[UIMA-5933] UIMA-DUCC: improve pull service http client error handling

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.2.2-Ducc
• Fix Version/s: 3.0.0-Ducc
• Component/s: DUCC
• Assignee: Jaroslaw Cwiklik
• Reporter: Jaroslaw Cwiklik
• Created: 13/Dec/18 14:24
• Updated: 13/Dec/18 17:07
• Resolved: 13/Dec/18 17:07

Description

The pull service error handling in HttpServiceTransport.dispatch() is not optimal. While it is catching and handling some exceptions like

NoHttpResponseException
HttpHostConnectException
UnknownHostException

its not handling other ones that HttpClient.execute() may throw. 

Simplify handling of exceptions from HttpClient.execute() by simply catching any IOException and automatically retry until success. The HttpClient.execute() API is documented as:

HttpResponse org.apache.http.client.HttpClient.execute(HttpUriRequest request) throws IOException, ClientProtocolException
 
Note: the ClientProtocolException is a kind of (extends from) IOException

Also, the http client may succeed but returns status code != 200. In such case, we should also retry.