Maintaining an /etc/hosts record

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by Lisa

I encountered an oddity at work — there’s a server on an internally located public IP space. Because it’s public space, it is not allowed to communicate with the internal interface of some of our security group’s servers. It has to use their public interface (not technically, just a policy on which they will not budge). I cannot just use a DNS server that resolves the public copy of our zone because then we’d lose access to everything else, so we are stuck making an /etc/hosts entry. Except this thing changes IPs fairly regularly (hey, we’re moving from AWS to Azure; hey, let’s try CloudFlare; nope, that is expensive so change it back) and the service it provides is application authentication so not something you want randomly falling over every couple of months.

So I’ve come up with a quick script to maintain the /etc/hosts record for the endpoint. 

# requires: dnspython, subprocess

import dns.resolver
import subprocess

strHostToCheck = 'hostname.example.com' # PingID endpoint for authentication
strDNSServer = "8.8.8.8"         # Google's public DNS server
listStrIPs = []

# Get current assignement from hosts file
listCurrentAssignment = [ line for line in open('/etc/hosts') if strHostToCheck in line]

if len(listCurrentAssignment) >= 1:
        strCurrentAssignment = listCurrentAssignment[0].split("\t")[0]

        # Get actual assignment from DNS
        objResolver = dns.resolver.Resolver()
        objResolver.nameservers = [strDNSServer]
        objHostResolution = objResolver.query(strHostToCheck)

        for objARecord in objHostResolution:
                listStrIPs.append(objARecord.to_text())

        if len(listStrIPs) >= 1:
                # Fix /etc/hosts if the assignment there doesn't match DNS
                if strCurrentAssignment in listStrIPs:
                        print(f"Nothing to do -- hosts file record {strCurrentAssignment} is in {listStrIPs}")
                else:
                        print(f"I do not find {strCurrentAssignment} here, so now fix it!")
                        subprocess.call([f"sed -i -e 's/{strCurrentAssignment}\t{strHostToCheck}/{listStrIPs[0]}\t{strHostToCheck}/g' /etc/hosts"], shell=True)
        else:
                print("No resolution from DNS ... that's not great")
else:
        print("No assignment found in /etc/hosts ... that's not great either")

NEO4J: Adding Indices

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by Lisa

Like SQL-based databases, you can create indices in Neo4j to optimize frequently performed searches. In my particular case, I am usually searching by the plant name. Adding an index on the plant’s name, therefore, makes sense:

CREATE INDEX index_tomato_name IF NOT EXISTS
FOR (n:TOMATO)
ON (n.name)

I am also interested in mapping the genetic lineage, so I’ve added indices for the male and female parent plants:

CREATE INDEX index_tomato_parentm IF NOT EXISTS
for ()-[r:PARENT_M]-()
on (r.name)

CREATE INDEX index_tomato_parentf IF NOT EXISTS
for ()-[r:PARENT_F]-()
on (r.name)

 

Hypothetically, you can use the procedure CALL db.indexes(); to view all of the indices in a database, but SHOW PROCEDURES; shows me that procedure isn’t registered in the community edition.

