influxdata/influxdb · error · Error

bitcode error

Error message

bitcode error: {0}

What it means

serialize::Error::Bitcode wraps a bitcode::Error produced while binary-decoding a WAL file's payload. After the header and checksum validate, the contents are decoded with the bitcode binary codec; a decode failure means the bytes are structurally inconsistent with the expected schema (wrong version, truncated body, or corruption that happened to pass CRC). The inner bitcode error is included via #[from].

Solutions

1. Check the influxdb3 version that wrote the file versus the one reading it; replay old files with the matching version or migrate them.
2. Inspect the inner bitcode::Error message to see whether it is a truncation (incomplete data) vs a schema mismatch (version problem).
3. If the file is from an incompatible format version, archive it out of the active WAL directory so replay can continue.
4. Restore the file from backup if the body should have been intact and corruption is suspected.

Example fix

// before: reading v2-schema WAL file with v1 reader
let batch = verify_file_type_and_deserialize(&bytes)?; // Bitcode(DecodeFailed {..})
// after: replay with the writer's version, or archive old files
mv wal/old-format/ wal-archive/old-format/

// record and compare the serialization schema version at write time vs read time
let writer_version = wal_file_header_version(&bytes);
if writer_version != SUPPORTED_VERSION { /* archive: incompatible schema */ }

match verify_file_type_and_deserialize(&bytes) {
    Err(serialize::Error::Bitcode(e)) => match e {
        bitcode::Error::UnexpectedEnd => /* truncated body: restore/skip */,
        _ => /* schema/version mismatch: archive file, replay with writer version */,
    },
    other => other?,
}

When it happens

Trigger: Deserializing a valid-header, valid-CRC WAL file whose body does not decode as the expected buffered-write batch — e.g. a file written by a different schema/format version than the reader's bitcode model.

Common situations: Mixing WAL files across influxdb3 versions with changed serialization schemas; a file truncated after the checksummed portion; incompatibility after an upgrade where old files remain in the directory.

Related errors

• crc32 checksum mismatch
• deserialize error
• Invalid wal file identifier
• try from slice error
• WAL file too small: expected at least

AI-assisted analysis of influxdata/influxdb@06200ef96b (2026-09-19). Data as JSON: /api/errors/dc009e32a5b51e1a. Report an issue: GitHub.

Appendix: source

Thrown at influxdb3_wal/src/serialize.rs:23

use crate::WalContents;
use byteorder::{BigEndian, ReadBytesExt};
use bytes::Bytes;
use std::io::Cursor;
use std::mem::size_of;
use thiserror::Error;

#[derive(Debug, Error)]
pub enum Error {
    #[error("Invalid wal file identifier")]
    InvalidWalFile,

    #[error("WAL file too small: expected at least {expected} bytes, but got {actual} bytes")]
    WalFileTooSmall { expected: usize, actual: usize },

    #[error("crc32 checksum mismatch")]
    Crc32Mismatch,

    #[error("bitcode error: {0}")]
    Bitcode(#[from] bitcode::Error),

    #[error("IO error: {0}")]
    Io(#[from] std::io::Error),

    #[error("try from slice error {0}")]
    TryFromSlice(#[from] std::array::TryFromSliceError),
}

pub(crate) type Result<T, E = Error> = std::result::Result<T, E>;

/// The first bytes written into a wal file to identify it and its version.
const FILE_TYPE_IDENTIFIER: &[u8] = b"idb3.001";

#[inline(always)]
pub fn verify_file_type_and_deserialize(b: Bytes) -> Result<WalContents> {
    let contents = b.to_vec();

View on GitHub (pinned to 06200ef96b)