I have two mix projects P1 and P2.
P1 depends on ecto and provides a genserver interface. It is also added as a dependency in P2 only to have access to some client functions. So P2 does not try to start P1. It is started independently.
The problem is that P2 cannot be compiled. mix compile says that the the adapter configuration for P1.Repo is missing.
I do not want to include any repo configuration for P1 inside P2. Is there any way to use functionality provided by P1's modules inside P2 under these circumstances?
This is Ecto specific, but you can provide compile-time config when defining a module as a repo.
defmodule MyApp.Repo do
use Ecto.Repo, otp_app: :my_app,
adapter: Ecto.Adapters.Postgres
end
You can then add runtime config in the repo's init/2 callback.
defmodule MyApp.Repo do
use Ecto.Repo, otp_app: :my_app,
adapter: Ecto.Adapters.Postgres
def init(_type, config) do
new_config = Keyword.put(config, :url, System.get_env("DATABASE_URL"))
{:ok, new_config}
end
end
A more generic solution would be to provide application config as part of mix.exs's :env option. I believe this is runtime only though (someone please correct me if I'm wrong).
Here's what mix help compile.app provides on this.
:env - default values for the application environment. The application
environment is one of the most common ways to configure applications. See
the Application module for mechanisms to read and write to the application
environment.
Here's an example of application/0 in mix.exs using :env.
def application do
[extra_applications: [:logger, :crypto],
env: [key: :value],
registered: [MyServer]]
end
If P1 is dependency of P2, P2 is responsible for configuration and nothing can change that, but you have couple of other options:
use umbrella project The umbrella project can have its own config with P1.Repo. This way you keep P1 and P2 configs cleaner.
additionally you can tear out meaningful chunk from P1 that is used by P2 and move it to P3. Both P1 and P2 depend on P3.
Related
I'm trying to implement python-social-auth in Flask. I've ironed out tons of kinks whilst trying to interpret about 4 tutorials and a full Flask-book at the same time, and feel I've reached sort of an impasse with Flask-migrate.
I'm currently using the following code to create the tables necessary for python-social-auth to function in a flask-sqlalchemy environment.
from social.apps.flask_app.default import models
models.PSABase.metadata.create_all(db.engine)
Now, they're obviously using some form of their own Base, not related to my actual db-object. This in turn causes Flask-Migrate to completely miss out on these tables and remove them in migrations. Now, obviously I can remove these db-drops from every removal, but I can imagine it being one of those things that at one point is going to get forgotten about and all of a sudden I have no OAuth-ties anymore.
I've gotten this solution to work with the usage (and modification) of the manage.py-command syncdb as suggested by the python-social-auth Flask example
Miguel Grinberg, the author of Flask-Migrate replies here to an issue that seems to very closely resemble mine.
The closest I could find on stack overflow was this, but it doesn't shed too much light on the entire thing for me, and the answer was never accepted (and I can't get it to work, I have tried a few times)
For reference, here is my manage.py:
#!/usr/bin/env python
from flask.ext.script import Server, Manager, Shell
from flask.ext.migrate import Migrate, MigrateCommand
from app import app, db
manager = Manager(app)
manager.add_command('runserver', Server())
manager.add_command('shell', Shell(make_context=lambda: {
'app': app,
'db_session': db.session
}))
migrate = Migrate(app, db)
manager.add_command('db', MigrateCommand)
#manager.command
def syncdb():
from social.apps.flask_app.default import models
models.PSABase.metadata.create_all(db.engine)
db.create_all()
if __name__ == '__main__':
manager.run()
And to clarify, the db init / migrate / upgrade commands only create my user table (and the migration one obviously), but not the social auth ones, while the syncdb command works for the python-social-auth tables.
I understand from the github response that this isn't supported by Flask-Migrate, but I'm wondering if there's a way to fiddle in the PSABase-tables so they are picked up by the db-object sent into Migrate.
Any suggestions welcome.
(Also, first-time poster. I feel I've done a lot of research and tried quite a few solutions before I finally came here to post. If I've missed something obvious in the guidelines of SO, don't hesitate to point that out to me in a private message and I'll happily oblige)
After the helpful answer from Miguel here I got some new keywords to research. I ended up at a helpful github-page which had further references to, amongst others, the Alembic bitbucket site which helped immensely.
In the end I did this to my Alembic migration env.py-file:
from sqlalchemy import engine_from_config, pool, MetaData
[...]
