# Controllers

Istio has a variety of [controllers](https://kubernetes.io/docs/concepts/architecture/controller/), which basically watch some inputs and do something.
This can be reading from Kubernetes and writing other objects back, writing to proxies over XDS, etc.

Unfortunately, writing controllers is very error prone, even for seemingly simple cases.
To work around this, Istio has a variety of abstractions meant to make writing controllers easier.

## Clients

        accessResultDataImpl.setTransformerName("transformer");

        setBaseDir();

        try {
            final Object obj = fileTransformer.getData(accessResultDataImpl);
            fail();
        } catch (final CrawlerSystemException e) {}
    }

    public void test_getData_nullData() throws Exception {
        final AccessResultDataImpl accessResultDataImpl = new AccessResultDataImpl();

  integrity sha512-8+9WqebbFzpX9OR+Wa6O29asIogeRMzcGtAINdpMHHyAg10f05aSFVBbcEqGf/PXw1EjAZ+q2/bEBg3DvurK3Q==

balanced-match@^1.0.0:
  version "1.0.2"
  resolved "https://registry.yarnpkg.com/balanced-match/-/balanced-match-1.0.2.tgz#e83e3a7e3f300b34cb9d87f615fa0cbf357690ee"
  integrity sha512-3oSeUO0TMV67hN1AmbXsK4yaqU7tjiHlbxRDZOpH0KW9+CeX4bRAaX0Anxt0tx2MrpRpWwQaPwIlISEJhYU5Pw==

                    raf.seek(6);
                    try {
                        raf.readFully(buf);
                        Assert.fail("Should have thrown exception");
                    }
                    catch ( SmbEndOfFileException e ) {}
                }

            }
            finally {
                f.delete();
            }
        }
    }


    @Test

        }
        Map<String, Object> target = dataMap;
        for (final Ingester ingester : ingestFactory.getIngesters()) {
            try {
                target = ingester.process(target, paramMap);
            } catch (final Exception e) {
                logger.warn("Failed to process Ingest[{}]", ingester.getClass().getSimpleName(), e);
            }
        }
        return target;
    }

    @Override

            builder.flush();
            try (OutputStream out = builder.getOutputStream()) {
                stats = ((ByteArrayOutputStream) out).toString(Constants.UTF_8);
            }
        } catch (final Exception e) {
            appendException(buf, e).append(',');
        }
        buf.append("\"search_engine\":").append(stats).append(',');
    }

      SortedMap<@Nullable Object, V> self = (SortedMap<@Nullable Object, V>) this;
      Object ceilingKey = self.tailMap(key).firstKey();
      return unsafeCompare(comparator(), ceilingKey, key) == 0;
    } catch (ClassCastException | NoSuchElementException | NullPointerException e) {
      return false;
    }
  }

  /**
   * A sensible default implementation of {@link #subMap(Object, Object)} in terms of {@link

     * @return {@code true} if the key mapping was successfully updated from the old value to the new value,
     *         {@code false} if the current key mapping didn't match the expected value and was not updated.
     */
    <T> boolean replace(@Nonnull Key<T> key, @Nullable T oldValue, @Nullable T newValue);

    /**
     * Gets the session data associated with the specified key.
     *

                break;
            default:
                Assume.assumeTrue("Unhandled OEM encoding " + oemEncoding, false);
            }
        }
        catch ( UnsupportedCharsetException e ) {
            Assume.assumeTrue("Charset is not supported on this VM " + oemEncoding, false);
        }
        runFilenameTest(splitString(str, 8));
    }

            // System.err.println("Linked("+requestedScope+")
            // subgraph("+linkedRes.getVertices().size()+"):\n"+linkedRes.toString());
            return findLinkedSubgraph(res);
        } catch (MetadataResolutionException e) {
            throw new GraphConflictResolutionException(e);
        }
    }

    // -------------------------------------------------------------------------------------