I use CouchDB extensively in numerous Mojo webapps. I've found the
combination to be very fast and powerful.
I use the built-in UserAgent in the running event loop rather than any kind
of driver. The amount of control you have using the raw UA and
Mojo::IOLoop functions rather than a driver just can't be beat. The Couch
RESTful API is relatively consistent in its response, and once you're used
to it, it codes fast.
I had thought of contributing something to the Mojo Wiki for CouchDB, but
just haven't had the time yet!
Here's some code examples to help you get a feel for things (all executing
in a running event loop):
Execute a view and retrieve all of its document contents returning the JSON
response to the callers 'delay'.
sub load_view_with_documents() {
my $delay=shift;
my $end=$delay->begin(0);
my $doc_retrieve_delay=Mojo::IOLoop->delay(sub {
my ($delay, $view_json)=@_;
if(! $view_json) {
$end->(0);
}
my $ids=[];
foreach my $row (@{$view_json->{'rows'}}) {
push($ids, $row->{'id'});
}
$ua->ua->post("/db/_all_docs?include_docs=true" => json =>
{ 'keys' => $ids } => sub {
my ($ua, $tx)=@_;
if($tx->error || $tx->res->code != 200) {
$end->(0);
} else {
$end->($tx->res->json);
}
});
});
my $doc_retrieve_end=$doc_retrieve_delay->begin(0);
$ua->ua->get("/db/_design/request/_view/new" => sub {
my ($ua, $tx)=@_;
if($tx->error || $tx->res->code != 200) {
$doc_retrieve_end->(0);
} else {
$doc_retrieve_end->($tx->res->json);
}
});
}
Which would be called with the callers 'delay' to create an artificial
'block' waiting on these results before proceeding. However it is run
non-blocking and won't jam up your web server.
A RESTful Mojo App rendering JSON:
sub get_event() {
my $self=shift;
my $key=$self->stash("key");
$self->ua->get("/db/_design/events/_view/by_key?key=".Mojo::JSON->encode($key)."&include_docs=true"
=> sub {
my ($ua, $tx)=@_;
if($tx->error() || $tx->res->code != 200) {
$self->app->log->error("View by_key failed:
".Dumper($tx));
return($self->render(
json => { "success" =>
Mojo::JSON->false,
"message" => "Internal
error retrieving key '$key' from database",
},
status => 500,
));
}
# Return an empty $doc hash or the contents of our row
document if found.
my $doc={};
if(defined $tx->res->json->{'rows'}->[0]->{'doc'}) {
$doc=$tx->res->json->{'rows'}->[0]->{'doc'};
}
$self->app->log->info("Returned event content for $key");
return($self->render(
json => { "success" => Mojo::JSON->true,
"message" => "Successfully
retrieved key '$omni_key' from database",
"data" => $doc,
},
status => 200,
));
});
$self->render_later();
}
The permutations are as deep as your imagination. I have some code that
runs 3 requests in parallel using 'delay', feeding to 1 request, then into
2, then finally rendering a result. All of it non-blocking and using
Mojo::UserAgent.
So in my opinion encapsulating the flexibility the built-in UA provides
would be a real challenge, and when you get used to the UA, IOLoop, and
Couch native API the combination is fast, powerful and scalable.
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