Add performance checks example

performance-checks/.gitignore

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+.gradle
+/build/
+!gradle/wrapper/gradle-wrapper.jar
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+/out/
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/

performance-checks/README.md

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+# Performance checks 
+
+This example has a few mechanisms to prevent your GraphQL server from dealing with expensive queries sent by abusive clients 
+(or maybe legitimate clients that running expensive queries unaware of the negative impacts they might cause).
+Also, it has a couple of timeout strategies that, although won't help ease the burden on the server (since the expensive
+operations are already under way), will provide a better experience to the consumer that won't have to wait forever for
+their requests to return.
+
+Here we introduce 4 mechanisms to help with that task. 3 of them are based on GraphQL Java instrumentation capabilities,
+and the forth one is a bit out GraphQL Java jurisdiction and more related to web servers.
+
+1. MaxQueryDepthInstrumentation: limit the depth of queries to 5
+2. MaxQueryComplexityInstrumentation: set complexity values to fields and limit query complexity to 5 
+3. A custom Instrumentation that sets a timeout period of 3 seconds for DataFetchers 
+4. A hard request timeout of 10 seconds, specified in the web server level (Spring) 
+
+The first 2 items will actually prevent server overload, since they act before the request reach the DataFetchers, which
+perform the expensive operations. Number 3 and 4 are timeouts that force long running executions to return early to customers.
+
+# The schema
+The schema we're using is quite simple:
+
+```graphql
+type Query {
+    instrumentedField(sleep: Int): String
+    characters: [Character]
+}
+
+type Character {
+    name: String!
+    friends: [Character]
+    energy: Float
+}
+```
+
+There are a few interesting facts related to this example.
+
+* instrumentedField: returns a fixed string ("value"). It receives a parameter "sleep" that forces the DataFetcher to
+  take that amount of seconds to return. Set that value to anything above 3 seconds and a timeout error will be thrown.
+  This simulates a long running DataFetcher that would be forcefully stopped.
+
+```graphql
+{
+  instrumentedField(sleep: 4) # will result in an error
+}
+``` 
+
+* friends: will return a list of characters, that can themselves have friends, and so on... It's quite clear that queries
+  might overuse this field and end up having a large number of nested friends and characters. Add 5 or more levels of 
+  friends and an error will be thrown.
+
+```graphql
+{
+  characters {
+    name
+    friends {
+      name
+      friends {
+        name
+        friends {
+          name
+          friends {
+            name     # an error will be thrown, since the depth is higher than the limit
+          }
+        }
+      }
+    }
+  }
+}
+```
+
+* energy: getting this field involves some expensive calculations, so we've established that it has a complexity value
+  of 3 (all the other fields have complexity 0). We've also defined that a query can have a maximum complexity of 5. So,
+  if "energy" is present 2 times or more in a given query, an error will be thrown.
+
+```graphql
+{
+  characters {
+    name
+    energy
+    friends {
+      name
+      energy   # an error will be thrown, since we've asked for "energy" 2 times
+    }
+  }
+}
+``` 
+
+# Request timeout
+Although this is not really GraphQL Java business, it might be useful to set a hard request timeout on the web server
+level.
+To achieve this using Spring, the following property can be used:
+
+```
+spring.mvc.async.request-timeout=10000
+```
+
+
+# Running the code
+
+ To build the example code in this repository type:
+
+``` 
+./gradlew build
+ ```
+
+To run the example code type:
+
+``` 
+./gradlew bootRun
+``` 
+
+To access the example application, point your browser at:
+     http://localhost:8080/  
+
+## Note about introspection and max query depth
+A bad side effect of specifying a maximum depth for queries is that this will prevent introspection queries to properly
+execute. This affects GraphiQL's documentation and autocomplete features, that will simply not work. 
+This is a tricky problem to fix and [has been discussed in the past](https://github.com/graphql-java/graphql-java/issues/1055). 
+
+You can still use GraphiQL to execute queries and inspect results. If you want documentation and autocomplete back in 
+GraphiQL, just temporarily disable the max depth instrumentation. 

performance-checks/build.gradle

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+buildscript {
+	ext {
+		springBootVersion = '2.0.5.RELEASE'
+	}
+	repositories {
+		mavenCentral()
+	}
+	dependencies {
+		classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
+	}
+}
+
+apply plugin: 'java'
+apply plugin: 'eclipse'
+apply plugin: 'org.springframework.boot'
+apply plugin: 'io.spring.dependency-management'
+
+group = 'com.graphql-java.examples'
+version = '0.0.1-SNAPSHOT'
+sourceCompatibility = 1.8
+
+repositories {
+	mavenCentral()
+}
+
+
+dependencies {
+	compile "io.reactivex.rxjava2:rxjava:2.1.5"
+	implementation('org.springframework.boot:spring-boot-starter-web')
+	implementation('com.graphql-java:graphql-java:10.0')
+    implementation('com.google.guava:guava:26.0-jre')
+	testImplementation('org.springframework.boot:spring-boot-starter-test')
+}

performance-checks/gradle/wrapper/gradle-wrapper.properties

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+#Sun Oct 07 10:24:43 AEDT 2018
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.8.1-all.zip

performance-checks/gradlew

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+#!/usr/bin/env sh
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS=""
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn ( ) {
+    echo "$*"
+}
+
+die ( ) {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=$((i+1))
+    done
+    case $i in
+        (0) set -- ;;
+        (1) set -- "$args0" ;;
+        (2) set -- "$args0" "$args1" ;;
+        (3) set -- "$args0" "$args1" "$args2" ;;
+        (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Escape application args
+save ( ) {
+    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+    echo " "
+}
+APP_ARGS=$(save "$@")
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
+  cd "$(dirname "$0")"
+fi
+
+exec "$JAVACMD" "$@"