A method, system, device and storage medium for fast metadata reading

Abstract

The application provides a method, system, device and storage medium for quickly reading metadata, the method comprising: in response to receiving a metadata request for accessing a first file by a service, a metadata server only reading metadata information of the first file; responding to the metadata request issued by a client according to the read metadata information of the first file; asynchronously issuing the metadata request to a metadata disk and batch loading metadata information of other files in a directory where the first file is located; and in response to again receiving metadata information of a target file in the directory where the first file is located, directly reading metadata information of the target file from the metadata disk. The application improves the metadata cache reading performance of a distributed file storage system in a sequential reading scenario and a random reading scenario. The stored metadata cache space is more efficiently utilized, and the cache hit rate is improved.

Description

Technical Field

[0001] This invention relates to the field of distributed file systems, and more specifically, to a method, system, device, and storage medium for quickly reading metadata. Background Technology

[0002] With the generation of massive amounts of data, the performance requirements for data storage and access are becoming increasingly stringent. In distributed file systems, metadata access is an essential part of the data access process, accounting for more than 50% of all accesses. Therefore, improving the performance of metadata access is particularly important.

[0003] The current technical processing logic, when a business client sends a metadata request to the metadata service, requires loading all metadata entries for all subfiles under the directory into the cache space if the directory cache is incomplete. Even when the directory cache is incomplete, but the requested file's metadata can be cached, the entire loading process must be executed before the client's request is processed. This method of loading the entire directory's metadata significantly degrades the overall storage performance. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method, system, computer device, and computer-readable storage medium for fast metadata reading. When a business needs to access the metadata of a file, the metadata server first reads only the metadata information of the file to be accessed and responds to the metadata request sent by the client. Simultaneously, it asynchronously sends a request to the metadata disk, batch loading the metadata information of other file entries in that directory. This improves the command rate of the metadata cache and the performance of sequential reads, as well as the performance of read operations with high randomness, when the business sends a file request again.

[0005] To achieve the above objectives, one aspect of the present invention provides a method for quickly reading metadata, comprising the following steps: in response to receiving a metadata request for accessing a first file, the metadata server reads only the metadata information of the first file; responds to the metadata request sent by the client based on the read metadata information of the first file; asynchronously sends the metadata request to the metadata disk and loads the metadata information of other files in the directory where the first file is located in batches; and in response to receiving again the metadata information of a target file in the directory where the first file is located, directly reads the metadata information of the target file from the metadata disk.

[0006] In some implementations, the metadata server reading only the metadata information of the first file includes: checking whether the metadata of all sub-file entries in the directory where the first file is located is complete; and in response to the incomplete metadata of all sub-file entries in the directory where the first file is located, checking whether the metadata information of the first file can be found in the cache space.

[0007] In some implementations, the metadata server reading only the metadata information of the first file includes: in response to the first file's metadata information not being found in the cache space, loading the first file's metadata information from the metadata disk.

[0008] In some implementations, the batch loading of metadata information of other files in the directory where the first file is located includes: performing a batch preloading process of metadata for other sub-file entries in the directory where the first file is located, and indicating that the directory metadata cache is being preloaded.

[0009] In some implementations, the method further includes responding to client requests in batches according to the preloading process of each directory, in response to traversing all sub-file entries of all directories.

[0010] In some implementations, the method further includes: indicating that the directory cache is in a complete state in response to the completion of preloading of all sub-file entries in all directories.

[0011] In some implementations, the method further includes: identifying the directory cache as incomplete in response to the metadata management process cleaning up the aging metadata cache.

[0012] In another aspect, this invention provides a system for quickly reading metadata, comprising: a reading module configured to, in response to receiving a metadata request for accessing a first file, read only the metadata information of the first file; a response module configured to, respond to the metadata request sent by the client based on the read metadata information of the first file; a loading module configured to, asynchronously send the metadata request to a metadata disk and load metadata information of other files in the directory where the first file is located in batches; and an execution module configured to, in response to receiving again the metadata information of a target file in the directory where the first file is located, directly read the metadata information of the target file from the metadata disk.

[0013] In another aspect of the present invention, a computer device is provided, comprising: at least one processor; and a memory storing computer instructions executable on the processor, the instructions, when executed by the processor, implementing the steps of the method described above.

[0014] In another aspect, the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method steps.