# add your model's MetaData object here
# for 'autogenerate' support
# from myapp import mymodel
# target_metadata = mymodel.Base.metadata
from flask import current_app
config.set_main_option('sqlalchemy.url',
current_app.config.get('SQLALCHEMY_DATABASE_URI'))
def combine_metadata(*args):
m = MetaData()
for metadata in args:
for t in metadata.tables.values():
t.tometadata(m)
return m
from social.apps.flask_app.default import models
target_metadata = combine_metadata(
current_app.extensions['migrate'].db.metadata,
models.PSABase.metadata)
This seems to work absolutely perfectly.
The problem is that you have two sets of models, each with a different SQLAlchemy metadata object. The models from PSA were generated directly from SQLAlchemy, while your own models were generated through Flask-SQLAlchemy.
Flask-Migrate only sees the models that are defined via Flask-SQLAlchemy, because the db object that you give it only knows about the metadata for those models, it knows nothing about these other PSA models that bypassed Flask-SQLAlchemy.
So yeah, end result is that each time you generate a migration, Flask-Migrate/Alembic find these PSA tables in the db and decides to delete them, because it does not see any models for them.
I think the best solution for your problem is to configure Alembic to ignore certain tables. For this you can use the include_object configuration in the env.py module stored in the migrations directory. Basically you are going to write a function that Alembic will call every time it comes upon a new entity while generating a migration script. The function will return False when the object in question is one of these PSA tables, and True for every thing else.
Update: Another option, which you included in the response you wrote, is to merge the two metadata objects into one, then the models from your application and PSA are inspected by Alembic together.
I have nothing against the technique of merging multiple metadata objects into one, but I think it is not a good idea for an application to track migrations in models that aren't yours. Many times Alembic will not be able to capture a migration accurately, so you may need to make minor corrections on the generated script before you apply it. For models that are yours, you are capable of detecting these inaccuracies that sometimes show up in migration scripts, but when the models aren't yours I think you can miss stuff, because you will not be familiar enough with the changes that went into those models to do a good review of the Alembic generated script.
For this reason, I think it is a better idea to use my proposed include_object configuration to leave the third party models out of your migrations. Those models should be migrated according to the third party project's instructions instead.
I use two models as following:-
One which is use using db as
db = SQLAlchemy()
app['SQLALCHEMY_DATABASE_URI'] = 'postgresql://postgres:' + POSTGRES_PASSWORD + '#localhost/Flask'
db.init_app(app)
class User(db.Model):
pass
the other with Base as
Base = declarative_base()
uri = 'postgresql://postgres:' + POSTGRES_PASSWORD + '#localhost/Flask'
engine = create_engine(uri)
metadata = MetaData(engine)
Session = sessionmaker(bind=engine)
session = Session()
class Address(Base):
pass
Since you created user with db.Model you can use flask migrate on User and class Address used Base which handles fetching pre-existing table from the database.
It seems like a very common issue with SSIS packages is releasing a package to Production that ends up with running the wrong connectionstring parameters. This could happen by making any one of many mistakes or ommisions. As a result, I find it helpful to dump all ConnectionString values to a log file. This helps me understand what connectionstrings were actually applied to the package at run time.
Now, I am considering having my packages check to see if every connnection object in my package had its connectionstring overriden by an entry in the config file and if not, return a warning or even fail the package. This is to allow easier configuration by extracting all environment variables to a config file. If a connectionstring is never overridden, this risks that a package, when run in production, may use development settings or a package, when run in a non production setting when testing, may accidentily be run against production.
I'd like to borrow from anyone who may have tried to do this. I'd also be interested in suggestions on how to accomplish this with minimal work.
Thx
Technical question 1 - what are my connection string
This is an easy question to answer. In your package, add a Script Task and enumerate through the Connections collection. I fire the OnInformation event and if I had this scheduled, I'd be sure to have the /rep iew options in my dtexec to ensure I record Information, Errors and Warnings.
namespace TurnDownForWhat
{
using System;
using System.Data;
using Microsoft.SqlServer.Dts.Runtime;
using System.Windows.Forms;
/// <summary>
/// ScriptMain is the entry point class of the script. Do not change the name, attributes,
/// or parent of this class.
/// </summary>
[Microsoft.SqlServer.Dts.Tasks.ScriptTask.SSISScriptTaskEntryPointAttribute]
public partial class ScriptMain : Microsoft.SqlServer.Dts.Tasks.ScriptTask.VSTARTScriptObjectModelBase
{
public void Main()
{
bool fireAgain = false;
foreach (var item in Dts.Connections)
{
Dts.Events.FireInformation(0, "SCR Enumerate Connections", string.Format("{0}->{1}", item.Name, item.ConnectionString), string.Empty, 0, ref fireAgain);
}
Dts.TaskResult = (int)ScriptResults.Success;
}
enum ScriptResults
{
Success = Microsoft.SqlServer.Dts.Runtime.DTSExecResult.Success,
Failure = Microsoft.SqlServer.Dts.Runtime.DTSExecResult.Failure
};
}
}
Running that on my package, I can see I had two Connection managers, CM_FF and CM_OLE along with their connection strings.
