Hi, Instead of message bus (mbus), I’d use terms message and message IO (similar to packets and packet IO).
odp_msg_t == message event odp_msgio_t == message io port/interface/tap/socket/mailbox/… // create msg io port odp_msgio_t odp_msgio_create(…); // msg io port local address odp_msgio_addr_t odp_msgio_addr(odp_msgio_t msgio); more comments inlined … From: ext Ola Liljedahl [mailto:[email protected]] Sent: Friday, May 22, 2015 2:20 PM To: Savolainen, Petri (Nokia - FI/Espoo) Cc: [email protected] Subject: Re: [lng-odp] [RFC] Add ipc.h On 21 May 2015 at 11:50, Savolainen, Petri (Nokia - FI/Espoo) <[email protected]<mailto:[email protected]>> wrote: > -----Original Message----- > From: lng-odp > [mailto:[email protected]<mailto:[email protected]>] > On Behalf Of ext > Ola Liljedahl > Sent: Tuesday, May 19, 2015 1:04 AM > To: [email protected]<mailto:[email protected]> > Subject: [lng-odp] [RFC] Add ipc.h > > As promised, here is my first attempt at a standalone API for IPC - inter > process communication in a shared nothing architecture (message passing > between processes which do not share memory). > > Currently all definitions are in the file ipc.h but it is possible to > break out some message/event related definitions (everything from > odp_ipc_sender) in a separate file message.h. This would mimic the > packet_io.h/packet.h separation. > > The semantics of message passing is that sending a message to an endpoint > will always look like it succeeds. The appearance of endpoints is > explicitly > notified through user-defined messages specified in the odp_ipc_resolve() > call. Similarly, the disappearance (e.g. death or otherwise lost > connection) > is also explicitly notified through user-defined messages specified in the > odp_ipc_monitor() call. The send call does not fail because the addressed > endpoints has disappeared. > > Messages (from endpoint A to endpoint B) are delivered in order. If > message > N sent to an endpoint is delivered, then all messages <N have also been > delivered. Message delivery does not guarantee actual processing by the Ordered is OK requirement, but "all messages <N have also been delivered" means in practice loss less delivery (== re-tries and retransmission windows, etc). Lossy vs loss less link should be an configuration option. Also what "delivered" means? Message: - transmitted successfully over the link ? - is now under control of the remote node (post office) ? - delivered into application input queue ? - has been dequeued from application queue ? > recipient. End-to-end acknowledgements (using messages) should be used if > this guarantee is important to the user. > > IPC endpoints can be seen as interfaces (taps) to an internal reliable > multidrop network where each endpoint has a unique address which is only > valid for the lifetime of the endpoint. I.e. if an endpoint is destroyed > and then recreated (with the same name), the new endpoint will have a > new address (eventually endpoints addresses will have to be recycled but > not for a very long time). Endpoints names do not necessarily have to be > unique. How widely these addresses are unique: inside one VM, multiple VMs under the same host, multiple devices on a LAN (VLAN), ... I have added that the scope is expected to be an OS instance (e.g. VM). OK, it’s likely the scope mostly needed anyway. Still need to define if addressing (and protocol) is implementation specific or standardized. I think you are suggesting implementation specific, which is fine but need to note that it’s suitable only between two ODP instances of the same _implementation_ version. E.g. messaging between linux-generic and odp-dpdk, or between odp-dpdk-1.1.0.0 and odp-dpdk-1.1.0.1 would not necessary work. A protocol spec (with version numbering) would be needed to guaranteed intra implementation version communication. Implementation specific messaging would be sufficient for SW (ODP instance) coming from single SW vendor, but integration of SW from multiple vendors would need packets or proper “IPC” protocol. > > Signed-off-by: Ola Liljedahl > <[email protected]<mailto:[email protected]>> > --- > (This document/code contribution attached is provided under the terms of > agreement LES-LTM-21309) > > +/** > + * Create IPC endpoint > + * > + * @param name Name of local IPC endpoint > + * @param pool Pool for incoming messages > + * > + * @return IPC handle on success > + * @retval ODP_IPC_INVALID on failure and errno set > + */ > +odp_ipc_t odp_ipc_create(const char *name, odp_pool_t pool); This creates (implicitly) the local end point address. Yes. Does that have to be described? Maybe to highlight that “name” is not the address. > + > +/** > + * Set the default input queue for an IPC endpoint > + * > + * @param ipc IPC handle > + * @param queue Queue handle > + * > + * @retval 0 on success > + * @retval <0 on failure > + */ > +int odp_ipc_inq_setdef(odp_ipc_t ipc, odp_queue_t queue); Multiple input queues are likely needed for different priority messages. I have added priorities (copied from queue.h SCHED priorities) and a priority parameter to the send() call. packet_io.h doesn't have any API for associating a list of queues with the different (packet) priorities so there is no template to follow. I could invent a new call for doing this on MBUS endpoints. E.g. int odp_mbus_inq_set(odp_mbus_t mbus, odp_mbus_prio_t prio, odp_queue_t queue); Call once for each priority, I think this is better than having a call which specifies all queues at once (the number of priorities is implementation specific). I now think that the default queue