simplify code; make several download attempts; delete local temporary file after downloading

Author: boriskaus

src/IO.jl

@@ -23,10 +23,11 @@ function save_GMG(filename::String, data::Union{GeoData, CartData, UTMData}; dir
 end 
 
 """
-    load_GMG(filename::String, dir=pwd())
+    load_GMG(filename::String, dir=pwd(); maxattempts=5)
 
 Loads a `GeoData`/`CartData`/`UTMData` data set from jld2 file `filename`
-Note: the `filename` can also be a remote `url`, in which case we first download that file to a temporary directory before opening it
+Note: the `filename` can also be a remote `url`, in which case we first download that file to a temporary directory before opening it.
+We make `maxattempts` attempts to download it before giving up.
 
 Example 1 - Load local file
 ====
@@ -56,11 +57,11 @@ GeoData
 ```
 
 """
-function load_GMG(filename::String, dir=pwd())
+function load_GMG(filename::String, dir=pwd(); maxattempts=5)
 
+    local_filename = "download_GMG_temp.jld2"
     if contains(filename,"http")
-        #download remote file to a local temporary directory
-        file_ext = Downloads.download(filename, joinpath(pwd(),"download_GMG_temp.jld2"))
+        file_ext = download_data(filename, local_filename, dir=dir, maxattempts=maxattempts)
     else
         # local file
         file_ext = joinpath(dir,filename*".jld2")
@@ -69,16 +70,20 @@ function load_GMG(filename::String, dir=pwd())
     # load data:
     data =  load_object(file_ext)
 
+    # remove local temporary file
+    rm(local_filename)
+
     return data
 end 
 
 
 
 
 """
-    download_data(url::String, local_filename="temp.dat"; dir=pwd() )
+    download_data(url::String, local_filename="temp.dat"; dir=pwd(), maxattempts=5 )
 
-Downloads a remote dataset with name `url` from a remote location and saves it to the current directory
+Downloads a remote dataset with name `url` from a remote location and saves it to the current directory.
+If download fails, we make `maxattempts` attempts before giving up.
 
 Example
 ====
@@ -89,14 +94,28 @@ julia> download_data(url)
 ```
 
 """
-function download_data(url::String, local_filename="temp.dat"; dir=pwd() )
+function download_data(url::String, local_filename="temp.dat"; dir=pwd(), maxattempts=5)
 
     if !contains(url,"http")
         @warn "the url does not contain http; please double check that it worked"
     end
 
-    # download remote file to a local temporary directory
-    file_ext = Downloads.download(url, joinpath(dir,local_filename))
+    #download remote file to a local temporary directory
+    file_ext = [];
+    attempt = 0
+    while attempt<maxattempts
+      try
+        file_ext = Downloads.download(url, joinpath(dir,local_filename))
+        break
+      catch
+        @warn "Failed downloading data on attempt $attempt/$maxattempts"
+        sleep(5)  # wait a few sec
+      end
+      attempt += 1
+    end
+    if isempty(file_ext)
+      error("Could not download GMT topography data")
+    end
 
     return file_ext
 end