Information: 0x0 at SCR Enum, SCR Enumerate Connections: CM_FF->C:\ssisdata\dba_72929.csv
Information: 0x0 at SCR Enum, SCR Enumerate Connections: CM_OLE->Data Source=localhost\dev2012;Initial Catalog=tempdb;Provider=SQLNCLI11;Integrated Security=SSPI;
Add that to ... your OnPreExecute event for all the packages and no one sees it but every reports back.
Technical question 2 - Missed configurations
I'm not aware of anything that will allow a package to know it's under configuration. I'm sure there's an event as you will see in your Information/Warning messages that a package attempted to apply a configuration, didn't find one and is going to retain it's design time value. Information - I'm configuring X via Y. Warning - tried to configure X but didn't find Y. But how to have a package inspect itself to find that out, I have no idea.
That said, I've seen reference to a property that fails package on missed configuration. I'm not seeing it now, but I'm certain it exists in some crevice. You can supply the /w parameter to dtexec which treats warnings as errors and really, warnings are just errors that haven't grown up yet.
Unspoken issue 1 - Permissions
I had a friend who botched an XML config file as part of their production deploy. Their production server started consuming data from a dev server. Bad things happened. It sounds like you have had a similar situation. The resolution is easy, insulate your environments. Are you using the same service account for your production class SQL Server boxes and dev/test/uat/qa/load/etc? STOP. Make a new one. Don't allow prod to talk to any boxes that aren't in their tier of service. Someone bones a package and doesn't set a configuration? First of all, you'll catch it when it goes from dev to something-before-production because that tier wouldn't be able to talk to anything else that's not that level. But if you're in the ultra cheap shop and you've only got dev and prod, so be it. Non-configured package goes to prod. Prod SQL Agent fires off the package. Package uses default connection manager and fails validation because it can't talk to the dev sales database.
Unspoken issue 2 - template
What's your process when you have a new package to build? Does your team really start from scratch? There are so many ways to solve this problem but the core concept is to define your best practices for Configuration, Logging, Package Protection Level, Transaction levels, etc into some easily consumable form. Maybe that's 3 starter packages: one for raw acquisition, maybe one stages and conforms the data and the last one moves data from conformed into the final destination. Teammates then simply have to pick one to start from and fill in the spots that need it. If they choose to do their own thing, that's the stick you beat them with when their package fails to run in production because they didn't follow the standard path.
There are other approaches here. If you're a strong .NET crew, you can gen your template packages that way. At this point, I create my templates with Biml and use that to drive basic package creation.
If I am understanding you correctly the below solution should work.
My suggestion to you is to turn on the Do not save sensitive option for the ProtectionLevel property at the top level of the package.
This will require you to use package configurations for every connection, otherwise it will not have the credentials to make a connection.
I have a set of parameters that should be configured by the user. But they are just too much to send them through RESTful services or something similar. Besides there may be another set of configurations of same parameters.
Assume that my configurations are: p1, p2, p3, ... p10
I want to make possible having more than set of initialization of these configurations such as:
(p1=x, p2=y, ... p10=1)
(p1=a, p2=b, ... p10=10)
To do that I currently implement my OSGI component with metatype=true and configurationFactory = true options so that each instance of my component will have a set of configurations initialized. Then, I process the instances in a manager component.
So the question what do you suggest for passing configurations to OSGI components from user?
Thanks
If this is really about configurations you should use the OSGi ConfigurationAdmin service. A console like the Apache Felix WebConsole can then be used to edit configurations.
If the values (or some values) can be different for each RESTful call to your application and they don't fit in a URL, you can make a POST request instead of a GET, and pass the values in the body of the request, in a suitable format.
Scenario: I am using Managed Extensibility Framework to load plugins (exports) at runtime based on an interface contract defined in a separate dll. In my Visual Studio solution, I have 3 different projects: The host application, a class library (defining the interface - "IPlugin") and another class library implementing the interface (the export - "MyPlugin.dll").
The host looks for exports in its own root directory, so during testing, I build the whole solution and copy Plugin.dll from the Plugin class library bin/release folder to the host's debug directory so that the host's DirectoryCatalog will find it and be able to add it to the CompositionContainer. Plugin.dll is not automatically copied after each rebuild, so I do that manually each time I've made changes to the contract/implementation.
