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authorbnewbold <bnewbold@robocracy.org>2022-06-23 10:35:06 -0700
committerbnewbold <bnewbold@robocracy.org>2022-06-23 10:35:06 -0700
commitc1def3cdf5569c892a75e84b8b23963371f3819d (patch)
tree225060a76fa55fd8e224c643e4cd7e3d88995505 /software
parent5be0eb7d31d792366eb1e1be0a6de477a348b723 (diff)
parent9eff4d99afc1ba861ae32dcd46d88ff6b3ef222f (diff)
downloadknowledge-master.tar.gz
knowledge-master.zip
Merge branch 'master' of adze:knowledgeHEADmaster
Diffstat (limited to 'software')
-rw-r--r--software/bash.page2
-rw-r--r--software/postgres.page17
-rw-r--r--software/python.page21
-rw-r--r--software/rsyslog.page20
-rw-r--r--software/rust.page117
5 files changed, 174 insertions, 3 deletions
diff --git a/software/bash.page b/software/bash.page
index 0d5325b..5d82fdc 100644
--- a/software/bash.page
+++ b/software/bash.page
@@ -37,6 +37,8 @@ Note that `join`, `grep`, and others sometimes exit non-zero return codes on
purpose (eg, pipe input closed or found no matches, as expected), which makes
life difficult. Sometimes `|| true` is enough to get around this.
+More on this: <http://redsymbol.net/articles/unofficial-bash-strict-mode/>
+
## General Style
Google has a style guide: https://google.github.io/styleguide/shell.xml
diff --git a/software/postgres.page b/software/postgres.page
index bdb01d8..7d05074 100644
--- a/software/postgres.page
+++ b/software/postgres.page
@@ -15,3 +15,20 @@ Basic status from the psql command line:
\l+ (list databases)
\dt+ (describe table)
+
+## Temporary Databases in Tests
+
+Try `pg_tmp`, though it may not work with high concurrency (due to internal
+postgres locking), and might need special configuration in CI environments.
+
+Debian also ships with `pg_virtualenv` for temporary databases.
+
+---------
+
+More refs/links:
+
+- https://stackoverflow.com/questions/9604723/alternate-output-format-for-psql
+- https://brandur.org/postgres-connections
+- https://www.citusdata.com/blog/2017/07/16/customizing-my-postgres-shell-using-psqlrc/
+- `bind "^R" em-inc-search-prev`
+
diff --git a/software/python.page b/software/python.page
index 0fd2531..0fc3c8d 100644
--- a/software/python.page
+++ b/software/python.page
@@ -205,3 +205,24 @@ and create a `pytest.ini` like:
norecursedirs = .svn _build tmp*
Need to mock? <https://blog.fugue.co/2016-02-11-python-mocking-101.html>
+
+Debugging Memory Usage
+------------------------
+
+Most helpful tools I found were `psutil` and `pympler` (both need to be
+installed).
+
+ import os, psutil
+ process = psutil.Process(os.getpid())
+ print(process.memory_info().rss)
+ # ... do some stuff ...
+ print(process.memory_info().rss)
+
+and
+
+ from pympler import tracker
+ tr = tracker.SummaryTracker()
+ tr.print_diff()
+
+ # ... do some stuff ...
+ tr.print_diff()
diff --git a/software/rsyslog.page b/software/rsyslog.page
new file mode 100644
index 0000000..b55c127
--- /dev/null
+++ b/software/rsyslog.page
@@ -0,0 +1,20 @@
+
+Put these in files like `/etc/rsyslog.d/40-grobid-skip.conf`.
+
+Filter out lines from a given program:
+
+ :programname, isequal, "GROBID" ~
+
+Or matching a pattern:
+
+ :msg, startswith, "inserting line to HBase: sha1:"
+ :msg, contains, " INFO GET http"
+
+For list of operations ("isequal", "regex", "contains"):
+
+ https://www.rsyslog.com/doc/v8-stable/configuration/filters.html
+
+For list of properties (":msg", ":programname"):
+
+ https://www.rsyslog.com/doc/v8-stable/configuration/properties.html
+
diff --git a/software/rust.page b/software/rust.page
index df99de4..dc900c8 100644
--- a/software/rust.page
+++ b/software/rust.page
@@ -3,9 +3,10 @@ Rust
## Resources
-- [http://xion.io/post/code/rust-iter-patterns.html]()
-- [https://deterministic.space/rust-cli-tips.html]()
-- [https://manishearth.github.io/blog/2018/01/10/whats-tokio-and-async-io-all-about/]()
+- <http://xion.io/post/code/rust-iter-patterns.html>
+- <https://deterministic.space/rust-cli-tips.htm>
+- <https://manishearth.github.io/blog/2018/01/10/whats-tokio-and-async-io-all-about/>
+- <https://saghm.github.io/five-rust-things/>
Optimization: use `RUSTFLAGS="-C target-cpu=native"` to take advantage of CPU
special features.