should be specified when the endpoint is created. Messages could start pouring in immediately and might have to be enqueued somewhere (in certain implementations, I did not experience this problem in my prototype so did not think about it). I think it’s better to create all input queues (or actually let the implementation create queues) before the “port” is activated, so that already the very first incoming message goes to the right queue (priority level). BTW, odp_pktio_inq_xxx() is likely removed and handled through classification API (and let implementation return queue handles). > + > +/** > + * Resolve endpoint by name > + * > + * Look up an existing or future endpoint by name. > + * When the endpoint exists, return the specified message with the > endpoint > + * as the sender. > + * > + * @param ipc IPC handle > + * @param name Name to resolve > + * @param msg Message to return > + */ > +void odp_ipc_resolve(odp_ipc_t ipc, > + const char *name, > + odp_ipc_msg_t msg); How widely these names are visible? Inside one VM, multiple VMs under the same host, multiple devices on a LAN (VLAN), ... I think name service (or address resolution) are better handled in middleware layer. If ODP provides unique addresses and message passing mechanism, additional services can be built on top. We still need an API for it. How should that API look like and where should it be declared? I am suggesting a definition above and that it be located in the ODP mbus.h. Please suggest an actual alternative. It’s not necessary an API call. Application could send a “name resolution request” message to the middleware name server, etc. The name server address can be delivered to application in many ways (command line, config file, init message, etc). > + > +/** > + * Monitor endpoint > + * > + * Monitor an existing (potentially already dead) endpoint. > + * When the endpoint is dead, return the specified message with the > endpoint > + * as the sender. > + * > + * Unrecognized or invalid endpoint addresses are treated as dead > endpoints. > + * > + * @param ipc IPC handle > + * @param addr Address of monitored endpoint > + * @param msg Message to return > + */ > +void odp_ipc_monitor(odp_ipc_t ipc, > + const uint8_t addr[ODP_IPC_ADDR_SIZE], > + odp_ipc_msg_t msg); Again, I'd see node health monitoring and alarms as middleware services. Same comment as for resolve/lookup. Again it could a message interface between application and the middleware alarm service, etc. > + > +/** > + * Send message > + * > + * Send a message to an endpoint (which may already be dead). > + * Message delivery is ordered and reliable. All (accepted) messages will > be > + * delivered up to the point of endpoint death or lost connection. > + * Actual reception and processing is not guaranteed (use end-to-end > + * acknowledgements for that). > + * Monitor the remote endpoint to detect death or lost connection. > + * > + * @param ipc IPC handle > + * @param msg Message to send > + * @param addr Address of remote endpoint > + * > + * @retval 0 on success > + * @retval <0 on error > + */ > +int odp_ipc_send(odp_ipc_t ipc, > + odp_ipc_msg_t msg, Message priority parameter added. > + const uint8_t addr[ODP_IPC_ADDR_SIZE]); This would be used to send a message to an address, but normal odp_queue_enq() could be used to circulate this event inside an application (ODP instance). Yes. Messages are events. > + > +/** > + * Get address of sender (source) of message > + * > + * @param msg Message handle > + * @param addr Address of sender endpoint > + */ > +void odp_ipc_sender(odp_ipc_msg_t msg, > + uint8_t addr[ODP_IPC_ADDR_SIZE]); > + > +/** > + * Message data pointer > + * > + * Return a pointer to the message data > + * > + * @param msg Message handle > + * > + * @return Pointer to the message data > + */ > +void *odp_ipc_data(odp_ipc_msg_t msg); > + > +/** > + * Message data length > + * > + * Return length of the message data. > + * > + * @param msg Message handle > + * > + * @return Message length > + */ > +uint32_t odp_ipc_length(const odp_ipc_msg_t msg); > + > +/** > + * Set message length > + * > + * Set length of the message data. > + * > + * @param msg Message handle > + * @param len New length > + * > + * @retval 0 on success > + * @retval <0 on error > + */ > +int odp_ipc_reset(const odp_ipc_msg_t msg, uint32_t len); Per Maxim's suggestion, I renamed this call to odp_message_length_set() (there is also an odp_message_length() call which gets the length). New length need to be in limits of the buffer size. Agree, that buffer size is constant, but it can large (e.g. multiple kB in maximum). If message delivery copies data, the actual data length need to be define (for low overhead). When data ptr or data len is modified: push/pull head, push/pull tail would be analogies from packet API Messages are not packets that you add and remove headers from. Or? Messages have structure and may very well have layers. E.g. middleware message header is in front. The data pointer and length are updated when message travels between ODP msgio, middleware and application. If we are going to replicate the whole packet.h API, perhaps we should just use packets for messages. Indeed this was in my original prototype but then I wasn't sure this was abstract and implementation independent enough. I do envision messages to be more like buffers but with a per-buffer size (length). Certainly all protocol flags/features are not needed and preferably no segmentation. But dynamic data ptr/len would bring in concepts of head, tail, etc. -Petri
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