1PMEMPOOL_SYNC(3) PMDK Programmer's Manual PMEMPOOL_SYNC(3)
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6 pmempool_sync(), pmempool_transform() - pool set synchronization and
7 transformation
8
10 #include <libpmempool.h>
11 int pmempool_sync(const char *poolset_file,
13 unsigned flags); (EXPERIMENTAL)
14 int pmempool_transform(const char *poolset_file_src,
15 const char *poolset_file_dst, unsigned flags); (EXPERIMENTAL)
16
18 The pmempool_sync() function synchronizes data between replicas within
19 a pool set.
20 pmempool_sync() accepts two arguments:
22 • poolset_file - a path to a pool set file,
24 • flags - a combination of flags (ORed) which modify how synchroniza‐
26 tion is performed.
27 NOTE: Only the pool set file used to create the pool should be used
29 for syncing the pool.
30 NOTE: The pmempool_sync() cannot do anything useful if there are no
32 replicas in the pool set. In such case, it fails with an error.
33 NOTE: At the moment, replication is only supported for libpmemobj(7)
35 pools, so pmempool_sync() cannot be used with other pool types (libp‐
36 memlog(7), libpmemblk(7)).
37 The following flags are available:
39 • PMEMPOOL_SYNC_DRY_RUN - do not apply changes, only check for viabili‐
41 ty of synchronization.
42 pmempool_sync() checks that the metadata of all replicas in a pool set
44 is consistent, i.e. all parts are healthy, and if any of them is not,
45 the corrupted or missing parts are recreated and filled with data from
46 one of the healthy replicas.
47 If a pool set has the option SINGLEHDR (see poolset(5)), the internal
49 metadata of each replica is limited to the beginning of the first part
50 in the replica. If the option NOHDRS is used, replicas contain no in‐
51 ternal metadata. In both cases, only the missing parts or the ones
52 which cannot be opened are recreated with the pmempool_sync() function.
53 pmempool_transform() modifies the internal structure of a pool set. It
55 supports the following operations:
56 • adding one or more replicas,
58 • removing one or more replicas ,
60 • adding or removing pool set options.
62 Only one of the above operations can be performed at a time.
64 pmempool_transform() accepts three arguments:
66 • poolset_file_src - pathname of the pool set file for the source pool
68 set to be changed,
69 • poolset_file_dst - pathname of the pool set file that defines the new
71 structure of the pool set,
72 • flags - a combination of flags (ORed) which modify how synchroniza‐
74 tion is performed.
75 The following flags are available:
77 • PMEMPOOL_TRANSFORM_DRY_RUN - do not apply changes, only check for vi‐
79 ability of transformation.
80 When adding or deleting replicas, the two pool set files can differ on‐
82 ly in the definitions of replicas which are to be added or deleted.
83 When adding or removing pool set options (see poolset(5)), the rest of
84 both pool set files have to be of the same structure. The operation of
85 adding/removing a pool set option can be performed on a pool set with
86 local replicas only. To add/remove a pool set option to/from a pool
87 set with remote replicas, one has to remove the remote replicas first,
88 then add/remove the option, and finally recreate the remote replicas
89 having added/removed the pool set option to/from the remote replicas’
90 poolset files. To add a replica it is necessary for its effective size
91 to match or exceed the pool size. Otherwise the whole operation fails
92 and no changes are applied. If none of the pool set options is used,
93 the effective size of a replica is the sum of sizes of all its part
94 files decreased by 4096 bytes per each part file. The 4096 bytes of
95 each part file is utilized for storing internal metadata of the pool
96 part files. If the option SINGLEHDR is used, the effective size of a
97 replica is the sum of sizes of all its part files decreased once by
98 4096 bytes. In this case only the first part contains internal metada‐
99 ta. If the option NOHDRS is used, the effective size of a replica is
100 the sum of sizes of all its part files. In this case none of the parts
101 contains internal metadata.
102 NOTE: At the moment, transform operation is only supported for
104 libpmemobj(7) pools, so pmempool_transform() cannot be used with
105 other pool types (libpmemlog(7), libpmemblk(7)).
106
108 pmempool_sync() and pmempool_transform() return 0 on success. Other‐
109 wise, they return -1 and set errno appropriately.
110
112 EINVAL Invalid format of the input/output pool set file.
113 EINVAL Unsupported flags value.
115 EINVAL There is only master replica defined in the input pool set
117 passed to pmempool_sync().
118 EINVAL The source pool set passed to pmempool_transform() is not a
120 libpmemobj pool.
121 EINVAL The input and output pool sets passed to pmempool_transform()
123 are identical.
124 EINVAL Attempt to perform more than one transform operation at a time.
126 ENOTSUP The pool set contains a remote replica, but remote replication
128 is not supported (librpmem(7) is not available).
129
131 The pmempool_sync() API is experimental and it may change in future
132 versions of the library.
133 The pmempool_transform() API is experimental and it may change in fu‐
135 ture versions of the library.
136
138 libpmemlog(7), libpmemobj(7) and <https://pmem.io>
139PMDK - pmempool API version 1.3 2020-10-28 PMEMPOOL_SYNC(3)