Data replication (client side, synchronous)

This MR adds support for data replication using one environment variable:

`LIBGKFS_NUM_REPL=<num repl>`
The number of replicas should go from 0 to the number of servers-1. The replicas are guided by the 
client, so it reduces write performance but we mantain the same level of consistency. 
On the other hand, it may increase read performance on some corner scenearios. 
Metadata replication is also implemented
The replication environment variable can be set up for each client, independently.

If a server is down, the data will be read from another replica. The metadata management is also done from another replica.

The replication is done in a synchronous way. A new function forward_write is used to sent to the different replicas. The reads are distributed, but this shouldn't produce an performance improvement as the distribution is similar to the original. 

In the case of the write, the original is sent to the target servers, and then the replicas are processed. This is done to avoid issues if a server, that should host a replica, is not available. 

In order to process the replicas a new method to check that a chunk needs to be processed inside a server is included, a bitset of 1024 is sent (coded in base-64 in a string). This represents 1024-chunks per write-read operation. If that is exceeded the normal hash check per chunk is done in the server. Exceeding this value, will disable the replica capabilities and produce unknown behaviours.

This can be potentially increased.

Finally, most of the operations are replica-aware, but some of them are missing yet. i.e., dirent.

See merge request !166

Ramon Nou authored Apr 13, 2023 and Marc Vef committed Mar 10, 2024

Added NUM_REPL env variable. (0 no replicas)

NUM_REPL  num replicas  (Replicas < servers)

Remove and truncate

Metadata replication

Metadata replication - Reattempt on stat

minimal compilation issues (c++20), srand for repl

Bitset

Bit set proposal (WIP)

Read - Write with bitset (<1024 chunks)

Changed bitset to vector

Added get_fs_config reattempt

Some more resilience on create

Added Replica_Check on write (disabled)

Added helper vector-bitset functions

Release 0.9.2


See merge request !181

Resolve "Client logging: Add per process log option"

Closes #278

Closes #278

See merge request !179