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/target/
/Cargo.lock

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[package]
name = "objcache"
version = "0.1.0"
edition = "2021"
authors = ["Hannes Körber <hannes@hkoerber.de>"]
rust-version = "1.70"
description = "Cache objects using redis"
license = "GPL-3.0-only"
[workspace]
members = ["examples"]
[dependencies]
tokio = { version = "1.*", default-features = false, features = [] }
serde = { version = "1.0.*", default-features = false, features = ["std", "derive"] }
chrono = { version = "0.4.*", default-features = false, features = ["std", "now", "serde"] }
serde_json = { version = "1.0.*", default-features = false, features = ["std"] }
redis = { version = "0.23.*", default-features = false, features = ["serde", "aio", "tokio-comp"] }
redlock = { version = "2.0.*", default-features = false }
tracing = { version = "0.1.*", default-features = false, features = ["attributes"] }
[lints.rust]
absolute_paths_not_starting_with_crate = "deny"
elided_lifetimes_in_paths = "deny"
explicit_outlives_requirements = "deny"
keyword_idents = "deny"
let_underscore_drop = "deny"
non_ascii_idents = "deny"
non_local_definitions = "deny"
single_use_lifetimes = "deny"
unit_bindings = "deny"
unreachable_pub = "deny"
unsafe_code = { level = "forbid", priority = -1 }
unsafe_op_in_unsafe_fn = "deny"
unstable_features = { level = "forbid", priority = -1 }
unused_crate_dependencies = "allow"
unused_import_braces = "deny"
unused_lifetimes = "deny"
unused_macro_rules = "deny"
unused_qualifications = "deny"
unused_results = "deny"
variant_size_differences = "deny"
[lints.clippy]
missing_errors_doc = "allow"
redundant_pub_crate = "allow"
must_use_candidate = "allow"
missing_const_for_fn = "allow"
too_many_lines = "allow"
type_complexity = "allow"
pedantic = { level = "deny", priority = -1 }
nursery = { level = "deny", priority = -1 }
# restrictions
print_stdout = "deny"
print_stderr = "deny"
dbg_macro = "deny"
arithmetic_side_effects = "deny"
as_conversions = "deny"
assertions_on_result_states = "deny"
clone_on_ref_ptr = "deny"
create_dir = "deny"
decimal_literal_representation = "deny"
default_numeric_fallback = "deny"
deref_by_slicing = "deny"
disallowed_script_idents = "deny"
else_if_without_else = "deny"
empty_drop = "deny"
empty_enum_variants_with_brackets = "deny"
empty_structs_with_brackets = "deny"
exit = "deny"
expect_used = "deny"
filetype_is_file = "deny"
float_arithmetic = "deny"
float_cmp_const = "deny"
fn_to_numeric_cast_any = "deny"
format_push_string = "deny"
get_unwrap = "deny"
if_then_some_else_none = "deny"
impl_trait_in_params = "deny"
indexing_slicing = "deny"
infinite_loop = "deny"
inline_asm_x86_att_syntax = "deny"
inline_asm_x86_intel_syntax = "deny"
integer_division = "deny"
iter_over_hash_type = "deny"
large_include_file = "deny"
let_underscore_must_use = "deny"
let_underscore_untyped = "deny"
little_endian_bytes = "deny"
lossy_float_literal = "deny"
map_err_ignore = "deny"
mem_forget = "deny"
missing_assert_message = "deny"
missing_asserts_for_indexing = "deny"
mixed_read_write_in_expression = "deny"
mod_module_files = "deny"
modulo_arithmetic = "deny"
multiple_inherent_impl = "deny"
multiple_unsafe_ops_per_block = "deny"
mutex_atomic = "deny"
panic = "deny"
panic_in_result_fn = "deny"
partial_pub_fields = "deny"
pattern_type_mismatch = "deny"
pub_without_shorthand = "deny"
rc_buffer = "deny"
rc_mutex = "deny"
redundant_type_annotations = "deny"
rest_pat_in_fully_bound_structs = "deny"
same_name_method = "deny"
self_named_module_files = "deny"
semicolon_outside_block = "deny"
str_to_string = "deny"
string_add = "deny"
string_lit_chars_any = "deny"
string_slice = "deny"
string_to_string = "deny"
suspicious_xor_used_as_pow = "deny"
tests_outside_test_module = "deny"
try_err = "deny"
undocumented_unsafe_blocks = "deny"
unimplemented = "deny"
unnecessary_safety_comment = "deny"
unnecessary_safety_doc = "deny"
unnecessary_self_imports = "deny"
unneeded_field_pattern = "deny"
unseparated_literal_suffix = "deny"
unwrap_used = "deny"
use_debug = "deny"
verbose_file_reads = "deny"

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or that patent license was granted, prior to 28 March 2007.
