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Parser Nginx logs like SQL

Project description



Meant to mimic, sort of, how the OG logparser for MS Server worked.

Very much a work-in-progress atm. Goal is to make this a standalone python executable for deployment on servers. Will probably have to change the name to make space on package repos.


tailparse has no dependencies to install. It only works with python 3 and has only been tested in python 3.10. Presumably it would work with any python 3.

python3 install --user

This will install it in your home directory (i.e. home/<username>/.local/bin/) and doesn't require sudo privileges.


tailparse -q <sqlite-query> your.logs


$ tailparse --help
usage: tailparse [-h] [-p] [-i INPUT_FORMAT] [-q QUERY] [-r MAX_ROWS] [-s SAVE_DB] [-f FILE] [logs]

Process logs as if they were SQL.

positional arguments:
  logs                  The path to the input log we're processing. If not present, will use stdin.

  -h, --help            show this help message and exit
  -p, --print           Print out the requisite columns
  -i INPUT_FORMAT, --input-format INPUT_FORMAT
                        The format of the log we're processing. Defaults to 'nginx'. Options include ['nginx']
  -q QUERY, --query QUERY
                        The query to execute. Don't include any 'FROM' statement as this is added automatically. If not
                        included, make sure to include a -f/--file arugmenet
  -r MAX_ROWS, --max-rows MAX_ROWS
                        Number of max rows to print. Defaults to 20. Put 0 to print all.
  -s SAVE_DB, --save-db SAVE_DB
                        Whether to save the resulting SQLite data file. Defaults to not saving it and using ':memory:'
                        instead. If the database exists, then the log file will not be used to populate it and instead it
                        will be read from. This can be helpful if you're running a lot of queries as the log file doesn't
                        need to be re-parsed everytime.
  -f FILE, --file FILE  Execute multiple queries contained with a file. Can be used in place of -q/--query

Caching the database on-disk

It can help to write the SQL database to disk instead of reading from memory. This can be done with the -s or --save-db arguments:

$ time tailparse -s tmp.sqlite3.db -q "SELECT COUNT(*) FROM logs" sample.logs

real    0m1.026s
user    0m0.835s
sys     0m0.117s
$ time tailparse -s tmp.sqlite3.db -q "SELECT COUNT(*) FROM logs" sample.logs

real    0m0.648s
user    0m0.533s
sys     0m0.095s

# and without any caching
$ time tailparse -q "SELECT COUNT(*) FROM logs" sample.logs

real    0m0.910s
user    0m0.866s
sys     0m0.045s

Note that if you do this, tailparse will not attempt to rewrite the database

Running Tests

To run tests, at the top level run the following:


To get coverage reports, which requires the coverage module, you can run:

./ -h

While testing relies entirely on unittest, which is built-in, coverage and mypy are used to do coverage reports and type checking, respectively. ./ will check for these installs at runtime.


Feel free to make a PR!

Note that this library is trying very hard to avoid any dependencies and stay core-python-only. If there is a strong reason to include one, please include a reason why.

black is used for all code formatting. Testing will be required for any contributions.


  • write proper tests

    • split the file up into separate chunks

    • tailparse.execute.execute_query: write integration tests against this and check for the output string -- all for 'nginx'

      • include sample.log via shuf -n N input > output
      • SELECT * FROM logs LIMIT 1
      • SELECT * FROM logs LIMIT 2
      • SELECT * FROM logs: stops at 20 by default
      • SELECT * FROM logs, w/max_rows=0: does not stop at 20
      • SELECT *: complains before it executes
      • w/query_file: write to /tmp and clean up after
      • w/save_db: write to /tmp and clean up after
      • w/print_columns: as True, should print just columns
    • tailparse.print_output.print_output: write unit tests against this and check for output string

    • write testing shell script -- should fail if mypy fails or if coverage and mypy aren't installed

  • update the README to use current version screenshots

  • add --version argument

  • write proper contribution guides, especially for new log formats

  • write proper Make file to make it easy for people to see whats going on

  • remove pandas dependency and only use pure python

  • support writing to disk for the sqlite3 database, not just to memory

  • support other formats, not just Nginx

  • Ability to process multiple SQL commands in a text file, separated by line

  • infer the table (e.g. FROM logs) so I don't have to specify it everytime



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