only add cron job if not exists

updated README

Author: dlebauer

experiment-trait-data-visualizer/README.md

@@ -14,10 +14,24 @@
 - leaflet
 - cronR
 
-#### Data cached in 'cache.RData'
-#### BETYdb remote access uses ssh tunnel: ssh -Nf -L 5432:localhost:5432 bety6.ncsa.illinois.edu
-#### [Request access](https://identity.ncsa.illinois.edu/join/TU49BUUEDM)
-#### Set the following environment variables
+```{r echo=FALSE}
+lapply(list('shiny', 'shinythemes', 'lubridate', 'dplyr', 'ggplot2', 'timevis', 'rgeos', 'leaflet', 'cronR'),
+       install.packages)
+```
+
+to install cron (Ubuntu)
+
+```sh
+apt-get update
+apt-get install cron
+```
+
+#### Setup and Notes
+
+* Data are cached in a file `cache.RData` and updated using the cronR R interface to cron
+* Access to BETYdb remote access requires ssh tunnel `ssh -Nf -L 5432:localhost:5432 bety6.ncsa.illinois.edu`
+  * requires access, which can be [requested here](https://identity.ncsa.illinois.edu/join/TU49BUUEDM)
+* Set the following environment variables
 
 - bety_dbname ('bety')
 - bety_password

experiment-trait-data-visualizer/app.R

@@ -10,8 +10,12 @@ source('render-site-map.R')
 
 # schedule daily execution of cache refresh
 cache_update_cmd <- cron_rscript('cache-refresh.R')
- try(cron_add(command = cache_update_cmd, frequency = 'daily', 
-            id = 'cache-update', description = 'daily update of BETYdb cache'))
+
+if(!grepl('cache-update', cronR::cron_ls())){
+  cron_add(command = cache_update_cmd, frequency = 'daily', 
+           id = 'cache-update', description = 'daily update of BETYdb cache')
+}
+
 
 # set page UI
 ui <- fluidPage(theme = shinytheme('flatly'),

experiment-trait-data-visualizer/cache-refresh.R

@@ -101,8 +101,9 @@ get_data_for_season <- function(season) {
 
   # load existing full_cache_data object if exists, otherwise use empty list object
   full_cache_data <- list()
-  if (file.exists("cache.RData"))
+  if (file.exists("cache.RData")){
     load("cache.RData")
+  }
 
   # save data for given season
   full_cache_data[[ toString(season[[ 'name' ]]) ]] <- season_data