pipeline: make errors easier to debug by including the request

Otherwise it's outright painful to figure out what failed in a
pipeline...

1 files changed, 10 insertions, 7 deletions

diff --git a/lib/mogilefs/backend.rb b/lib/mogilefs/backend.rb
index 24ce81a..89f88a3 100644
--- a/lib/mogilefs/backend.rb
+++ b/lib/mogilefs/backend.rb
@@ -178,7 +178,7 @@ class MogileFS::Backend
       raise MogileFS::PipelineError,
             "EOF with #{@pending.size} requests in-flight"
     ready = @pending.shift
-    ready.call(parse_response(line, false))
+    ready[1].call(parse_response(line, ready[0]))
   end
 
   def timeout_update(timeout, t0) # :nodoc:
@@ -221,7 +221,7 @@ class MogileFS::Backend
       # send the request out...
       begin
         io.timed_write(request, timeout)
-        @pending << block
+        @pending << [ request, block ]
       rescue SystemCallError, MogileFS::RequestTruncatedError => err
         @dead[@active_host] = [ Time.now, err ]
         shutdown_unlocked(@pending[0])
@@ -254,7 +254,7 @@ class MogileFS::Backend
     @mutex.synchronize do
       begin
         io = dispatch_unlocked(request)
-        line = io.timed_gets(@timeout) and return parse_response(line, true)
+        line = io.timed_gets(@timeout) and return parse_response(line)
 
         idempotent or
           raise EOFError, "end of file reached after: #{request.inspect}"
@@ -290,13 +290,16 @@ class MogileFS::Backend
 
   # Turns the +line+ response from the server into a Hash of options, an
   # error, or raises, as appropriate.
-  def parse_response(line, raise_ok = true)
+  def parse_response(line, request = nil)
     if line =~ /^ERR\s+(\w+)\s*([^\r\n]*)/
       @lasterr = $1
       @lasterrstr = $2 ? url_unescape($2) : nil
-      e = error(@lasterr).new(@lasterrstr)
-      raise e if raise_ok
-      return e
+      if request
+        request = " request=#{request.strip}"
+        @lasterrstr = @lasterrstr ? (@lasterrstr << request) : request
+        return error(@lasterr).new(@lasterrstr)
+      end
+      raise error(@lasterr).new(@lasterrstr)
     end
 
     return url_decode($1) if line =~ /^OK\s+\d*\s*(\S*)\r\n\z/