Re: Actually using component.
I really am dense at times. :(
I was confusing the 'component' for the system map in this
line:
https://github.com/weavejester/duct/blob/master/duct/src/duct/component/endpoint.clj#L6
#PalmToFace
-d
On Tuesday, June 9, 2015 at 5:57:48 PM UTC-5, James Reeves wrote:
On 9 June 2015 at 23:16, Dru Sellers d...@drusellers.com javascript:
wrote:
@James do you only have one component that has all of your routes? or do
you have each component supply its own routes? If you imagine a component
providing its own routes, I'd love to see a duct example with two routes
set up.
I believe that would be multiple endpoint components.
Looking at
https://github.com/weavejester/duct/blob/master/duct/src/duct/component/endpoint.clj#L7
I'm guessing that duct only expects one endpoint-component - is that
correct?
No, you can have as many endpoint components as you want.
Duct has a handler component that looks for endpoint components in its
dependencies, and combines their routes together using
compojure.core/routes.
One of the ideas in Duct is to group routes together by purpose, to
achieve the modularity of micro-service architecture without the overhead.
For example, let's say you have endpoints foo, bar and baz. Then your
system builder in Duct would look like:
(defn new-system [config]
(let [config (meta-merge base-config config)]
(- (component/system-map
:http (jetty-server (:http config))
:app (handler-component (:app config))
:foo (endpoint-component foo-endpoint)
:bar (endpoint-component bar-endpoint)
:baz (endpoint-component baz-endpoint))
(component/system-using
{:http [:app]
:app [:foo :bar :baz]}
- James
--
You received this message because you are subscribed to the Google
Groups Clojure group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
---
You received this message because you are subscribed to the Google Groups
Clojure group.
To unsubscribe from this group and stop receiving emails from it, send an email
to clojure+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
Re: Actually using component.
I think the most important rule when using component is to only use local
state like Timothy stated, i.e. nothings gets def-ed. You could write an
application that a -main function that starts the system and you would
never need a global reference to the system.
In practise however, you do make references to the current system to
support working in the REPL (see README here
https://github.com/stuartsierra/component/#reloading) and I also use
references to the system to inspect db state etc in tests, but for that
`let` blocks also work well.
I would recommend to continue playing with the bare metal component for a
while to get an understanding of the concept, after a while I think you
will want something smarter. We're using system-graph
https://github.com/RedBrainLabs/system-graph that helps to stop thinking
and managing dependencies and recently we have a built a small layer on top
of that so we even have flexible graphs in a convenient way.
On Tue, Jun 9, 2015 at 8:33 AM, Atamert Ölçgen mu...@muhuk.com wrote:
On Tue, Jun 9, 2015 at 6:12 AM, Timothy Baldridge tbaldri...@gmail.com
wrote:
Stuart addresses two anti-patterns in your PRs. Perhaps I can help
explain them.
Let's say we have a system that looks like this:
(defrecord DBConnection [])
(defrecord DBLayer [db-connection])
(defrecord AppLayer [db-layer])
We can construct a system thusly:
{:db-connection (-DBConnection ...)
:db-layer (-DBLayer ...)
:app-layer (-AppLayer ...)}
And start it up:
(def my-system (start-system system-map))
First of all, what you need to recognize is that every component now has
it's dependencies assoc'ed into the component. So each component should
only deal with it's local view of the system:
(defrecord AppLayer [db-layer]
IDoStuff
(do-stuff [this]
(print-data (get-data db-layer)
(get-data2 (:db-layer this)))
What should not happen is that the AppLayer should do this:
(print-data (:db-layer my-system))
If a component does this it now has access to the entire system, and that
circumvents one of the reasons component was created, to help improve
separation of concerns.
In your other example you're doing something like this:
(defrecord AppLayer [db-layer]
IDoStuff
(do-stuff [this]
(run-query (:db-conn db-layer) select foo from bar)))
The problem with this is that AppLayer is assuming that the db-layer has
a connection to the db. This also violates the separation of concerns.
Instead AppLayer should include a db-connection as a dependency if it is
needed by the app layer code.