Nothing in this License shall be construed as excluding or limiting
any implied license or other defenses to infringement that may
otherwise be available to you under applicable patent law.
12. No Surrender of Others' Freedom.
If conditions are imposed on you (whether by court order, agreement or
otherwise) that contradict the conditions of this License, they do not
excuse you from the conditions of this License. If you cannot convey a
covered work so as to satisfy simultaneously your obligations under this
License and any other pertinent obligations, then as a consequence you may
not convey it at all. For example, if you agree to terms that obligate you
to collect a royalty for further conveying from those to whom you convey
the Program, the only way you could satisfy both those terms and this
License would be to refrain entirely from conveying the Program.
13. Use with the GNU Affero General Public License.
Notwithstanding any other provision of this License, you have
permission to link or combine any covered work with a work licensed
under version 3 of the GNU Affero General Public License into a single
combined work, and to convey the resulting work. The terms of this
License will continue to apply to the part which is the covered work,
but the special requirements of the GNU Affero General Public License,
section 13, concerning interaction through a network will apply to the
combination as such.
14. Revised Versions of this License.
The Free Software Foundation may publish revised and/or new versions of
the GNU General Public License from time to time. Such new versions will
be similar in spirit to the present version, but may differ in detail to
address new problems or concerns.
Each version is given a distinguishing version number. If the
Program specifies that a certain numbered version of the GNU General
Public License "or any later version" applies to it, you have the
option of following the terms and conditions either of that numbered
version or of any later version published by the Free Software
Foundation. If the Program does not specify a version number of the
GNU General Public License, you may choose any version ever published
by the Free Software Foundation.
If the Program specifies that a proxy can decide which future
versions of the GNU General Public License can be used, that proxy's
public statement of acceptance of a version permanently authorizes you
to choose that version for the Program.
Later license versions may give you additional or different
permissions. However, no additional obligations are imposed on any
author or copyright holder as a result of your choosing to follow a
later version.
15. Disclaimer of Warranty.
THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
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OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
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IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
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THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
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SUCH DAMAGES.
17. Interpretation of Sections 15 and 16.
If the disclaimer of warranty and limitation of liability provided
above cannot be given local legal effect according to their terms,
reviewing courts shall apply local law that most closely approximates
an absolute waiver of all civil liability in connection with the
Program, unless a warranty or assumption of liability accompanies a
copy of the Program in return for a fee.
END OF TERMS AND CONDITIONS
How to Apply These Terms to Your New Programs
If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.
<one line to give the program's name and a brief idea of what it does.>
Copyright (C) <year> <name of author>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
Also add information on how to contact you by electronic and paper mail.
If the program does terminal interaction, make it output a short
notice like this when it starts in an interactive mode:
<program> Copyright (C) <year> <name of author>
This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the appropriate
parts of the General Public License. Of course, your program's commands
might be different; for a GUI interface, you would use an "about box".
You should also get your employer (if you work as a programmer) or school,
if any, to sign a "copyright disclaimer" for the program, if necessary.
For more information on this, and how to apply and follow the GNU GPL, see
<https://www.gnu.org/licenses/>.
The GNU General Public License does not permit incorporating your program
into proprietary programs. If your program is a subroutine library, you
may consider it more useful to permit linking proprietary applications with
the library. If this is what you want to do, use the GNU Lesser General
Public License instead of this License. But first, please read
<https://www.gnu.org/licenses/why-not-lgpl.html>.