╒═════════════════════════════════════════════════════════╤══════════════════════════════════════════════════════════════════════╤═══════╤═════════════╕
│name                                                     │description                                                           │mode   │worksOnSystem│
╞═════════════════════════════════════════════════════════╪══════════════════════════════════════════════════════════════════════╪═══════╪═════════════╡
│"db.awaitIndex"                                          │"Wait for an index to come online (for example: CALL db.awaitIndex(\"M│"READ" │true         │
│                                                         │yIndex\", 300))."                                                     │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.awaitIndexes"                                        │"Wait for all indexes to come online (for example: CALL db.awaitIndexe│"READ" │true         │
│                                                         │s(300))."                                                             │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.clearQueryCaches"                                    │"Clears all query caches."                                            │"DBMS" │true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.createLabel"                                         │"Create a label"                                                      │"WRITE"│false        │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.createProperty"                                      │"Create a Property"                                                   │"WRITE"│false        │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.createRelationshipType"                              │"Create a RelationshipType"                                           │"WRITE"│false        │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.index.fulltext.awaitEventuallyConsistentIndexRefresh"│"Wait for the updates from recently committed transactions to be appli│"READ" │true         │
│                                                         │ed to any eventually-consistent full-text indexes."                   │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.index.fulltext.listAvailableAnalyzers"               │"List the available analyzers that the full-text indexes can be config│"READ" │true         │
│                                                         │ured with."                                                           │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.index.fulltext.queryNodes"                           │"Query the given full-text index. Returns the matching nodes, and thei│"READ" │true         │
│                                                         │r Lucene query score, ordered by score. Valid keys for the options map│       │             │
│                                                         │ are: 'skip' to skip the top N results; 'limit' to limit the number of│       │             │
│                                                         │ results returned; 'analyzer' to use the specified analyzer as search │       │             │
│                                                         │analyzer for this query."                                             │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.index.fulltext.queryRelationships"                   │"Query the given full-text index. Returns the matching relationships, │"READ" │true         │
│                                                         │and their Lucene query score, ordered by score. Valid keys for the opt│       │             │
│                                                         │ions map are: 'skip' to skip the top N results; 'limit' to limit the n│       │             │
│                                                         │umber of results returned; 'analyzer' to use the specified analyzer as│       │             │
│                                                         │ search analyzer for this query."                                     │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.info"                                                │"Provides information regarding the database."                        │"READ" │true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.labels"                                              │"List all available labels in the database."                          │"READ" │true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.ping"                                                │"This procedure can be used by client side tooling to test whether the│"READ" │true         │
│                                                         │y are correctly connected to a database. The procedure is available in│       │             │
│                                                         │ all databases and always returns true. A faulty connection can be det│       │             │
│                                                         │ected by not being able to call this procedure."                      │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.prepareForReplanning"                                │"Triggers an index resample and waits for it to complete, and after th│"READ" │true         │
│                                                         │at clears query caches. After this procedure has finished queries will│       │             │
│                                                         │ be planned using the latest database statistics."                    │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.propertyKeys"                                        │"List all property keys in the database."                             │"READ" │true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.relationshipTypes"                                   │"List all available relationship types in the database."              │"READ" │true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.resampleIndex"                                       │"Schedule resampling of an index (for example: CALL db.resampleIndex(\│"READ" │true         │
│                                                         │"MyIndex\"))."                                                        │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.resampleOutdatedIndexes"                             │"Schedule resampling of all outdated indexes."                        │"READ" │true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.schema.nodeTypeProperties"                           │"Show the derived property schema of the nodes in tabular form."      │"READ" │true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.schema.relTypeProperties"                            │"Show the derived property schema of the relationships in tabular form│"READ" │true         │
│                                                         │."                                                                    │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.schema.visualization"                                │"Visualizes the schema of the data based on available statistics. A ne│"READ" │true         │
