/// <summary>
/// Get the host name associated with the specified host id.
/// </summary>
/// <param name="hostID">The host id to look up.</param>
/// <returns>The name of the host.</returns>
protected virtual String GetHost(int hostID)
{
RepeatableStatement.Results rs = null;
try
{
rs = this.stmtGetHost.ExecuteQuery(hostID);
if (!rs.DataReader.Read())
{
throw new WorkloadException("Can't find previously created host.");
}
return((String)rs.DataReader[0]);
}
catch (Exception e)
{
throw new WorkloadException(e);
}
finally
{
if (rs != null)
{
rs.Close();
}
}
}
/// <summary>
/// Return true if there are no more workload units.
/// </summary>
/// <returns>Returns true if there are no more workload units.</returns>
public virtual bool WorkloadEmpty()
{
RepeatableStatement.Results rs = null;
try
{
rs = this.stmtWorkloadEmpty.ExecuteQuery(this.currentHostID);
if (!rs.DataReader.Read())
{
return(true);
}
return((int)rs.DataReader[0] < 1);
}
catch (Exception e)
{
throw (new WorkloadException(e));
}
finally
{
if (rs != null)
{
rs.Close();
}
}
}
/// <summary>
/// Setup the workload so that it can be resumed from where
/// the last spider left the workload.
/// </summary>
public virtual void Resume()
{
RepeatableStatement.Results rs = null;
try
{
rs = this.stmtResume.ExecuteQuery();
if (!rs.DataReader.Read())
{
throw (new WorkloadException(
"Can't resume, unable to determine current host."));
}
this.currentHostID = (int)rs.DataReader[0];
this.currentHost = (String)GetHost(this.currentHostID);
}
catch (Exception e)
{
throw (new WorkloadException(e));
}
finally
{
if (rs != null)
{
rs.Close();
}
}
this.stmtResume2.Execute();
}
/// <summary>
/// Get the source page that contains the specified URL.
/// </summary>
/// <param name="url">The Uri to seek the source for.</param>
/// <returns>The source of the specified URL.</returns>
public virtual Uri GetSource(Uri url)
{
RepeatableStatement.Results rs = null;
try
{
rs = this.stmtGetSource.ExecuteQuery(ComputeHash(url));
while (rs.DataReader.Read())
{
String u = (String)rs.DataReader[0];
if (u.Equals(url.ToString()))
{
return(new Uri((String)rs.DataReader[0]));
}
}
return(null);
}
catch (UriFormatException e)
{
throw (new WorkloadException(e));
}
catch (Exception e)
{
throw (new WorkloadException(e));
}
finally
{
if (rs != null)
{
rs.Close();
}
}
}
/// <summary>
/// Close the workload.
/// </summary>
public void Close()
{
if (this.workResultSet != null)
{
try
{
this.workResultSet.Close();
}
catch (Exception)
{
spider.Logging.Log(Logger.Level.ERROR,
"Error trying to close workload result set, ignoring...");
}
this.workResultSet = null;
}
foreach (RepeatableStatement statement in this.statements)
{
statement.Close();
}
if (this.connection != null)
{
this.connection.Close();
}
}
/// <summary>
/// Called internally to get a work unit. This function
/// does not wait for work, rather it simply returns null.
/// </summary>
/// <returns>The next Uri to process.</returns>
protected virtual Uri GetWorkInternal()
{
if (this.currentHostID == -1)
{
throw new WorkloadException(
"Attempting to obtain work before adding first URL.");
}
try
{
bool requery = false;
if (this.workResultSet == null)
{
requery = true;
}
else
{
if (!this.workResultSet.DataReader.Read())
{
requery = true;
}
}
if (requery)
{
if (this.workResultSet != null)
{
this.workResultSet.Close();
}
this.workResultSet = this.stmtGetWork.ExecuteQuery(Status.STATUS_WAITING,
this.currentHostID);
if (!this.workResultSet.DataReader.Read())
{
return(null);
}
}
int id = (int)this.workResultSet.DataReader[0];
String url = (String)this.workResultSet.DataReader[1];
this.stmtGetWork2.Execute(Status.STATUS_PROCESSING, id);
return(new Uri(url));
}
catch (UriFormatException e)
{
throw (new WorkloadException(e));
}
catch (Exception e)
{
throw (new WorkloadException(e));
}
}
/// <summary>
/// Move on to process the next host. This should only be
/// called after getWork returns null.
/// </summary>
/// <returns>The name of the next host.</returns>
public virtual String NextHost()
{
if (this.currentHostID == -1)
{
throw new WorkloadException(
"Attempting to obtain host before adding first URL.");
}
else
{
MarkHostProcessed(this.currentHost);
}
try
{
bool requery = false;
if (this.hostResultSet == null)
{
requery = true;
}
else
{
if (!this.hostResultSet.DataReader.Read())
{
requery = true;
}
}
if (requery)
{
if (this.hostResultSet != null)
{
this.hostResultSet.Close();
}
this.hostResultSet = this.stmtGetNextHost.ExecuteQuery(Status.STATUS_WAITING);
if (!this.hostResultSet.DataReader.Read())
{
return(null);
}
}
this.currentHostID = (int)this.hostResultSet.DataReader[0];
this.currentHost = (String)this.hostResultSet.DataReader[1];
this.stmtSetHostStatus.Execute(Status.STATUS_PROCESSING, this.currentHostID);
spider.Logging.Log(Logger.Level.INFO, "Moving to new host: " + this.currentHost);
return(this.currentHost);
}
catch (Exception e)
{
throw (new WorkloadException(e));
}
}
/// <summary>
/// Get the id for the specified host name.
