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Update documentation to create an empty wal file #411

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52ff6b8
Update documentation to create an empty wal file
Dec 19, 2023
4a11d35
Merge remote-tracking branch 'upstream/main' into update_empty_wal_cmds
May 28, 2024
23a1898
Update create-empty utility usage in Advanced Troubleshooting
May 28, 2024
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30 changes: 19 additions & 11 deletions _docs-2/troubleshooting/advanced.md
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Expand Up @@ -249,21 +249,29 @@ metadata table!), the following process can be followed to create a valid, empty
WAL file. Run the following commands as the Accumulo unix user (to ensure that
the proper file permissions in HDFS)

$ echo -n -e '--- Log File Header (v2) ---\x00\x00\x00\x00' > empty.wal
```
$ UUID=$(uuidgen); \
echo -n -e '--- Log File Header (v4) ---U+1F47B$'"${UUID}"'\x00\x00\x00\x00' > "${UUID}".wal; \
echo 'created: '"${UUID}"'.wal'
```

The above creates a file with the text "--- Log File Header (v2) ---" and then
four bytes. You should verify the contents of the file with a hexdump tool.
The above creates a file with the text "--- Log File Header (v4) ---" a unicode character to flag no decryption
parameters, a UUID and then four bytes. The file created will be `[uuid]`.wal and the name is echoed to the command
line. You should verify the contents of the file with a hexdump tool.

Then, place this empty WAL in HDFS and then replace the corrupt WAL file in HDFS
with the empty WAL.
Then, place this empty WAL in HDFS and then replace the corrupt WAL file in HDFS with the empty WAL for the
tserver / host pair with the following hdfs commands:

$ hdfs dfs -moveFromLocal empty.wal /user/accumulo/empty.wal
$ hdfs dfs -mv /user/accumulo/empty.wal /accumulo/wal/tserver-4.example.com+10011/26abec5b-63e7-40dd-9fa1-b8ad2436606e
$ hdfs dfs -moveFromLocal [uuid].wal /user/accumulo/[uuid].wal
$ hdfs dfs -mv /user/accumulo/[uuid].wal /accumulo/wal/[tserver+port]/[uuid]

After the corrupt WAL file has been replaced, the system should automatically recover.
It may be necessary to restart the Accumulo Manager process as an exponential
backup policy is used which could lead to a long wait before Accumulo will
try to re-load the WAL file.
Note:
- the `+` separator for port.
- the wal file is the uuid, without an extension

After the corrupt WAL file has been replaced, the system should automatically recover. It may be necessary to restart
the Accumulo Manager process as an exponential backup policy is used which could lead to a long wait before Accumulo
will try to re-load the WAL file.

## Zookeeper Failures

Expand Down