│                                                         │w node is returned for each label. The properties represented on the n│       │             │
│                                                         │ode include: `name` (label name), `indexes` (list of indexes), and `co│       │             │
│                                                         │nstraints` (list of constraints). A relationship of a given type is re│       │             │
│                                                         │turned for all possible combinations of start and end nodes. The prope│       │             │
│                                                         │rties represented on the relationship include: `name` (type name). Not│       │             │
│                                                         │e that this may include additional relationships that do not exist in │       │             │
│                                                         │the data due to the information available in the count store. "       │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.stats.clear"                                         │"Clear collected data of a given data section. Valid sections are 'QUE│"READ" │true         │
│                                                         │RIES'"                                                                │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.stats.collect"                                       │"Start data collection of a given data section. Valid sections are 'QU│"READ" │true         │
│                                                         │ERIES'"                                                               │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.stats.retrieve"                                      │"Retrieve statistical data about the current database. Valid sections │"READ" │true         │
│                                                         │are 'GRAPH COUNTS', 'TOKENS', 'QUERIES', 'META'"                      │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.stats.retrieveAllAnonymized"                         │"Retrieve all available statistical data about the current database, i│"READ" │true         │
│                                                         │n an anonymized form."                                                │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.stats.status"                                        │"Retrieve the status of all available collector daemons, for this data│"READ" │true         │
│                                                         │base."                                                                │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"db.stats.stop"                                          │"Stop data collection of a given data section. Valid sections are 'QUE│"READ" │true         │
│                                                         │RIES'"                                                                │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"dbms.cluster.routing.getRoutingTable"                   │"Returns the advertised bolt capable endpoints for a given database, d│"DBMS" │true         │
│                                                         │ivided by each endpoint's capabilities. For example an endpoint may se│       │             │
│                                                         │rve read queries, write queries and/or future getRoutingTable requests│       │             │
│                                                         │."                                                                    │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"dbms.components"                                        │"List DBMS components and their versions."                            │"DBMS" │true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"dbms.info"                                              │"Provides information regarding the DBMS."                            │"DBMS" │true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"dbms.killConnection"                                    │"Kill network connection with the given connection id."               │"DBMS" │true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"dbms.killConnections"                                   │"Kill all network connections with the given connection ids."         │"DBMS" │true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"dbms.listCapabilities"                                  │"List capabilities"                                                   │"DBMS" │true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"dbms.listConfig"                                        │"List the currently active config of Neo4j."                          │"DBMS" │true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"dbms.listConnections"                                   │"List all accepted network connections at this instance that are visib│"DBMS" │true         │
│                                                         │le to the user."                                                      │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"dbms.queryJmx"                                          │"Query JMX management data by domain and name. For instance, \"*:*\"" │"DBMS" │true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"dbms.routing.getRoutingTable"                           │"Returns the advertised bolt capable endpoints for a given database, d│"DBMS" │true         │
│                                                         │ivided by each endpoint's capabilities. For example an endpoint may se│       │             │
│                                                         │rve read queries, write queries and/or future getRoutingTable requests│       │             │
│                                                         │."                                                                    │       │             │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"dbms.upgrade"                                           │"Upgrade the system database schema if it is not the current schema." │"WRITE"│true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"dbms.upgradeStatus"                                     │"Report the current status of the system database sub-graph schema."  │"READ" │true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"tx.getMetaData"                                         │"Provides attached transaction metadata."                             │"DBMS" │true         │
├─────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────────────┼───────┼─────────────┤
│"tx.setMetaData"                                         │"Attaches a map of data to the transaction. The data will be printed w│"DBMS" │false        │
│                                                         │hen listing queries, and inserted into the query log."                │       │             │
└─────────────────────────────────────────────────────────┴──────────────────────────────────────────────────────────────────────┴

