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Corruption
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==========
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Important step
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--------------
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Make sure you have a backup of the Tendermint data directory.
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Possible causes
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---------------
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Remember that most corruption is caused by hardware issues:
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- RAID controllers with faulty / worn out battery backup, and an unexpected power loss
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- Hard disk drives with write-back cache enabled, and an unexpected power loss
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- Cheap SSDs with insufficient power-loss protection, and an unexpected power-loss
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- Defective RAM
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- Defective or overheating CPU(s)
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Other causes can be:
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- Database systems configured with fsync=off and an OS crash or power loss
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- Filesystems configured to use write barriers plus a storage layer that ignores write barriers. LVM is a particular culprit.
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- Tendermint bugs
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- Operating system bugs
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- Admin error
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- directly modifying Tendermint data-directory contents
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(Source: https://wiki.postgresql.org/wiki/Corruption)
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WAL Corruption
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--------------
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If consensus WAL is corrupted at the lastest height and you are trying to start
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Tendermint, replay will fail with panic.
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Recovering from data corruption can be hard and time-consuming. Here are two approaches you can take:
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1) Delete the WAL file and restart Tendermint. It will attempt to sync with other peers.
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2) Try to repair the WAL file manually:
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1. Create a backup of the corrupted WAL file:
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.. code:: bash
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cp "$TMHOME/data/cs.wal/wal" > /tmp/corrupted_wal_backup
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2. Use ./scripts/wal2json to create a human-readable version
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.. code:: bash
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./scripts/wal2json/wal2json "$TMHOME/data/cs.wal/wal" > /tmp/corrupted_wal
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3. Search for a "CORRUPTED MESSAGE" line.
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4. By looking at the previous message and the message after the corrupted one
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and looking at the logs, try to rebuild the message. If the consequent
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messages are marked as corrupted too (this may happen if length header
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got corrupted or some writes did not make it to the WAL ~ truncation),
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then remove all the lines starting from the corrupted one and restart
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Tendermint.
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.. code:: bash
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$EDITOR /tmp/corrupted_wal
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5. After editing, convert this file back into binary form by running:
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.. code:: bash
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./scripts/json2wal/json2wal /tmp/corrupted_wal > "$TMHOME/data/cs.wal/wal"
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