16
examples/Cargo.toml Normal file
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@@ -0,0 +1,16 @@
[package]
name = "objcache_examples"
version = "0.1.0"
edition = "2021"
rust-version = "1.81"
[[bin]]
name = "objcache"
path = "src/main.rs"
[dependencies]
tokio = { version = "1.*", default-features = false, features = ["rt-multi-thread", "macros"] }
tracing = { version = "0.1.40", default-features = false }
tracing-subscriber = { version = "0.3", default-features = false, features = ["fmt", "ansi"] }
serde = { version = "1.0.210", default-features = false, features = ["std", "derive"] }
objcache = { path = "../" }

74
examples/src/main.rs Normal file
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@@ -0,0 +1,74 @@
use std::{
fmt,
net::{IpAddr, Ipv4Addr},
time::Duration,
};
use serde::{Deserialize, Serialize};
use tracing::Level;
use objcache::{CacheError, Client, RedisCacheArgs, RedisClient};
#[derive(Debug, Serialize, Deserialize)]
struct Item {
val: usize,
}
#[derive(Debug)]
struct Error(String);
impl std::error::Error for Error {}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "{}", self.0)
}
}
impl From<CacheError> for Error {
fn from(value: CacheError) -> Self {
Self(format!("cache error: {value}"))
}
}
async fn get_item(v: usize) -> Result<Item, Error> {
Ok(Item { val: v })
}
#[tokio::main]
async fn main() -> Result<(), Error> {
tracing_subscriber::fmt::Subscriber::builder()
.with_span_events(tracing_subscriber::fmt::format::FmtSpan::FULL)
.with_ansi(true)
.pretty()
.with_max_level(Level::TRACE)
.try_init()
.unwrap();
let client = RedisClient::new((IpAddr::V4(Ipv4Addr::LOCALHOST), 6379)).unwrap();
let item = client.wrap(
get_item,
&RedisCacheArgs {
lock_name: b"item_lock",
key_name: b"item",
expiry: Duration::from_secs(5),
},
)(100)
.await?;
println!("{item:?}");
let item = client.wrap(
|v| Box::pin(async move { Ok::<_, Error>(Item { val: v }) }),
&RedisCacheArgs {
lock_name: b"item_lock",
key_name: b"item",
expiry: Duration::from_secs(5),
},
)(100)
.await?;
println!("{item:?}");
Ok(())
}

34
src/error.rs Normal file
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use std::fmt;
#[derive(Debug)]
pub enum CacheError {
Serde(String),
Redis(String),
Consistency(String),
DurationOutOfRange,
}
impl From<redis::RedisError> for CacheError {
fn from(value: redis::RedisError) -> Self {
Self::Redis(value.to_string())
}
}
impl From<serde_json::Error> for CacheError {
fn from(value: serde_json::Error) -> Self {
Self::Serde(value.to_string())
}
}
impl std::error::Error for CacheError {}
impl fmt::Display for CacheError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match *self {
Self::Serde(ref msg) => write!(f, "serde error: {msg}"),
Self::Redis(ref msg) => write!(f, "redis error: {msg}"),
Self::Consistency(ref msg) => write!(f, "consistency error: {msg}"),
Self::DurationOutOfRange => write!(f, "duration is out of range"),
}
}
}

206
src/lib.rs Normal file
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use std::{future::Future, net, pin::Pin, time::Duration};
use chrono::{DateTime, TimeDelta, Utc};
use redis::AsyncCommands;
use serde::{de::DeserializeOwned, Deserialize, Serialize};
use tokio::time;
use tracing::Level;
mod error;
pub use error::CacheError;
#[derive(Clone)]
pub struct RedisClient {
redis: redis::Client,
}
pub struct RedisCacheArgs<'a> {
pub lock_name: &'a [u8],
pub key_name: &'a [u8],
pub expiry: Duration,
}
pub trait Client<T>
where
Self: Sized,
{
type ConnArgs;
fn new(args: Self::ConnArgs) -> Result<Self, CacheError>;
fn get(&self) -> &T;
fn wrap<'c, 'f, 'a, Func, Inner, Args, Item, E>(
&'c self,
f: Func,
cache_args: &'a RedisCacheArgs<'a>,