NEO4J: Searching

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by Lisa

Returning data from NEO4J is matching — we can match a node using MATCH p=(a:TOMATO {name: 'Black Krim'}) return p;

where the object “p” becomes a set of nodes labeled with ‘TOMATO’ where the value of ‘name’ is ‘Black Krim’

More advanced matches set the return object to a set of nodes and relationships — here we set p to the set of items starting at the node labeled TOMATO with name ‘PLANT0’ with relationships and nodes until you get to a node labeled TOMATO with name ‘Tomato0000007’

MATCH p=(a:TOMATO {name: 'PLANT0'})-[*]->(b:TOMATO {name: 'Tomato0000007'}) RETURN p

Got ’em

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by Lisa

We finally saw the new kittens, well kitten, on the back patio. Anya put a trap out, and the curious little one walked right in. She put another trap out, and we caught the mommy cat too! We’ll get her into the vet shortly, and the barn cats won’t sprout more kittens.

NEO4J: Relational Databases

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by Lisa

I always found it odd that relational databases didn’t really have relationships as part of the stored data. Technically, they could if you had a view or stored procedure with a bunch of JOIN’s in there. But relational databases stored data about which you could build relationships. And people using the data may not even know about relationships that other people saw within that data. Some of our databases at work have amazing documentation — a hundred meg of PDF files detailing the relationships that the database creator wanted people to use. Other databases? No such luck!

To me, that’s the big advantage of a Graph database — the relationships are stored within the data, so anyone viewing it for the first time doesn’t need to poke around, see where values could be correlated across tables, and create their own JOIN statements to build out the relationship. Recording data in the database means defining those relationships. It would still be good to document a graph model (we have ‘people’ nodes who ‘act in’, ‘cast’, ‘produce’, or ‘direct’ ‘movie’ nodes), but you could figure all of those things out by perusing the database content.

Creamy Tomato Sauce for Pasta

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by Lisa

I needed a quick meal last night — so I made a carrot-y, creamy tomato sauce for pasta.

Ingredients

  • 1/4 cup olive oil
  • 2 carrots, diced into small pieces
  • 1/2 large onion, diced into small pieces
  • 3-4 cloves of garlic, diced
  • 3 oz tomato paste
  • 1/3 cup plain Greek yogurt
  • salt, pepper, Italian herbs

Method

  • Heat olive oil in a pan. Add diced carrots and cook for a few minutes. Add garlic and onions and cook for a few more minutes until the onions become translucent.
  • Add salt, pepper, and herbs. Then add tomato paste and stir to incorporate oil. Cook for a few minutes.
  • Add pasta cooking water to thin to a reasonable consistency.
  • Remove from heat and stir in yogurt. Add salt/pepper/herbs to taste.

NEO4J: Applications

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by Lisa

I remember a friend of mine who taught introductory computer programming classes in University. One test question he always used was essentially ‘do something that people can do easily’. The exact details would change year to year, but the important thing is that the instructions simply stated “Sort the following list in alphabetical order”. Not write a program that sorts an arbitrary list into alphabetical order — sort this list. And, sure, you could write a program to do it. A program that would successfully accomplish the goal got an A grade. But so did someone who just took the list, sorted it alphabetically in their head, and wrote the list in alphabetical order. That answer? Would get extra credit. Because knowing when not to program is really important too. From a business standpoint, it’s a waste of money for someone to write a program to perform some easy one-off task that is never going to be done again.

I think about that a lot when I see “new” technologies getting picked up. I call it the “CIO magazine” approach to technology adoption. You see some new thing, have a very basic understanding of how it works, and decide we need to use one of these. And fail to consider if your use case is reasonable or if you’re willing to do the extra work for the “new” thing. The biggest example I experience of “not reasonable” is the prevalence of Java programming. If I am selling software, cross-platform compilation is A Very Good Thing. If I can maintain a single pipeline and a single release that all of my customers can use? Score! Internally developed software, though? We requisition specific platforms. Our Linux servers are not going to be Windows servers next Tuesday. I can write code, compile it for Linux, and be fine even if it doesn’t run under Windows. Because it doesn’t need to run under Windows. The extra work — our internal support groups adopted Agile. Except no one was willing to prioritize the ticket queue — so there’s no prioritized list of work to select from. Everyone has two “issues” for their sprint — “incident support” and “admin time”. A few people might get involved in a specific project and add “dns decom” or “nextgen vpn testing”. But sprint planning is repetitive (I’ve got incident support & admin time, too!), daily standups were a joke (I did tickets yesterday & had a meeting), and techs still didn’t know what ticket was the priority that should be pulled next. Which doesn’t make Java or Agile a bad idea — it just makes them overly complicated for the situation in which they are being used.

I think of all of this when I see Graph databases being implemented — step #0 is does a graph database make sense for my data? What would that mean? It would mean that the data elements are interconnected somehow — if you’d be using a lot of JOIN queries to interact with the stored data, then a graph model might make sense. If you’re just selecting items from individual tables where values are whatever? Then a graph database is a complex way of storing and accessing that data.