This is also known as The Law of Demeter. (
http://en.wikipedia.org/wiki/Law_of_Demeter)
- Each unit should have only limited knowledge about other units: only
units closely related to the current unit.
- Each unit should only talk to its friends; don't talk to strangers.
- Only talk to your immediate friends.
So that sums up Stuart's two replies. a) don't touch the system from
inside a component, the system map is only for starting and stopping the
system, and to provide an entry point. b) don't reach into other components
from a component
Timothy
On Mon, Jun 8, 2015 at 9:35 PM, James Reeves ja...@booleanknot.com
wrote:
My recommendation is to use a closure. So I'd write your example as:
(defn username-endpoint [{:keys [db]}]
(routes
(GET /:username [username]
(let [user (users/get-user db username)]
(str h1Hello (:name user) /h1)
So you pass your configuration map into the endpoint function, which
returns a handler.
You can then wrap this in a component:
(defrecord EndpointComponent [build-routes]
component/Lifecycle
(start [component]
(if (:routes component)
component
(assoc component :routes (build-routes component
(stop [component]
(dissoc component :routes)))
Incidentally, the above code is taken directly from Duct
https://github.com/weavejester/duct, a template and small supporting
library I've written for building component-based web apps.
I've also written a blog article
https://www.booleanknot.com/blog/2015/05/22/structuring-clojure-web-apps.html
around
general best practice for this type of style.
- James
On 8 June 2015 at 22:51, Dru Sellers d...@drusellers.com wrote:
So, I guess I am a bit lost, how does someone actually use component? I
have an application all set up with it and it seems to be working as I
would expect but Stuart seems to be steering me in a different direction.
https://github.com/stuartsierra/component/pull/35
https://github.com/stuartsierra/component/issues/34
So I'll try and paint a full picture.
https://gist.github.com/drusellers/8109dce4b9fb19c14ebb
I know compojure and component / reloaded may not play well, but I'm
trying to figure out how to best use the system var. Am I close, I'd love
to give back a decent PR to the README.md of the component repo to help
others as they come along.
-d
--
Re: Actually using component.
On Tue, Jun 9, 2015 at 6:12 AM, Timothy Baldridge tbaldri...@gmail.com
wrote:
Stuart addresses two anti-patterns in your PRs. Perhaps I can help explain
them.
Let's say we have a system that looks like this:
(defrecord DBConnection [])
(defrecord DBLayer [db-connection])
(defrecord AppLayer [db-layer])
We can construct a system thusly:
{:db-connection (-DBConnection ...)
:db-layer (-DBLayer ...)
:app-layer (-AppLayer ...)}
And start it up:
(def my-system (start-system system-map))
First of all, what you need to recognize is that every component now has
it's dependencies assoc'ed into the component. So each component should
only deal with it's local view of the system:
(defrecord AppLayer [db-layer]
IDoStuff
(do-stuff [this]
(print-data (get-data db-layer)
(get-data2 (:db-layer this)))
What should not happen is that the AppLayer should do this:
(print-data (:db-layer my-system))
If a component does this it now has access to the entire system, and that
circumvents one of the reasons component was created, to help improve
separation of concerns.
In your other example you're doing something like this:
(defrecord AppLayer [db-layer]
IDoStuff
(do-stuff [this]
(run-query (:db-conn db-layer) select foo from bar)))
The problem with this is that AppLayer is assuming that the db-layer has a
connection to the db. This also violates the separation of concerns.
Instead AppLayer should include a db-connection as a dependency if it is
needed by the app layer code.
This is also known as The Law of Demeter. (
http://en.wikipedia.org/wiki/Law_of_Demeter)
- Each unit should have only limited knowledge about other units: only
units closely related to the current unit.
- Each unit should only talk to its friends; don't talk to strangers.
- Only talk to your immediate friends.
So that sums up Stuart's two replies. a) don't touch the system from
inside a component, the system map is only for starting and stopping the
system, and to provide an entry point. b) don't reach into other components
from a component
Timothy
On Mon, Jun 8, 2015 at 9:35 PM, James Reeves ja...@booleanknot.com
wrote:
My recommendation is to use a closure. So I'd write your example as:
(defn username-endpoint [{:keys [db]}]
(routes
(GET /:username [username]
(let [user (users/get-user db username)]
(str h1Hello (:name user) /h1)
So you pass your configuration map into the endpoint function, which
returns a handler.
