Database Reference
In-Depth Information
SQL fetchlet
: This fetchlet allows you to run a SQL statement or PL/SQL block against an
Oracle database and return a table of values. Multiple input parameters can be specified
for both SQL and PL/SQL. In case of a PL/SQL block, a single output parameter must be
defined and returned from PL/SQL as a PL/SQL REF CURSOR or as a named type defined
as an array of objects. The fetchlet's properties define the database connection and
credentials as well as SQL parameters, the inline SQL statement or SQL file to run, and the
maximum number of rows to retrieve. This fetchlet cannot be used to run SQL against
non-Oracle databases. Some use cases for this fetchlet include collecting application metrics
from status tables in the Oracle database or monitoring applications that are running inside
the database, such as Oracle Application Express (APEX) applications.
SNMP fetchlet
: This fetchlet allows metric collection from SNMP targets. The metric
based on the SNMP fetchlet can collect values from multiple object identifiers (OIDs).
Each OID can refer to either a single variable or multiple instances (one per network
interface, for example). The fetchlet also supports PINGMODE, a simple way of creating
a
Response
metric returning 1 if the SNMP port is responding, and 0 if a time-out occurs.
This is better than generating a metric collection error. The fetchlet supports SNMP v1
and v2 protocols based on community strings as well as the more secure v3 protocol
that requires credentials rather than a community string. Obvious use cases are for
monitoring remote network equipment or remote hosts that are not natively supported
by the Oracle agent (such as Ubuntu Linux) or that cannot have an agent installed for
some reason. Metric extensions' SNMP adapter is based on this fetchlet, as you might
have guessed. However, the SNMP adapter configuration is so limited that it makes it
practically useless in metric extensions context.
HTTP Data fetchlets
: This family of fetchlets is very similar to the OS Command fetchlets
but takes output from an HTTP GET request by using a specified URL instead of executing
an OS command. The output can be a raw value or lines of values or a delimiter-based
tokenized lines of values—all the same options as for OS Command fetchlets.
URLXML fetchlet
: This fetchlet can process an XML response retrieved from an HTTP URL
and extract tabular data following predefined pattern matching. It supports HTTP GET
requests only and can also be configured with a proxy server similar to HTTP Data fetchlets.
Note that a pattern is defined so that it extracts rows from a hierarchical XML structure,
because metrics accept tables of values. Each value is a number or a string, so no complex
types can be returned and processed. You need to flatten your data collection.
REST fetchlet
: This provides a mean of collecting data from RESTful web sources. It
supports GET and POST HTTP methods and Basic Authentication. The response can be
either in XML or in JavaScript Object Notation (JSON) formats and can be transformed
into a tabular presentation for metrics by using either XPath or JSONPath. HTTPS is
also supported.
URL Timing fetchlet
: This is a useful collection mechanism to test the performance of
web applications. It supports a simple proxy and can be used for both HTTP and HTTPS
protocols. The fetchlet supports Basic Authentication for HTTP. It has capabilities for
defining a connection time-out and retries and is flexible in configuring the metrics it
collects. The fetchlet can accept multiple URLs. For each URL, it retrieves not only the page
itself but any content required on the page such as images, style sheets, and so forth. It
can provide detailed statistics for each URL or per URL. There are couple dozen statistics
from obvious ones such as total bytes received and total time to retrieve the page as well
as advanced statistics such as DNS resolution time or average time before the first byte is
received for each request.
