ pn_disposition_condition()

pn_condition_t* pn_disposition_condition ( pn_disposition_t disposition)

Access the condition object associated with a disposition.

The pn_condition_t object retrieved by this operation may be modified prior to updating a delivery. When a delivery is updated, the condition described by the disposition is reported to the peer if applicable to the current delivery state, e.g. states such as PN_REJECTED.

The pointer returned by this operation is valid until the parent delivery is settled.

Parameters
[in]dispositiona disposition object
Returns
a pointer to the disposition condition

◆ pn_disposition_data()

pn_data_t* pn_disposition_data ( pn_disposition_t disposition)

Access the disposition as a raw pn_data_t.

Dispositions are an extension point in the AMQP protocol. The disposition interface provides setters/getters for those dispositions that are predefined by the specification, however access to the raw disposition data is provided so that other dispositions can be used.

The pn_data_t pointer returned by this operation is valid until the parent delivery is settled.

Parameters
[in]dispositiona disposition object
Returns
a pointer to the raw disposition data

◆ pn_disposition_get_section_number()

uint32_t pn_disposition_get_section_number ( pn_disposition_t disposition)

Get the section number associated with a disposition.

Parameters
[in]dispositiona disposition object
Returns
a section number

◆ pn_disposition_set_section_number()

void pn_disposition_set_section_number ( pn_disposition_t disposition,
uint32_t  section_number 
)

Set the section number associated with a disposition.

Parameters
[in]dispositiona disposition object
[in]section_numbera section number

◆ pn_disposition_get_section_offset()

uint64_t pn_disposition_get_section_offset ( pn_disposition_t disposition)

Get the section offset associated with a disposition.

Parameters
[in]dispositiona disposition object
Returns
a section offset

◆ pn_disposition_set_section_offset()

void pn_disposition_set_section_offset ( pn_disposition_t disposition,
uint64_t  section_offset 
)

Set the section offset associated with a disposition.

Parameters
[in]dispositiona disposition object
[in]section_offseta section offset

◆ pn_disposition_is_failed()

bool pn_disposition_is_failed ( pn_disposition_t disposition)

Check if a disposition has the failed flag set.

Parameters
[in]dispositiona disposition object
Returns
true if the disposition has the failed flag set, false otherwise

◆ pn_disposition_set_failed()

void pn_disposition_set_failed ( pn_disposition_t disposition,
bool  failed 
)

Set the failed flag on a disposition.

Parameters
[in]dispositiona disposition object
[in]failedthe value of the failed flag

◆ pn_disposition_is_undeliverable()

bool pn_disposition_is_undeliverable ( pn_disposition_t disposition)

Check if a disposition has the undeliverable flag set.

Parameters
[in]dispositiona disposition object
Returns
true if the disposition has the undeliverable flag set, false otherwise

◆ pn_disposition_set_undeliverable()

void pn_disposition_set_undeliverable ( pn_disposition_t disposition,
bool  undeliverable 
)

Set the undeliverable flag on a disposition.

Parameters
[in]dispositiona disposition object
[in]undeliverablethe value of the undeliverable flag

◆ pn_disposition_annotations()

pn_data_t* pn_disposition_annotations ( pn_disposition_t disposition)

Access the annotations associated with a disposition.

The pn_data_t object retrieved by this operation may be modified prior to updating a delivery. When a delivery is updated, the annotations described by the pn_data_t are reported to the peer if applicable to the current delivery state, e.g. states such as PN_MODIFIED. The pn_data_t must be empty or contain a symbol keyed map.

The pointer returned by this operation is valid until the parent delivery is settled.

Parameters
[in]dispositiona disposition object
Returns
the annotations associated with the disposition