Method, electronic device and computer program product for creating metadata index
Embodiments of the present disclosure relate to a method, an electronic device and a computer program product for creating metadata index. The method disclosed herein comprises: generating a first-level index to index a metadata item; inserting a first indication into the first-level index to indicate a position of the metadata item in a set of metadata; generating a second-level index to index a set of first-level indexes; and inserting a second indication into the second-level index to indicate a set of positions of the set of metadata. In this way, embodiments of the present disclosure can create an index structure which can indicate the position of the metadata item, so as to rapidly determine the position of the metadata item.
1. A method for creating a metadata index for metadata of a multi-node system in which operation of the multi-node system depends on a consistency of the metadata across the multi-node system, comprising:
identifying all locations of copies of a metadata item within the multi-node system, one of the locations being on a first electronic device of the multi-node system and a second of the locations being on a second electronic device of the multi-node system;
generating a first-level index for each of the copies of the metadata index;
inserting an indication into each first-level index to indicate a position of a corresponding copy of the metadata item, the position usable to identify the locations of the corresponding copy of the metadata item;
generating a first second-level index for the metadata index to index a first set of the first-level index, the first set of the first-level index all being associated with copies of the metadata item having locations of the first electronic device;
inserting a second indication into the first second-level index that directly specifies a first set of positions associated with the copies of the metadata item having the locations of the first electronic device;
generating a second second-level index for the metadata index to index a second set of first-level index, the second set of first-level index all being associated with copies of the metadata item having locations of the second electronic device;
inserting a third indication into the second second-level index that directly specifies a second set of positions associated with the copies of the metadata item having the locations of the second electronic device;
identifying an inconsistency between the metadata index and a remote metadata index from the second electronic device, the inconsistency being based on the second second-level index of the metadata index being different from a corresponding second second-level index of the remote metadata index, wherein the metadata index and the remote metadata index are generated using a same process; and
updating the metadata index based on the identified inconsistency to obtain an updated metadata index that is consistent with the remote metadata index.
2. The method of claim 1 , wherein generating the first-level index comprises:
performing a hash algorithm on one of the copies of the metadata item, to generate a first character string associated with the one of the copies of the metadata item as the first-level index.
3. The method of claim 1 , wherein generating the first second-level index comprises:
performing a hash algorithm on the first set of the first-level indexes, to generate a second character string associated with the first set of the first-level indexes as the first second-level index.
4. A method for indexing metadata for metadata of a multi-node computing system in which operation of the multi-node computing system depends on a consistency of the metadata across the multi-node computing system, comprising:
obtaining, by an electronic device of the multi-node computing system, a metadata index to provide metadata inconsistency identification;
obtaining, by the electronic device, a remote metadata index from a second electronic device of the multi-node computing system, the metadata index and the remote metadata index indexing a same set of metadata distributed across the multi-node computing system, the set of metadata being redundantly stored across the multi-node computing system;
identifying, by the electronic device, a second-level index of the metadata index and a corresponding second-level index of the remote metadata index;
identifying, by the electronic device, an inconsistency between the metadata index and the remote metadata index, the inconsistency being based on the second-level index being different from the corresponding second-level index;
obtaining a second indication contained in the second-level index, the second indication indicating a position of a metadata item that is redundantly stored in the electronic device for the second electronic device, the metadata item being inconsistent with a corresponding metadata item stored in the second electronic device; and
accessing the metadata item based on the position.
5. The method of claim 4 , wherein the second-level index is a second character string associated with a set of first-level indexes that is generated by performing a hash algorithm on the set of first-level indexes.