@@ -22,3 +23,113 @@ Run tests with stdout output:
To run tests with logging enabled (eg, with `env_logger`), make sure you add
`env_logger::init()` to the test function itself.
+
+
+## map() and Result Ergonomics
+
+`.collect()` has some magical features! In addition to turning an iterator of
+`Item` into `Vec<Item>`, it will turn an iterator of `Result<Item>` into
+`Result<Vec<Item>>`. This makes it really useful for the end of functions.
+
+This is particularly useful for resolving some categories of "error handling in
+map closures": you can use `?` in the map closure as long as you wrap the happy
+path with `Ok()` and call collect on the outside. Eg:
+
+ let list: Vec<Item> = junk
+ .iter()
+ .map(|thing| Ok(Item {
+ a: thing.a,
+ b: fixup(thing.widget)?,
+ }))
+ .collect::Result<Vec<Item>>()?;
+
+What about when `map` over an `Option`? Eg:
+
+ let toy = Shiny {
+ a: 123,
+ b: component.map(|v| paint(v).expect("paint to succeed"),
+ };
+
+Should use match in this case:
+
+ let toy = Shiny {
+ a: 123,
+ b: match component {
+ None => None,
+ Some(v) => Some(paint(v)?),
+ },
+ };
+
+## 2020-05-17 Reading
+
+While working on fatcat-cli tool, checked the The Rust Programming Language
+book to read about trait objects and the `dyn` keyword, which I had ignored
+previously.
+
+They seem like they could be used in a few places in fatcat-server rust code.
+We don't particularly care about per-function-call performance there, and most
+entities are already allocated on the heap.
+
+Other small syntax and thing learned:
+
+Can copy a struct while only updating specific fields with ".." syntax. Might
+use this in fatcat-cli for update mutation.
+
+This is the cleanest example of using ErrorKind that I have seen:
+
+ let f = match f {
+ Ok(file) => file,
+ Err(error) => match error.kind() {
+ ErrorKind::NotFound => match File::create("hello.txt") {
+ Ok(fc) => fc,
+ Err(e) => panic!("Problem creating the file: {:?}", e),
+ },
+ other_error => {
+ panic!("Problem opening the file: {:?}", other_error)
+ }
+ },
+ };
+
+I didn't realize that test code may get compiled into non-test binaries unless
+annotated with `#[cfg(test)]`. You are supposed to create a sub-module within
+each `src/` file with unittests, like:
+
+ #[cfg(test)]
+ mod tests {
+ use super::*;
+
+ #[test]
+ fn it_works() {
+ assert_eq!(2 + 2, 4);
+ }
+ }
+This doesn't apply to `tests/` directory, which is for integration tests.
+
+The common pattern for binary crates (vs. library crates) is to have `main.rs`
+and `lib.rs`, with any code that needs to be tested in `lib.rs` (aka, all the
+actual logic).
+
+I think I knew `eprintln!()` (for stderr) vs. `println!()` (for stdout), but
+good to remember.
+
+There is a description of how to avoid memory leaks with reference counting
+using "weak" `Rc` references. Probably worth reading the [entire chapter on smart pointers](https://doc.rust-lang.org/book/ch15-06-reference-cycles.html#preventing-reference-cycles-turning-an-rct-into-a-weakt)
+(including Box, Rc, RefCell) again.
+
+For the `Sized` trait, and `Sized` trait alone, can specify an ambiguous trait
+constraint with `?` to indicate "may or may not be Sized", which doesn't really
+mean anything but does explicitly allow generic functions over non-sized traits
+like:
+
+ fn my_generic_func<T: ?Sized>(t: &T) {
+ // --snip--
+ }
+
+A trait can depend on another trait. For example, a PrettyPrint trait could
+rely on Display (and impl functions could call functions from Display). This is
+done on the trait definition line. Such a trait is called a "supertrait".
+
+Implementing Deref on a wrapper type allows transparent access to all the trait
+methods on the interior object.
+
+Also, a new longer post on error handling: <https://nick.groenen.me/posts/rust-error-handling/>