[0015] This invention offers the following beneficial technical effects: When a business needs to access the metadata of a file, the metadata server first reads only the metadata information of the file to be accessed and responds to the metadata request sent by the client. Simultaneously, it asynchronously sends a request to the metadata disk, batch loading the metadata information of other file entries in that directory. This improves the command rate of the metadata cache, enhances the performance of sequential reads, and also improves the performance of read operations with high randomness. It improves the high-performance metadata access requirements of distributed file storage systems in small file scenarios, thereby enhancing the product competitiveness of the storage solution. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic diagram illustrating an embodiment of the method for quickly reading metadata provided by the present invention;

[0018] Figure 2 A logic diagram of the method for quickly reading metadata provided by the present invention;

[0019] Figure 3 A schematic diagram illustrating an embodiment of the system for rapidly reading metadata provided by the present invention;

[0020] Figure 4 A schematic diagram of the hardware structure of an embodiment of a computer device for rapidly reading metadata provided by the present invention;

[0021] Figure 5 A schematic diagram illustrating an embodiment of a computer storage medium for fast metadata reading provided by the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0023] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0024] In a first aspect, an embodiment of a method for quickly reading metadata is proposed. Figure 1 The diagram shown is an embodiment of the method for quickly reading metadata provided by the present invention. Figure 1 As shown, the embodiments of the present invention include the following steps:

[0025] S1. In response to receiving a business request to access the metadata of the first file, the metadata server only reads the metadata information of the first file;

[0026] S2. Respond to the metadata request sent by the client based on the metadata information of the first file read;

[0027] S3. Asynchronously send the metadata request to the metadata disk, and batch load the metadata information of other files in the directory where the first file is located; and

[0028] S4. In response to receiving the target file metadata information in the directory where the first file is located again, directly read the target file metadata information from the metadata disk.

[0029] In this embodiment of the invention, when a cache miss occurs, only the metadata of the file to be accessed needs to be loaded. After responding to the client's request, the metadata is asynchronously sent to the disk to load the metadata of other files in the same directory in batches. This achieves the performance requirements of sequentially reading metadata in existing technologies, while also improving the performance of random access to metadata.

[0030] Figure 2 A logic diagram of the method for quickly reading metadata provided by the present invention, combined with Figure 2 The embodiments of the present invention will be described.

[0031] In response to receiving a business request to access the metadata of the first file, the metadata server only reads the metadata information of the first file.

[0032] In some implementations, the metadata server reading only the metadata information of the first file includes: checking whether the metadata of all sub-file entries in the directory where the first file is located is complete; and, in response to incomplete metadata of all sub-file entries in the directory where the first file is located, checking whether the metadata information of the first file can be found in the cache space. When a business client sends a request to access the metadata of a certain file (the first file), it first checks whether the metadata of all sub-file entries in the directory where the file is located is complete (this can be done by checking the integrity flag in the directory metadata cache). If complete, the metadata information of the file can be directly found in the cache, and the metadata request from the business client can be directly responded to.

[0033] In some implementations, the metadata server reading only the metadata information of the first file includes: in response to the first file's metadata information not being found in the cache space, loading the first file's metadata information from the metadata disk. When the directory's metadata cache is incomplete, checking whether the metadata information of the accessed file can be found in the cache space. If it can be found, the file's metadata information is read from the cache space to respond to the client's request. Otherwise, it needs to be loaded from the metadata disk, which may only load the metadata information of the file to be accessed. After being loaded into the metadata cache space, the client's metadata request can be responded to.

[0034] The metadata request sent by the client is responded to based on the metadata information of the first file read.

[0035] The metadata request is asynchronously sent to the metadata disk, and the metadata information of other files in the directory where the first file is located is loaded in batches.

[0036] In some implementations, the batch loading of metadata information for other files in the directory containing the first file includes: performing a batch preloading process for metadata of other sub-file entries in the directory containing the first file, and indicating that the directory metadata cache is in the process of preloading. When the directory metadata is incomplete, and after responding to the client's file metadata request, the metadata preloading process for other sub-file entries in that directory is initiated simultaneously. This preloading process can be performed in batches, and the directory metadata cache is indicated to be in the process of preloading.

[0037] In response to receiving metadata information for a target file in the directory containing the first file again, the metadata information of the target file is read directly from the metadata disk. When the business client accesses the metadata information of a file in this directory again, the cache hit rate can be improved. If the cache is not found, the metadata information of that file entry is read directly from the metadata disk without waiting for the preloading process to complete. Simultaneously, since the directory is currently undergoing a preloading process, there is no need to repeatedly send preloading requests.

[0038] In some implementations, the method further includes responding to client requests in batches according to the preloading process of each directory, in response to traversing all sub-file entries of all directories. When a business client needs to traverse all sub-file entries of the entire directory, since the directory is in the process of preloading in batches, the client's request can be responded to in batches. During the response to client interactions, the storage system performs asynchronous preloading, without waiting for all sub-file entries to be loaded before the metadata server responds to the client's traversal request. In this way, directory traversal requests can be responded to in advance and loaded asynchronously simultaneously, improving the access performance of traversal requests.

