Lightweight log utility for Solana programs.

Overview

Currently, logging messages that require formatting are a bit heavy on the CU consumption. There are two aspects when comes to determining the cost of a log message:

1. base cost: this is the cost of the log syscall. It will either be the syscall_base_cost (currently 100 CU) or a number of CUs equal to the length of the message, whichever value is higher.

2. formatting cost: the compute units required to format the message. This is variable and depends on the number and type of the arguments. Formatting is performed using Rust built-in format! routines, which in turn use format_args!.

It is known that Rust formatting routines are CPU-intensive for constrained environments. This has been noted on both the solana-program msg! documentation and more generally on rust development.

While the cost related to (1) is fixed, in the sense that it does not change with the addition of formatting, it is possible to improve the overall cost of logging a formatted message using a lightweight formatting routine — this is what this crate does.

This crate defines a lightweight Logger type to format log messages and a companion log! macro. The logger is a fixed size buffer that can be used to format log messages before sending them to the log output. Any type that implements the Log trait can be appended to the logger.

Below is a sample of the improvements observed when formatting log messages, measured in terms of compute units (CU):

Note: The improvement in CU is accumulative, meaning that if you are logging multiple u64 values, there will be a 40% improvement per formatted u64 value.

Features

• Zero dependencies and no_std crate
• Independent of SDK (i.e., works with pinocchio, solana-program or anchor)
• Support for &str, unsigned and signed integer types
• log! macro to facilitate log message formatting

Getting Started

From your project folder:

cargo add pinocchio-log

Usage

The Logger can be used directly:

use pinocchio_log::logger::Logger;

let mut logger = Logger::<100>::default();
logger.append("Hello ");
logger.append("world!");
logger.log();

or via the log! macro:

use pinocchio_log::log

let amount = 1_000_000_000;
log!("transfer amount: {}", amount);

Since the formatting routine does not perform additional allocations, the Logger type has a fixed size specified on its creation. When using the log! macro, it is also possible to specify the size of the logger buffer:

use pinocchio_log::log

let amount = 1_000_000_000;
log!(100, "transfer amount: {}", amount);

Limitations

Currently the log! macro does not offer extra formatting options apart from the placeholder "{}" for argument values.

License

The code is licensed under the Apache License Version 2.0