How do I ensure that File.write finished?

[Emil Kampp]

Hi there.

I am trying to make a form to update the values in a yml file (my
applications configuration file). This is working kind of fine.
Sometimes it works, sometimes not.

I have confirmed (through logging) that a content for +string+ is always
there. So there is always something trying to be written into the yml
file, but still sometimes it ends up being empty. And an empty
configuration file is no good!

# server-controller (user generated controller in rails)
def update
# This inserts a new setting into the hash
unless params[:new_setting][:key].blank? and
params[:new_setting][:value].blank?
params[:settings].collect{ |env, settings|
settings[params[:new_setting][:key].to_sym] =
params[:new_setting][:value].to_s }
end

# This writes the hash to the file (See the second snippet for
details)
ServerSystem::update_configuration(params[:settings])

# Redirects to the action that restarts the server to load the new
configurations
redirect_to admin_server_restart_path
end

# Custom class
def update_configuration(settings)
string = settings.to_yaml
File.new(APP_CONFIG_FILE, "w").write string
end

The problem is that the setup is dodgy, sometimes it works, sometimes it
looks like the server is restarted before the content of +string+ is
written to the configuration file.
How can I ensure that the content has been written before executing next
line of code (the restart in this case)?

 

[Stefano Crocco]

|Hi there.
|
|I am trying to make a form to update the values in a yml file (my
|applications configuration file). This is working kind of fine.
|Sometimes it works, sometimes not.
|
|I have confirmed (through logging) that a content for +string+ is always
|there. So there is always something trying to be written into the yml
|file, but still sometimes it ends up being empty. And an empty
|configuration file is no good!
|
|

|# server-controller (user generated controller in rails)
|  def update
|    # This inserts a new setting into the hash
|    unless params[:new_setting][:key].blank? and
|params[:new_setting][:value].blank?
|      params[:settings].collect{ |env, settings|
|settings[params[:new_setting][:key].to_sym] =
|params[:new_setting][:value].to_s }
|    end
|
|    # This writes the hash to the file (See the second snippet for
|details)
|    ServerSystem::update_configuration(params[:settings])
|
|    # Redirects to the action that restarts the server to load the new
|configurations
|    redirect_to admin_server_restart_path
|  end
|

|
|

|# Custom class
|    def update_configuration(settings)
|      string = settings.to_yaml
|      File.new(APP_CONFIG_FILE, "w").write string
|    end
|

|
|The problem is that the setup is dodgy, sometimes it works, sometimes it
|looks like the server is restarted before the content of +string+ is
|written to the configuration file.
|How can I ensure that the content has been written before executing next
|line of code (the restart in this case)?
|

I'm not sure, but maybe the fact you're not closing the file after writing has
something to do with that. Try replacing the last line of update_configuration
with:

File.open(APP_CONFIG_FILE, 'w'){|f| f.write string}

When given a block, File.open closes the file after calling the block, which
should ensure that everything you wrote to file should have actually been
written.

I hope this helps

Stefano

 

[Robert Klemme]

|Hi there.
|
|I am trying to make a form to update the values in a yml file (my
|applications configuration file). This is working kind of fine.
|Sometimes it works, sometimes not.
|
|I have confirmed (through logging) that a content for +string+ is alway= s
|there. So there is always something trying to be written into the yml
|file, but still sometimes it ends up being empty. And an empty
|configuration file is no good!
|
|

|# server-controller (user generated controller in rails)
| =A0def update
| =A0 =A0# This inserts a new setting into the hash
| =A0 =A0unless params[:new_setting][:key].blank? and
|params[:new_setting][:value].blank?
| =A0 =A0 =A0params[:settings].collect{ |env, settings|
|settings[params[:new_setting][:key].to_sym] =3D
|params[:new_setting][:value].to_s }
| =A0 =A0end
|
| =A0 =A0# This writes the hash to the file (See the second snippet for
|details)
| =A0 =A0ServerSystem::update_configuration(params[:settings])
|
| =A0 =A0# Redirects to the action that restarts the server to load the = new
|configurations
| =A0 =A0redirect_to admin_server_restart_path
| =A0end
|

|
|

|# Custom class
| =A0 =A0def update_configuration(settings)
| =A0 =A0 =A0string =3D settings.to_yaml
| =A0 =A0 =A0File.new(APP_CONFIG_FILE, "w").write string
| =A0 =A0end
|

|
|The problem is that the setup is dodgy, sometimes it works, sometimes i= t
|looks like the server is restarted before the content of +string+ is
|written to the configuration file.
|How can I ensure that the content has been written before executing nex= t
|line of code (the restart in this case)?
|

I'm not sure, but maybe the fact you're not closing the file after writin= g has
something to do with that.

That's definitively the reason.

Try replacing the last line of update_configuration
with:

File.open(APP_CONFIG_FILE, 'w'){|f| f.write string}

When given a block, File.open closes the file after calling the block, wh= ich
should ensure that everything you wrote to file should have actually been
written.

[ADV]: see also
http://blog.rubybestpractices.com/posts/rklemme/001-Using_blocks_for_Robust=
ness.html

Cheers

robert


--=20
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

 

[Roger Pack]

File.new(APP_CONFIG_FILE, "w").write string

This file is never closed, so if the process is exited without running
its finalizers for some reason, buffered data could be lost.

-r

 

[Emil Kampp]

It seems that that did the job. Thank you very much