You can then wrap this in a component:
(defrecord EndpointComponent [build-routes]
component/Lifecycle
(start [component]
(if (:routes component)
component
(assoc component :routes (build-routes component
(stop [component]
(dissoc component :routes)))
Incidentally, the above code is taken directly from Duct
https://github.com/weavejester/duct, a template and small supporting
library I've written for building component-based web apps.
I've also written a blog article
https://www.booleanknot.com/blog/2015/05/22/structuring-clojure-web-apps.html
around
general best practice for this type of style.
- James
On 8 June 2015 at 22:51, Dru Sellers d...@drusellers.com wrote:
So, I guess I am a bit lost, how does someone actually use component? I
have an application all set up with it and it seems to be working as I
would expect but Stuart seems to be steering me in a different direction.
https://github.com/stuartsierra/component/pull/35
https://github.com/stuartsierra/component/issues/34
So I'll try and paint a full picture.
https://gist.github.com/drusellers/8109dce4b9fb19c14ebb
I know compojure and component / reloaded may not play well, but I'm
trying to figure out how to best use the system var. Am I close, I'd love
to give back a decent PR to the README.md of the component repo to help
others as they come along.
-d
--
You received this message because you are subscribed to the Google
Groups Clojure group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with
your first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
---
You received this message because you are subscribed to the Google
Groups Clojure group.
To unsubscribe from this group and stop receiving emails from it, send
an email to clojure+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
--
You received this message because you are subscribed to the Google
Groups Clojure group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with
your first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more
Re: Actually using component.
On 9 June 2015 at 23:16, Dru Sellers d...@drusellers.com wrote:
@James do you only have one component that has all of your routes? or do
you have each component supply its own routes? If you imagine a component
providing its own routes, I'd love to see a duct example with two routes
set up.
I believe that would be multiple endpoint components.
Looking at
https://github.com/weavejester/duct/blob/master/duct/src/duct/component/endpoint.clj#L7
I'm guessing that duct only expects one endpoint-component - is that
correct?
No, you can have as many endpoint components as you want.
Duct has a handler component that looks for endpoint components in its
dependencies, and combines their routes together using
compojure.core/routes.
One of the ideas in Duct is to group routes together by purpose, to achieve
the modularity of micro-service architecture without the overhead.
For example, let's say you have endpoints foo, bar and baz. Then your
system builder in Duct would look like:
(defn new-system [config]
(let [config (meta-merge base-config config)]
(- (component/system-map
:http (jetty-server (:http config))
:app (handler-component (:app config))
:foo (endpoint-component foo-endpoint)
:bar (endpoint-component bar-endpoint)
:baz (endpoint-component baz-endpoint))
(component/system-using
{:http [:app]
:app [:foo :bar :baz]}
- James
--
You received this message because you are subscribed to the Google
Groups Clojure group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
---
You received this message because you are subscribed to the Google Groups
Clojure group.
To unsubscribe from this group and stop receiving emails from it, send an email
to clojure+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
Re: Actually using component.
@James do you only have one component that has all of your routes? or do
you have each component supply its own routes? If you imagine a component
providing its own routes, I'd love to see a duct example with two routes
set up.
I believe that would be multiple endpoint components.
Looking
at
https://github.com/weavejester/duct/blob/master/duct/src/duct/component/endpoint.clj#L7
I'm guessing that duct only expects one endpoint-component - is that
correct?
-d
On Monday, June 8, 2015 at 8:36:36 PM UTC-5, James Reeves wrote:
My recommendation is to use a closure. So I'd write your example as:
(defn username-endpoint [{:keys [db]}]
(routes
(GET /:username [username]
(let [user (users/get-user db username)]
(str h1Hello (:name user) /h1)
So you pass your configuration map into the endpoint function, which
returns a handler.
