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| author | Eliza Weisman <eliza@buoyant.io> | 2020-11-01 10:48:44 -0800 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2020-11-01 10:48:44 -0800 |
| commit | fede3db76aef95c010c3e0c3da3b732380285097 (patch) | |
| tree | 0aa934da682d7f31cf093e69e420ba88601acb6e /tokio/Cargo.toml | |
| parent | 2b23aa7389686f341e564c8da565a3b4c8b1188f (diff) | |
tracing: replace future names with spawn locations in task spans (#3074)
## Motivation
Currently, the per-task `tracing` spans generated by tokio's `tracing`
feature flag include the `std::any::type_name` of the future that was
spawned. When future combinators and/or libraries like Tower are in use,
these future names can get _quite_ long. Furthermore, when formatting
the `tracing` spans with their parent spans as context, any other task
spans in the span context where the future was spawned from can _also_
include extremely long future names.
In some cases, this can result in extremely high memory use just to
store the future names. For example, in Linkerd, when we enable
`tokio=trace` to enable the task spans, there's a spawned task whose
future name is _232990 characters long_. A proxy with only 14 spawned
tasks generates a task list that's over 690 KB. Enabling task spans
under load results in the process getting OOM killed very quickly.
## Solution
This branch removes future type names from the spans generated by
`spawn`. As a replacement, to allow identifying which `spawn` call a
span corresponds to, the task span now contains the source code location
where `spawn` was called, when the compiler supports the
`#[track_caller]` attribute. Since `track_caller` was stabilized in Rust
1.46.0, and our minimum supported Rust version is 1.45.0, we can't
assume that `#[track_caller]` is always available. Instead, we have a
RUSTFLAGS cfg, `tokio_track_caller`, that guards whether or not we use
it. I've also added a `build.rs` that detects the compiler minor
version, and sets the cfg flag automatically if the current compiler
version is >= 1.46. This means users shouldn't have to enable
`tokio_track_caller` manually.
Here's the trace output from the `chat` example, before this change:
...and after:
Closes #3073
Signed-off-by: Eliza Weisman <eliza@buoyant.io>
Diffstat (limited to 'tokio/Cargo.toml')
| -rw-r--r-- | tokio/Cargo.toml | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/tokio/Cargo.toml b/tokio/Cargo.toml index 6c5de90d..c4825c20 100644 --- a/tokio/Cargo.toml +++ b/tokio/Cargo.toml @@ -102,7 +102,7 @@ mio = { version = "0.7.3", optional = true } num_cpus = { version = "1.8.0", optional = true } parking_lot = { version = "0.11.0", optional = true } # Not in full slab = { version = "0.4.1", optional = true } -tracing = { version = "0.1.16", default-features = false, features = ["std"], optional = true } # Not in full +tracing = { version = "0.1.21", default-features = false, features = ["std"], optional = true } # Not in full [target.'cfg(unix)'.dependencies] libc = { version = "0.2.42", optional = true } @@ -126,9 +126,12 @@ tempfile = "3.1.0" [target.'cfg(loom)'.dev-dependencies] loom = { version = "0.3.5", features = ["futures", "checkpoint"] } +[build-dependencies] +autocfg = "1" # Needed for conditionally enabling `track-caller` + [package.metadata.docs.rs] all-features = true rustdoc-args = ["--cfg", "docsrs"] [package.metadata.playground] -features = ["full"] +features = ["full"]
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