Skip to main content

Tutkin diplomityössäni älypuhelinten hyödyntämistä maatalouskäytössä. Tutkimukseen liittyy GPS träkkäysohjelma, jota olen ollut kehittämässä jo lähes vuoden. Ohjelman tarkoitus on automatisoida maatalouteen liittyvän tyokirjanpidon muodostamista

Ohjelman on pystyttävä seuraavaan maanviljelijän liikkeitä koko vuorokauden. Ohjelman virrankulutus on pidettävä sellaisena, ettei se kuluta koko akkua loppuun ainakaan kymmeneen tuntiin. GPS palvelu on siis pystyttävä katkaisemaan väliajoin eikä muu puhelimen käyttö saa katkaista träkkäystä.

Android-implementaatiossani GPS kuuntelusta vastaa oma Androidin Service. Servicet sinänsä eivät ole erityisen soveltuvia tähän käyttöön, koska ne ajetaan samassa säikeessä muun ohjelman (käyttöliittymä) kanssa ja myös Servicen säie lopetetaan, jos laite menee näppäinlukkoon tai on käyttämättä jonkin aikaa. Ongelma ei poistu, vaikka Servicessä luotaisiin uusia säikeitä.

Ratkaisuna käytin WakeLockia, joka mahdollistaa näytön sammumisen ja näppäinlukon, mutta ei pysäytä prosessoria ja säikeet pysyvät päällä. Periaatteessa tämä on aika huono ominaisuus kännykkäohjelmalla, mutta paras löytämäni tapa pitää träkkäys hengissä. Jos GPS pollausintervalli pidetään yli minuutin mittaisena eli GPS on vähintään minuutin pois päältä ja taas minuutin päällä, virrankulutus pysyy melko inhimillisenä. Ohjelma lisää virrankulutusta noin 15mA.
private void startListening() {
  new Thread(new Runnable() {
   @Override
   public void run() {
    PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
    PowerManager.WakeLock wl = pm.newWakeLock(
      PowerManager.PARTIAL_WAKE_LOCK, "AlkioGPS");
    wl.acquire();
    Looper.prepare();
    while (!die) {
     mloc.requestLocationUpdates(LocationManager.GPS_PROVIDER,
       1000, 0, listener);
     try {
      Thread.sleep((gpsinterval / 2));
     } catch (InterruptedException e) {
      e.printStackTrace();
     }
     mloc.removeUpdates(listener);
     try {
      Thread.sleep(gpsinterval / 2);
     } catch (InterruptedException e) {
      e.printStackTrace();
     }
    }
    gpstimer.cancel();
    try {
     unregisterReceiver(rec);
    } catch (Exception e) {

    }
    wl.release();
   }
  }).start();
 }

Comments

Popular posts from this blog

RocksDB data recovery

I recently needed to do some maintenance on a RocksDB key-value store. The task was simple enough, just delete some keys as the db served as a cache and did not contain any permanent data. I used the RocksDB cli administration tool ldb to erase the keys. After running a key scan with it, I got this error Failed: Corruption: Snappy not supported or corrupted Snappy compressed block contents So a damaged database. Fortunately, there's a tool to fix it, and after running it, I had access to the db via the admin tool. All the data was lost though. Adding and removing keys worked fine but all the old keys were gone. It turned out that the corrupted data was all the data there was. The recovery tool made a backup folder, and I recovered the data by taking the files from the backup folder and manually changing the CURRENT file to point to the old MANIFEST file which is apparently how RocksDB knows which sst (table) files to use. I could not access the data with the admin tool, ...

I'm not a passionate developer

A family friend of mine is an airlane pilot. A dream job for most, right? As a child, I certainly thought so. Now that I can have grown-up talks with him, I have discovered a more accurate description of his profession. He says that the truth about the job is that it is boring. To me, that is not that surprising. Airplanes are cool and all, but when you are in the middle of the Atlantic sitting next to the colleague you have been talking to past five years, how stimulating can that be? When he says the job is boring, it is not a bad kind of boring. It is a very specific boring. The "boring" you would want as a passenger. Uneventful.  Yet, he loves his job. According to him, an experienced pilot is most pleased when each and every tiny thing in the flight plan - goes according to plan. Passengers in the cabin of an expert pilot sit in the comfort of not even noticing who is flying. As someone employed in a field where being boring is not exactly in high demand, this sounds pro...

Careful with externalTrafficPolicy

On a project I am working on is hosted in an EKS cluster with the NGINX ingress controller (the one maintained by Kubernetes). It is deployed using it's official official Helm chart, which I realized, after a lengthy debugging session, was a mistake. The initial setup I aimed to improve had several flaws. Firstly, we were using the AWS Classic Load Balancer in front of the nginx ingress in the cluster, which has been deprecated for some time (years?). Continuing to use it makes little sense to us. The second issue was that we were only running one(!) nginx pod, which is quite sketchy since the exposed web services had essentially no high availability.  I switched to the Network Load Balancer (NLB), which was straightforward - I just needed to change the ingress-nginx service annotation to specify the load balancer type as NLB: service.beta.kubernetes.io/aws-load-balancer-type: nlb However, increasing the replica count turned out to be tricky. When I bumped it up to two, I began to ...