You can then wrap this in a component:
(defrecord EndpointComponent [build-routes]
component/Lifecycle
(start [component]
(if (:routes component)
component
(assoc component :routes (build-routes component
(stop [component]
(dissoc component :routes)))
Incidentally, the above code is taken directly from Duct
https://github.com/weavejester/duct, a template and small supporting
library I've written for building component-based web apps.
I've also written a blog article
https://www.booleanknot.com/blog/2015/05/22/structuring-clojure-web-apps.html
around
general best practice for this type of style.
- James
On 8 June 2015 at 22:51, Dru Sellers d...@drusellers.com javascript:
wrote:
So, I guess I am a bit lost, how does someone actually use component? I
have an application all set up with it and it seems to be working as I
would expect but Stuart seems to be steering me in a different direction.
https://github.com/stuartsierra/component/pull/35
https://github.com/stuartsierra/component/issues/34
So I'll try and paint a full picture.
https://gist.github.com/drusellers/8109dce4b9fb19c14ebb
I know compojure and component / reloaded may not play well, but I'm
trying to figure out how to best use the system var. Am I close, I'd love
to give back a decent PR to the README.md of the component repo to help
others as they come along.
-d
--
You received this message because you are subscribed to the Google
Groups Clojure group.
To post to this group, send email to clo...@googlegroups.com
javascript:
Note that posts from new members are moderated - please be patient with
your first post.
To unsubscribe from this group, send email to
clojure+u...@googlegroups.com javascript:
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
---
You received this message because you are subscribed to the Google Groups
Clojure group.
To unsubscribe from this group and stop receiving emails from it, send an
email to clojure+u...@googlegroups.com javascript:.
For more options, visit https://groups.google.com/d/optout.
--
You received this message because you are subscribed to the Google
Groups Clojure group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
---
You received this message because you are subscribed to the Google Groups
Clojure group.
To unsubscribe from this group and stop receiving emails from it, send an email
to clojure+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
Re: Actually using component.
Hey Dru Take a look at Duct: https://github.com/weavejester/duct If you make a new app using that template, you should get some pointers from the boilerplate it generates. cheers, Jonathan On Mon, Jun 8, 2015 at 5:51 PM, Dru Sellers d...@drusellers.com wrote: So, I guess I am a bit lost, how does someone actually use component? I have an application all set up with it and it seems to be working as I would expect but Stuart seems to be steering me in a different direction. https://github.com/stuartsierra/component/pull/35 https://github.com/stuartsierra/component/issues/34 So I'll try and paint a full picture. https://gist.github.com/drusellers/8109dce4b9fb19c14ebb I know compojure and component / reloaded may not play well, but I'm trying to figure out how to best use the system var. Am I close, I'd love to give back a decent PR to the README.md of the component repo to help others as they come along. -d -- You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups Clojure group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups Clojure group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: Actually using component.
My recommendation is to use a closure. So I'd write your example as:
(defn username-endpoint [{:keys [db]}]
(routes
(GET /:username [username]
(let [user (users/get-user db username)]
(str h1Hello (:name user) /h1)
So you pass your configuration map into the endpoint function, which
returns a handler.
You can then wrap this in a component:
(defrecord EndpointComponent [build-routes]
component/Lifecycle
(start [component]
(if (:routes component)
component
(assoc component :routes (build-routes component
(stop [component]
(dissoc component :routes)))
Incidentally, the above code is taken directly from Duct
https://github.com/weavejester/duct, a template and small supporting
library I've written for building component-based web apps.
I've also written a blog article
https://www.booleanknot.com/blog/2015/05/22/structuring-clojure-web-apps.html
around
general best practice for this type of style.
- James
On 8 June 2015 at 22:51, Dru Sellers d...@drusellers.com wrote:
So, I guess I am a bit lost, how does someone actually use component? I
have an application all set up with it and it seems to be working as I
would expect but Stuart seems to be steering me in a different direction.
https://github.com/stuartsierra/component/pull/35
https://github.com/stuartsierra/component/issues/34
So I'll try and paint a full picture.
https://gist.github.com/drusellers/8109dce4b9fb19c14ebb
I know compojure and component / reloaded may not play well, but I'm
trying to figure out how to best use the system var. Am I close, I'd love
to give back a decent PR to the README.md of the component repo to help
others as they come along.
