Add Clean Up Memory-Hungry Rails Console Processes as a Rails TIL

README.md

@@ -10,7 +10,7 @@ working across different projects via [VisualMode](https://www.visualmode.dev/).
 
 For a steady stream of TILs, [sign up for my newsletter](https://visualmode.kit.com/newsletter).
 
-_1728 TILs and counting..._
+_1730 TILs and counting..._
 
 See some of the other learning resources I work on:
 
@@ -1073,6 +1073,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Check If ActiveRecord Update Fails](rails/check-if-activerecord-update-fails.md)
 - [Check If Any Records Have A Null Value](rails/check-if-any-records-have-a-null-value.md)
 - [Check Specific Attributes On ActiveRecord Array](rails/check-specific-attributes-on-activerecord-array.md)
+- [Clean Up Memory Hungry Rails Console Processes](rails/clean-up-memory-hungry-rails-console-processes.md)
 - [Code Statistics For An Application](rails/code-statistics-for-an-application.md)
 - [Columns With Default Values Are Nil On Create](rails/columns-with-default-values-are-nil-on-create.md)
 - [Comparing DateTimes Down To Second Precision](rails/comparing-datetimes-down-to-second-precision.md)
@@ -1773,6 +1774,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Unrestrict Where ripgrep Searches](unix/unrestrict-where-ripgrep-searches.md)
 - [Update Package Versions Known By asdf Plugin](unix/update-package-versions-known-by-asdf-plugin.md)
 - [Use fzf To Change Directories](unix/use-fzf-to-change-directories.md)
+- [Use Negative Lookbehind Matching With ripgrep](unix/use-negative-lookbehind-matching-with-ripgrep.md)
 - [Use Regex Pattern Matching With Grep](unix/use-regex-pattern-matching-with-grep.md)
 - [View A Web Page In The Terminal](unix/view-a-web-page-in-the-terminal.md)
 - [View The Source For A Brew Formula](unix/view-the-source-for-a-brew-formula.md)

rails/clean-up-memory-hungry-rails-console-processes.md

@@ -0,0 +1,43 @@
+# Clean Up Memory Hungry Rails Console Processes
+
+I noticed (using `htop`) that a remote server hosting a Rails app had most of
+its RAM being actively consumed. This was hindering my ability to run a fresh
+deploy because the deploy processes had to do a ton of memory swapping which
+drastically slowed the whole thing down.
+
+With some investigation, I discovered that most of the memory was being consumed
+by a handful of `rails console` processes. I didn't have any known active `rails console` processes that I was using. That combined with the dates of these
+processes starting way in the past suggested to me that these were abandoned
+processes that hadn't been properly cleaned up.
+
+```bash
+server:~# ps aux | grep rails
+32767     878915  0.0  0.0 1227160  936 pts/0    Ssl+  2025   0:03 /exec rails console
+32767     878942  0.9  6.5 830996 261748 pts/0   Rl+   2025 249:51 ruby /app/bin/rails console
+32767    3004097  0.0  0.0 1227160  692 pts/0    Ssl+  2025   0:04 /exec rails console
+32767    3004129  0.9  6.4 834672 257228 pts/0   Dl+   2025 406:31 ruby /app/bin/rails console
+32767    3048582  0.0  0.0 1227160  940 pts/0    Ssl+ Jan09   0:00 /exec rails console
+32767    3048611  1.1  6.3 829936 253484 pts/0   Dl+  Jan09  60:50 ruby /app/bin/rails console
+32767    3060033  0.0  0.0 1227160  944 pts/0    Ssl+  2025   0:04 /exec rails console
+32767    3060063  0.9  6.5 838084 260812 pts/0   Rl+   2025 405:37 ruby /app/bin/rails console
+root     3699372  0.0  0.0   7008  1300 pts/0    S+   15:51   0:00 grep --color=auto rails
+server:~# ps aux | grep 'rails console' | awk '{sum+=$6} END {print sum/1024 " MB"}'
+1014.64 MB
+```
+
+As we can see by tacking on this `awk` command, these processes are consuming
+1GB of memory.
+
+Each of these is a pair of processes. A parent process (`/exec rails console`)
+that kicks off and supervises the memory-hungry child process (`ruby /app/bin/rails console`).
+
+To free up this memory, I targeted each of the parent processes with a `kill`
+command one by one. For example:
+
+```bash
+server:~# kill 878915
+```
+
+I suspect that I may have left the occasional terminal tab open with one of
+these `rails console` processes running and the SSH connection was getting
+killed without the `rails console` getting killed with it.

unix/use-negative-lookbehind-matching-with-ripgrep.md

@@ -0,0 +1,42 @@
+# Use Negative Lookbehind Matching With ripgrep
+
+The most straightforward way to use `ripgrep` is to hand it a pattern. It will
+take that pattern and move forward through each file trying to find matches.
+
+```bash
+$ rg 'TwilioClient\.new'
+```
+
+That will find all occurrences of `TwilioClient.new` in available project files.
+
+What if that pattern is too permissive though? That is going to match on
+occurrences of `TwilioClient.new` as well as things like
+`LoggingTwilioClient.new`. If we want to exclude the latter, there are a few
+ways to do that. One of them being the use of [the _negative lookbehind_ regex
+feature](https://www.pcre.org/current/doc/html/pcre2syntax.html#SEC23) that is
+available with PCRE2 (Perl-Compatible Regular Expressions).
+
+A _negative lookbehind_ is like a standard pattern. We look forward through the
+document for the base pattern (like `TwilioClient\.new`). However, once we find
+that match, we then look back at the previous characters and if they match our
+negative lookbehind pattern, then it is no longer a positive match.
+
+We can use one of the following to forms to achieve this:
+
+```
+  (?<!...)                    )
+  (*nlb:...)                  ) negative lookbehind
+  (*negative_lookbehind:...)  )
+```
+
+For instance, here is what this looks like for our example:
+
+```bash
+$ rg -P '(?<!Logging)TwilioClient\.new'
+```
+
+Note: we have to use the `-P` flag to tell `ripgrep` that we are using PCRE2
+syntax. Otherwise, it assumes a simpler regex syntax that doesn't support
+_negative lookbehind_.
+
+See `man rg` for more details.