Cross-blockchain interaction method, apparatus, system, and electronic device

1. A computer-implemented method, comprising: receiving, by a cross-blockchain interaction end, a subscription request initiated by a blockchain node associated with a first blockchain, wherein the subscription request comprises a subscription condition; obtaining, by the cross-blockchain interaction end and from a publishing client that corresponds to a second blockchain, a message that satisfies the subscription condition; and sending, from the cross-blockchain interaction end, the message to a subscribing client that corresponds to the blockchain node, where the blockchain node calls a first smart contract associated with the first blockchain to trigger a corresponding contract operation based on the message, prior to obtaining the message: initiating, by the cross-blockchain interaction end, a status query request to the subscribing client, wherein the subscribing client maintains a message queue that corresponds to the blockchain node; receiving, at the cross-blockchain interaction end, a queue status associated with the message queue from the subscribing client; determining, by the cross-blockchain interaction end, whether the message queue comprises a message that satisfies the subscription condition based on the received queue status; and if it is determined that the message queue does not comprise a message that satisfies the subscription condition, obtaining, by the cross-blockchain interaction end, another message that satisfies the subscription condition from the publishing client that corresponds to the second blockchain.

2. The computer-implemented method of claim 1 , wherein the message is generated by a second smart contract associated with the second blockchain.

3. The computer-implemented method of claim 1 , wherein obtaining the message comprises: sending, from the cross-blockchain interaction end, a message acquisition request to the publishing client, wherein the message acquisition request matches the subscription condition; and receiving, at the cross-blockchain interaction end and from the publishing client, the message, wherein the message matches the message acquisition request and is generated by a second smart contract associated with the second blockchain.

4. The computer-implemented method of claim 3 , further comprising: prior to sending a message acquisition request to the publishing client: querying, by the cross-blockchain interaction end and using a query interface provided by the publishing client, as to whether a predetermined storage space in the second blockchain comprises a particular message that satisfies the subscription condition, wherein the predetermined storage space stores a plurality of messages generated by a second smart contract that corresponds to the second blockchain; and if the determination is YES, initiating, by the cross-blockchain interaction end, a message acquisition request to the publishing client to obtain the particular message that satisfies the subscription condition from the predetermined storage space.

5. The computer-implemented method of claim 1 , wherein the message includes a signature added by the publishing client, and wherein the subscribing client updates a message queue that corresponds to the blockchain node by adding the message to that particular message queue after the subscribing client verifies the signature.

6. The computer-implemented method of claim 5 , wherein the blockchain node calls the first smart contract if it is determined that the message queue is updated.

7. A non-transitory, computer-readable medium storing one or more instructions executable by a computer system to perform operations comprising: receiving, by a cross-blockchain interaction end, a subscription request initiated by a blockchain node associated with a first blockchain, wherein the subscription request comprises a subscription condition; obtaining, by the cross-blockchain interaction end and from a publishing client that corresponds to a second blockchain, a message that satisfies the subscription condition; and sending, from the cross-blockchain interaction end, the message to a subscribing client that corresponds to the blockchain node, where the blockchain node calls a first smart contract associated with the first blockchain to trigger a corresponding contract operation based on the message, prior to obtaining the message: initiating, by the cross-blockchain interaction end, a status query request to the subscribing client, wherein the subscribing client maintains a message queue that corresponds to the blockchain node; receiving, at the cross-blockchain interaction end, a queue status associated with the message queue from the subscribing client; determining, by the cross-blockchain interaction end, whether the message queue comprises a message that satisfies the subscription condition based on the received queue status; and if it is determined that the message queue does not comprise a message that satisfies the subscription condition, obtaining, by the cross-blockchain interaction end, another message that satisfies the subscription condition from the publishing client that corresponds to the second blockchain.

8. The non-transitory, computer-readable medium of claim 7 , wherein the message is generated by a second smart contract associated with the second blockchain.