[0039] In some implementations, the method further includes: indicating that the directory cache is in a complete state in response to the completion of preloading of all sub-file entries in all directories.

[0040] In some implementations, the method further includes: identifying the directory cache as incomplete in response to the metadata management process cleaning up the aging metadata cache.

[0041] In this embodiment of the invention, when a service needs to access the metadata of a file, the metadata server first reads only the metadata information of the file to be accessed and responds to the metadata request sent by the client. Simultaneously, it asynchronously sends a request to the metadata disk, loading the metadata information of other file entries in that directory in batches. This improves the command rate of the metadata cache, enhances the performance of sequential reads, and also improves the performance of read operations with high randomness. This improves the high-performance metadata access requirements of distributed file storage systems in small file scenarios, enhancing the product competitiveness of the storage.

[0042] It should be noted that the steps in each embodiment of the above-described method for quickly reading metadata can be interleaved, substituted, added, or deleted. Therefore, these reasonable permutations and combinations of the method for quickly reading metadata should also fall within the protection scope of this invention, and the protection scope of this invention should not be limited to the embodiments.

[0043] Based on the above objectives, a second aspect of this invention proposes a system for quickly reading metadata. For example... Figure 3 As shown, system 200 includes the following modules: a reading module, configured to read only the metadata information of the first file in response to a received metadata request for accessing the first file; a response module, configured to respond to the metadata request sent by the client based on the read metadata information of the first file; a loading module, configured to asynchronously send the metadata request to the metadata disk and load the metadata information of other files in the directory where the first file is located in batches; and an execution module, configured to directly read the metadata information of the target file from the metadata disk in response to receiving again the metadata information of the target file in the directory where the first file is located.

[0044] In some implementations, the reading module is configured to: check whether the metadata of all sub-file entries in the directory where the first file is located is complete; and in response to the incomplete metadata of all sub-file entries in the directory where the first file is located, check whether the metadata information of the first file can be found in the cache space.

[0045] In some implementations, the reading module is configured to: load the metadata information of the first file from the metadata disk in response to a cache miss in the first file's metadata information.

[0046] In some implementations, the loading module is configured to: perform a batch preloading process of metadata for other sub-file entries in the directory where the first file is located, and indicate that the directory metadata cache is being preloaded.

[0047] In some implementations, the system also includes a traversal module configured to: respond to client requests in batches according to the preloading process of each directory in response to traversing all subfile entries of all directories.

[0048] In some implementations, the system also includes a first identification module configured to: identify that the directory cache is in a complete state in response to the completion of preloading of all sub-file entries in all directories.

[0049] In some implementations, the system also includes a second identification module configured to: identify the directory cache as incomplete in response to the metadata management process cleaning up the aging metadata cache.

[0050] In this embodiment of the invention, when a service needs to access the metadata of a file, the metadata server first reads only the metadata information of the file to be accessed and responds to the metadata request sent by the client. Simultaneously, it asynchronously sends a request to the metadata disk, loading the metadata information of other file entries in that directory in batches. This improves the command rate of the metadata cache, enhances the performance of sequential reads, and also improves the performance of read operations with high randomness. This improves the high-performance metadata access requirements of distributed file storage systems in small file scenarios, enhancing the product competitiveness of the storage.

[0051] Based on the above objectives, a third aspect of the present invention provides a computer device, comprising: at least one processor; and a memory storing computer instructions executable by the processor to perform the following steps: S1, in response to receiving a metadata request for access to a first file, a metadata server reads only the metadata information of the first file; S2, responding to the metadata request sent by the client based on the read metadata information of the first file; S3, asynchronously sending the metadata request to a metadata disk and batch loading metadata information of other files in the directory where the first file is located; and S4, in response to receiving again metadata information for a target file in the directory where the first file is located, directly reading the metadata information of the target file from the metadata disk.

[0052] In some implementations, the metadata server reading only the metadata information of the first file includes: checking whether the metadata of all sub-file entries in the directory where the first file is located is complete; and in response to the incomplete metadata of all sub-file entries in the directory where the first file is located, checking whether the metadata information of the first file can be found in the cache space.

[0053] In some implementations, the metadata server reading only the metadata information of the first file includes: in response to the first file's metadata information not being found in the cache space, loading the first file's metadata information from the metadata disk.

[0054] In some implementations, the batch loading of metadata information of other files in the directory where the first file is located includes: performing a batch preloading process of metadata for other sub-file entries in the directory where the first file is located, and indicating that the directory metadata cache is being preloaded.

