zhangw

Common

export OPT=/opt
export BUILDS=/some/where/mini_linux
mkdir -p $BUILDS

Linux kernel

zhangw

Libuv and libev, two I/O libraries with similar names, recently had the privilege to use both libraries to write something. Now let's talk about my own subjective expression of common and different points.

The topic of high-performance network programming has been discussed. Asynchronous, asynchronous, or asynchronous. Whether it is epoll or kqueue, it is always indispensable to the asynchronous topic.

Libuv is asynchronous, and libev is synchronous multiplexing IO multiplexing.

Libev is a simple encapsulation of system I/O reuse. Basically, it solves the problem of different APIs between epoll and kqueuq. Ensure that programs written using livev's API can run on most *nix platforms. However, the disadvantages of libev are also obvious. Because it basically just encapsulates the Event Library, it is inconvenient to use. For example, accept(3) requires manual setnonblocking after connection. EAGAIN, EWOULDBLOCK, and EINTER need to be detected when reading from a socket. This is a

zhangw

• Scaling k8s daemonset down to zero

kubectl -n kube-system patch daemonset myDaemonset -p '{"spec": {"template": {"spec": {"nodeSelector": {"non-existing": "true"}}}}}'

• Scaling up k8s daemonset

kubectl -n kube-system patch daemonset myDaemonset --type json -p='[{"op": "remove", "path": "/spec/template/spec/nodeSelector/non-existing"}]'

zhangw

Attach to a running process with

  gdb -x trace-dyn-mem -p $PID

After every malloc the returned value (the allocated address) will be read from the RAX (64 bits) register.

After every free the last item in the backtrace (the free itself) will be shown. With the libc6-dbg package installed you can see the address passed as the first argument of free.

zhangw

# Install the toolchain
```bash
brew tap SergioBenitez/osxct
brew install x86_64-unknown-linux-gnu
```

# this should get installed in:
# /opt/homebrew/Cellar/x86_64-unknown-linux-gnu/

# Installing the macOS OpenSSL - if not already installed

zhangw

Installation

1. mkdir -p ~/.config && touch ~/.config/ssh-agent.pid
2. Paste the contents of ssh-agent-manage.sh into your .bashrc or .bash_profile or similar
3. killall -9 ssh-agent
4. Start a new terminal session (note: old sessions will not see ssh-agent, only new ones)

Details

This snippet, when included in .bashrc, will ensure that your session has a working ssh-agent with all your ssh keys loaded into it. It does this without creating separate ssh-agent processes by:

zhangw

CREATE TABLE
  `testing.insert` (date DATE OPTIONS( description='date' ),
    unique_visits INT64 OPTIONS( description='counts' ))
PARTITION BY
  date
CLUSTER BY
  unique_visits OPTIONS ( description="A table with a date partition",
    labels=[("testing",
      "data_is_great")],
      expiration_timestamp=TIMESTAMP "2023-01-01 00:00:00 UTC"

zhangw

SELECT 
date,
COUNT(DISTINCT(visitid)) as unique_visits
FROM `bigquery-public-data.google_analytics_sample.ga_sessions_*` 
WHERE _table_suffix = '20170801'   # use date_sub to programmatically select your table
GROUP BY date
ORDER BY date

zhangw

 
CREATE TEMP FUNCTION
  PROPER(str STRING) AS ((
    SELECT
      STRING_AGG(CONCAT(UPPER(SUBSTR(w,1,1)), LOWER(SUBSTR(w,2))), ' '
      ORDER BY
        pos)
    FROM
      UNNEST(SPLIT(str, ' ')) w
    WITH

zhangw

 DECLARE
  SQLRUN STRING DEFAULT '';
CREATE TEMP FUNCTION
  ga4_firebase( key1 STRING,
    params ARRAY <STRUCT <key STRING,
    value STRUCT <string_value STRING,
    int_value INT64,
    float_value FLOAT64,
    double_value FLOAT64 >>>) AS ( (
    SELECT