jmarca/couch_set_state

# Couch Set State


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This is a small package that uses superagent to set  "state" stored
in CouchDB.  What I often do is to use a CouchDB database as a way to
store state across machines.  For example, I might stash that a
detector is being processed, or that a detector has completed a step
in its processing.

The basic idea is that a document holds all of the information for a
particular detector, but that the detector might have multiple years
of processing (or months or whatever).  So the structure of the doc
might look like:

```json
{
   "_id": "801230",
   "_rev": "99-7ce940b60ed44a6ad07e6b5b21b4cc01",
   "2010": {
   },
   "2009": {
   },
   "2008": {
       "wim_neigbors_ready": {
           "direction": "west",
           "wim_id": 78,
           "distance": 18339
       },
       "vdsdata": "0",
       "occupancy_averaged": 1,
       "wim_neigbors": {
           "direction": "west",
           "wim_id": 78,
           "distance": 18339
       },
       "vdsraw_chain_lengths": [
           11,
           23,
           19,
           22,
           15
       ],
       "vdsimputed": 1,
       "truckimputation_max_iterations": 0,
       "csv_parse_2cdb": {
           "58cc79c6ebc92027a1a23da619932287": {
               "records": 35136,
               "file": "/data/wim/vds_id.801230.truck.imputed.2008.csv"
           },
           "375a3024b7049e75aadb6dddbaddd9fc": {
               "records": 175680,
               "file": "./imputed/vds_id.801230.truck.imputed.2008.csv"
           },
           "437944d40c7396e95a25ad7162ee64fe": {
               "records": 8784,
               "file": "/var/lib/data/imputed/vds_id.801230.truck.imputed.2008.csv"
           },
           "3437fe0a243bcdf6c07a5fc684abbb83": {
               "records": 35136,
               "file": "/data/wim/vds_id.801230.truck.imputed.2008.csv.gz"
           }
       },
       "csv_parse": {
           "58cc79c6ebc92027a1a23da619932287": "/data/wim/vds_id.801230.truck.imputed.2008.csv",
           "records": 35136,
           "437944d40c7396e95a25ad7162ee64fe": "Rwork/imputed/vds_id.801230.truck.imputed.2008.csv"
       },
       "rawdata": "1",
       "row": 1,
       "truckimputation_chain_lengths": [
           75,
           76,
           91,
           83,
           70
       ],
       "truckimputed": "2012-01-31b finished",
       "vdsraw_max_iterations": 0
   },
   ...
```

In such a case, one might want to set the state of
`vdsraw_chain_lengths` for 2010, say to show that it is being worked
on by some process.

This library helps with that.  To set 2010's `vdsraw_chain_length`
entry, you would do something like this:


``` javascript

var seter = require('couch_set_state')
var value = {'some':['arbitrary','data']}
seter({'db':'vdsdata%2ftracking'
         ,'doc':detector_id
         ,'year':yr
         ,'state':'vdsraw_chain_lengths'
         ,'value':value}
         ,function(err,state){
             // make sure state was set properly
             if(err) throw new Error(err)
             // do something
             return null
         })

```