github.com/yacovm/fabric@v2.0.0-alpha.0.20191128145320-c5d4087dc723+incompatible/docs/source/peer_event_services.rst (about) 1 Peer channel-based event services 2 ================================= 3 4 General overview 5 ---------------- 6 7 In previous versions of Fabric, the peer event service was known as the event 8 hub. This service sent events any time a new block was added to the peer's 9 ledger, regardless of the channel to which that block pertained, and it was only 10 accessible to members of the organization running the eventing peer (i.e., the 11 one being connected to for events). 12 13 Starting with v1.1, there are two new services which provide events. These services use an 14 entirely different design to provide events on a per-channel basis. This means 15 that registration for events occurs at the level of the channel instead of the peer, 16 allowing for fine-grained control over access to the peer's data. Requests to 17 receive events are accepted from identities outside of the peer's organization (as 18 defined by the channel configuration). This also provides greater reliability and a 19 way to receive events that may have been missed (whether due to a connectivity issue 20 or because the peer is joining a network that has already been running). 21 22 Available services 23 ------------------ 24 25 * ``Deliver`` 26 27 This service sends entire blocks that have been committed to the ledger. If 28 any events were set by a chaincode, these can be found within the 29 ``ChaincodeActionPayload`` of the block. 30 31 * ``DeliverFiltered`` 32 33 This service sends "filtered" blocks, minimal sets of information about blocks 34 that have been committed to the ledger. It is intended to be used in a network 35 where owners of the peers wish for external clients to primarily receive 36 information about their transactions and the status of those transactions. If 37 any events were set by a chaincode, these can be found within the 38 ``FilteredChaincodeAction`` of the filtered block. 39 40 .. note:: The payload of chaincode events will not be included in filtered blocks. 41 42 How to register for events 43 -------------------------- 44 45 Registration for events from either service is done by sending an envelope 46 containing a deliver seek info message to the peer that contains the desired start 47 and stop positions, the seek behavior (block until ready or fail if not ready). 48 There are helper variables ``SeekOldest`` and ``SeekNewest`` that can be used to 49 indicate the oldest (i.e. first) block or the newest (i.e. last) block on the ledger. 50 To have the services send events indefinitely, the ``SeekInfo`` message should 51 include a stop position of ``MAXINT64``. 52 53 .. note:: If mutual TLS is enabled on the peer, the TLS certificate hash must be 54 set in the envelope's channel header. 55 56 By default, both services use the Channel Readers policy to determine whether 57 to authorize requesting clients for events. 58 59 Overview of deliver response messages 60 ------------------------------------- 61 62 The event services send back ``DeliverResponse`` messages. 63 64 Each message contains one of the following: 65 66 * status -- HTTP status code. Both services will return the appropriate failure 67 code if any failure occurs; otherwise, it will return ``200 - SUCCESS`` once 68 the service has completed sending all information requested by the ``SeekInfo`` 69 message. 70 * block -- returned only by the ``Deliver`` service. 71 * filtered block -- returned only by the ``DeliverFiltered`` service. 72 73 A filtered block contains: 74 75 * channel ID. 76 * number (i.e. the block number). 77 * array of filtered transactions. 78 * transaction ID. 79 80 * type (e.g. ``ENDORSER_TRANSACTION``, ``CONFIG``. 81 * transaction validation code. 82 83 * filtered transaction actions. 84 * array of filtered chaincode actions. 85 * chaincode event for the transaction (with the payload nilled out). 86 87 SDK event documentation 88 ----------------------- 89 90 For further details on using the event services, refer to the `SDK documentation. <https://fabric-sdk-node.github.io/tutorial-channel-events.html>`_ 91 92 .. Licensed under Creative Commons Attribution 4.0 International License 93 https://creativecommons.org/licenses/by/4.0/