[0055] In some implementations, the steps further include: responding to client requests in batches according to the preloading process of each directory in response to traversing all sub-file entries of all directories.

[0056] In some implementations, the steps further include: indicating that the directory cache is in a complete state in response to the completion of preloading of all sub-file entries in all directories.

[0057] In some implementations, the steps further include: in response to the metadata management process cleaning up the aging metadata cache, identifying the directory cache as incomplete.

[0058] In this embodiment of the invention, when a service needs to access the metadata of a file, the metadata server first reads only the metadata information of the file to be accessed and responds to the metadata request sent by the client. Simultaneously, it asynchronously sends a request to the metadata disk, loading the metadata information of other file entries in that directory in batches. This improves the command rate of the metadata cache, enhances the performance of sequential reads, and also improves the performance of read operations with high randomness. This improves the high-performance metadata access requirements of distributed file storage systems in small file scenarios, enhancing the product competitiveness of the storage.

[0059] like Figure 4 The diagram shown is a hardware structure schematic of an embodiment of the computer device for quickly reading metadata provided by the present invention.

[0060] For example Figure 4 Taking the device shown as an example, the device includes a processor 301 and a memory 302.

[0061] Processor 301 and memory 302 can be connected via a bus or other means. Figure 4 Taking the example of a connection between China and Israel via a bus.

[0062] The memory 302, as a non-volatile computer-readable storage medium, can be used to store non-volatile software programs, non-volatile computer-executable programs, and modules, such as the program instructions / modules corresponding to the method for quickly reading metadata in this embodiment. The processor 301 executes various functional applications and data processing of the server by running the non-volatile software programs, instructions, and modules stored in the memory 302, thereby realizing the method for quickly reading metadata.

[0063] Memory 302 may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created using methods for quickly reading metadata, etc. Furthermore, memory 302 may include high-speed random access memory and may also include non-volatile memory, such as at least one disk storage device, flash memory device, or other non-volatile solid-state storage device. In some embodiments, memory 302 may optionally include memory remotely located relative to processor 301, and these remote memories may be connected to the local module via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0064] One or more methods for quickly reading metadata are stored in memory 302. When executed by processor 301, the method for quickly reading metadata in any of the above method embodiments is executed.

[0065] The method for quickly reading metadata includes the following steps: In response to receiving a metadata request from a business to access a first file, the metadata server reads only the metadata information of the first file; responds to the metadata request sent by the client based on the read metadata information of the first file; asynchronously sends the metadata request to the metadata disk and loads the metadata information of other files in the directory where the first file is located in batches; and in response to receiving again the metadata information of a target file in the directory where the first file is located, directly reads the metadata information of the target file from the metadata disk.

[0066] In some implementations, the metadata server reading only the metadata information of the first file includes: checking whether the metadata of all sub-file entries in the directory where the first file is located is complete; and in response to the incomplete metadata of all sub-file entries in the directory where the first file is located, checking whether the metadata information of the first file can be found in the cache space.

[0067] In some implementations, the metadata server reading only the metadata information of the first file includes: in response to the first file's metadata information not being found in the cache space, loading the first file's metadata information from the metadata disk.

[0068] In some implementations, the batch loading of metadata information of other files in the directory where the first file is located includes: performing a batch preloading process of metadata for other sub-file entries in the directory where the first file is located, and indicating that the directory metadata cache is being preloaded.

[0069] In some implementations, the method further includes responding to client requests in batches according to the preloading process of each directory, in response to traversing all sub-file entries of all directories.

[0070] In some implementations, the method further includes: indicating that the directory cache is in a complete state in response to the completion of preloading of all sub-file entries in all directories.

[0071] In some implementations, the method further includes: identifying the directory cache as incomplete in response to the metadata management process cleaning up the aging metadata cache.

[0072] Any embodiment of the computer device that performs the above-described method for quickly reading metadata can achieve the same or similar effects as any of the aforementioned method embodiments.

[0073] The present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, performs a method for quickly reading metadata.

[0074] The method for quickly reading metadata includes the following steps: In response to receiving a metadata request from a business to access a first file, the metadata server reads only the metadata information of the first file; responds to the metadata request sent by the client based on the read metadata information of the first file; asynchronously sends the metadata request to the metadata disk and loads the metadata information of other files in the directory where the first file is located in batches; and in response to receiving again the metadata information of a target file in the directory where the first file is located, directly reads the metadata information of the target file from the metadata disk.

