influxdata/influxdb · error · HeapDumpError

tempfile i/o

Error message

tempfile i/o: {0}

What it means

HeapDumpError::Io wraps a std::io::Error from tempfile creation/usage during dump_heap_profile. The heap profile is written into a temporary file before being streamed to the caller; any filesystem I/O failure along that path (create, open for reading, metadata) surfaces as this variant via #[from].

Solutions

1. Fix temp-dir permissions/availability or point TMPDIR at a writable location and restart
2. Free disk space or raise the container tmpfs/disk limit
3. Retry the dump after addressing the I/O condition; the error's inner io::Error names the exact failing operation

Example fix

// before
MALLOC_CONF=prof:true TMPDIR=/read-only ./myapp
// after
MALLOC_CONF=prof:true TMPDIR=/var/tmp ./myapp

fn tempdir_writable() -> bool {
    tempfile::tempdir().map(|d| d.path().is_dir()).unwrap_or(false)
}

match dump_heap_profile().await {
    Err(HeapDumpError::Io(e)) => { tracing::error!(%e, "tempfile i/o"); /* check disk/permissions */ }
    other => other?,
}

When it happens

Trigger: Calling dump_heap_profile() when the temp directory is unwritable or missing, the filesystem is full, or the tempfile cannot be reopened after jemalloc writes the dump.

Common situations: Read-only or exhausted /tmp; restrictive TMPDIR in hardened containers; disk quota exceeded; tmpfs size limits on small Kubernetes pods.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• error writing wal file
• io error
• IO error
• tempfile path was not valid C string (non-utf8 or interior…
• blocking task join

AI-assisted analysis of influxdata/influxdb@06200ef96b (2026-09-19). Data as JSON: /api/errors/dd37359eac56604a. Report an issue: GitHub.

Appendix: source

Thrown at core/jemalloc_stats/src/lib.rs:98

    target_os = "android",
    target_os = "dragonfly",
    target_env = "musl",
)) {
    "_RJEM_MALLOC_CONF"
} else {
    "MALLOC_CONF"
};

/// Errors returned by [`dump_heap_profile`].
#[derive(Debug, thiserror::Error)]
pub enum HeapDumpError {
    #[error("tempfile path was not valid C string (non-utf8 or interior NUL)")]
    BadTempPath,
    #[error("heap profiling is disabled; restart with {MALLOC_CONF_ENV}=prof:true to enable")]
    ProfilingDisabled,
    #[error("jemalloc prof.dump failed: {0}")]
    Jemalloc(#[from] tikv_jemalloc_ctl::Error),
    #[error("tempfile i/o: {0}")]
    Io(#[from] std::io::Error),
    #[error("blocking task join: {0}")]
    Join(#[from] tokio::task::JoinError),
}

/// Trigger a jemalloc heap profile dump and return a streaming reader for
/// the resulting `heap_v2` bytes.
///
/// Requires jemalloc built with `--enable-prof` (i.e. `tikv-jemallocator`
/// `profiling` feature) AND the binary started with `prof:true` in the
/// platform-appropriate `MALLOC_CONF` env var (or via a baked-in
/// `malloc_conf` static — see [`DEFAULT_MALLOC_CONF`]). When profiling is
/// disabled at startup this returns [`HeapDumpError::ProfilingDisabled`].
///
/// The function handles all file machinery internally: it allocates a
/// tempfile, runs jemalloc's synchronous `prof.dump`, unlinks the path, and
/// hands back an open fd wrapped in a [`HeapProfileStream`]. The tempfile
/// is unlinked before this call returns — POSIX semantics keep the inode

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