6. An electronic device of a multi-node system in which operation of the multi-node system depends on a consistency of metadata across the multi-node system, comprising:
a processor; and
a memory storing computer program instructions, the processor executing the computer program instructions in the memory to control the electronic device to perform operations for creating a metadata index for metadata of a multi-node system in which operation of the multi-node system depends on a consistency of the metadata across the multi-node system, the operations comprising:
identifying all locations of copies of a metadata item within the multi-node system, one of the locations being on a first electronic device of the multi-node system and a second of the locations being on a second electronic device of the multi-node system;
generating a first-level index for each of the copies of the metadata index;
inserting an indication into each first-level index to indicate a position of a corresponding copy of the metadata item, the position usable to identify the locations of the corresponding copy of the metadata item;
generating a first second-level index for the metadata index to index a first set of the first-level index, the first set of the first-level index all being associated with copies of the metadata item having locations of the first electronic device;
inserting a second indication into the first second-level index that directly specifies a first set of positions associated with the copies of the metadata item having the locations of the first electronic device;
generating a second second-level index for the metadata index to index a second set of first-level index, the second set of first-level index all being associated with copies of the metadata item having locations of the second electronic device;
inserting a third indication into the second second-level index that directly specifies a second set of positions associated with the copies of the metadata item having the locations of the second electronic device;
identifying an inconsistency between the metadata index and a remote metadata index from the second electronic device, the inconsistency being based on the second second-level index of the metadata index being different from a corresponding second second-level index of the remote metadata index, wherein the metadata index and the remote metadata index are generated using a same process; and
updating the metadata index based on the identified inconsistency to obtain an updated metadata index that is consistent with the remote metadata index.
7. A computer program product being tangibly stored on a non-transitory computer-readable medium and comprising computer-executable instructions, the computer-executable instructions usable to create a metadata index for metadata of a multi-node system in which operation of the multi-node system depends on a consistency of the metadata across the multi-node system, the computer-executable instructions when executed, causing a computer to perform operations, the operations comprising:
identifying all locations of copies of a metadata item within the multi-node system, one of the locations being on a first electronic device of the multi-node system and a second of the locations being on a second electronic device of the multi-node system;
generating a first-level index for each of the copies of the metadata index;
inserting an indication into each first-level index to indicate a position of a corresponding copy of the metadata item, the position usable to identify the locations of the corresponding copy of the metadata item;
generating a first second-level index for the metadata index to index a first set of the first-level index, the first set of the first-level index all being associated with copies of the metadata item having locations of the first electronic device;
inserting a second indication into the first second-level index that directly specifies a first set of positions associated with the copies of the metadata item having the locations of the first electronic device;
generating a second second-level index for the metadata index to index a second set of first-level index, the second set of first-level index all being associated with copies of the metadata item having locations of the second electronic device;
inserting a third indication into the second second-level index that directly specifies a second set of positions associated with the copies of the metadata item having the locations of the second electronic device;
identifying an inconsistency between the metadata index and a remote metadata index from the second electronic device, the inconsistency being based on the second second-level index of the metadata index being different from a corresponding second second-level index of the remote metadata index, wherein the metadata index and the remote metadata index are generated using a same process; and
updating the metadata index based on the identified inconsistency to obtain an updated metadata index that is consistent with the remote metadata index.
8. The electronic device of claim 6 , wherein generating the first-level index comprises:
performing a hash algorithm on one of the copies of the metadata item, to generate a first character string associated with the one of the copies of the metadata item as the first-level index.
9. The electronic device of claim 6 , wherein generating the first second-level index comprises:
performing a hash algorithm on the first set of the first-level indexes, to generate a second character string associated with the first set of the first-level indexes as the first second-level index.
10. The computer program product of claim 7 , wherein generating the first-level index comprises:
performing a hash algorithm on one of the copies of the metadata item, to generate a first character string associated with the one of the copies of the metadata item as the first-level index.
11. The computer program product of claim 7 , wherein generating the first second-level index comprises:
performing a hash algorithm on the first set of the first-level indexes, to generate a second character string associated with the first set of the first-level indexes as the first second-level index.
12. The method of claim 1 , wherein the corresponding second second-level index of the remote metadata index contains a third indication that directly specifies a third set of positions associated with the copies of the metadata item having the locations of the second electronic device.
13. The electronic device of claim 6 , wherein the corresponding second second-level index of the remote metadata index contains a third indication that directly specifies a third set of positions associated with the copies of the metadata item having the locations of the second electronic device.
14. The computer program product of claim 7 , wherein the corresponding second second-level index of the remote metadata index contains a third indication that directly specifies a third set of positions associated with the copies of the metadata item having the locations of the second electronic device.
15. The method of claim 4 , wherein the corresponding second-level index contains a third indication that directly specifies a position associated with the metadata item that is originally stored in the second electronic device.