ERROR: attempt to write a readonly database

[vreddy10]

What is your question?

Description:
We are facing attempt to write a readonly database when two users used the shared Conan directory in Linux with Conan v2 version 2.10.0.

Steps to reproduce:

Part-1: Run the below command login as the user has admin access.

1. Create a common folder for conan tools chains to download and install:
   $ mkdir -p /data/conan/
2. Create group:
   $ sudo groupadd conan_developers
3. Change the Ownership of the common conan folder as mentioned below:
   $ sudo chown -R root:conan_developers /data/conan/
4. Give the folder/file permission to the user and group as “770”
   $ sudo chmod -R 770 /data/conan/
5. Perform the following command to add the user1 and user2 to the 'conan_developers' group and sets their primary group to 'conan_developers'.
   $ usermod -aG conan_developers -g conan_developers

Part-2: Run the below command login as - user1.

$ echo 'export PATH=${HOME}/.local/bin:${PATH}' >> ${HOME}/.bashrc
$ source ${HOME}/.bashrc
$ sudo apt-get update
$ sudo apt-get install python3-pip -y
$ python3 -m pip install pip==23.3.2
$ echo 'export CONAN_HOME=/data/conan/.conan2’ >> ${HOME}/.bashrc
$ echo 'umask 0007' >> ${HOME}/.bashrc
$ source ~/.bashrc
$ chmod 700 ~
$ python3 -m pip install conan==2.10.0
$ conan profile detect --force
$ conan profile show -pr default

conanfile.txt

[requires]
cmake/3.20.6

[generators]
VirtualRunEnv

$ conan install .

Part-3: Run the below command login as – user2.

$ echo 'export PATH=${HOME}/.local/bin:${PATH}' >> ${HOME}/.bashrc
$ source ${HOME}/.bashrc
$ echo 'export CONAN_HOME=/data/conan/.conan2’ >> ${HOME}/.bashrc
$ echo 'umask 0007' >> ${HOME}/.bashrc
$ source ~/.bashrc
$ chmod 700 ~
$ python3 -m pip install conan==2.10.0

user2@IND6LXPKL3:~/cmake$ conan install .

======== Input profiles ========
Profile host:
[settings]
arch=x86_64
build_type=Release
compiler=gcc
compiler.cppstd=gnu14
compiler.libcxx=libstdc++11
compiler.version=9
os=Linux

Profile build:
[settings]
arch=x86_64
build_type=Release
compiler=gcc
compiler.cppstd=gnu14
compiler.libcxx=libstdc++11
compiler.version=9
os=Linux


======== Computing dependency graph ========
ERROR: Traceback (most recent call last):
  File "/home/user2/.local/lib/python3.8/site-packages/conan/cli/cli.py", line 307, in main
    cli.run(args)
  File "/home/user2/.local/lib/python3.8/site-packages/conan/cli/cli.py", line 192, in run
    command.run(self._conan_api, args[0][1:])
  File "/home/user2/.local/lib/python3.8/site-packages/conan/cli/command.py", line 180, in run
    info = self._method(conan_api, parser, *args)
  File "/home/user2/.local/lib/python3.8/site-packages/conan/cli/commands/install.py", line 63, in install
    deps_graph = gapi.load_graph_consumer(path, args.name, args.version, args.user, args.channel,
  File "/home/user2/.local/lib/python3.8/site-packages/conan/api/subapi/graph.py", line 148, in load_graph_consumer
    deps_graph = self.load_graph(root_node, profile_host=profile_host,
  File "/home/user2/.local/lib/python3.8/site-packages/conan/api/subapi/graph.py", line 180, in load_graph
    deps_graph = builder.load_graph(root_node, profile_host, profile_build, lockfile)
  File "/home/user2/.local/lib/python3.8/site-packages/conans/client/graph/graph_builder.py", line 55, in load_graph
    new_node = self._expand_require(require, node, dep_graph, profile_host,
  File "/home/user2/.local/lib/python3.8/site-packages/conans/client/graph/graph_builder.py", line 101, in _expand_require
    new_node = self._create_new_node(node, require, graph, profile_host, profile_build,
  File "/home/user2/.local/lib/python3.8/site-packages/conans/client/graph/graph_builder.py", line 367, in _create_new_node
    resolved = self._resolve_recipe(require.ref, graph_lock)
  File "/home/user2/.local/lib/python3.8/site-packages/conans/client/graph/graph_builder.py", line 264, in _resolve_recipe
    result = self._proxy.get_recipe(ref, self._remotes, self._update, self._check_update)
  File "/home/user2/.local/lib/python3.8/site-packages/conans/client/graph/proxy.py", line 26, in get_recipe
    resolved = self._get_recipe(ref, remotes, update, check_update)
  File "/home/user2/.local/lib/python3.8/site-packages/conans/client/graph/proxy.py", line 49, in _get_recipe
    self._cache.update_recipe_lru(ref)
  File "/home/user2/.local/lib/python3.8/site-packages/conan/internal/cache/cache.py", line 275, in update_recipe_lru
    self._db.update_recipe_lru(ref)
  File "/home/user2/.local/lib/python3.8/site-packages/conan/internal/cache/db/cache_database.py", line 44, in update_recipe_lru
    self._recipes.update_lru(ref)
  File "/home/user2/.local/lib/python3.8/site-packages/conan/internal/cache/db/recipes_table.py", line 72, in update_lru
    conn.execute(query)
sqlite3.OperationalError: attempt to write a readonly database

ERROR: attempt to write a readonly database
user2@IND6LXPKL3:~/cmake$

Have you read the CONTRIBUTING guide?

• I've read the CONTRIBUTING guide

[memsharded]

Hi @vreddy10

Thanks for your report

We are facing attempt to write a readonly database when two users used the shared Conan directory in Linux with Conan v2 version 2.10.0.

I am afraid there is some misconception there.
The Conan cache is not concurrent, it is not designed to be concurrent, see https://docs.conan.io/2/knowledge/guidelines.html

for example different parallel CI jobs should use different caches (with CONAN_HOME env-var)

This also applies to any other system-level concurrency, like being accessed by different system users.

Some notes:

• Conan is designed to run at the user level, not requiring sudo or root permissions
• Conan cache should be owned by the user.
• Package storage in the cache, including the DB should be owned by the user

In any case, it seems this might be more related to Python+sqlite behavior than something related to Conan, as Conan doesn't do any thing related to permissions or cache file permissions or putting the sqlite3 DB in read-only. So it looks like Python sqlite management doesn't like accessing a DB when Python is running under some user, unless there is some very specific configuration and permissions, see for example https://stackoverflow.com/questions/3319112/sqlite-error-attempt-to-write-a-readonly-database-during-insert, or https://forums.raspberrypi.com/viewtopic.php?t=285406.

Still, even if this was possible from the python+sqlite+system file permissions, sharing the cache is still very discouraged, so I wouldn't recommend doing it anyway.

[vreddy10]

Hi @memsharded

Thank you for the quick response and information provided, Will check on the provided response and get back to you if any further info is required.