-d
--
You received this message because you are subscribed to the Google
Groups Clojure group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with
your first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
---
You received this message because you are subscribed to the Google Groups
Clojure group.
To unsubscribe from this group and stop receiving emails from it, send an
email to clojure+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
--
You received this message because you are subscribed to the Google
Groups Clojure group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
---
You received this message because you are subscribed to the Google Groups
Clojure group.
To unsubscribe from this group and stop receiving emails from it, send an email
to clojure+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
Re: Actually using component.
Stuart addresses two anti-patterns in your PRs. Perhaps I can help explain
them.
Let's say we have a system that looks like this:
(defrecord DBConnection [])
(defrecord DBLayer [db-connection])
(defrecord AppLayer [db-layer])
We can construct a system thusly:
{:db-connection (-DBConnection ...)
:db-layer (-DBLayer ...)
:app-layer (-AppLayer ...)}
And start it up:
(def my-system (start-system system-map))
First of all, what you need to recognize is that every component now has
it's dependencies assoc'ed into the component. So each component should
only deal with it's local view of the system:
(defrecord AppLayer [db-layer]
IDoStuff
(do-stuff [this]
(print-data (get-data db-layer)
(get-data2 (:db-layer this)))
What should not happen is that the AppLayer should do this:
(print-data (:db-layer my-system))
If a component does this it now has access to the entire system, and that
circumvents one of the reasons component was created, to help improve
separation of concerns.
In your other example you're doing something like this:
(defrecord AppLayer [db-layer]
IDoStuff
(do-stuff [this]
(run-query (:db-conn db-layer) select foo from bar)))
The problem with this is that AppLayer is assuming that the db-layer has a
connection to the db. This also violates the separation of concerns.
Instead AppLayer should include a db-connection as a dependency if it is
needed by the app layer code.
So that sums up Stuart's two replies. a) don't touch the system from inside
a component, the system map is only for starting and stopping the system,
and to provide an entry point. b) don't reach into other components from a
component
Timothy
On Mon, Jun 8, 2015 at 9:35 PM, James Reeves ja...@booleanknot.com wrote:
My recommendation is to use a closure. So I'd write your example as:
(defn username-endpoint [{:keys [db]}]
(routes
(GET /:username [username]
(let [user (users/get-user db username)]
(str h1Hello (:name user) /h1)
So you pass your configuration map into the endpoint function, which
returns a handler.
You can then wrap this in a component:
(defrecord EndpointComponent [build-routes]
component/Lifecycle
(start [component]
(if (:routes component)
component
(assoc component :routes (build-routes component
(stop [component]
(dissoc component :routes)))
Incidentally, the above code is taken directly from Duct
https://github.com/weavejester/duct, a template and small supporting
library I've written for building component-based web apps.
I've also written a blog article
https://www.booleanknot.com/blog/2015/05/22/structuring-clojure-web-apps.html
around
general best practice for this type of style.
- James
On 8 June 2015 at 22:51, Dru Sellers d...@drusellers.com wrote:
So, I guess I am a bit lost, how does someone actually use component? I
have an application all set up with it and it seems to be working as I
would expect but Stuart seems to be steering me in a different direction.
https://github.com/stuartsierra/component/pull/35
https://github.com/stuartsierra/component/issues/34
So I'll try and paint a full picture.
https://gist.github.com/drusellers/8109dce4b9fb19c14ebb
I know compojure and component / reloaded may not play well, but I'm
trying to figure out how to best use the system var. Am I close, I'd love
to give back a decent PR to the README.md of the component repo to help
others as they come along.
-d
--
You received this message because you are subscribed to the Google
Groups Clojure group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with
your first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
---
You received this message because you are subscribed to the Google Groups
Clojure group.
To unsubscribe from this group and stop receiving emails from it, send an
email to clojure+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
--
You received this message because you are subscribed to the Google
Groups Clojure group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with
your first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
---
You received this message because you are subscribed to the Google Groups
Clojure group.
To unsubscribe from this group and stop receiving emails from it, send an
email to clojure+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
--
“One of the main causes of the fall of the Roman Empire was that–lacking