) -> Box<dyn FnOnce(Args) -> Pin<Box<dyn Future<Output = Result<Item, E>> + Send + 'f>> + 'f>
where
Func: Fn(Args) -> Inner + Sync + Send + 'f,
Inner: Future<Output = Result<Item, E>> + Send + 'f,
Args: Send + 'f,
Item: Send + Serialize + DeserializeOwned,
E: From<CacheError>,
'a: 'f,
'c: 'f;
}
impl Client<redis::Client> for RedisClient {
type ConnArgs = (net::IpAddr, u16);
fn new((ip, port): (net::IpAddr, u16)) -> Result<Self, CacheError> {
Ok(Self {
redis: redis::Client::open((ip.to_string(), port))?,
})
}
fn get(&self) -> &redis::Client {
&self.redis
}
fn wrap<'c, 'f, 'a, Func, Inner, Args, Item, E>(
&'c self,
f: Func,
cache_args: &'a RedisCacheArgs<'a>,
) -> Box<dyn FnOnce(Args) -> Pin<Box<dyn Future<Output = Result<Item, E>> + Send + 'f>> + 'f>
where
Func: Fn(Args) -> Inner + Sync + Send + 'f,
Inner: Future<Output = Result<Item, E>> + Send + 'f,
Args: Send + 'f,
Item: Send + Serialize + DeserializeOwned,
E: From<CacheError>,
'a: 'f,
'c: 'f,
{
const LOCK_TTL: usize = 60_000; // milliseconds
const LOCK_RETRY_TIME: Duration = Duration::from_secs(1);
#[derive(Serialize, Deserialize)]
struct CacheItem<Item> {
timestamp: DateTime<Utc>,
payload: Item,
}
#[tracing::instrument(skip_all, level = Level::TRACE)]
async fn query_cache<Item>(
conn: &mut redis::aio::MultiplexedConnection,
key_name: &[u8],
) -> Result<Option<CacheItem<Item>>, CacheError>
where
Item: DeserializeOwned,
{
Ok(conn
.get::<&[u8], Option<String>>(key_name)
.await?
.map(|s| serde_json::from_str(&s))
.transpose()?)
}
Box::new(move |args: Args| {
Box::pin(async move {
let expiry = TimeDelta::from_std(cache_args.expiry)
.map_err(|_e| CacheError::DurationOutOfRange)?;
let mut conn = tracing::span!(Level::TRACE, "connection")
.in_scope(|| async {
self.get()
.get_multiplexed_async_connection()
.await
.map_err(Into::into)
})
.await?;
match query_cache::<Item>(&mut conn, cache_args.key_name).await? {
Some(response)
if Utc::now().signed_duration_since(response.timestamp) <= expiry =>
{
tracing::trace!(
"found valid cache entry (timestamp: {})",
response.timestamp
);
Ok(response.payload)
}
_ => {
tracing::trace!("cache stale, regenerating response");
let lock_manager = redlock::RedLock::with_client(self.get().clone());
if let Some(lock) = lock_manager
.lock(cache_args.lock_name, LOCK_TTL)
.map_err(Into::into)?
{
tracing::trace!("acquired lock");
tracing::span!(Level::TRACE, "regenerate")
.in_scope(|| async {
let payload = f(args).await?;
let cache_item = CacheItem {
timestamp: Utc::now(),
payload,
};
let _: () = conn
.set(
cache_args.key_name,
serde_json::to_string(&cache_item)
.map_err(Into::into)?,
)
.await
.map_err(Into::into)?;
lock_manager.unlock(&lock);
tracing::trace!("cache updated");
Ok(cache_item.payload)
})
.await
} else {
// Could not get lock because it's already. so some other process is already
// gathering data. Wait for it to finish and then just return
// the cached response.
tracing::trace!("could not acquire lock");
tracing::span!(Level::TRACE, "wait_for_lock")
.in_scope(|| async {
loop {
tracing::trace!("waiting for unlock");
time::sleep(LOCK_RETRY_TIME).await;
if let Some(lock) = lock_manager
.lock(cache_args.lock_name, LOCK_TTL)
.map_err(Into::into)?
{
lock_manager.unlock(&lock);
match query_cache::<Item>(
&mut conn,
cache_args.key_name,
)
.await?
{
Some(response) => {
if Utc::now()
.signed_duration_since(response.timestamp)
> expiry
{
break Err(CacheError::Consistency(
"newly generated item older than max cache time"
.to_owned(),
)
.into());
}
tracing::trace!("serving response from cache");
break Ok(response.payload);
}
None => {
break Err(CacheError::Consistency(
"cached item expected but not found"
.to_owned(),
)
.into())
}
}
}
}
})
.await
}
}
}
})
})
}
}