However, a couple of times I've run the host application without having copied (an updated) Plugin.dll first, and it has thrown an exception during composition:
Unable to load one or more of the requested types. Retrieve the LoaderExceptions for more information
This is of course due to the fact that the Plugin.dll it's trying to import from implements a different version of IPlugin, where the property/method signatures don't match. Although it's easy to avoid this in a controlled and monitored environment, by simply avoiding (duh) obsolete IPlugin implementations in the plugin folder, I cannot rely on such assumptions in the production environment, where legacy plugins could be encountered.
The problem is that this exception effectively botches the whole Compose action and no exports are imported. I would have preferred that the mismatching IPlugin implementations are simply ignored, so that other exports in the catalog(s), implementing the correct version of IPlugin, are still imported.
Is there a way to accomplish this? I'm thinking either of several potential options:
There is a flag to set on the CompositionContainer ("ignore failing imports") prior to or when calling Compose
There is a similar flag to specify on the <ImportMany()> attribute
There is a way to "hook" on to the iteration process underlying Compose(), and be able to deal with each (failed) import individually
Using strong name signing to somehow only look for imports implementing the current version of IPlugin
Ideas?
I have also run into a similar problem.
If you are sure that you want to ignore such "bad" assemblies, then the solution is to call AssemblyCatalog.Parts.ToArray() right after creating each assembly catalog. This will trigger the ReflectionTypeLoadException which you mention. You then have a chance to catch the exception and ignore the bad assembly.
When you have created AssemblyCatalog objects for all the "good" assemblies, you can aggregate them in an AggregateCatalog and pass that to the CompositionContainer constructor.
This issue can be caused by several factors (any exceptions on the loaded assemblies), like the exception says, look at the ExceptionLoader to (hopefully) get some idea
Another problem/solution that I found, is when using DirectoryCatalog, if you don't specify the second parameter "searchPattern", MEF will load ALL the dlls in that folder (including third party), and start looking for export types, that can also cause this issue, a solution is to have a convention name on all the assemblies that export types, and specify that in the DirectoryCatalog constructor, I use *_Plugin.dll, that way MEF will only load assemblies that contain exported types
In my case MEF was loading a NHibernate dll and throwing some assembly version error on the LoaderException (this error can happen with any of the dlls in the directory), this approach solved the problem
Here is an example of above mentioned methods:
var di = new DirectoryInfo(Server.MapPath("../../bin/"));
if (!di.Exists) throw new Exception("Folder not exists: " + di.FullName);
var dlls = di.GetFileSystemInfos("*.dll");
AggregateCatalog agc = new AggregateCatalog();
foreach (var fi in dlls)
{
try
{
var ac = new AssemblyCatalog(Assembly.LoadFile(fi.FullName));
var parts = ac.Parts.ToArray(); // throws ReflectionTypeLoadException
agc.Catalogs.Add(ac);
}
catch (ReflectionTypeLoadException ex)
{
Elmah.ErrorSignal.FromCurrentContext().Raise(ex);
}
}
CompositionContainer cc = new CompositionContainer(agc);
_providers = cc.GetExports<IDataExchangeProvider>();
What is an alternative to autotools in Haskell world? I want to be able to choose between different configurations of the same source code.
For example, there are at least two implementations of MD5 in Haskell: Data.Digest.OpenSSL.MD5 and Data.Digest.Pure.MD5. I'd like to write code in such a way that it can figure out which library is already installed, and didn't require to install the other.
In C I can use Autotools/Scons/CMake + cpp. In Python I can catch ImportError. Which tools should I use in Haskell?
In Haskell you use Cabal configurations. At your project top-level directory, you put a file with the extension .cabal, e.g., <yourprojectname>.cabal. The contents are roughly:
Name: myfancypackage
Version: 0.0
Description: myfancypackage
License: BSD3
License-file: LICENSE
Author: John Doe
Maintainer: john#example.com
Build-Type: Simple
Cabal-Version: >=1.4
Flag pure-haskell-md5
Description: Choose the purely Haskell MD5 implementation
Default: False
Executable haq
Main-is: Haq.hs
Build-Depends: base-4.*
if flag(pure-haskell-md5)
Build-Depends: pureMD5-0.2.*
else
Build-Depends: hopenssl-1.1.*
The Cabal documentation has more details, in particular the section on Configurations.
As nominolo says, Cabal is the tool to use. In particular, the 'configurations" syntax.