[0075] In some implementations, the metadata server reading only the metadata information of the first file includes: checking whether the metadata of all sub-file entries in the directory where the first file is located is complete; and in response to the incomplete metadata of all sub-file entries in the directory where the first file is located, checking whether the metadata information of the first file can be found in the cache space.

[0076] In some implementations, the metadata server reading only the metadata information of the first file includes: in response to the first file's metadata information not being found in the cache space, loading the first file's metadata information from the metadata disk.

[0077] In some implementations, the batch loading of metadata information of other files in the directory where the first file is located includes: performing a batch preloading process of metadata for other sub-file entries in the directory where the first file is located, and indicating that the directory metadata cache is being preloaded.

[0078] In some implementations, the method further includes responding to client requests in batches according to the preloading process of each directory, in response to traversing all sub-file entries of all directories.

[0079] In some implementations, the method further includes: indicating that the directory cache is in a complete state in response to the completion of preloading of all sub-file entries in all directories.

[0080] In some implementations, the method further includes: identifying the directory cache as incomplete in response to the metadata management process cleaning up the aging metadata cache.

[0081] like Figure 5 The diagram shown is a schematic representation of an embodiment of the computer storage medium for fast metadata reading provided by the present invention. Figure 5 Taking the computer storage medium shown as an example, the computer-readable storage medium 401 stores a computer program 402 that, when executed by a processor, performs the above method.

[0082] Finally, it should be noted that those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program for the method of quickly reading metadata can be stored in a computer-readable storage medium. When executed, the program can include the processes of the embodiments of the above methods. The storage medium for the program can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc. The above computer program embodiments can achieve the same or similar effects as any of the corresponding foregoing method embodiments.

[0083] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular number.

[0084] It should be understood that, as used herein, the singular form “a” is intended to include the plural form as well, unless the context clearly supports an exception. It should also be understood that, as used herein, “and / or” refers to any and all possible combinations of one or more of the associated listed items.

[0085] The embodiment numbers disclosed in the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0086] Those skilled in the art will understand that all or part of the steps of the above embodiments can be implemented by hardware or by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0087] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for quickly reading metadata, characterized in that, Includes the following steps: In response to receiving a business request to access the metadata of the first file, the metadata server only reads the metadata information of the first file; The client's metadata request is responded to based on the metadata information of the first file read; The metadata request is asynchronously sent to the metadata disk, and the metadata information of other files in the directory where the first file is located is loaded in batches; as well as In response to receiving target file metadata information in the directory where the first file is located again, the target file metadata information is read directly from the metadata disk; The metadata server reads only the metadata information of the first file, including: Check if the metadata of all sub-file entries in the directory where the first file is located is complete; In response to incomplete metadata for all subfile entries in the directory where the first file is located, check whether the metadata information of the first file can be found in the cache space; The metadata server reads only the metadata information of the first file, including: In response to the fact that the metadata information of the first file cannot be found in the cache space, the metadata information of the first file is loaded from the metadata disk.

2. The method according to claim 1, characterized in that, The metadata information of other files in the directory where the first file is located is loaded in batches includes: The metadata preloading process for other sub-file entries in the directory where the first file is located is performed in batches, and the directory metadata cache is marked as being preloaded.

3. The method according to claim 1, characterized in that, The method also includes: In response to the traversal of all subfile entries in all directories, the system responds to client requests in batches according to the preloading process of each directory.

4. The method according to claim 3, characterized in that, The method also includes: The directory cache is considered complete once all subfile entries in all directories have been preloaded.

5. The method according to claim 4, characterized in that, The method also includes: In response to the metadata management process cleaning up aging metadata cache, the directory cache is identified as being in an incomplete state.

6. A system for quickly reading metadata, characterized in that, include: The reading module is configured to respond to a business request to access the metadata of the first file, and the metadata server will only read the metadata information of the first file. The response module is configured to respond to the metadata request sent by the client based on the metadata information of the first file read. The loading module is configured to asynchronously send the metadata request to the metadata disk and load the metadata information of other files in the directory where the first file is located in batches; as well as The execution module is configured to, in response to receiving target file metadata information accessing the directory where the first file is located again, directly read the metadata information of the target file from the metadata disk; The reading module is further configured to: check whether the metadata of all sub-file entries in the directory where the first file is located is complete; in response to the incomplete metadata of all sub-file entries in the directory where the first file is located, check whether the metadata information of the first file can be found in the cache space; in response to the incomplete metadata information of the first file in the cache space, load the metadata information of the first file from the metadata disk.

7. A computer device, characterized in that, include: At least one processor; as well as A memory storing computer instructions executable on the processor, which, when executed by the processor, implement the steps of the method according to any one of claims 1-5.

8. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1-5.

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