/// </summary>
/// <param name="host">The host to lookup.</param>
/// <param name="require">Should an exception be thrown if the host is not located.</param>
/// <returns>The id of the specified host name.</returns>
protected virtual int GetHostID(String host, bool require)
{
RepeatableStatement.Results rs = null;
// is this the current host?
if (this.currentHostID != -1)
{
if (String.Compare(this.currentHost, host, true) == 0)
{
return(this.currentHostID);
}
}
// use the database to find it
try
{
rs = this.stmtGetHostID.ExecuteQuery(host);
if (rs.DataReader.Read())
{
return((int)rs.DataReader[0]);
}
}
finally
{
if (rs != null)
{
rs.Close();
}
}
if (require)
{
StringBuilder str = new StringBuilder();
str.Append("Failed to find previously visited Host,");
str.Append("Host=\"");
str.Append(host);
str.Append("\".");
throw (new WorkloadException(str.ToString()));
}
else
{
return(-1);
}
}
/// <summary>
/// Get the workload ID, given a URL.
/// </summary>
/// <param name="url"> The URL to look up.</param>
/// <param name="require">Should an exception be thrown if the workload
/// is not located.</param>
/// <returns>The ID of the workload.</returns>
protected virtual int GetWorkloadID(Uri url, bool require)
{
int hash = 0;
RepeatableStatement.Results rs = null;
try
{
hash = ComputeHash(url);
rs = this.stmtGetWorkloadID.ExecuteQuery(hash);
while (rs.DataReader.Read())
{
if (rs.DataReader[1].Equals(url.ToString()))
{
return((int)rs.DataReader[0]);
}
}
}
finally
{
if (rs != null)
{
rs.Close();
}
}
if (require)
{
StringBuilder str = new StringBuilder();
str.Append("Failed to find previously visited URL, hash=\"");
str.Append(hash);
str.Append("\", URL=\"");
str.Append(url.ToString());
str.Append("\".");
throw (new WorkloadException(str.ToString()));
}
else
{
return(-1);
}
}
/// <summary>
/// Called internally to get a work unit. This function
/// does not wait for work, rather it simply returns null.
/// </summary>
/// <returns>The next Uri to process.</returns>
protected virtual Uri GetWorkInternal()
{
if (this.currentHostID == -1)
{
throw new WorkloadException(
"Attempting to obtain work before adding first URL.");
}
try
{
bool requery = false;
if (this.workResultSet == null)
{
requery = true;
}
else
{
if (!this.workResultSet.DataReader.Read())
{
requery = true;
}
}
if (requery)
{
if (this.workResultSet != null)
{
this.workResultSet.Close();
}
this.workResultSet = this.stmtGetWork.ExecuteQuery(Status.STATUS_WAITING,
this.currentHostID);
if (!this.workResultSet.DataReader.Read())
{
return null;
}
}
int id = (int)this.workResultSet.DataReader[0];
String url = (String)this.workResultSet.DataReader[1];
this.stmtGetWork2.Execute(Status.STATUS_PROCESSING, id);
return new Uri(url);
}
catch (UriFormatException e)
{
throw (new WorkloadException(e));
}
catch (Exception e)
{
throw (new WorkloadException(e));
}
}
/// <summary>
/// Move on to process the next host. This should only be
/// called after getWork returns null.
/// </summary>
/// <returns>The name of the next host.</returns>
public virtual String NextHost()
{
if (this.currentHostID == -1)
{
throw new WorkloadException(
"Attempting to obtain host before adding first URL.");
}
else
{
MarkHostProcessed(this.currentHost);
}
try
{
bool requery = false;
if (this.hostResultSet == null)
{
requery = true;
}
else
{
if (!this.hostResultSet.DataReader.Read())
{
requery = true;
}
}
if (requery)
{
if (this.hostResultSet != null)
{
this.hostResultSet.Close();
}
this.hostResultSet = this.stmtGetNextHost.ExecuteQuery(Status.STATUS_WAITING);
if (!this.hostResultSet.DataReader.Read())
{
return null;
}
}
this.currentHostID = (int)this.hostResultSet.DataReader[0];
this.currentHost = (String)this.hostResultSet.DataReader[1];
this.stmtSetHostStatus.Execute(Status.STATUS_PROCESSING, this.currentHostID);
spider.Logging.Log(Logger.Level.INFO, "Moving to new host: " + this.currentHost);
return this.currentHost;
}
catch (Exception e)
{
throw (new WorkloadException(e));
}
}
/// <summary>
/// Close the workload.
/// </summary>
public void Close()
{
if (this.workResultSet != null)
{
try
{
this.workResultSet.Close();
}
catch (Exception)
{
spider.Logging.Log(Logger.Level.ERROR,
"Error trying to close workload result set, ignoring...");
}
this.workResultSet = null;
}
foreach (RepeatableStatement statement in this.statements)
{
statement.Close();
}
if (this.connection != null)
{
this.connection.Close();
}
}