9. The non-transitory, computer-readable medium of claim 7 , wherein obtaining the message comprises: sending, from the cross-blockchain interaction end, a message acquisition request to the publishing client, wherein the message acquisition request matches the subscription condition; and receiving, at the cross-blockchain interaction end and from the publishing client, the message, wherein the message matches the message acquisition request and is generated by a second smart contract associated with the second blockchain.

10. The non-transitory, computer-readable medium of claim 9 , further comprising: prior to sending a message acquisition request to the publishing client: querying, by the cross-blockchain interaction end and using a query interface provided by the publishing client, as to whether a predetermined storage space in the second blockchain comprises a particular message that satisfies the subscription condition, wherein the predetermined storage space stores a plurality of messages generated by a second smart contract that corresponds to the second blockchain; and if the determination is YES, initiating, by the cross-blockchain interaction end, a message acquisition request to the publishing client to obtain the particular message that satisfies the subscription condition from the predetermined storage space.

11. The non-transitory, computer-readable medium of claim 7 , wherein the message includes a signature added by the publishing client, and wherein the subscribing client updates a message queue that corresponds to the blockchain node by adding the message to that particular message queue after the subscribing client verifies the signature.

12. The non-transitory, computer-readable medium of claim 11 , wherein the blockchain node calls the first smart contract if it is determined that the message queue is updated.

13. A computer-implemented system, comprising: one or more computers; and one or more computer memory devices interoperably coupled with the one or more computers and having tangible, non-transitory, machine-readable media storing one or more instructions that, when executed by the one or more computers, perform one or more operations comprising: receiving, by a cross-blockchain interaction end, a subscription request initiated by a blockchain node associated with a first blockchain, wherein the subscription request comprises a subscription condition; obtaining, by the cross-blockchain interaction end and from a publishing client that corresponds to a second blockchain, a message that satisfies the subscription condition; and sending, from the cross-blockchain interaction end, the message to a subscribing client that corresponds to the blockchain node, where the blockchain node calls a first smart contract associated with the first blockchain to trigger a corresponding contract operation based on the message, prior to obtaining the message: initiating, by the cross-blockchain interaction end, a status query request to the subscribing client, wherein the subscribing client maintains a message queue that corresponds to the blockchain node; receiving, at the cross-blockchain interaction end, a queue status associated with the message queue from the subscribing client; determining, by the cross-blockchain interaction end, whether the message queue comprises a message that satisfies the subscription condition based on the received queue status; and if it is determined that the message queue does not comprise a message that satisfies the subscription condition, obtaining, by the cross-blockchain interaction end, another message that satisfies the subscription condition from the publishing client that corresponds to the second blockchain.

14. The computer-implemented system of claim 13 , wherein the message is generated by a second smart contract associated with the second blockchain.

15. The computer-implemented system of claim 13 , wherein obtaining the message comprises: sending, from the cross-blockchain interaction end, a message acquisition request to the publishing client, wherein the message acquisition request matches the subscription condition; and receiving, at the cross-blockchain interaction end and from the publishing client, the message, wherein the message matches the message acquisition request and is generated by a second smart contract associated with the second blockchain.

16. The computer-implemented system of claim 15 , further comprising: prior to sending a message acquisition request to the publishing client: querying, by the cross-blockchain interaction end and using a query interface provided by the publishing client, as to whether a predetermined storage space in the second blockchain comprises a particular message that satisfies the subscription condition, wherein the predetermined storage space stores a plurality of messages generated by a second smart contract that corresponds to the second blockchain; and if the determination is YES, initiating, by the cross-blockchain interaction end, a message acquisition request to the publishing client to obtain the particular message that satisfies the subscription condition from the predetermined storage space.

17. The computer-implemented system of claim 13 , wherein the message includes a signature added by the publishing client, and wherein the subscribing client updates a message queue that corresponds to the blockchain node by adding the message to that particular message queue after the subscribing client verifies the signature.